c6b10de537
UDP doesn't support tx memory accounting, and sysctl udp_wmem_min
is not really used anywhere. So we should fix the description in
ip-sysctl.rst accordingly.
Fixes: 95766fff6b ("[UDP]: Add memory accounting.")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Link: https://lore.kernel.org/r/c880a963d9b1fb5f442ae3c9e4dfa70d45296a16.1658167019.git.lucien.xin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2976 lines
101 KiB
ReStructuredText
2976 lines
101 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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=========
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IP Sysctl
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=========
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/proc/sys/net/ipv4/* Variables
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==============================
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ip_forward - BOOLEAN
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- 0 - disabled (default)
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- not 0 - enabled
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Forward Packets between interfaces.
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This variable is special, its change resets all configuration
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parameters to their default state (RFC1122 for hosts, RFC1812
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for routers)
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ip_default_ttl - INTEGER
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Default value of TTL field (Time To Live) for outgoing (but not
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forwarded) IP packets. Should be between 1 and 255 inclusive.
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Default: 64 (as recommended by RFC1700)
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ip_no_pmtu_disc - INTEGER
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Disable Path MTU Discovery. If enabled in mode 1 and a
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fragmentation-required ICMP is received, the PMTU to this
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destination will be set to the smallest of the old MTU to
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this destination and min_pmtu (see below). You will need
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to raise min_pmtu to the smallest interface MTU on your system
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manually if you want to avoid locally generated fragments.
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In mode 2 incoming Path MTU Discovery messages will be
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discarded. Outgoing frames are handled the same as in mode 1,
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implicitly setting IP_PMTUDISC_DONT on every created socket.
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Mode 3 is a hardened pmtu discover mode. The kernel will only
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accept fragmentation-needed errors if the underlying protocol
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can verify them besides a plain socket lookup. Current
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protocols for which pmtu events will be honored are TCP, SCTP
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and DCCP as they verify e.g. the sequence number or the
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association. This mode should not be enabled globally but is
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only intended to secure e.g. name servers in namespaces where
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TCP path mtu must still work but path MTU information of other
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protocols should be discarded. If enabled globally this mode
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could break other protocols.
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Possible values: 0-3
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Default: FALSE
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min_pmtu - INTEGER
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default 552 - minimum Path MTU. Unless this is changed mannually,
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each cached pmtu will never be lower than this setting.
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ip_forward_use_pmtu - BOOLEAN
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By default we don't trust protocol path MTUs while forwarding
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because they could be easily forged and can lead to unwanted
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fragmentation by the router.
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You only need to enable this if you have user-space software
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which tries to discover path mtus by itself and depends on the
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kernel honoring this information. This is normally not the
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case.
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Default: 0 (disabled)
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Possible values:
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- 0 - disabled
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- 1 - enabled
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fwmark_reflect - BOOLEAN
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Controls the fwmark of kernel-generated IPv4 reply packets that are not
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associated with a socket for example, TCP RSTs or ICMP echo replies).
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If unset, these packets have a fwmark of zero. If set, they have the
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fwmark of the packet they are replying to.
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Default: 0
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fib_multipath_use_neigh - BOOLEAN
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Use status of existing neighbor entry when determining nexthop for
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multipath routes. If disabled, neighbor information is not used and
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packets could be directed to a failed nexthop. Only valid for kernels
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built with CONFIG_IP_ROUTE_MULTIPATH enabled.
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Default: 0 (disabled)
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Possible values:
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- 0 - disabled
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- 1 - enabled
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fib_multipath_hash_policy - INTEGER
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Controls which hash policy to use for multipath routes. Only valid
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for kernels built with CONFIG_IP_ROUTE_MULTIPATH enabled.
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Default: 0 (Layer 3)
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Possible values:
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- 0 - Layer 3
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- 1 - Layer 4
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- 2 - Layer 3 or inner Layer 3 if present
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- 3 - Custom multipath hash. Fields used for multipath hash calculation
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are determined by fib_multipath_hash_fields sysctl
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fib_multipath_hash_fields - UNSIGNED INTEGER
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When fib_multipath_hash_policy is set to 3 (custom multipath hash), the
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fields used for multipath hash calculation are determined by this
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sysctl.
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This value is a bitmask which enables various fields for multipath hash
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calculation.
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Possible fields are:
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====== ============================
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0x0001 Source IP address
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0x0002 Destination IP address
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0x0004 IP protocol
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0x0008 Unused (Flow Label)
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0x0010 Source port
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0x0020 Destination port
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0x0040 Inner source IP address
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0x0080 Inner destination IP address
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0x0100 Inner IP protocol
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0x0200 Inner Flow Label
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0x0400 Inner source port
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0x0800 Inner destination port
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====== ============================
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Default: 0x0007 (source IP, destination IP and IP protocol)
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fib_sync_mem - UNSIGNED INTEGER
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Amount of dirty memory from fib entries that can be backlogged before
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synchronize_rcu is forced.
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Default: 512kB Minimum: 64kB Maximum: 64MB
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ip_forward_update_priority - INTEGER
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Whether to update SKB priority from "TOS" field in IPv4 header after it
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is forwarded. The new SKB priority is mapped from TOS field value
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according to an rt_tos2priority table (see e.g. man tc-prio).
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Default: 1 (Update priority.)
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Possible values:
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- 0 - Do not update priority.
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- 1 - Update priority.
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route/max_size - INTEGER
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Maximum number of routes allowed in the kernel. Increase
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this when using large numbers of interfaces and/or routes.
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From linux kernel 3.6 onwards, this is deprecated for ipv4
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as route cache is no longer used.
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neigh/default/gc_thresh1 - INTEGER
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Minimum number of entries to keep. Garbage collector will not
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purge entries if there are fewer than this number.
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Default: 128
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neigh/default/gc_thresh2 - INTEGER
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Threshold when garbage collector becomes more aggressive about
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purging entries. Entries older than 5 seconds will be cleared
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when over this number.
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Default: 512
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neigh/default/gc_thresh3 - INTEGER
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Maximum number of non-PERMANENT neighbor entries allowed. Increase
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this when using large numbers of interfaces and when communicating
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with large numbers of directly-connected peers.
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Default: 1024
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neigh/default/unres_qlen_bytes - INTEGER
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The maximum number of bytes which may be used by packets
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queued for each unresolved address by other network layers.
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(added in linux 3.3)
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Setting negative value is meaningless and will return error.
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Default: SK_WMEM_MAX, (same as net.core.wmem_default).
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Exact value depends on architecture and kernel options,
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but should be enough to allow queuing 256 packets
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of medium size.
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neigh/default/unres_qlen - INTEGER
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The maximum number of packets which may be queued for each
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unresolved address by other network layers.
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(deprecated in linux 3.3) : use unres_qlen_bytes instead.
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Prior to linux 3.3, the default value is 3 which may cause
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unexpected packet loss. The current default value is calculated
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according to default value of unres_qlen_bytes and true size of
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packet.
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Default: 101
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mtu_expires - INTEGER
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Time, in seconds, that cached PMTU information is kept.
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min_adv_mss - INTEGER
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The advertised MSS depends on the first hop route MTU, but will
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never be lower than this setting.
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fib_notify_on_flag_change - INTEGER
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Whether to emit RTM_NEWROUTE notifications whenever RTM_F_OFFLOAD/
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RTM_F_TRAP/RTM_F_OFFLOAD_FAILED flags are changed.
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After installing a route to the kernel, user space receives an
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acknowledgment, which means the route was installed in the kernel,
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but not necessarily in hardware.
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It is also possible for a route already installed in hardware to change
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its action and therefore its flags. For example, a host route that is
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trapping packets can be "promoted" to perform decapsulation following
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the installation of an IPinIP/VXLAN tunnel.
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The notifications will indicate to user-space the state of the route.
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Default: 0 (Do not emit notifications.)
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Possible values:
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- 0 - Do not emit notifications.
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- 1 - Emit notifications.
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- 2 - Emit notifications only for RTM_F_OFFLOAD_FAILED flag change.
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IP Fragmentation:
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ipfrag_high_thresh - LONG INTEGER
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Maximum memory used to reassemble IP fragments.
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ipfrag_low_thresh - LONG INTEGER
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(Obsolete since linux-4.17)
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Maximum memory used to reassemble IP fragments before the kernel
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begins to remove incomplete fragment queues to free up resources.
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The kernel still accepts new fragments for defragmentation.
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ipfrag_time - INTEGER
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Time in seconds to keep an IP fragment in memory.
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ipfrag_max_dist - INTEGER
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ipfrag_max_dist is a non-negative integer value which defines the
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maximum "disorder" which is allowed among fragments which share a
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common IP source address. Note that reordering of packets is
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not unusual, but if a large number of fragments arrive from a source
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IP address while a particular fragment queue remains incomplete, it
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probably indicates that one or more fragments belonging to that queue
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have been lost. When ipfrag_max_dist is positive, an additional check
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is done on fragments before they are added to a reassembly queue - if
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ipfrag_max_dist (or more) fragments have arrived from a particular IP
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address between additions to any IP fragment queue using that source
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address, it's presumed that one or more fragments in the queue are
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lost. The existing fragment queue will be dropped, and a new one
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started. An ipfrag_max_dist value of zero disables this check.
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Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can
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result in unnecessarily dropping fragment queues when normal
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reordering of packets occurs, which could lead to poor application
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performance. Using a very large value, e.g. 50000, increases the
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likelihood of incorrectly reassembling IP fragments that originate
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from different IP datagrams, which could result in data corruption.
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Default: 64
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bc_forwarding - INTEGER
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bc_forwarding enables the feature described in rfc1812#section-5.3.5.2
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and rfc2644. It allows the router to forward directed broadcast.
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To enable this feature, the 'all' entry and the input interface entry
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should be set to 1.
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Default: 0
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INET peer storage
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=================
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inet_peer_threshold - INTEGER
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The approximate size of the storage. Starting from this threshold
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entries will be thrown aggressively. This threshold also determines
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entries' time-to-live and time intervals between garbage collection
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passes. More entries, less time-to-live, less GC interval.
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inet_peer_minttl - INTEGER
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Minimum time-to-live of entries. Should be enough to cover fragment
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time-to-live on the reassembling side. This minimum time-to-live is
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guaranteed if the pool size is less than inet_peer_threshold.
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Measured in seconds.
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inet_peer_maxttl - INTEGER
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Maximum time-to-live of entries. Unused entries will expire after
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this period of time if there is no memory pressure on the pool (i.e.
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when the number of entries in the pool is very small).
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Measured in seconds.
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TCP variables
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=============
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somaxconn - INTEGER
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Limit of socket listen() backlog, known in userspace as SOMAXCONN.
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Defaults to 4096. (Was 128 before linux-5.4)
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See also tcp_max_syn_backlog for additional tuning for TCP sockets.
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tcp_abort_on_overflow - BOOLEAN
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If listening service is too slow to accept new connections,
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reset them. Default state is FALSE. It means that if overflow
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occurred due to a burst, connection will recover. Enable this
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option _only_ if you are really sure that listening daemon
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cannot be tuned to accept connections faster. Enabling this
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option can harm clients of your server.
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tcp_adv_win_scale - INTEGER
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Count buffering overhead as bytes/2^tcp_adv_win_scale
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(if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
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if it is <= 0.
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Possible values are [-31, 31], inclusive.
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Default: 1
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tcp_allowed_congestion_control - STRING
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Show/set the congestion control choices available to non-privileged
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processes. The list is a subset of those listed in
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tcp_available_congestion_control.
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Default is "reno" and the default setting (tcp_congestion_control).
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tcp_app_win - INTEGER
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Reserve max(window/2^tcp_app_win, mss) of window for application
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buffer. Value 0 is special, it means that nothing is reserved.
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Default: 31
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tcp_autocorking - BOOLEAN
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Enable TCP auto corking :
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When applications do consecutive small write()/sendmsg() system calls,
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we try to coalesce these small writes as much as possible, to lower
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total amount of sent packets. This is done if at least one prior
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packet for the flow is waiting in Qdisc queues or device transmit
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queue. Applications can still use TCP_CORK for optimal behavior
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when they know how/when to uncork their sockets.
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Default : 1
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tcp_available_congestion_control - STRING
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Shows the available congestion control choices that are registered.
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More congestion control algorithms may be available as modules,
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but not loaded.
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tcp_base_mss - INTEGER
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The initial value of search_low to be used by the packetization layer
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Path MTU discovery (MTU probing). If MTU probing is enabled,
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this is the initial MSS used by the connection.
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tcp_mtu_probe_floor - INTEGER
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If MTU probing is enabled this caps the minimum MSS used for search_low
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for the connection.
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Default : 48
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tcp_min_snd_mss - INTEGER
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TCP SYN and SYNACK messages usually advertise an ADVMSS option,
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as described in RFC 1122 and RFC 6691.
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If this ADVMSS option is smaller than tcp_min_snd_mss,
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it is silently capped to tcp_min_snd_mss.
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Default : 48 (at least 8 bytes of payload per segment)
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tcp_congestion_control - STRING
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Set the congestion control algorithm to be used for new
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connections. The algorithm "reno" is always available, but
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additional choices may be available based on kernel configuration.
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Default is set as part of kernel configuration.
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For passive connections, the listener congestion control choice
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is inherited.
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[see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ]
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tcp_dsack - BOOLEAN
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Allows TCP to send "duplicate" SACKs.
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tcp_early_retrans - INTEGER
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Tail loss probe (TLP) converts RTOs occurring due to tail
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losses into fast recovery (draft-ietf-tcpm-rack). Note that
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TLP requires RACK to function properly (see tcp_recovery below)
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Possible values:
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- 0 disables TLP
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- 3 or 4 enables TLP
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Default: 3
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tcp_ecn - INTEGER
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Control use of Explicit Congestion Notification (ECN) by TCP.
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ECN is used only when both ends of the TCP connection indicate
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support for it. This feature is useful in avoiding losses due
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to congestion by allowing supporting routers to signal
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congestion before having to drop packets.
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Possible values are:
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= =====================================================
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0 Disable ECN. Neither initiate nor accept ECN.
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1 Enable ECN when requested by incoming connections and
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also request ECN on outgoing connection attempts.
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2 Enable ECN when requested by incoming connections
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but do not request ECN on outgoing connections.
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= =====================================================
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Default: 2
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tcp_ecn_fallback - BOOLEAN
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If the kernel detects that ECN connection misbehaves, enable fall
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back to non-ECN. Currently, this knob implements the fallback
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from RFC3168, section 6.1.1.1., but we reserve that in future,
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additional detection mechanisms could be implemented under this
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knob. The value is not used, if tcp_ecn or per route (or congestion
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control) ECN settings are disabled.
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Default: 1 (fallback enabled)
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tcp_fack - BOOLEAN
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This is a legacy option, it has no effect anymore.
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tcp_fin_timeout - INTEGER
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The length of time an orphaned (no longer referenced by any
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application) connection will remain in the FIN_WAIT_2 state
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before it is aborted at the local end. While a perfectly
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valid "receive only" state for an un-orphaned connection, an
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orphaned connection in FIN_WAIT_2 state could otherwise wait
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forever for the remote to close its end of the connection.
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Cf. tcp_max_orphans
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Default: 60 seconds
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tcp_frto - INTEGER
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Enables Forward RTO-Recovery (F-RTO) defined in RFC5682.
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F-RTO is an enhanced recovery algorithm for TCP retransmission
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timeouts. It is particularly beneficial in networks where the
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RTT fluctuates (e.g., wireless). F-RTO is sender-side only
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modification. It does not require any support from the peer.
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By default it's enabled with a non-zero value. 0 disables F-RTO.
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tcp_fwmark_accept - BOOLEAN
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If set, incoming connections to listening sockets that do not have a
|
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socket mark will set the mark of the accepting socket to the fwmark of
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the incoming SYN packet. This will cause all packets on that connection
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(starting from the first SYNACK) to be sent with that fwmark. The
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listening socket's mark is unchanged. Listening sockets that already
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have a fwmark set via setsockopt(SOL_SOCKET, SO_MARK, ...) are
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unaffected.
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Default: 0
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tcp_invalid_ratelimit - INTEGER
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Limit the maximal rate for sending duplicate acknowledgments
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in response to incoming TCP packets that are for an existing
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connection but that are invalid due to any of these reasons:
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(a) out-of-window sequence number,
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(b) out-of-window acknowledgment number, or
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(c) PAWS (Protection Against Wrapped Sequence numbers) check failure
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This can help mitigate simple "ack loop" DoS attacks, wherein
|
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a buggy or malicious middlebox or man-in-the-middle can
|
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rewrite TCP header fields in manner that causes each endpoint
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to think that the other is sending invalid TCP segments, thus
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causing each side to send an unterminating stream of duplicate
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acknowledgments for invalid segments.
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Using 0 disables rate-limiting of dupacks in response to
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invalid segments; otherwise this value specifies the minimal
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space between sending such dupacks, in milliseconds.
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Default: 500 (milliseconds).
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tcp_keepalive_time - INTEGER
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How often TCP sends out keepalive messages when keepalive is enabled.
|
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Default: 2hours.
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tcp_keepalive_probes - INTEGER
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How many keepalive probes TCP sends out, until it decides that the
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connection is broken. Default value: 9.
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tcp_keepalive_intvl - INTEGER
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How frequently the probes are send out. Multiplied by
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tcp_keepalive_probes it is time to kill not responding connection,
|
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after probes started. Default value: 75sec i.e. connection
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will be aborted after ~11 minutes of retries.
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tcp_l3mdev_accept - BOOLEAN
|
|
Enables child sockets to inherit the L3 master device index.
|
|
Enabling this option allows a "global" listen socket to work
|
|
across L3 master domains (e.g., VRFs) with connected sockets
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|
derived from the listen socket to be bound to the L3 domain in
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which the packets originated. Only valid when the kernel was
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compiled with CONFIG_NET_L3_MASTER_DEV.
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Default: 0 (disabled)
|
|
|
|
tcp_low_latency - BOOLEAN
|
|
This is a legacy option, it has no effect anymore.
|
|
|
|
tcp_max_orphans - INTEGER
|
|
Maximal number of TCP sockets not attached to any user file handle,
|
|
held by system. If this number is exceeded orphaned connections are
|
|
reset immediately and warning is printed. This limit exists
|
|
only to prevent simple DoS attacks, you _must_ not rely on this
|
|
or lower the limit artificially, but rather increase it
|
|
(probably, after increasing installed memory),
|
|
if network conditions require more than default value,
|
|
and tune network services to linger and kill such states
|
|
more aggressively. Let me to remind again: each orphan eats
|
|
up to ~64K of unswappable memory.
|
|
|
|
tcp_max_syn_backlog - INTEGER
|
|
Maximal number of remembered connection requests (SYN_RECV),
|
|
which have not received an acknowledgment from connecting client.
|
|
|
|
This is a per-listener limit.
|
|
|
|
The minimal value is 128 for low memory machines, and it will
|
|
increase in proportion to the memory of machine.
|
|
|
|
If server suffers from overload, try increasing this number.
|
|
|
|
Remember to also check /proc/sys/net/core/somaxconn
|
|
A SYN_RECV request socket consumes about 304 bytes of memory.
|
|
|
|
tcp_max_tw_buckets - INTEGER
|
|
Maximal number of timewait sockets held by system simultaneously.
|
|
If this number is exceeded time-wait socket is immediately destroyed
|
|
and warning is printed. This limit exists only to prevent
|
|
simple DoS attacks, you _must_ not lower the limit artificially,
|
|
but rather increase it (probably, after increasing installed memory),
|
|
if network conditions require more than default value.
|
|
|
|
tcp_mem - vector of 3 INTEGERs: min, pressure, max
|
|
min: below this number of pages TCP is not bothered about its
|
|
memory appetite.
|
|
|
|
pressure: when amount of memory allocated by TCP exceeds this number
|
|
of pages, TCP moderates its memory consumption and enters memory
|
|
pressure mode, which is exited when memory consumption falls
|
|
under "min".
|
|
|
|
max: number of pages allowed for queueing by all TCP sockets.
|
|
|
|
Defaults are calculated at boot time from amount of available
|
|
memory.
|
|
|
|
tcp_min_rtt_wlen - INTEGER
|
|
The window length of the windowed min filter to track the minimum RTT.
|
|
A shorter window lets a flow more quickly pick up new (higher)
|
|
minimum RTT when it is moved to a longer path (e.g., due to traffic
|
|
engineering). A longer window makes the filter more resistant to RTT
|
|
inflations such as transient congestion. The unit is seconds.
|
|
|
|
Possible values: 0 - 86400 (1 day)
|
|
|
|
Default: 300
|
|
|
|
tcp_moderate_rcvbuf - BOOLEAN
|
|
If set, TCP performs receive buffer auto-tuning, attempting to
|
|
automatically size the buffer (no greater than tcp_rmem[2]) to
|
|
match the size required by the path for full throughput. Enabled by
|
|
default.
|
|
|
|
tcp_mtu_probing - INTEGER
|
|
Controls TCP Packetization-Layer Path MTU Discovery. Takes three
|
|
values:
|
|
|
|
- 0 - Disabled
|
|
- 1 - Disabled by default, enabled when an ICMP black hole detected
|
|
- 2 - Always enabled, use initial MSS of tcp_base_mss.
|
|
|
|
tcp_probe_interval - UNSIGNED INTEGER
|
|
Controls how often to start TCP Packetization-Layer Path MTU
|
|
Discovery reprobe. The default is reprobing every 10 minutes as
|
|
per RFC4821.
|
|
|
|
tcp_probe_threshold - INTEGER
|
|
Controls when TCP Packetization-Layer Path MTU Discovery probing
|
|
will stop in respect to the width of search range in bytes. Default
|
|
is 8 bytes.
|
|
|
|
tcp_no_metrics_save - BOOLEAN
|
|
By default, TCP saves various connection metrics in the route cache
|
|
when the connection closes, so that connections established in the
|
|
near future can use these to set initial conditions. Usually, this
|
|
increases overall performance, but may sometimes cause performance
|
|
degradation. If set, TCP will not cache metrics on closing
|
|
connections.
|
|
|
|
tcp_no_ssthresh_metrics_save - BOOLEAN
|
|
Controls whether TCP saves ssthresh metrics in the route cache.
|
|
|
|
Default is 1, which disables ssthresh metrics.
|
|
|
|
tcp_orphan_retries - INTEGER
|
|
This value influences the timeout of a locally closed TCP connection,
|
|
when RTO retransmissions remain unacknowledged.
|
|
See tcp_retries2 for more details.
|
|
|
|
The default value is 8.
|
|
|
|
If your machine is a loaded WEB server,
|
|
you should think about lowering this value, such sockets
|
|
may consume significant resources. Cf. tcp_max_orphans.
|
|
|
|
tcp_recovery - INTEGER
|
|
This value is a bitmap to enable various experimental loss recovery
|
|
features.
|
|
|
|
========= =============================================================
|
|
RACK: 0x1 enables the RACK loss detection for fast detection of lost
|
|
retransmissions and tail drops. It also subsumes and disables
|
|
RFC6675 recovery for SACK connections.
|
|
|
|
RACK: 0x2 makes RACK's reordering window static (min_rtt/4).
|
|
|
|
RACK: 0x4 disables RACK's DUPACK threshold heuristic
|
|
========= =============================================================
|
|
|
|
Default: 0x1
|
|
|
|
tcp_reordering - INTEGER
|
|
Initial reordering level of packets in a TCP stream.
|
|
TCP stack can then dynamically adjust flow reordering level
|
|
between this initial value and tcp_max_reordering
|
|
|
|
Default: 3
|
|
|
|
tcp_max_reordering - INTEGER
|
|
Maximal reordering level of packets in a TCP stream.
|
|
300 is a fairly conservative value, but you might increase it
|
|
if paths are using per packet load balancing (like bonding rr mode)
|
|
|
|
Default: 300
|
|
|
|
tcp_retrans_collapse - BOOLEAN
|
|
Bug-to-bug compatibility with some broken printers.
|
|
On retransmit try to send bigger packets to work around bugs in
|
|
certain TCP stacks.
|
|
|
|
tcp_retries1 - INTEGER
|
|
This value influences the time, after which TCP decides, that
|
|
something is wrong due to unacknowledged RTO retransmissions,
|
|
and reports this suspicion to the network layer.
|
|
See tcp_retries2 for more details.
|
|
|
|
RFC 1122 recommends at least 3 retransmissions, which is the
|
|
default.
|
|
|
|
tcp_retries2 - INTEGER
|
|
This value influences the timeout of an alive TCP connection,
|
|
when RTO retransmissions remain unacknowledged.
|
|
Given a value of N, a hypothetical TCP connection following
|
|
exponential backoff with an initial RTO of TCP_RTO_MIN would
|
|
retransmit N times before killing the connection at the (N+1)th RTO.
|
|
|
|
The default value of 15 yields a hypothetical timeout of 924.6
|
|
seconds and is a lower bound for the effective timeout.
|
|
TCP will effectively time out at the first RTO which exceeds the
|
|
hypothetical timeout.
|
|
|
|
RFC 1122 recommends at least 100 seconds for the timeout,
|
|
which corresponds to a value of at least 8.
|
|
|
|
tcp_rfc1337 - BOOLEAN
|
|
If set, the TCP stack behaves conforming to RFC1337. If unset,
|
|
we are not conforming to RFC, but prevent TCP TIME_WAIT
|
|
assassination.
|
|
|
|
Default: 0
|
|
|
|
tcp_rmem - vector of 3 INTEGERs: min, default, max
|
|
min: Minimal size of receive buffer used by TCP sockets.
|
|
It is guaranteed to each TCP socket, even under moderate memory
|
|
pressure.
|
|
|
|
Default: 4K
|
|
|
|
default: initial size of receive buffer used by TCP sockets.
|
|
This value overrides net.core.rmem_default used by other protocols.
|
|
Default: 131072 bytes.
|
|
This value results in initial window of 65535.
|
|
|
|
max: maximal size of receive buffer allowed for automatically
|
|
selected receiver buffers for TCP socket. This value does not override
|
|
net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables
|
|
automatic tuning of that socket's receive buffer size, in which
|
|
case this value is ignored.
|
|
Default: between 131072 and 6MB, depending on RAM size.
|
|
|
|
tcp_sack - BOOLEAN
|
|
Enable select acknowledgments (SACKS).
|
|
|
|
tcp_comp_sack_delay_ns - LONG INTEGER
|
|
TCP tries to reduce number of SACK sent, using a timer
|
|
based on 5% of SRTT, capped by this sysctl, in nano seconds.
|
|
The default is 1ms, based on TSO autosizing period.
|
|
|
|
Default : 1,000,000 ns (1 ms)
|
|
|
|
tcp_comp_sack_slack_ns - LONG INTEGER
|
|
This sysctl control the slack used when arming the
|
|
timer used by SACK compression. This gives extra time
|
|
for small RTT flows, and reduces system overhead by allowing
|
|
opportunistic reduction of timer interrupts.
|
|
|
|
Default : 100,000 ns (100 us)
|
|
|
|
tcp_comp_sack_nr - INTEGER
|
|
Max number of SACK that can be compressed.
|
|
Using 0 disables SACK compression.
|
|
|
|
Default : 44
|
|
|
|
tcp_slow_start_after_idle - BOOLEAN
|
|
If set, provide RFC2861 behavior and time out the congestion
|
|
window after an idle period. An idle period is defined at
|
|
the current RTO. If unset, the congestion window will not
|
|
be timed out after an idle period.
|
|
|
|
Default: 1
|
|
|
|
tcp_stdurg - BOOLEAN
|
|
Use the Host requirements interpretation of the TCP urgent pointer field.
|
|
Most hosts use the older BSD interpretation, so if you turn this on
|
|
Linux might not communicate correctly with them.
|
|
|
|
Default: FALSE
|
|
|
|
tcp_synack_retries - INTEGER
|
|
Number of times SYNACKs for a passive TCP connection attempt will
|
|
be retransmitted. Should not be higher than 255. Default value
|
|
is 5, which corresponds to 31seconds till the last retransmission
|
|
with the current initial RTO of 1second. With this the final timeout
|
|
for a passive TCP connection will happen after 63seconds.
|
|
|
|
tcp_syncookies - INTEGER
|
|
Only valid when the kernel was compiled with CONFIG_SYN_COOKIES
|
|
Send out syncookies when the syn backlog queue of a socket
|
|
overflows. This is to prevent against the common 'SYN flood attack'
|
|
Default: 1
|
|
|
|
Note, that syncookies is fallback facility.
|
|
It MUST NOT be used to help highly loaded servers to stand
|
|
against legal connection rate. If you see SYN flood warnings
|
|
in your logs, but investigation shows that they occur
|
|
because of overload with legal connections, you should tune
|
|
another parameters until this warning disappear.
|
|
See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow.
|
|
|
|
syncookies seriously violate TCP protocol, do not allow
|
|
to use TCP extensions, can result in serious degradation
|
|
of some services (f.e. SMTP relaying), visible not by you,
|
|
but your clients and relays, contacting you. While you see
|
|
SYN flood warnings in logs not being really flooded, your server
|
|
is seriously misconfigured.
|
|
|
|
If you want to test which effects syncookies have to your
|
|
network connections you can set this knob to 2 to enable
|
|
unconditionally generation of syncookies.
|
|
|
|
tcp_migrate_req - BOOLEAN
|
|
The incoming connection is tied to a specific listening socket when
|
|
the initial SYN packet is received during the three-way handshake.
|
|
When a listener is closed, in-flight request sockets during the
|
|
handshake and established sockets in the accept queue are aborted.
|
|
|
|
If the listener has SO_REUSEPORT enabled, other listeners on the
|
|
same port should have been able to accept such connections. This
|
|
option makes it possible to migrate such child sockets to another
|
|
listener after close() or shutdown().
|
|
|
|
The BPF_SK_REUSEPORT_SELECT_OR_MIGRATE type of eBPF program should
|
|
usually be used to define the policy to pick an alive listener.
|
|
Otherwise, the kernel will randomly pick an alive listener only if
|
|
this option is enabled.
|
|
|
|
Note that migration between listeners with different settings may
|
|
crash applications. Let's say migration happens from listener A to
|
|
B, and only B has TCP_SAVE_SYN enabled. B cannot read SYN data from
|
|
the requests migrated from A. To avoid such a situation, cancel
|
|
migration by returning SK_DROP in the type of eBPF program, or
|
|
disable this option.
|
|
|
|
Default: 0
|
|
|
|
tcp_fastopen - INTEGER
|
|
Enable TCP Fast Open (RFC7413) to send and accept data in the opening
|
|
SYN packet.
|
|
|
|
The client support is enabled by flag 0x1 (on by default). The client
|
|
then must use sendmsg() or sendto() with the MSG_FASTOPEN flag,
|
|
rather than connect() to send data in SYN.
|
|
|
|
The server support is enabled by flag 0x2 (off by default). Then
|
|
either enable for all listeners with another flag (0x400) or
|
|
enable individual listeners via TCP_FASTOPEN socket option with
|
|
the option value being the length of the syn-data backlog.
|
|
|
|
The values (bitmap) are
|
|
|
|
===== ======== ======================================================
|
|
0x1 (client) enables sending data in the opening SYN on the client.
|
|
0x2 (server) enables the server support, i.e., allowing data in
|
|
a SYN packet to be accepted and passed to the
|
|
application before 3-way handshake finishes.
|
|
0x4 (client) send data in the opening SYN regardless of cookie
|
|
availability and without a cookie option.
|
|
0x200 (server) accept data-in-SYN w/o any cookie option present.
|
|
0x400 (server) enable all listeners to support Fast Open by
|
|
default without explicit TCP_FASTOPEN socket option.
|
|
===== ======== ======================================================
|
|
|
|
Default: 0x1
|
|
|
|
Note that additional client or server features are only
|
|
effective if the basic support (0x1 and 0x2) are enabled respectively.
|
|
|
|
tcp_fastopen_blackhole_timeout_sec - INTEGER
|
|
Initial time period in second to disable Fastopen on active TCP sockets
|
|
when a TFO firewall blackhole issue happens.
|
|
This time period will grow exponentially when more blackhole issues
|
|
get detected right after Fastopen is re-enabled and will reset to
|
|
initial value when the blackhole issue goes away.
|
|
0 to disable the blackhole detection.
|
|
|
|
By default, it is set to 0 (feature is disabled).
|
|
|
|
tcp_fastopen_key - list of comma separated 32-digit hexadecimal INTEGERs
|
|
The list consists of a primary key and an optional backup key. The
|
|
primary key is used for both creating and validating cookies, while the
|
|
optional backup key is only used for validating cookies. The purpose of
|
|
the backup key is to maximize TFO validation when keys are rotated.
|
|
|
|
A randomly chosen primary key may be configured by the kernel if
|
|
the tcp_fastopen sysctl is set to 0x400 (see above), or if the
|
|
TCP_FASTOPEN setsockopt() optname is set and a key has not been
|
|
previously configured via sysctl. If keys are configured via
|
|
setsockopt() by using the TCP_FASTOPEN_KEY optname, then those
|
|
per-socket keys will be used instead of any keys that are specified via
|
|
sysctl.
|
|
|
|
A key is specified as 4 8-digit hexadecimal integers which are separated
|
|
by a '-' as: xxxxxxxx-xxxxxxxx-xxxxxxxx-xxxxxxxx. Leading zeros may be
|
|
omitted. A primary and a backup key may be specified by separating them
|
|
by a comma. If only one key is specified, it becomes the primary key and
|
|
any previously configured backup keys are removed.
|
|
|
|
tcp_syn_retries - INTEGER
|
|
Number of times initial SYNs for an active TCP connection attempt
|
|
will be retransmitted. Should not be higher than 127. Default value
|
|
is 6, which corresponds to 63seconds till the last retransmission
|
|
with the current initial RTO of 1second. With this the final timeout
|
|
for an active TCP connection attempt will happen after 127seconds.
|
|
|
|
tcp_timestamps - INTEGER
|
|
Enable timestamps as defined in RFC1323.
|
|
|
|
- 0: Disabled.
|
|
- 1: Enable timestamps as defined in RFC1323 and use random offset for
|
|
each connection rather than only using the current time.
|
|
- 2: Like 1, but without random offsets.
|
|
|
|
Default: 1
|
|
|
|
tcp_min_tso_segs - INTEGER
|
|
Minimal number of segments per TSO frame.
|
|
|
|
Since linux-3.12, TCP does an automatic sizing of TSO frames,
|
|
depending on flow rate, instead of filling 64Kbytes packets.
|
|
For specific usages, it's possible to force TCP to build big
|
|
TSO frames. Note that TCP stack might split too big TSO packets
|
|
if available window is too small.
|
|
|
|
Default: 2
|
|
|
|
tcp_tso_rtt_log - INTEGER
|
|
Adjustment of TSO packet sizes based on min_rtt
|
|
|
|
Starting from linux-5.18, TCP autosizing can be tweaked
|
|
for flows having small RTT.
|
|
|
|
Old autosizing was splitting the pacing budget to send 1024 TSO
|
|
per second.
|
|
|
|
tso_packet_size = sk->sk_pacing_rate / 1024;
|
|
|
|
With the new mechanism, we increase this TSO sizing using:
|
|
|
|
distance = min_rtt_usec / (2^tcp_tso_rtt_log)
|
|
tso_packet_size += gso_max_size >> distance;
|
|
|
|
This means that flows between very close hosts can use bigger
|
|
TSO packets, reducing their cpu costs.
|
|
|
|
If you want to use the old autosizing, set this sysctl to 0.
|
|
|
|
Default: 9 (2^9 = 512 usec)
|
|
|
|
tcp_pacing_ss_ratio - INTEGER
|
|
sk->sk_pacing_rate is set by TCP stack using a ratio applied
|
|
to current rate. (current_rate = cwnd * mss / srtt)
|
|
If TCP is in slow start, tcp_pacing_ss_ratio is applied
|
|
to let TCP probe for bigger speeds, assuming cwnd can be
|
|
doubled every other RTT.
|
|
|
|
Default: 200
|
|
|
|
tcp_pacing_ca_ratio - INTEGER
|
|
sk->sk_pacing_rate is set by TCP stack using a ratio applied
|
|
to current rate. (current_rate = cwnd * mss / srtt)
|
|
If TCP is in congestion avoidance phase, tcp_pacing_ca_ratio
|
|
is applied to conservatively probe for bigger throughput.
|
|
|
|
Default: 120
|
|
|
|
tcp_tso_win_divisor - INTEGER
|
|
This allows control over what percentage of the congestion window
|
|
can be consumed by a single TSO frame.
|
|
The setting of this parameter is a choice between burstiness and
|
|
building larger TSO frames.
|
|
|
|
Default: 3
|
|
|
|
tcp_tw_reuse - INTEGER
|
|
Enable reuse of TIME-WAIT sockets for new connections when it is
|
|
safe from protocol viewpoint.
|
|
|
|
- 0 - disable
|
|
- 1 - global enable
|
|
- 2 - enable for loopback traffic only
|
|
|
|
It should not be changed without advice/request of technical
|
|
experts.
|
|
|
|
Default: 2
|
|
|
|
tcp_window_scaling - BOOLEAN
|
|
Enable window scaling as defined in RFC1323.
|
|
|
|
tcp_wmem - vector of 3 INTEGERs: min, default, max
|
|
min: Amount of memory reserved for send buffers for TCP sockets.
|
|
Each TCP socket has rights to use it due to fact of its birth.
|
|
|
|
Default: 4K
|
|
|
|
default: initial size of send buffer used by TCP sockets. This
|
|
value overrides net.core.wmem_default used by other protocols.
|
|
|
|
It is usually lower than net.core.wmem_default.
|
|
|
|
Default: 16K
|
|
|
|
max: Maximal amount of memory allowed for automatically tuned
|
|
send buffers for TCP sockets. This value does not override
|
|
net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables
|
|
automatic tuning of that socket's send buffer size, in which case
|
|
this value is ignored.
|
|
|
|
Default: between 64K and 4MB, depending on RAM size.
|
|
|
|
tcp_notsent_lowat - UNSIGNED INTEGER
|
|
A TCP socket can control the amount of unsent bytes in its write queue,
|
|
thanks to TCP_NOTSENT_LOWAT socket option. poll()/select()/epoll()
|
|
reports POLLOUT events if the amount of unsent bytes is below a per
|
|
socket value, and if the write queue is not full. sendmsg() will
|
|
also not add new buffers if the limit is hit.
|
|
|
|
This global variable controls the amount of unsent data for
|
|
sockets not using TCP_NOTSENT_LOWAT. For these sockets, a change
|
|
to the global variable has immediate effect.
|
|
|
|
Default: UINT_MAX (0xFFFFFFFF)
|
|
|
|
tcp_workaround_signed_windows - BOOLEAN
|
|
If set, assume no receipt of a window scaling option means the
|
|
remote TCP is broken and treats the window as a signed quantity.
|
|
If unset, assume the remote TCP is not broken even if we do
|
|
not receive a window scaling option from them.
|
|
|
|
Default: 0
|
|
|
|
tcp_thin_linear_timeouts - BOOLEAN
|
|
Enable dynamic triggering of linear timeouts for thin streams.
|
|
If set, a check is performed upon retransmission by timeout to
|
|
determine if the stream is thin (less than 4 packets in flight).
|
|
As long as the stream is found to be thin, up to 6 linear
|
|
timeouts may be performed before exponential backoff mode is
|
|
initiated. This improves retransmission latency for
|
|
non-aggressive thin streams, often found to be time-dependent.
|
|
For more information on thin streams, see
|
|
Documentation/networking/tcp-thin.rst
|
|
|
|
Default: 0
|
|
|
|
tcp_limit_output_bytes - INTEGER
|
|
Controls TCP Small Queue limit per tcp socket.
|
|
TCP bulk sender tends to increase packets in flight until it
|
|
gets losses notifications. With SNDBUF autotuning, this can
|
|
result in a large amount of packets queued on the local machine
|
|
(e.g.: qdiscs, CPU backlog, or device) hurting latency of other
|
|
flows, for typical pfifo_fast qdiscs. tcp_limit_output_bytes
|
|
limits the number of bytes on qdisc or device to reduce artificial
|
|
RTT/cwnd and reduce bufferbloat.
|
|
|
|
Default: 1048576 (16 * 65536)
|
|
|
|
tcp_challenge_ack_limit - INTEGER
|
|
Limits number of Challenge ACK sent per second, as recommended
|
|
in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks)
|
|
Default: 1000
|
|
|
|
UDP variables
|
|
=============
|
|
|
|
udp_l3mdev_accept - BOOLEAN
|
|
Enabling this option allows a "global" bound socket to work
|
|
across L3 master domains (e.g., VRFs) with packets capable of
|
|
being received regardless of the L3 domain in which they
|
|
originated. Only valid when the kernel was compiled with
|
|
CONFIG_NET_L3_MASTER_DEV.
|
|
|
|
Default: 0 (disabled)
|
|
|
|
udp_mem - vector of 3 INTEGERs: min, pressure, max
|
|
Number of pages allowed for queueing by all UDP sockets.
|
|
|
|
min: Number of pages allowed for queueing by all UDP sockets.
|
|
|
|
pressure: This value was introduced to follow format of tcp_mem.
|
|
|
|
max: This value was introduced to follow format of tcp_mem.
|
|
|
|
Default is calculated at boot time from amount of available memory.
|
|
|
|
udp_rmem_min - INTEGER
|
|
Minimal size of receive buffer used by UDP sockets in moderation.
|
|
Each UDP socket is able to use the size for receiving data, even if
|
|
total pages of UDP sockets exceed udp_mem pressure. The unit is byte.
|
|
|
|
Default: 4K
|
|
|
|
udp_wmem_min - INTEGER
|
|
UDP does not have tx memory accounting and this tunable has no effect.
|
|
|
|
RAW variables
|
|
=============
|
|
|
|
raw_l3mdev_accept - BOOLEAN
|
|
Enabling this option allows a "global" bound socket to work
|
|
across L3 master domains (e.g., VRFs) with packets capable of
|
|
being received regardless of the L3 domain in which they
|
|
originated. Only valid when the kernel was compiled with
|
|
CONFIG_NET_L3_MASTER_DEV.
|
|
|
|
Default: 1 (enabled)
|
|
|
|
CIPSOv4 Variables
|
|
=================
|
|
|
|
cipso_cache_enable - BOOLEAN
|
|
If set, enable additions to and lookups from the CIPSO label mapping
|
|
cache. If unset, additions are ignored and lookups always result in a
|
|
miss. However, regardless of the setting the cache is still
|
|
invalidated when required when means you can safely toggle this on and
|
|
off and the cache will always be "safe".
|
|
|
|
Default: 1
|
|
|
|
cipso_cache_bucket_size - INTEGER
|
|
The CIPSO label cache consists of a fixed size hash table with each
|
|
hash bucket containing a number of cache entries. This variable limits
|
|
the number of entries in each hash bucket; the larger the value is, the
|
|
more CIPSO label mappings that can be cached. When the number of
|
|
entries in a given hash bucket reaches this limit adding new entries
|
|
causes the oldest entry in the bucket to be removed to make room.
|
|
|
|
Default: 10
|
|
|
|
cipso_rbm_optfmt - BOOLEAN
|
|
Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of
|
|
the CIPSO draft specification (see Documentation/netlabel for details).
|
|
This means that when set the CIPSO tag will be padded with empty
|
|
categories in order to make the packet data 32-bit aligned.
|
|
|
|
Default: 0
|
|
|
|
cipso_rbm_structvalid - BOOLEAN
|
|
If set, do a very strict check of the CIPSO option when
|
|
ip_options_compile() is called. If unset, relax the checks done during
|
|
ip_options_compile(). Either way is "safe" as errors are caught else
|
|
where in the CIPSO processing code but setting this to 0 (False) should
|
|
result in less work (i.e. it should be faster) but could cause problems
|
|
with other implementations that require strict checking.
|
|
|
|
Default: 0
|
|
|
|
IP Variables
|
|
============
|
|
|
|
ip_local_port_range - 2 INTEGERS
|
|
Defines the local port range that is used by TCP and UDP to
|
|
choose the local port. The first number is the first, the
|
|
second the last local port number.
|
|
If possible, it is better these numbers have different parity
|
|
(one even and one odd value).
|
|
Must be greater than or equal to ip_unprivileged_port_start.
|
|
The default values are 32768 and 60999 respectively.
|
|
|
|
ip_local_reserved_ports - list of comma separated ranges
|
|
Specify the ports which are reserved for known third-party
|
|
applications. These ports will not be used by automatic port
|
|
assignments (e.g. when calling connect() or bind() with port
|
|
number 0). Explicit port allocation behavior is unchanged.
|
|
|
|
The format used for both input and output is a comma separated
|
|
list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and
|
|
10). Writing to the file will clear all previously reserved
|
|
ports and update the current list with the one given in the
|
|
input.
|
|
|
|
Note that ip_local_port_range and ip_local_reserved_ports
|
|
settings are independent and both are considered by the kernel
|
|
when determining which ports are available for automatic port
|
|
assignments.
|
|
|
|
You can reserve ports which are not in the current
|
|
ip_local_port_range, e.g.::
|
|
|
|
$ cat /proc/sys/net/ipv4/ip_local_port_range
|
|
32000 60999
|
|
$ cat /proc/sys/net/ipv4/ip_local_reserved_ports
|
|
8080,9148
|
|
|
|
although this is redundant. However such a setting is useful
|
|
if later the port range is changed to a value that will
|
|
include the reserved ports. Also keep in mind, that overlapping
|
|
of these ranges may affect probability of selecting ephemeral
|
|
ports which are right after block of reserved ports.
|
|
|
|
Default: Empty
|
|
|
|
ip_unprivileged_port_start - INTEGER
|
|
This is a per-namespace sysctl. It defines the first
|
|
unprivileged port in the network namespace. Privileged ports
|
|
require root or CAP_NET_BIND_SERVICE in order to bind to them.
|
|
To disable all privileged ports, set this to 0. They must not
|
|
overlap with the ip_local_port_range.
|
|
|
|
Default: 1024
|
|
|
|
ip_nonlocal_bind - BOOLEAN
|
|
If set, allows processes to bind() to non-local IP addresses,
|
|
which can be quite useful - but may break some applications.
|
|
|
|
Default: 0
|
|
|
|
ip_autobind_reuse - BOOLEAN
|
|
By default, bind() does not select the ports automatically even if
|
|
the new socket and all sockets bound to the port have SO_REUSEADDR.
|
|
ip_autobind_reuse allows bind() to reuse the port and this is useful
|
|
when you use bind()+connect(), but may break some applications.
|
|
The preferred solution is to use IP_BIND_ADDRESS_NO_PORT and this
|
|
option should only be set by experts.
|
|
Default: 0
|
|
|
|
ip_dynaddr - INTEGER
|
|
If set non-zero, enables support for dynamic addresses.
|
|
If set to a non-zero value larger than 1, a kernel log
|
|
message will be printed when dynamic address rewriting
|
|
occurs.
|
|
|
|
Default: 0
|
|
|
|
ip_early_demux - BOOLEAN
|
|
Optimize input packet processing down to one demux for
|
|
certain kinds of local sockets. Currently we only do this
|
|
for established TCP and connected UDP sockets.
|
|
|
|
It may add an additional cost for pure routing workloads that
|
|
reduces overall throughput, in such case you should disable it.
|
|
|
|
Default: 1
|
|
|
|
ping_group_range - 2 INTEGERS
|
|
Restrict ICMP_PROTO datagram sockets to users in the group range.
|
|
The default is "1 0", meaning, that nobody (not even root) may
|
|
create ping sockets. Setting it to "100 100" would grant permissions
|
|
to the single group. "0 4294967295" would enable it for the world, "100
|
|
4294967295" would enable it for the users, but not daemons.
|
|
|
|
tcp_early_demux - BOOLEAN
|
|
Enable early demux for established TCP sockets.
|
|
|
|
Default: 1
|
|
|
|
udp_early_demux - BOOLEAN
|
|
Enable early demux for connected UDP sockets. Disable this if
|
|
your system could experience more unconnected load.
|
|
|
|
Default: 1
|
|
|
|
icmp_echo_ignore_all - BOOLEAN
|
|
If set non-zero, then the kernel will ignore all ICMP ECHO
|
|
requests sent to it.
|
|
|
|
Default: 0
|
|
|
|
icmp_echo_enable_probe - BOOLEAN
|
|
If set to one, then the kernel will respond to RFC 8335 PROBE
|
|
requests sent to it.
|
|
|
|
Default: 0
|
|
|
|
icmp_echo_ignore_broadcasts - BOOLEAN
|
|
If set non-zero, then the kernel will ignore all ICMP ECHO and
|
|
TIMESTAMP requests sent to it via broadcast/multicast.
|
|
|
|
Default: 1
|
|
|
|
icmp_ratelimit - INTEGER
|
|
Limit the maximal rates for sending ICMP packets whose type matches
|
|
icmp_ratemask (see below) to specific targets.
|
|
0 to disable any limiting,
|
|
otherwise the minimal space between responses in milliseconds.
|
|
Note that another sysctl, icmp_msgs_per_sec limits the number
|
|
of ICMP packets sent on all targets.
|
|
|
|
Default: 1000
|
|
|
|
icmp_msgs_per_sec - INTEGER
|
|
Limit maximal number of ICMP packets sent per second from this host.
|
|
Only messages whose type matches icmp_ratemask (see below) are
|
|
controlled by this limit. For security reasons, the precise count
|
|
of messages per second is randomized.
|
|
|
|
Default: 1000
|
|
|
|
icmp_msgs_burst - INTEGER
|
|
icmp_msgs_per_sec controls number of ICMP packets sent per second,
|
|
while icmp_msgs_burst controls the burst size of these packets.
|
|
For security reasons, the precise burst size is randomized.
|
|
|
|
Default: 50
|
|
|
|
icmp_ratemask - INTEGER
|
|
Mask made of ICMP types for which rates are being limited.
|
|
|
|
Significant bits: IHGFEDCBA9876543210
|
|
|
|
Default mask: 0000001100000011000 (6168)
|
|
|
|
Bit definitions (see include/linux/icmp.h):
|
|
|
|
= =========================
|
|
0 Echo Reply
|
|
3 Destination Unreachable [1]_
|
|
4 Source Quench [1]_
|
|
5 Redirect
|
|
8 Echo Request
|
|
B Time Exceeded [1]_
|
|
C Parameter Problem [1]_
|
|
D Timestamp Request
|
|
E Timestamp Reply
|
|
F Info Request
|
|
G Info Reply
|
|
H Address Mask Request
|
|
I Address Mask Reply
|
|
= =========================
|
|
|
|
.. [1] These are rate limited by default (see default mask above)
|
|
|
|
icmp_ignore_bogus_error_responses - BOOLEAN
|
|
Some routers violate RFC1122 by sending bogus responses to broadcast
|
|
frames. Such violations are normally logged via a kernel warning.
|
|
If this is set to TRUE, the kernel will not give such warnings, which
|
|
will avoid log file clutter.
|
|
|
|
Default: 1
|
|
|
|
icmp_errors_use_inbound_ifaddr - BOOLEAN
|
|
|
|
If zero, icmp error messages are sent with the primary address of
|
|
the exiting interface.
|
|
|
|
If non-zero, the message will be sent with the primary address of
|
|
the interface that received the packet that caused the icmp error.
|
|
This is the behaviour many network administrators will expect from
|
|
a router. And it can make debugging complicated network layouts
|
|
much easier.
|
|
|
|
Note that if no primary address exists for the interface selected,
|
|
then the primary address of the first non-loopback interface that
|
|
has one will be used regardless of this setting.
|
|
|
|
Default: 0
|
|
|
|
igmp_max_memberships - INTEGER
|
|
Change the maximum number of multicast groups we can subscribe to.
|
|
Default: 20
|
|
|
|
Theoretical maximum value is bounded by having to send a membership
|
|
report in a single datagram (i.e. the report can't span multiple
|
|
datagrams, or risk confusing the switch and leaving groups you don't
|
|
intend to).
|
|
|
|
The number of supported groups 'M' is bounded by the number of group
|
|
report entries you can fit into a single datagram of 65535 bytes.
|
|
|
|
M = 65536-sizeof (ip header)/(sizeof(Group record))
|
|
|
|
Group records are variable length, with a minimum of 12 bytes.
|
|
So net.ipv4.igmp_max_memberships should not be set higher than:
|
|
|
|
(65536-24) / 12 = 5459
|
|
|
|
The value 5459 assumes no IP header options, so in practice
|
|
this number may be lower.
|
|
|
|
igmp_max_msf - INTEGER
|
|
Maximum number of addresses allowed in the source filter list for a
|
|
multicast group.
|
|
|
|
Default: 10
|
|
|
|
igmp_qrv - INTEGER
|
|
Controls the IGMP query robustness variable (see RFC2236 8.1).
|
|
|
|
Default: 2 (as specified by RFC2236 8.1)
|
|
|
|
Minimum: 1 (as specified by RFC6636 4.5)
|
|
|
|
force_igmp_version - INTEGER
|
|
- 0 - (default) No enforcement of a IGMP version, IGMPv1/v2 fallback
|
|
allowed. Will back to IGMPv3 mode again if all IGMPv1/v2 Querier
|
|
Present timer expires.
|
|
- 1 - Enforce to use IGMP version 1. Will also reply IGMPv1 report if
|
|
receive IGMPv2/v3 query.
|
|
- 2 - Enforce to use IGMP version 2. Will fallback to IGMPv1 if receive
|
|
IGMPv1 query message. Will reply report if receive IGMPv3 query.
|
|
- 3 - Enforce to use IGMP version 3. The same react with default 0.
|
|
|
|
.. note::
|
|
|
|
this is not the same with force_mld_version because IGMPv3 RFC3376
|
|
Security Considerations does not have clear description that we could
|
|
ignore other version messages completely as MLDv2 RFC3810. So make
|
|
this value as default 0 is recommended.
|
|
|
|
``conf/interface/*``
|
|
changes special settings per interface (where
|
|
interface" is the name of your network interface)
|
|
|
|
``conf/all/*``
|
|
is special, changes the settings for all interfaces
|
|
|
|
log_martians - BOOLEAN
|
|
Log packets with impossible addresses to kernel log.
|
|
log_martians for the interface will be enabled if at least one of
|
|
conf/{all,interface}/log_martians is set to TRUE,
|
|
it will be disabled otherwise
|
|
|
|
accept_redirects - BOOLEAN
|
|
Accept ICMP redirect messages.
|
|
accept_redirects for the interface will be enabled if:
|
|
|
|
- both conf/{all,interface}/accept_redirects are TRUE in the case
|
|
forwarding for the interface is enabled
|
|
|
|
or
|
|
|
|
- at least one of conf/{all,interface}/accept_redirects is TRUE in the
|
|
case forwarding for the interface is disabled
|
|
|
|
accept_redirects for the interface will be disabled otherwise
|
|
|
|
default:
|
|
|
|
- TRUE (host)
|
|
- FALSE (router)
|
|
|
|
forwarding - BOOLEAN
|
|
Enable IP forwarding on this interface. This controls whether packets
|
|
received _on_ this interface can be forwarded.
|
|
|
|
mc_forwarding - BOOLEAN
|
|
Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE
|
|
and a multicast routing daemon is required.
|
|
conf/all/mc_forwarding must also be set to TRUE to enable multicast
|
|
routing for the interface
|
|
|
|
medium_id - INTEGER
|
|
Integer value used to differentiate the devices by the medium they
|
|
are attached to. Two devices can have different id values when
|
|
the broadcast packets are received only on one of them.
|
|
The default value 0 means that the device is the only interface
|
|
to its medium, value of -1 means that medium is not known.
|
|
|
|
Currently, it is used to change the proxy_arp behavior:
|
|
the proxy_arp feature is enabled for packets forwarded between
|
|
two devices attached to different media.
|
|
|
|
proxy_arp - BOOLEAN
|
|
Do proxy arp.
|
|
|
|
proxy_arp for the interface will be enabled if at least one of
|
|
conf/{all,interface}/proxy_arp is set to TRUE,
|
|
it will be disabled otherwise
|
|
|
|
proxy_arp_pvlan - BOOLEAN
|
|
Private VLAN proxy arp.
|
|
|
|
Basically allow proxy arp replies back to the same interface
|
|
(from which the ARP request/solicitation was received).
|
|
|
|
This is done to support (ethernet) switch features, like RFC
|
|
3069, where the individual ports are NOT allowed to
|
|
communicate with each other, but they are allowed to talk to
|
|
the upstream router. As described in RFC 3069, it is possible
|
|
to allow these hosts to communicate through the upstream
|
|
router by proxy_arp'ing. Don't need to be used together with
|
|
proxy_arp.
|
|
|
|
This technology is known by different names:
|
|
|
|
In RFC 3069 it is called VLAN Aggregation.
|
|
Cisco and Allied Telesyn call it Private VLAN.
|
|
Hewlett-Packard call it Source-Port filtering or port-isolation.
|
|
Ericsson call it MAC-Forced Forwarding (RFC Draft).
|
|
|
|
shared_media - BOOLEAN
|
|
Send(router) or accept(host) RFC1620 shared media redirects.
|
|
Overrides secure_redirects.
|
|
|
|
shared_media for the interface will be enabled if at least one of
|
|
conf/{all,interface}/shared_media is set to TRUE,
|
|
it will be disabled otherwise
|
|
|
|
default TRUE
|
|
|
|
secure_redirects - BOOLEAN
|
|
Accept ICMP redirect messages only to gateways listed in the
|
|
interface's current gateway list. Even if disabled, RFC1122 redirect
|
|
rules still apply.
|
|
|
|
Overridden by shared_media.
|
|
|
|
secure_redirects for the interface will be enabled if at least one of
|
|
conf/{all,interface}/secure_redirects is set to TRUE,
|
|
it will be disabled otherwise
|
|
|
|
default TRUE
|
|
|
|
send_redirects - BOOLEAN
|
|
Send redirects, if router.
|
|
|
|
send_redirects for the interface will be enabled if at least one of
|
|
conf/{all,interface}/send_redirects is set to TRUE,
|
|
it will be disabled otherwise
|
|
|
|
Default: TRUE
|
|
|
|
bootp_relay - BOOLEAN
|
|
Accept packets with source address 0.b.c.d destined
|
|
not to this host as local ones. It is supposed, that
|
|
BOOTP relay daemon will catch and forward such packets.
|
|
conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay
|
|
for the interface
|
|
|
|
default FALSE
|
|
|
|
Not Implemented Yet.
|
|
|
|
accept_source_route - BOOLEAN
|
|
Accept packets with SRR option.
|
|
conf/all/accept_source_route must also be set to TRUE to accept packets
|
|
with SRR option on the interface
|
|
|
|
default
|
|
|
|
- TRUE (router)
|
|
- FALSE (host)
|
|
|
|
accept_local - BOOLEAN
|
|
Accept packets with local source addresses. In combination with
|
|
suitable routing, this can be used to direct packets between two
|
|
local interfaces over the wire and have them accepted properly.
|
|
default FALSE
|
|
|
|
route_localnet - BOOLEAN
|
|
Do not consider loopback addresses as martian source or destination
|
|
while routing. This enables the use of 127/8 for local routing purposes.
|
|
|
|
default FALSE
|
|
|
|
rp_filter - INTEGER
|
|
- 0 - No source validation.
|
|
- 1 - Strict mode as defined in RFC3704 Strict Reverse Path
|
|
Each incoming packet is tested against the FIB and if the interface
|
|
is not the best reverse path the packet check will fail.
|
|
By default failed packets are discarded.
|
|
- 2 - Loose mode as defined in RFC3704 Loose Reverse Path
|
|
Each incoming packet's source address is also tested against the FIB
|
|
and if the source address is not reachable via any interface
|
|
the packet check will fail.
|
|
|
|
Current recommended practice in RFC3704 is to enable strict mode
|
|
to prevent IP spoofing from DDos attacks. If using asymmetric routing
|
|
or other complicated routing, then loose mode is recommended.
|
|
|
|
The max value from conf/{all,interface}/rp_filter is used
|
|
when doing source validation on the {interface}.
|
|
|
|
Default value is 0. Note that some distributions enable it
|
|
in startup scripts.
|
|
|
|
src_valid_mark - BOOLEAN
|
|
- 0 - The fwmark of the packet is not included in reverse path
|
|
route lookup. This allows for asymmetric routing configurations
|
|
utilizing the fwmark in only one direction, e.g., transparent
|
|
proxying.
|
|
|
|
- 1 - The fwmark of the packet is included in reverse path route
|
|
lookup. This permits rp_filter to function when the fwmark is
|
|
used for routing traffic in both directions.
|
|
|
|
This setting also affects the utilization of fmwark when
|
|
performing source address selection for ICMP replies, or
|
|
determining addresses stored for the IPOPT_TS_TSANDADDR and
|
|
IPOPT_RR IP options.
|
|
|
|
The max value from conf/{all,interface}/src_valid_mark is used.
|
|
|
|
Default value is 0.
|
|
|
|
arp_filter - BOOLEAN
|
|
- 1 - Allows you to have multiple network interfaces on the same
|
|
subnet, and have the ARPs for each interface be answered
|
|
based on whether or not the kernel would route a packet from
|
|
the ARP'd IP out that interface (therefore you must use source
|
|
based routing for this to work). In other words it allows control
|
|
of which cards (usually 1) will respond to an arp request.
|
|
|
|
- 0 - (default) The kernel can respond to arp requests with addresses
|
|
from other interfaces. This may seem wrong but it usually makes
|
|
sense, because it increases the chance of successful communication.
|
|
IP addresses are owned by the complete host on Linux, not by
|
|
particular interfaces. Only for more complex setups like load-
|
|
balancing, does this behaviour cause problems.
|
|
|
|
arp_filter for the interface will be enabled if at least one of
|
|
conf/{all,interface}/arp_filter is set to TRUE,
|
|
it will be disabled otherwise
|
|
|
|
arp_announce - INTEGER
|
|
Define different restriction levels for announcing the local
|
|
source IP address from IP packets in ARP requests sent on
|
|
interface:
|
|
|
|
- 0 - (default) Use any local address, configured on any interface
|
|
- 1 - Try to avoid local addresses that are not in the target's
|
|
subnet for this interface. This mode is useful when target
|
|
hosts reachable via this interface require the source IP
|
|
address in ARP requests to be part of their logical network
|
|
configured on the receiving interface. When we generate the
|
|
request we will check all our subnets that include the
|
|
target IP and will preserve the source address if it is from
|
|
such subnet. If there is no such subnet we select source
|
|
address according to the rules for level 2.
|
|
- 2 - Always use the best local address for this target.
|
|
In this mode we ignore the source address in the IP packet
|
|
and try to select local address that we prefer for talks with
|
|
the target host. Such local address is selected by looking
|
|
for primary IP addresses on all our subnets on the outgoing
|
|
interface that include the target IP address. If no suitable
|
|
local address is found we select the first local address
|
|
we have on the outgoing interface or on all other interfaces,
|
|
with the hope we will receive reply for our request and
|
|
even sometimes no matter the source IP address we announce.
|
|
|
|
The max value from conf/{all,interface}/arp_announce is used.
|
|
|
|
Increasing the restriction level gives more chance for
|
|
receiving answer from the resolved target while decreasing
|
|
the level announces more valid sender's information.
|
|
|
|
arp_ignore - INTEGER
|
|
Define different modes for sending replies in response to
|
|
received ARP requests that resolve local target IP addresses:
|
|
|
|
- 0 - (default): reply for any local target IP address, configured
|
|
on any interface
|
|
- 1 - reply only if the target IP address is local address
|
|
configured on the incoming interface
|
|
- 2 - reply only if the target IP address is local address
|
|
configured on the incoming interface and both with the
|
|
sender's IP address are part from same subnet on this interface
|
|
- 3 - do not reply for local addresses configured with scope host,
|
|
only resolutions for global and link addresses are replied
|
|
- 4-7 - reserved
|
|
- 8 - do not reply for all local addresses
|
|
|
|
The max value from conf/{all,interface}/arp_ignore is used
|
|
when ARP request is received on the {interface}
|
|
|
|
arp_notify - BOOLEAN
|
|
Define mode for notification of address and device changes.
|
|
|
|
== ==========================================================
|
|
0 (default): do nothing
|
|
1 Generate gratuitous arp requests when device is brought up
|
|
or hardware address changes.
|
|
== ==========================================================
|
|
|
|
arp_accept - BOOLEAN
|
|
Define behavior for gratuitous ARP frames who's IP is not
|
|
already present in the ARP table:
|
|
|
|
- 0 - don't create new entries in the ARP table
|
|
- 1 - create new entries in the ARP table
|
|
|
|
Both replies and requests type gratuitous arp will trigger the
|
|
ARP table to be updated, if this setting is on.
|
|
|
|
If the ARP table already contains the IP address of the
|
|
gratuitous arp frame, the arp table will be updated regardless
|
|
if this setting is on or off.
|
|
|
|
arp_evict_nocarrier - BOOLEAN
|
|
Clears the ARP cache on NOCARRIER events. This option is important for
|
|
wireless devices where the ARP cache should not be cleared when roaming
|
|
between access points on the same network. In most cases this should
|
|
remain as the default (1).
|
|
|
|
- 1 - (default): Clear the ARP cache on NOCARRIER events
|
|
- 0 - Do not clear ARP cache on NOCARRIER events
|
|
|
|
mcast_solicit - INTEGER
|
|
The maximum number of multicast probes in INCOMPLETE state,
|
|
when the associated hardware address is unknown. Defaults
|
|
to 3.
|
|
|
|
ucast_solicit - INTEGER
|
|
The maximum number of unicast probes in PROBE state, when
|
|
the hardware address is being reconfirmed. Defaults to 3.
|
|
|
|
app_solicit - INTEGER
|
|
The maximum number of probes to send to the user space ARP daemon
|
|
via netlink before dropping back to multicast probes (see
|
|
mcast_resolicit). Defaults to 0.
|
|
|
|
mcast_resolicit - INTEGER
|
|
The maximum number of multicast probes after unicast and
|
|
app probes in PROBE state. Defaults to 0.
|
|
|
|
disable_policy - BOOLEAN
|
|
Disable IPSEC policy (SPD) for this interface
|
|
|
|
disable_xfrm - BOOLEAN
|
|
Disable IPSEC encryption on this interface, whatever the policy
|
|
|
|
igmpv2_unsolicited_report_interval - INTEGER
|
|
The interval in milliseconds in which the next unsolicited
|
|
IGMPv1 or IGMPv2 report retransmit will take place.
|
|
|
|
Default: 10000 (10 seconds)
|
|
|
|
igmpv3_unsolicited_report_interval - INTEGER
|
|
The interval in milliseconds in which the next unsolicited
|
|
IGMPv3 report retransmit will take place.
|
|
|
|
Default: 1000 (1 seconds)
|
|
|
|
ignore_routes_with_linkdown - BOOLEAN
|
|
Ignore routes whose link is down when performing a FIB lookup.
|
|
|
|
promote_secondaries - BOOLEAN
|
|
When a primary IP address is removed from this interface
|
|
promote a corresponding secondary IP address instead of
|
|
removing all the corresponding secondary IP addresses.
|
|
|
|
drop_unicast_in_l2_multicast - BOOLEAN
|
|
Drop any unicast IP packets that are received in link-layer
|
|
multicast (or broadcast) frames.
|
|
|
|
This behavior (for multicast) is actually a SHOULD in RFC
|
|
1122, but is disabled by default for compatibility reasons.
|
|
|
|
Default: off (0)
|
|
|
|
drop_gratuitous_arp - BOOLEAN
|
|
Drop all gratuitous ARP frames, for example if there's a known
|
|
good ARP proxy on the network and such frames need not be used
|
|
(or in the case of 802.11, must not be used to prevent attacks.)
|
|
|
|
Default: off (0)
|
|
|
|
|
|
tag - INTEGER
|
|
Allows you to write a number, which can be used as required.
|
|
|
|
Default value is 0.
|
|
|
|
xfrm4_gc_thresh - INTEGER
|
|
(Obsolete since linux-4.14)
|
|
The threshold at which we will start garbage collecting for IPv4
|
|
destination cache entries. At twice this value the system will
|
|
refuse new allocations.
|
|
|
|
igmp_link_local_mcast_reports - BOOLEAN
|
|
Enable IGMP reports for link local multicast groups in the
|
|
224.0.0.X range.
|
|
|
|
Default TRUE
|
|
|
|
Alexey Kuznetsov.
|
|
kuznet@ms2.inr.ac.ru
|
|
|
|
Updated by:
|
|
|
|
- Andi Kleen
|
|
ak@muc.de
|
|
- Nicolas Delon
|
|
delon.nicolas@wanadoo.fr
|
|
|
|
|
|
|
|
|
|
/proc/sys/net/ipv6/* Variables
|
|
==============================
|
|
|
|
IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also
|
|
apply to IPv6 [XXX?].
|
|
|
|
bindv6only - BOOLEAN
|
|
Default value for IPV6_V6ONLY socket option,
|
|
which restricts use of the IPv6 socket to IPv6 communication
|
|
only.
|
|
|
|
- TRUE: disable IPv4-mapped address feature
|
|
- FALSE: enable IPv4-mapped address feature
|
|
|
|
Default: FALSE (as specified in RFC3493)
|
|
|
|
flowlabel_consistency - BOOLEAN
|
|
Protect the consistency (and unicity) of flow label.
|
|
You have to disable it to use IPV6_FL_F_REFLECT flag on the
|
|
flow label manager.
|
|
|
|
- TRUE: enabled
|
|
- FALSE: disabled
|
|
|
|
Default: TRUE
|
|
|
|
auto_flowlabels - INTEGER
|
|
Automatically generate flow labels based on a flow hash of the
|
|
packet. This allows intermediate devices, such as routers, to
|
|
identify packet flows for mechanisms like Equal Cost Multipath
|
|
Routing (see RFC 6438).
|
|
|
|
= ===========================================================
|
|
0 automatic flow labels are completely disabled
|
|
1 automatic flow labels are enabled by default, they can be
|
|
disabled on a per socket basis using the IPV6_AUTOFLOWLABEL
|
|
socket option
|
|
2 automatic flow labels are allowed, they may be enabled on a
|
|
per socket basis using the IPV6_AUTOFLOWLABEL socket option
|
|
3 automatic flow labels are enabled and enforced, they cannot
|
|
be disabled by the socket option
|
|
= ===========================================================
|
|
|
|
Default: 1
|
|
|
|
flowlabel_state_ranges - BOOLEAN
|
|
Split the flow label number space into two ranges. 0-0x7FFFF is
|
|
reserved for the IPv6 flow manager facility, 0x80000-0xFFFFF
|
|
is reserved for stateless flow labels as described in RFC6437.
|
|
|
|
- TRUE: enabled
|
|
- FALSE: disabled
|
|
|
|
Default: true
|
|
|
|
flowlabel_reflect - INTEGER
|
|
Control flow label reflection. Needed for Path MTU
|
|
Discovery to work with Equal Cost Multipath Routing in anycast
|
|
environments. See RFC 7690 and:
|
|
https://tools.ietf.org/html/draft-wang-6man-flow-label-reflection-01
|
|
|
|
This is a bitmask.
|
|
|
|
- 1: enabled for established flows
|
|
|
|
Note that this prevents automatic flowlabel changes, as done
|
|
in "tcp: change IPv6 flow-label upon receiving spurious retransmission"
|
|
and "tcp: Change txhash on every SYN and RTO retransmit"
|
|
|
|
- 2: enabled for TCP RESET packets (no active listener)
|
|
If set, a RST packet sent in response to a SYN packet on a closed
|
|
port will reflect the incoming flow label.
|
|
|
|
- 4: enabled for ICMPv6 echo reply messages.
|
|
|
|
Default: 0
|
|
|
|
fib_multipath_hash_policy - INTEGER
|
|
Controls which hash policy to use for multipath routes.
|
|
|
|
Default: 0 (Layer 3)
|
|
|
|
Possible values:
|
|
|
|
- 0 - Layer 3 (source and destination addresses plus flow label)
|
|
- 1 - Layer 4 (standard 5-tuple)
|
|
- 2 - Layer 3 or inner Layer 3 if present
|
|
- 3 - Custom multipath hash. Fields used for multipath hash calculation
|
|
are determined by fib_multipath_hash_fields sysctl
|
|
|
|
fib_multipath_hash_fields - UNSIGNED INTEGER
|
|
When fib_multipath_hash_policy is set to 3 (custom multipath hash), the
|
|
fields used for multipath hash calculation are determined by this
|
|
sysctl.
|
|
|
|
This value is a bitmask which enables various fields for multipath hash
|
|
calculation.
|
|
|
|
Possible fields are:
|
|
|
|
====== ============================
|
|
0x0001 Source IP address
|
|
0x0002 Destination IP address
|
|
0x0004 IP protocol
|
|
0x0008 Flow Label
|
|
0x0010 Source port
|
|
0x0020 Destination port
|
|
0x0040 Inner source IP address
|
|
0x0080 Inner destination IP address
|
|
0x0100 Inner IP protocol
|
|
0x0200 Inner Flow Label
|
|
0x0400 Inner source port
|
|
0x0800 Inner destination port
|
|
====== ============================
|
|
|
|
Default: 0x0007 (source IP, destination IP and IP protocol)
|
|
|
|
anycast_src_echo_reply - BOOLEAN
|
|
Controls the use of anycast addresses as source addresses for ICMPv6
|
|
echo reply
|
|
|
|
- TRUE: enabled
|
|
- FALSE: disabled
|
|
|
|
Default: FALSE
|
|
|
|
idgen_delay - INTEGER
|
|
Controls the delay in seconds after which time to retry
|
|
privacy stable address generation if a DAD conflict is
|
|
detected.
|
|
|
|
Default: 1 (as specified in RFC7217)
|
|
|
|
idgen_retries - INTEGER
|
|
Controls the number of retries to generate a stable privacy
|
|
address if a DAD conflict is detected.
|
|
|
|
Default: 3 (as specified in RFC7217)
|
|
|
|
mld_qrv - INTEGER
|
|
Controls the MLD query robustness variable (see RFC3810 9.1).
|
|
|
|
Default: 2 (as specified by RFC3810 9.1)
|
|
|
|
Minimum: 1 (as specified by RFC6636 4.5)
|
|
|
|
max_dst_opts_number - INTEGER
|
|
Maximum number of non-padding TLVs allowed in a Destination
|
|
options extension header. If this value is less than zero
|
|
then unknown options are disallowed and the number of known
|
|
TLVs allowed is the absolute value of this number.
|
|
|
|
Default: 8
|
|
|
|
max_hbh_opts_number - INTEGER
|
|
Maximum number of non-padding TLVs allowed in a Hop-by-Hop
|
|
options extension header. If this value is less than zero
|
|
then unknown options are disallowed and the number of known
|
|
TLVs allowed is the absolute value of this number.
|
|
|
|
Default: 8
|
|
|
|
max_dst_opts_length - INTEGER
|
|
Maximum length allowed for a Destination options extension
|
|
header.
|
|
|
|
Default: INT_MAX (unlimited)
|
|
|
|
max_hbh_length - INTEGER
|
|
Maximum length allowed for a Hop-by-Hop options extension
|
|
header.
|
|
|
|
Default: INT_MAX (unlimited)
|
|
|
|
skip_notify_on_dev_down - BOOLEAN
|
|
Controls whether an RTM_DELROUTE message is generated for routes
|
|
removed when a device is taken down or deleted. IPv4 does not
|
|
generate this message; IPv6 does by default. Setting this sysctl
|
|
to true skips the message, making IPv4 and IPv6 on par in relying
|
|
on userspace caches to track link events and evict routes.
|
|
|
|
Default: false (generate message)
|
|
|
|
nexthop_compat_mode - BOOLEAN
|
|
New nexthop API provides a means for managing nexthops independent of
|
|
prefixes. Backwards compatibilty with old route format is enabled by
|
|
default which means route dumps and notifications contain the new
|
|
nexthop attribute but also the full, expanded nexthop definition.
|
|
Further, updates or deletes of a nexthop configuration generate route
|
|
notifications for each fib entry using the nexthop. Once a system
|
|
understands the new API, this sysctl can be disabled to achieve full
|
|
performance benefits of the new API by disabling the nexthop expansion
|
|
and extraneous notifications.
|
|
Default: true (backward compat mode)
|
|
|
|
fib_notify_on_flag_change - INTEGER
|
|
Whether to emit RTM_NEWROUTE notifications whenever RTM_F_OFFLOAD/
|
|
RTM_F_TRAP/RTM_F_OFFLOAD_FAILED flags are changed.
|
|
|
|
After installing a route to the kernel, user space receives an
|
|
acknowledgment, which means the route was installed in the kernel,
|
|
but not necessarily in hardware.
|
|
It is also possible for a route already installed in hardware to change
|
|
its action and therefore its flags. For example, a host route that is
|
|
trapping packets can be "promoted" to perform decapsulation following
|
|
the installation of an IPinIP/VXLAN tunnel.
|
|
The notifications will indicate to user-space the state of the route.
|
|
|
|
Default: 0 (Do not emit notifications.)
|
|
|
|
Possible values:
|
|
|
|
- 0 - Do not emit notifications.
|
|
- 1 - Emit notifications.
|
|
- 2 - Emit notifications only for RTM_F_OFFLOAD_FAILED flag change.
|
|
|
|
ioam6_id - INTEGER
|
|
Define the IOAM id of this node. Uses only 24 bits out of 32 in total.
|
|
|
|
Min: 0
|
|
Max: 0xFFFFFF
|
|
|
|
Default: 0xFFFFFF
|
|
|
|
ioam6_id_wide - LONG INTEGER
|
|
Define the wide IOAM id of this node. Uses only 56 bits out of 64 in
|
|
total. Can be different from ioam6_id.
|
|
|
|
Min: 0
|
|
Max: 0xFFFFFFFFFFFFFF
|
|
|
|
Default: 0xFFFFFFFFFFFFFF
|
|
|
|
IPv6 Fragmentation:
|
|
|
|
ip6frag_high_thresh - INTEGER
|
|
Maximum memory used to reassemble IPv6 fragments. When
|
|
ip6frag_high_thresh bytes of memory is allocated for this purpose,
|
|
the fragment handler will toss packets until ip6frag_low_thresh
|
|
is reached.
|
|
|
|
ip6frag_low_thresh - INTEGER
|
|
See ip6frag_high_thresh
|
|
|
|
ip6frag_time - INTEGER
|
|
Time in seconds to keep an IPv6 fragment in memory.
|
|
|
|
``conf/default/*``:
|
|
Change the interface-specific default settings.
|
|
|
|
These settings would be used during creating new interfaces.
|
|
|
|
|
|
``conf/all/*``:
|
|
Change all the interface-specific settings.
|
|
|
|
[XXX: Other special features than forwarding?]
|
|
|
|
conf/all/disable_ipv6 - BOOLEAN
|
|
Changing this value is same as changing ``conf/default/disable_ipv6``
|
|
setting and also all per-interface ``disable_ipv6`` settings to the same
|
|
value.
|
|
|
|
Reading this value does not have any particular meaning. It does not say
|
|
whether IPv6 support is enabled or disabled. Returned value can be 1
|
|
also in the case when some interface has ``disable_ipv6`` set to 0 and
|
|
has configured IPv6 addresses.
|
|
|
|
conf/all/forwarding - BOOLEAN
|
|
Enable global IPv6 forwarding between all interfaces.
|
|
|
|
IPv4 and IPv6 work differently here; e.g. netfilter must be used
|
|
to control which interfaces may forward packets and which not.
|
|
|
|
This also sets all interfaces' Host/Router setting
|
|
'forwarding' to the specified value. See below for details.
|
|
|
|
This referred to as global forwarding.
|
|
|
|
proxy_ndp - BOOLEAN
|
|
Do proxy ndp.
|
|
|
|
fwmark_reflect - BOOLEAN
|
|
Controls the fwmark of kernel-generated IPv6 reply packets that are not
|
|
associated with a socket for example, TCP RSTs or ICMPv6 echo replies).
|
|
If unset, these packets have a fwmark of zero. If set, they have the
|
|
fwmark of the packet they are replying to.
|
|
|
|
Default: 0
|
|
|
|
``conf/interface/*``:
|
|
Change special settings per interface.
|
|
|
|
The functional behaviour for certain settings is different
|
|
depending on whether local forwarding is enabled or not.
|
|
|
|
accept_ra - INTEGER
|
|
Accept Router Advertisements; autoconfigure using them.
|
|
|
|
It also determines whether or not to transmit Router
|
|
Solicitations. If and only if the functional setting is to
|
|
accept Router Advertisements, Router Solicitations will be
|
|
transmitted.
|
|
|
|
Possible values are:
|
|
|
|
== ===========================================================
|
|
0 Do not accept Router Advertisements.
|
|
1 Accept Router Advertisements if forwarding is disabled.
|
|
2 Overrule forwarding behaviour. Accept Router Advertisements
|
|
even if forwarding is enabled.
|
|
== ===========================================================
|
|
|
|
Functional default:
|
|
|
|
- enabled if local forwarding is disabled.
|
|
- disabled if local forwarding is enabled.
|
|
|
|
accept_ra_defrtr - BOOLEAN
|
|
Learn default router in Router Advertisement.
|
|
|
|
Functional default:
|
|
|
|
- enabled if accept_ra is enabled.
|
|
- disabled if accept_ra is disabled.
|
|
|
|
ra_defrtr_metric - UNSIGNED INTEGER
|
|
Route metric for default route learned in Router Advertisement. This value
|
|
will be assigned as metric for the default route learned via IPv6 Router
|
|
Advertisement. Takes affect only if accept_ra_defrtr is enabled.
|
|
|
|
Possible values:
|
|
1 to 0xFFFFFFFF
|
|
|
|
Default: IP6_RT_PRIO_USER i.e. 1024.
|
|
|
|
accept_ra_from_local - BOOLEAN
|
|
Accept RA with source-address that is found on local machine
|
|
if the RA is otherwise proper and able to be accepted.
|
|
|
|
Default is to NOT accept these as it may be an un-intended
|
|
network loop.
|
|
|
|
Functional default:
|
|
|
|
- enabled if accept_ra_from_local is enabled
|
|
on a specific interface.
|
|
- disabled if accept_ra_from_local is disabled
|
|
on a specific interface.
|
|
|
|
accept_ra_min_hop_limit - INTEGER
|
|
Minimum hop limit Information in Router Advertisement.
|
|
|
|
Hop limit Information in Router Advertisement less than this
|
|
variable shall be ignored.
|
|
|
|
Default: 1
|
|
|
|
accept_ra_pinfo - BOOLEAN
|
|
Learn Prefix Information in Router Advertisement.
|
|
|
|
Functional default:
|
|
|
|
- enabled if accept_ra is enabled.
|
|
- disabled if accept_ra is disabled.
|
|
|
|
accept_ra_rt_info_min_plen - INTEGER
|
|
Minimum prefix length of Route Information in RA.
|
|
|
|
Route Information w/ prefix smaller than this variable shall
|
|
be ignored.
|
|
|
|
Functional default:
|
|
|
|
* 0 if accept_ra_rtr_pref is enabled.
|
|
* -1 if accept_ra_rtr_pref is disabled.
|
|
|
|
accept_ra_rt_info_max_plen - INTEGER
|
|
Maximum prefix length of Route Information in RA.
|
|
|
|
Route Information w/ prefix larger than this variable shall
|
|
be ignored.
|
|
|
|
Functional default:
|
|
|
|
* 0 if accept_ra_rtr_pref is enabled.
|
|
* -1 if accept_ra_rtr_pref is disabled.
|
|
|
|
accept_ra_rtr_pref - BOOLEAN
|
|
Accept Router Preference in RA.
|
|
|
|
Functional default:
|
|
|
|
- enabled if accept_ra is enabled.
|
|
- disabled if accept_ra is disabled.
|
|
|
|
accept_ra_mtu - BOOLEAN
|
|
Apply the MTU value specified in RA option 5 (RFC4861). If
|
|
disabled, the MTU specified in the RA will be ignored.
|
|
|
|
Functional default:
|
|
|
|
- enabled if accept_ra is enabled.
|
|
- disabled if accept_ra is disabled.
|
|
|
|
accept_redirects - BOOLEAN
|
|
Accept Redirects.
|
|
|
|
Functional default:
|
|
|
|
- enabled if local forwarding is disabled.
|
|
- disabled if local forwarding is enabled.
|
|
|
|
accept_source_route - INTEGER
|
|
Accept source routing (routing extension header).
|
|
|
|
- >= 0: Accept only routing header type 2.
|
|
- < 0: Do not accept routing header.
|
|
|
|
Default: 0
|
|
|
|
autoconf - BOOLEAN
|
|
Autoconfigure addresses using Prefix Information in Router
|
|
Advertisements.
|
|
|
|
Functional default:
|
|
|
|
- enabled if accept_ra_pinfo is enabled.
|
|
- disabled if accept_ra_pinfo is disabled.
|
|
|
|
dad_transmits - INTEGER
|
|
The amount of Duplicate Address Detection probes to send.
|
|
|
|
Default: 1
|
|
|
|
forwarding - INTEGER
|
|
Configure interface-specific Host/Router behaviour.
|
|
|
|
.. note::
|
|
|
|
It is recommended to have the same setting on all
|
|
interfaces; mixed router/host scenarios are rather uncommon.
|
|
|
|
Possible values are:
|
|
|
|
- 0 Forwarding disabled
|
|
- 1 Forwarding enabled
|
|
|
|
**FALSE (0)**:
|
|
|
|
By default, Host behaviour is assumed. This means:
|
|
|
|
1. IsRouter flag is not set in Neighbour Advertisements.
|
|
2. If accept_ra is TRUE (default), transmit Router
|
|
Solicitations.
|
|
3. If accept_ra is TRUE (default), accept Router
|
|
Advertisements (and do autoconfiguration).
|
|
4. If accept_redirects is TRUE (default), accept Redirects.
|
|
|
|
**TRUE (1)**:
|
|
|
|
If local forwarding is enabled, Router behaviour is assumed.
|
|
This means exactly the reverse from the above:
|
|
|
|
1. IsRouter flag is set in Neighbour Advertisements.
|
|
2. Router Solicitations are not sent unless accept_ra is 2.
|
|
3. Router Advertisements are ignored unless accept_ra is 2.
|
|
4. Redirects are ignored.
|
|
|
|
Default: 0 (disabled) if global forwarding is disabled (default),
|
|
otherwise 1 (enabled).
|
|
|
|
hop_limit - INTEGER
|
|
Default Hop Limit to set.
|
|
|
|
Default: 64
|
|
|
|
mtu - INTEGER
|
|
Default Maximum Transfer Unit
|
|
|
|
Default: 1280 (IPv6 required minimum)
|
|
|
|
ip_nonlocal_bind - BOOLEAN
|
|
If set, allows processes to bind() to non-local IPv6 addresses,
|
|
which can be quite useful - but may break some applications.
|
|
|
|
Default: 0
|
|
|
|
router_probe_interval - INTEGER
|
|
Minimum interval (in seconds) between Router Probing described
|
|
in RFC4191.
|
|
|
|
Default: 60
|
|
|
|
router_solicitation_delay - INTEGER
|
|
Number of seconds to wait after interface is brought up
|
|
before sending Router Solicitations.
|
|
|
|
Default: 1
|
|
|
|
router_solicitation_interval - INTEGER
|
|
Number of seconds to wait between Router Solicitations.
|
|
|
|
Default: 4
|
|
|
|
router_solicitations - INTEGER
|
|
Number of Router Solicitations to send until assuming no
|
|
routers are present.
|
|
|
|
Default: 3
|
|
|
|
use_oif_addrs_only - BOOLEAN
|
|
When enabled, the candidate source addresses for destinations
|
|
routed via this interface are restricted to the set of addresses
|
|
configured on this interface (vis. RFC 6724, section 4).
|
|
|
|
Default: false
|
|
|
|
use_tempaddr - INTEGER
|
|
Preference for Privacy Extensions (RFC3041).
|
|
|
|
* <= 0 : disable Privacy Extensions
|
|
* == 1 : enable Privacy Extensions, but prefer public
|
|
addresses over temporary addresses.
|
|
* > 1 : enable Privacy Extensions and prefer temporary
|
|
addresses over public addresses.
|
|
|
|
Default:
|
|
|
|
* 0 (for most devices)
|
|
* -1 (for point-to-point devices and loopback devices)
|
|
|
|
temp_valid_lft - INTEGER
|
|
valid lifetime (in seconds) for temporary addresses.
|
|
|
|
Default: 172800 (2 days)
|
|
|
|
temp_prefered_lft - INTEGER
|
|
Preferred lifetime (in seconds) for temporary addresses.
|
|
|
|
Default: 86400 (1 day)
|
|
|
|
keep_addr_on_down - INTEGER
|
|
Keep all IPv6 addresses on an interface down event. If set static
|
|
global addresses with no expiration time are not flushed.
|
|
|
|
* >0 : enabled
|
|
* 0 : system default
|
|
* <0 : disabled
|
|
|
|
Default: 0 (addresses are removed)
|
|
|
|
max_desync_factor - INTEGER
|
|
Maximum value for DESYNC_FACTOR, which is a random value
|
|
that ensures that clients don't synchronize with each
|
|
other and generate new addresses at exactly the same time.
|
|
value is in seconds.
|
|
|
|
Default: 600
|
|
|
|
regen_max_retry - INTEGER
|
|
Number of attempts before give up attempting to generate
|
|
valid temporary addresses.
|
|
|
|
Default: 5
|
|
|
|
max_addresses - INTEGER
|
|
Maximum number of autoconfigured addresses per interface. Setting
|
|
to zero disables the limitation. It is not recommended to set this
|
|
value too large (or to zero) because it would be an easy way to
|
|
crash the kernel by allowing too many addresses to be created.
|
|
|
|
Default: 16
|
|
|
|
disable_ipv6 - BOOLEAN
|
|
Disable IPv6 operation. If accept_dad is set to 2, this value
|
|
will be dynamically set to TRUE if DAD fails for the link-local
|
|
address.
|
|
|
|
Default: FALSE (enable IPv6 operation)
|
|
|
|
When this value is changed from 1 to 0 (IPv6 is being enabled),
|
|
it will dynamically create a link-local address on the given
|
|
interface and start Duplicate Address Detection, if necessary.
|
|
|
|
When this value is changed from 0 to 1 (IPv6 is being disabled),
|
|
it will dynamically delete all addresses and routes on the given
|
|
interface. From now on it will not possible to add addresses/routes
|
|
to the selected interface.
|
|
|
|
accept_dad - INTEGER
|
|
Whether to accept DAD (Duplicate Address Detection).
|
|
|
|
== ==============================================================
|
|
0 Disable DAD
|
|
1 Enable DAD (default)
|
|
2 Enable DAD, and disable IPv6 operation if MAC-based duplicate
|
|
link-local address has been found.
|
|
== ==============================================================
|
|
|
|
DAD operation and mode on a given interface will be selected according
|
|
to the maximum value of conf/{all,interface}/accept_dad.
|
|
|
|
force_tllao - BOOLEAN
|
|
Enable sending the target link-layer address option even when
|
|
responding to a unicast neighbor solicitation.
|
|
|
|
Default: FALSE
|
|
|
|
Quoting from RFC 2461, section 4.4, Target link-layer address:
|
|
|
|
"The option MUST be included for multicast solicitations in order to
|
|
avoid infinite Neighbor Solicitation "recursion" when the peer node
|
|
does not have a cache entry to return a Neighbor Advertisements
|
|
message. When responding to unicast solicitations, the option can be
|
|
omitted since the sender of the solicitation has the correct link-
|
|
layer address; otherwise it would not have be able to send the unicast
|
|
solicitation in the first place. However, including the link-layer
|
|
address in this case adds little overhead and eliminates a potential
|
|
race condition where the sender deletes the cached link-layer address
|
|
prior to receiving a response to a previous solicitation."
|
|
|
|
ndisc_notify - BOOLEAN
|
|
Define mode for notification of address and device changes.
|
|
|
|
* 0 - (default): do nothing
|
|
* 1 - Generate unsolicited neighbour advertisements when device is brought
|
|
up or hardware address changes.
|
|
|
|
ndisc_tclass - INTEGER
|
|
The IPv6 Traffic Class to use by default when sending IPv6 Neighbor
|
|
Discovery (Router Solicitation, Router Advertisement, Neighbor
|
|
Solicitation, Neighbor Advertisement, Redirect) messages.
|
|
These 8 bits can be interpreted as 6 high order bits holding the DSCP
|
|
value and 2 low order bits representing ECN (which you probably want
|
|
to leave cleared).
|
|
|
|
* 0 - (default)
|
|
|
|
ndisc_evict_nocarrier - BOOLEAN
|
|
Clears the neighbor discovery table on NOCARRIER events. This option is
|
|
important for wireless devices where the neighbor discovery cache should
|
|
not be cleared when roaming between access points on the same network.
|
|
In most cases this should remain as the default (1).
|
|
|
|
- 1 - (default): Clear neighbor discover cache on NOCARRIER events.
|
|
- 0 - Do not clear neighbor discovery cache on NOCARRIER events.
|
|
|
|
mldv1_unsolicited_report_interval - INTEGER
|
|
The interval in milliseconds in which the next unsolicited
|
|
MLDv1 report retransmit will take place.
|
|
|
|
Default: 10000 (10 seconds)
|
|
|
|
mldv2_unsolicited_report_interval - INTEGER
|
|
The interval in milliseconds in which the next unsolicited
|
|
MLDv2 report retransmit will take place.
|
|
|
|
Default: 1000 (1 second)
|
|
|
|
force_mld_version - INTEGER
|
|
* 0 - (default) No enforcement of a MLD version, MLDv1 fallback allowed
|
|
* 1 - Enforce to use MLD version 1
|
|
* 2 - Enforce to use MLD version 2
|
|
|
|
suppress_frag_ndisc - INTEGER
|
|
Control RFC 6980 (Security Implications of IPv6 Fragmentation
|
|
with IPv6 Neighbor Discovery) behavior:
|
|
|
|
* 1 - (default) discard fragmented neighbor discovery packets
|
|
* 0 - allow fragmented neighbor discovery packets
|
|
|
|
optimistic_dad - BOOLEAN
|
|
Whether to perform Optimistic Duplicate Address Detection (RFC 4429).
|
|
|
|
* 0: disabled (default)
|
|
* 1: enabled
|
|
|
|
Optimistic Duplicate Address Detection for the interface will be enabled
|
|
if at least one of conf/{all,interface}/optimistic_dad is set to 1,
|
|
it will be disabled otherwise.
|
|
|
|
use_optimistic - BOOLEAN
|
|
If enabled, do not classify optimistic addresses as deprecated during
|
|
source address selection. Preferred addresses will still be chosen
|
|
before optimistic addresses, subject to other ranking in the source
|
|
address selection algorithm.
|
|
|
|
* 0: disabled (default)
|
|
* 1: enabled
|
|
|
|
This will be enabled if at least one of
|
|
conf/{all,interface}/use_optimistic is set to 1, disabled otherwise.
|
|
|
|
stable_secret - IPv6 address
|
|
This IPv6 address will be used as a secret to generate IPv6
|
|
addresses for link-local addresses and autoconfigured
|
|
ones. All addresses generated after setting this secret will
|
|
be stable privacy ones by default. This can be changed via the
|
|
addrgenmode ip-link. conf/default/stable_secret is used as the
|
|
secret for the namespace, the interface specific ones can
|
|
overwrite that. Writes to conf/all/stable_secret are refused.
|
|
|
|
It is recommended to generate this secret during installation
|
|
of a system and keep it stable after that.
|
|
|
|
By default the stable secret is unset.
|
|
|
|
addr_gen_mode - INTEGER
|
|
Defines how link-local and autoconf addresses are generated.
|
|
|
|
= =================================================================
|
|
0 generate address based on EUI64 (default)
|
|
1 do no generate a link-local address, use EUI64 for addresses
|
|
generated from autoconf
|
|
2 generate stable privacy addresses, using the secret from
|
|
stable_secret (RFC7217)
|
|
3 generate stable privacy addresses, using a random secret if unset
|
|
= =================================================================
|
|
|
|
drop_unicast_in_l2_multicast - BOOLEAN
|
|
Drop any unicast IPv6 packets that are received in link-layer
|
|
multicast (or broadcast) frames.
|
|
|
|
By default this is turned off.
|
|
|
|
drop_unsolicited_na - BOOLEAN
|
|
Drop all unsolicited neighbor advertisements, for example if there's
|
|
a known good NA proxy on the network and such frames need not be used
|
|
(or in the case of 802.11, must not be used to prevent attacks.)
|
|
|
|
By default this is turned off.
|
|
|
|
accept_untracked_na - BOOLEAN
|
|
Add a new neighbour cache entry in STALE state for routers on receiving a
|
|
neighbour advertisement (either solicited or unsolicited) with target
|
|
link-layer address option specified if no neighbour entry is already
|
|
present for the advertised IPv6 address. Without this knob, NAs received
|
|
for untracked addresses (absent in neighbour cache) are silently ignored.
|
|
|
|
This is as per router-side behaviour documented in RFC9131.
|
|
|
|
This has lower precedence than drop_unsolicited_na.
|
|
|
|
This will optimize the return path for the initial off-link communication
|
|
that is initiated by a directly connected host, by ensuring that
|
|
the first-hop router which turns on this setting doesn't have to
|
|
buffer the initial return packets to do neighbour-solicitation.
|
|
The prerequisite is that the host is configured to send
|
|
unsolicited neighbour advertisements on interface bringup.
|
|
This setting should be used in conjunction with the ndisc_notify setting
|
|
on the host to satisfy this prerequisite.
|
|
|
|
By default this is turned off.
|
|
|
|
enhanced_dad - BOOLEAN
|
|
Include a nonce option in the IPv6 neighbor solicitation messages used for
|
|
duplicate address detection per RFC7527. A received DAD NS will only signal
|
|
a duplicate address if the nonce is different. This avoids any false
|
|
detection of duplicates due to loopback of the NS messages that we send.
|
|
The nonce option will be sent on an interface unless both of
|
|
conf/{all,interface}/enhanced_dad are set to FALSE.
|
|
|
|
Default: TRUE
|
|
|
|
``icmp/*``:
|
|
===========
|
|
|
|
ratelimit - INTEGER
|
|
Limit the maximal rates for sending ICMPv6 messages.
|
|
|
|
0 to disable any limiting,
|
|
otherwise the minimal space between responses in milliseconds.
|
|
|
|
Default: 1000
|
|
|
|
ratemask - list of comma separated ranges
|
|
For ICMPv6 message types matching the ranges in the ratemask, limit
|
|
the sending of the message according to ratelimit parameter.
|
|
|
|
The format used for both input and output is a comma separated
|
|
list of ranges (e.g. "0-127,129" for ICMPv6 message type 0 to 127 and
|
|
129). Writing to the file will clear all previous ranges of ICMPv6
|
|
message types and update the current list with the input.
|
|
|
|
Refer to: https://www.iana.org/assignments/icmpv6-parameters/icmpv6-parameters.xhtml
|
|
for numerical values of ICMPv6 message types, e.g. echo request is 128
|
|
and echo reply is 129.
|
|
|
|
Default: 0-1,3-127 (rate limit ICMPv6 errors except Packet Too Big)
|
|
|
|
echo_ignore_all - BOOLEAN
|
|
If set non-zero, then the kernel will ignore all ICMP ECHO
|
|
requests sent to it over the IPv6 protocol.
|
|
|
|
Default: 0
|
|
|
|
echo_ignore_multicast - BOOLEAN
|
|
If set non-zero, then the kernel will ignore all ICMP ECHO
|
|
requests sent to it over the IPv6 protocol via multicast.
|
|
|
|
Default: 0
|
|
|
|
echo_ignore_anycast - BOOLEAN
|
|
If set non-zero, then the kernel will ignore all ICMP ECHO
|
|
requests sent to it over the IPv6 protocol destined to anycast address.
|
|
|
|
Default: 0
|
|
|
|
xfrm6_gc_thresh - INTEGER
|
|
(Obsolete since linux-4.14)
|
|
The threshold at which we will start garbage collecting for IPv6
|
|
destination cache entries. At twice this value the system will
|
|
refuse new allocations.
|
|
|
|
|
|
IPv6 Update by:
|
|
Pekka Savola <pekkas@netcore.fi>
|
|
YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org>
|
|
|
|
|
|
/proc/sys/net/bridge/* Variables:
|
|
=================================
|
|
|
|
bridge-nf-call-arptables - BOOLEAN
|
|
- 1 : pass bridged ARP traffic to arptables' FORWARD chain.
|
|
- 0 : disable this.
|
|
|
|
Default: 1
|
|
|
|
bridge-nf-call-iptables - BOOLEAN
|
|
- 1 : pass bridged IPv4 traffic to iptables' chains.
|
|
- 0 : disable this.
|
|
|
|
Default: 1
|
|
|
|
bridge-nf-call-ip6tables - BOOLEAN
|
|
- 1 : pass bridged IPv6 traffic to ip6tables' chains.
|
|
- 0 : disable this.
|
|
|
|
Default: 1
|
|
|
|
bridge-nf-filter-vlan-tagged - BOOLEAN
|
|
- 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables.
|
|
- 0 : disable this.
|
|
|
|
Default: 0
|
|
|
|
bridge-nf-filter-pppoe-tagged - BOOLEAN
|
|
- 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables.
|
|
- 0 : disable this.
|
|
|
|
Default: 0
|
|
|
|
bridge-nf-pass-vlan-input-dev - BOOLEAN
|
|
- 1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan
|
|
interface on the bridge and set the netfilter input device to the
|
|
vlan. This allows use of e.g. "iptables -i br0.1" and makes the
|
|
REDIRECT target work with vlan-on-top-of-bridge interfaces. When no
|
|
matching vlan interface is found, or this switch is off, the input
|
|
device is set to the bridge interface.
|
|
|
|
- 0: disable bridge netfilter vlan interface lookup.
|
|
|
|
Default: 0
|
|
|
|
``proc/sys/net/sctp/*`` Variables:
|
|
==================================
|
|
|
|
addip_enable - BOOLEAN
|
|
Enable or disable extension of Dynamic Address Reconfiguration
|
|
(ADD-IP) functionality specified in RFC5061. This extension provides
|
|
the ability to dynamically add and remove new addresses for the SCTP
|
|
associations.
|
|
|
|
1: Enable extension.
|
|
|
|
0: Disable extension.
|
|
|
|
Default: 0
|
|
|
|
pf_enable - INTEGER
|
|
Enable or disable pf (pf is short for potentially failed) state. A value
|
|
of pf_retrans > path_max_retrans also disables pf state. That is, one of
|
|
both pf_enable and pf_retrans > path_max_retrans can disable pf state.
|
|
Since pf_retrans and path_max_retrans can be changed by userspace
|
|
application, sometimes user expects to disable pf state by the value of
|
|
pf_retrans > path_max_retrans, but occasionally the value of pf_retrans
|
|
or path_max_retrans is changed by the user application, this pf state is
|
|
enabled. As such, it is necessary to add this to dynamically enable
|
|
and disable pf state. See:
|
|
https://datatracker.ietf.org/doc/draft-ietf-tsvwg-sctp-failover for
|
|
details.
|
|
|
|
1: Enable pf.
|
|
|
|
0: Disable pf.
|
|
|
|
Default: 1
|
|
|
|
pf_expose - INTEGER
|
|
Unset or enable/disable pf (pf is short for potentially failed) state
|
|
exposure. Applications can control the exposure of the PF path state
|
|
in the SCTP_PEER_ADDR_CHANGE event and the SCTP_GET_PEER_ADDR_INFO
|
|
sockopt. When it's unset, no SCTP_PEER_ADDR_CHANGE event with
|
|
SCTP_ADDR_PF state will be sent and a SCTP_PF-state transport info
|
|
can be got via SCTP_GET_PEER_ADDR_INFO sockopt; When it's enabled,
|
|
a SCTP_PEER_ADDR_CHANGE event will be sent for a transport becoming
|
|
SCTP_PF state and a SCTP_PF-state transport info can be got via
|
|
SCTP_GET_PEER_ADDR_INFO sockopt; When it's diabled, no
|
|
SCTP_PEER_ADDR_CHANGE event will be sent and it returns -EACCES when
|
|
trying to get a SCTP_PF-state transport info via SCTP_GET_PEER_ADDR_INFO
|
|
sockopt.
|
|
|
|
0: Unset pf state exposure, Compatible with old applications.
|
|
|
|
1: Disable pf state exposure.
|
|
|
|
2: Enable pf state exposure.
|
|
|
|
Default: 0
|
|
|
|
addip_noauth_enable - BOOLEAN
|
|
Dynamic Address Reconfiguration (ADD-IP) requires the use of
|
|
authentication to protect the operations of adding or removing new
|
|
addresses. This requirement is mandated so that unauthorized hosts
|
|
would not be able to hijack associations. However, older
|
|
implementations may not have implemented this requirement while
|
|
allowing the ADD-IP extension. For reasons of interoperability,
|
|
we provide this variable to control the enforcement of the
|
|
authentication requirement.
|
|
|
|
== ===============================================================
|
|
1 Allow ADD-IP extension to be used without authentication. This
|
|
should only be set in a closed environment for interoperability
|
|
with older implementations.
|
|
|
|
0 Enforce the authentication requirement
|
|
== ===============================================================
|
|
|
|
Default: 0
|
|
|
|
auth_enable - BOOLEAN
|
|
Enable or disable Authenticated Chunks extension. This extension
|
|
provides the ability to send and receive authenticated chunks and is
|
|
required for secure operation of Dynamic Address Reconfiguration
|
|
(ADD-IP) extension.
|
|
|
|
- 1: Enable this extension.
|
|
- 0: Disable this extension.
|
|
|
|
Default: 0
|
|
|
|
prsctp_enable - BOOLEAN
|
|
Enable or disable the Partial Reliability extension (RFC3758) which
|
|
is used to notify peers that a given DATA should no longer be expected.
|
|
|
|
- 1: Enable extension
|
|
- 0: Disable
|
|
|
|
Default: 1
|
|
|
|
max_burst - INTEGER
|
|
The limit of the number of new packets that can be initially sent. It
|
|
controls how bursty the generated traffic can be.
|
|
|
|
Default: 4
|
|
|
|
association_max_retrans - INTEGER
|
|
Set the maximum number for retransmissions that an association can
|
|
attempt deciding that the remote end is unreachable. If this value
|
|
is exceeded, the association is terminated.
|
|
|
|
Default: 10
|
|
|
|
max_init_retransmits - INTEGER
|
|
The maximum number of retransmissions of INIT and COOKIE-ECHO chunks
|
|
that an association will attempt before declaring the destination
|
|
unreachable and terminating.
|
|
|
|
Default: 8
|
|
|
|
path_max_retrans - INTEGER
|
|
The maximum number of retransmissions that will be attempted on a given
|
|
path. Once this threshold is exceeded, the path is considered
|
|
unreachable, and new traffic will use a different path when the
|
|
association is multihomed.
|
|
|
|
Default: 5
|
|
|
|
pf_retrans - INTEGER
|
|
The number of retransmissions that will be attempted on a given path
|
|
before traffic is redirected to an alternate transport (should one
|
|
exist). Note this is distinct from path_max_retrans, as a path that
|
|
passes the pf_retrans threshold can still be used. Its only
|
|
deprioritized when a transmission path is selected by the stack. This
|
|
setting is primarily used to enable fast failover mechanisms without
|
|
having to reduce path_max_retrans to a very low value. See:
|
|
http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt
|
|
for details. Note also that a value of pf_retrans > path_max_retrans
|
|
disables this feature. Since both pf_retrans and path_max_retrans can
|
|
be changed by userspace application, a variable pf_enable is used to
|
|
disable pf state.
|
|
|
|
Default: 0
|
|
|
|
ps_retrans - INTEGER
|
|
Primary.Switchover.Max.Retrans (PSMR), it's a tunable parameter coming
|
|
from section-5 "Primary Path Switchover" in rfc7829. The primary path
|
|
will be changed to another active path when the path error counter on
|
|
the old primary path exceeds PSMR, so that "the SCTP sender is allowed
|
|
to continue data transmission on a new working path even when the old
|
|
primary destination address becomes active again". Note this feature
|
|
is disabled by initializing 'ps_retrans' per netns as 0xffff by default,
|
|
and its value can't be less than 'pf_retrans' when changing by sysctl.
|
|
|
|
Default: 0xffff
|
|
|
|
rto_initial - INTEGER
|
|
The initial round trip timeout value in milliseconds that will be used
|
|
in calculating round trip times. This is the initial time interval
|
|
for retransmissions.
|
|
|
|
Default: 3000
|
|
|
|
rto_max - INTEGER
|
|
The maximum value (in milliseconds) of the round trip timeout. This
|
|
is the largest time interval that can elapse between retransmissions.
|
|
|
|
Default: 60000
|
|
|
|
rto_min - INTEGER
|
|
The minimum value (in milliseconds) of the round trip timeout. This
|
|
is the smallest time interval the can elapse between retransmissions.
|
|
|
|
Default: 1000
|
|
|
|
hb_interval - INTEGER
|
|
The interval (in milliseconds) between HEARTBEAT chunks. These chunks
|
|
are sent at the specified interval on idle paths to probe the state of
|
|
a given path between 2 associations.
|
|
|
|
Default: 30000
|
|
|
|
sack_timeout - INTEGER
|
|
The amount of time (in milliseconds) that the implementation will wait
|
|
to send a SACK.
|
|
|
|
Default: 200
|
|
|
|
valid_cookie_life - INTEGER
|
|
The default lifetime of the SCTP cookie (in milliseconds). The cookie
|
|
is used during association establishment.
|
|
|
|
Default: 60000
|
|
|
|
cookie_preserve_enable - BOOLEAN
|
|
Enable or disable the ability to extend the lifetime of the SCTP cookie
|
|
that is used during the establishment phase of SCTP association
|
|
|
|
- 1: Enable cookie lifetime extension.
|
|
- 0: Disable
|
|
|
|
Default: 1
|
|
|
|
cookie_hmac_alg - STRING
|
|
Select the hmac algorithm used when generating the cookie value sent by
|
|
a listening sctp socket to a connecting client in the INIT-ACK chunk.
|
|
Valid values are:
|
|
|
|
* md5
|
|
* sha1
|
|
* none
|
|
|
|
Ability to assign md5 or sha1 as the selected alg is predicated on the
|
|
configuration of those algorithms at build time (CONFIG_CRYPTO_MD5 and
|
|
CONFIG_CRYPTO_SHA1).
|
|
|
|
Default: Dependent on configuration. MD5 if available, else SHA1 if
|
|
available, else none.
|
|
|
|
rcvbuf_policy - INTEGER
|
|
Determines if the receive buffer is attributed to the socket or to
|
|
association. SCTP supports the capability to create multiple
|
|
associations on a single socket. When using this capability, it is
|
|
possible that a single stalled association that's buffering a lot
|
|
of data may block other associations from delivering their data by
|
|
consuming all of the receive buffer space. To work around this,
|
|
the rcvbuf_policy could be set to attribute the receiver buffer space
|
|
to each association instead of the socket. This prevents the described
|
|
blocking.
|
|
|
|
- 1: rcvbuf space is per association
|
|
- 0: rcvbuf space is per socket
|
|
|
|
Default: 0
|
|
|
|
sndbuf_policy - INTEGER
|
|
Similar to rcvbuf_policy above, this applies to send buffer space.
|
|
|
|
- 1: Send buffer is tracked per association
|
|
- 0: Send buffer is tracked per socket.
|
|
|
|
Default: 0
|
|
|
|
sctp_mem - vector of 3 INTEGERs: min, pressure, max
|
|
Number of pages allowed for queueing by all SCTP sockets.
|
|
|
|
min: Below this number of pages SCTP is not bothered about its
|
|
memory appetite. When amount of memory allocated by SCTP exceeds
|
|
this number, SCTP starts to moderate memory usage.
|
|
|
|
pressure: This value was introduced to follow format of tcp_mem.
|
|
|
|
max: Number of pages allowed for queueing by all SCTP sockets.
|
|
|
|
Default is calculated at boot time from amount of available memory.
|
|
|
|
sctp_rmem - vector of 3 INTEGERs: min, default, max
|
|
Only the first value ("min") is used, "default" and "max" are
|
|
ignored.
|
|
|
|
min: Minimal size of receive buffer used by SCTP socket.
|
|
It is guaranteed to each SCTP socket (but not association) even
|
|
under moderate memory pressure.
|
|
|
|
Default: 4K
|
|
|
|
sctp_wmem - vector of 3 INTEGERs: min, default, max
|
|
Currently this tunable has no effect.
|
|
|
|
addr_scope_policy - INTEGER
|
|
Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00
|
|
|
|
- 0 - Disable IPv4 address scoping
|
|
- 1 - Enable IPv4 address scoping
|
|
- 2 - Follow draft but allow IPv4 private addresses
|
|
- 3 - Follow draft but allow IPv4 link local addresses
|
|
|
|
Default: 1
|
|
|
|
udp_port - INTEGER
|
|
The listening port for the local UDP tunneling sock. Normally it's
|
|
using the IANA-assigned UDP port number 9899 (sctp-tunneling).
|
|
|
|
This UDP sock is used for processing the incoming UDP-encapsulated
|
|
SCTP packets (from RFC6951), and shared by all applications in the
|
|
same net namespace. This UDP sock will be closed when the value is
|
|
set to 0.
|
|
|
|
The value will also be used to set the src port of the UDP header
|
|
for the outgoing UDP-encapsulated SCTP packets. For the dest port,
|
|
please refer to 'encap_port' below.
|
|
|
|
Default: 0
|
|
|
|
encap_port - INTEGER
|
|
The default remote UDP encapsulation port.
|
|
|
|
This value is used to set the dest port of the UDP header for the
|
|
outgoing UDP-encapsulated SCTP packets by default. Users can also
|
|
change the value for each sock/asoc/transport by using setsockopt.
|
|
For further information, please refer to RFC6951.
|
|
|
|
Note that when connecting to a remote server, the client should set
|
|
this to the port that the UDP tunneling sock on the peer server is
|
|
listening to and the local UDP tunneling sock on the client also
|
|
must be started. On the server, it would get the encap_port from
|
|
the incoming packet's source port.
|
|
|
|
Default: 0
|
|
|
|
plpmtud_probe_interval - INTEGER
|
|
The time interval (in milliseconds) for the PLPMTUD probe timer,
|
|
which is configured to expire after this period to receive an
|
|
acknowledgment to a probe packet. This is also the time interval
|
|
between the probes for the current pmtu when the probe search
|
|
is done.
|
|
|
|
PLPMTUD will be disabled when 0 is set, and other values for it
|
|
must be >= 5000.
|
|
|
|
Default: 0
|
|
|
|
reconf_enable - BOOLEAN
|
|
Enable or disable extension of Stream Reconfiguration functionality
|
|
specified in RFC6525. This extension provides the ability to "reset"
|
|
a stream, and it includes the Parameters of "Outgoing/Incoming SSN
|
|
Reset", "SSN/TSN Reset" and "Add Outgoing/Incoming Streams".
|
|
|
|
- 1: Enable extension.
|
|
- 0: Disable extension.
|
|
|
|
Default: 0
|
|
|
|
intl_enable - BOOLEAN
|
|
Enable or disable extension of User Message Interleaving functionality
|
|
specified in RFC8260. This extension allows the interleaving of user
|
|
messages sent on different streams. With this feature enabled, I-DATA
|
|
chunk will replace DATA chunk to carry user messages if also supported
|
|
by the peer. Note that to use this feature, one needs to set this option
|
|
to 1 and also needs to set socket options SCTP_FRAGMENT_INTERLEAVE to 2
|
|
and SCTP_INTERLEAVING_SUPPORTED to 1.
|
|
|
|
- 1: Enable extension.
|
|
- 0: Disable extension.
|
|
|
|
Default: 0
|
|
|
|
ecn_enable - BOOLEAN
|
|
Control use of Explicit Congestion Notification (ECN) by SCTP.
|
|
Like in TCP, ECN is used only when both ends of the SCTP connection
|
|
indicate support for it. This feature is useful in avoiding losses
|
|
due to congestion by allowing supporting routers to signal congestion
|
|
before having to drop packets.
|
|
|
|
1: Enable ecn.
|
|
0: Disable ecn.
|
|
|
|
Default: 1
|
|
|
|
|
|
``/proc/sys/net/core/*``
|
|
========================
|
|
|
|
Please see: Documentation/admin-guide/sysctl/net.rst for descriptions of these entries.
|
|
|
|
|
|
``/proc/sys/net/unix/*``
|
|
========================
|
|
|
|
max_dgram_qlen - INTEGER
|
|
The maximum length of dgram socket receive queue
|
|
|
|
Default: 10
|
|
|