iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
c319b4d76b
linux/net/ipv4/icmp.c
Vasiliy Kulikov c319b4d76b net: ipv4: add IPPROTO_ICMP socket kind 
This patch adds IPPROTO_ICMP socket kind.  It makes it possible to send
ICMP_ECHO messages and receive the corresponding ICMP_ECHOREPLY messages
without any special privileges.  In other words, the patch makes it
possible to implement setuid-less and CAP_NET_RAW-less /bin/ping.  In
order not to increase the kernel's attack surface, the new functionality
is disabled by default, but is enabled at bootup by supporting Linux
distributions, optionally with restriction to a group or a group range
(see below).

Similar functionality is implemented in Mac OS X:
http://www.manpagez.com/man/4/icmp/

A new ping socket is created with

    socket(PF_INET, SOCK_DGRAM, PROT_ICMP)

Message identifiers (octets 4-5 of ICMP header) are interpreted as local
ports. Addresses are stored in struct sockaddr_in. No port numbers are
reserved for privileged processes, port 0 is reserved for API ("let the
kernel pick a free number"). There is no notion of remote ports, remote
port numbers provided by the user (e.g. in connect()) are ignored.

Data sent and received include ICMP headers. This is deliberate to:
1) Avoid the need to transport headers values like sequence numbers by
other means.
2) Make it easier to port existing programs using raw sockets.

ICMP headers given to send() are checked and sanitized. The type must be
ICMP_ECHO and the code must be zero (future extensions might relax this,
see below). The id is set to the number (local port) of the socket, the
checksum is always recomputed.

ICMP reply packets received from the network are demultiplexed according
to their id's, and are returned by recv() without any modifications.
IP header information and ICMP errors of those packets may be obtained
via ancillary data (IP_RECVTTL, IP_RETOPTS, and IP_RECVERR). ICMP source
quenches and redirects are reported as fake errors via the error queue
(IP_RECVERR); the next hop address for redirects is saved to ee_info (in
network order).

socket(2) is restricted to the group range specified in
"/proc/sys/net/ipv4/ping_group_range".  It is "1 0" by default, meaning
that nobody (not even root) may create ping sockets.  Setting it to "100
100" would grant permissions to the single group (to either make
/sbin/ping g+s and owned by this group or to grant permissions to the
"netadmins" group), "0 4294967295" would enable it for the world, "100
4294967295" would enable it for the users, but not daemons.

The existing code might be (in the unlikely case anyone needs it)
extended rather easily to handle other similar pairs of ICMP messages
(Timestamp/Reply, Information Request/Reply, Address Mask Request/Reply
etc.).

Userspace ping util & patch for it:
http://openwall.info/wiki/people/segoon/ping

For Openwall GNU/*/Linux it was the last step on the road to the
setuid-less distro.  A revision of this patch (for RHEL5/OpenVZ kernels)
is in use in Owl-current, such as in the 2011/03/12 LiveCD ISOs:
http://mirrors.kernel.org/openwall/Owl/current/iso/

Initially this functionality was written by Pavel Kankovsky for
Linux 2.4.32, but unfortunately it was never made public.

All ping options (-b, -p, -Q, -R, -s, -t, -T, -M, -I), are tested with
the patch.

PATCH v3:
    - switched to flowi4.
    - minor changes to be consistent with raw sockets code.

PATCH v2:
    - changed ping_debug() to pr_debug().
    - removed CONFIG_IP_PING.
    - removed ping_seq_fops.owner field (unused for procfs).
    - switched to proc_net_fops_create().
    - switched to %pK in seq_printf().

PATCH v1:
    - fixed checksumming bug.
    - CAP_NET_RAW may not create icmp sockets anymore.

RFC v2:
    - minor cleanups.
    - introduced sysctl'able group range to restrict socket(2).

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-05-13 16:08:13 -04:00

1206 lines
29 KiB
C
Raw Blame History

/*
* NET3: Implementation of the ICMP protocol layer.
*
* Alan Cox, <alan@lxorguk.ukuu.org.uk>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Some of the function names and the icmp unreach table for this
* module were derived from [icmp.c 1.0.11 06/02/93] by
* Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting.
* Other than that this module is a complete rewrite.
*
* Fixes:
* Clemens Fruhwirth : introduce global icmp rate limiting
* with icmp type masking ability instead
* of broken per type icmp timeouts.
* Mike Shaver : RFC1122 checks.
* Alan Cox : Multicast ping reply as self.
* Alan Cox : Fix atomicity lockup in ip_build_xmit
* call.
* Alan Cox : Added 216,128 byte paths to the MTU
* code.
* Martin Mares : RFC1812 checks.
* Martin Mares : Can be configured to follow redirects
* if acting as a router _without_ a
* routing protocol (RFC 1812).
* Martin Mares : Echo requests may be configured to
* be ignored (RFC 1812).
* Martin Mares : Limitation of ICMP error message
* transmit rate (RFC 1812).
* Martin Mares : TOS and Precedence set correctly
* (RFC 1812).
* Martin Mares : Now copying as much data from the
* original packet as we can without
* exceeding 576 bytes (RFC 1812).
* Willy Konynenberg : Transparent proxying support.
* Keith Owens : RFC1191 correction for 4.2BSD based
* path MTU bug.
* Thomas Quinot : ICMP Dest Unreach codes up to 15 are
* valid (RFC 1812).
* Andi Kleen : Check all packet lengths properly
* and moved all kfree_skb() up to
* icmp_rcv.
* Andi Kleen : Move the rate limit bookkeeping
* into the dest entry and use a token
* bucket filter (thanks to ANK). Make
* the rates sysctl configurable.
* Yu Tianli : Fixed two ugly bugs in icmp_send
* - IP option length was accounted wrongly
* - ICMP header length was not accounted
* at all.
* Tristan Greaves : Added sysctl option to ignore bogus
* broadcast responses from broken routers.
*
* To Fix:
*
* - Should use skb_pull() instead of all the manual checking.
* This would also greatly simply some upper layer error handlers. --AK
*
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/fcntl.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/inetdevice.h>
#include <linux/netdevice.h>
#include <linux/string.h>
#include <linux/netfilter_ipv4.h>
#include <linux/slab.h>
#include <net/snmp.h>
#include <net/ip.h>
#include <net/route.h>
#include <net/protocol.h>
#include <net/icmp.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/raw.h>
#include <net/ping.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <linux/init.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <net/checksum.h>
#include <net/xfrm.h>
#include <net/inet_common.h>
/*
* Build xmit assembly blocks
*/
struct icmp_bxm {
struct sk_buff *skb;
int offset;
int data_len;
struct {
struct icmphdr icmph;
__be32 times[3];
} data;
int head_len;
struct ip_options_data replyopts;
};
/* An array of errno for error messages from dest unreach. */
/* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */
const struct icmp_err icmp_err_convert[] = {
{
.errno = ENETUNREACH, /* ICMP_NET_UNREACH */
.fatal = 0,
},
{
.errno = EHOSTUNREACH, /* ICMP_HOST_UNREACH */
.fatal = 0,
},
{
.errno = ENOPROTOOPT /* ICMP_PROT_UNREACH */,
.fatal = 1,
},
{
.errno = ECONNREFUSED, /* ICMP_PORT_UNREACH */
.fatal = 1,
},
{
.errno = EMSGSIZE, /* ICMP_FRAG_NEEDED */
.fatal = 0,
},
{
.errno = EOPNOTSUPP, /* ICMP_SR_FAILED */
.fatal = 0,
},
{
.errno = ENETUNREACH, /* ICMP_NET_UNKNOWN */
.fatal = 1,
},
{
.errno = EHOSTDOWN, /* ICMP_HOST_UNKNOWN */
.fatal = 1,
},
{
.errno = ENONET, /* ICMP_HOST_ISOLATED */
.fatal = 1,
},
{
.errno = ENETUNREACH, /* ICMP_NET_ANO */
.fatal = 1,
},
{
.errno = EHOSTUNREACH, /* ICMP_HOST_ANO */
.fatal = 1,
},
{
.errno = ENETUNREACH, /* ICMP_NET_UNR_TOS */
.fatal = 0,
},
{
.errno = EHOSTUNREACH, /* ICMP_HOST_UNR_TOS */
.fatal = 0,
},
{
.errno = EHOSTUNREACH, /* ICMP_PKT_FILTERED */
.fatal = 1,
},
{
.errno = EHOSTUNREACH, /* ICMP_PREC_VIOLATION */
.fatal = 1,
},
{
.errno = EHOSTUNREACH, /* ICMP_PREC_CUTOFF */
.fatal = 1,
},
};
EXPORT_SYMBOL(icmp_err_convert);
/*
* ICMP control array. This specifies what to do with each ICMP.
*/
struct icmp_control {
void (*handler)(struct sk_buff *skb);
short error; /* This ICMP is classed as an error message */
};
static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
/*
* The ICMP socket(s). This is the most convenient way to flow control
* our ICMP output as well as maintain a clean interface throughout
* all layers. All Socketless IP sends will soon be gone.
*
* On SMP we have one ICMP socket per-cpu.
*/
static struct sock *icmp_sk(struct net *net)
{
return net->ipv4.icmp_sk[smp_processor_id()];
}
static inline struct sock *icmp_xmit_lock(struct net *net)
{
struct sock *sk;
local_bh_disable();
sk = icmp_sk(net);
if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
/* This can happen if the output path signals a
* dst_link_failure() for an outgoing ICMP packet.
*/
local_bh_enable();
return NULL;
}
return sk;
}
static inline void icmp_xmit_unlock(struct sock *sk)
{
spin_unlock_bh(&sk->sk_lock.slock);
}
/*
* Send an ICMP frame.
*/
static inline bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
int type, int code)
{
struct dst_entry *dst = &rt->dst;
bool rc = true;
if (type > NR_ICMP_TYPES)
goto out;
/* Don't limit PMTU discovery. */
if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
goto out;
/* No rate limit on loopback */
if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
goto out;
/* Limit if icmp type is enabled in ratemask. */
if ((1 << type) & net->ipv4.sysctl_icmp_ratemask) {
if (!rt->peer)
rt_bind_peer(rt, 1);
rc = inet_peer_xrlim_allow(rt->peer,
net->ipv4.sysctl_icmp_ratelimit);
}
out:
return rc;
}
/*
* Maintain the counters used in the SNMP statistics for outgoing ICMP
*/
void icmp_out_count(struct net *net, unsigned char type)
{
ICMPMSGOUT_INC_STATS(net, type);
ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS);
}
/*
* Checksum each fragment, and on the first include the headers and final
* checksum.
*/
static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
struct sk_buff *skb)
{
struct icmp_bxm *icmp_param = (struct icmp_bxm *)from;
__wsum csum;
csum = skb_copy_and_csum_bits(icmp_param->skb,
icmp_param->offset + offset,
to, len, 0);
skb->csum = csum_block_add(skb->csum, csum, odd);
if (icmp_pointers[icmp_param->data.icmph.type].error)
nf_ct_attach(skb, icmp_param->skb);
return 0;
}
static void icmp_push_reply(struct icmp_bxm *icmp_param,
struct flowi4 *fl4,
struct ipcm_cookie *ipc, struct rtable **rt)
{
struct sock *sk;
struct sk_buff *skb;
sk = icmp_sk(dev_net((*rt)->dst.dev));
if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
icmp_param->data_len+icmp_param->head_len,
icmp_param->head_len,
ipc, rt, MSG_DONTWAIT) < 0) {
ICMP_INC_STATS_BH(sock_net(sk), ICMP_MIB_OUTERRORS);
ip_flush_pending_frames(sk);
} else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
struct icmphdr *icmph = icmp_hdr(skb);
__wsum csum = 0;
struct sk_buff *skb1;
skb_queue_walk(&sk->sk_write_queue, skb1) {
csum = csum_add(csum, skb1->csum);
}
csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
(char *)icmph,
icmp_param->head_len, csum);
icmph->checksum = csum_fold(csum);
skb->ip_summed = CHECKSUM_NONE;
ip_push_pending_frames(sk, fl4);
}
}
/*
* Driving logic for building and sending ICMP messages.
*/
static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
{
struct ipcm_cookie ipc;
struct rtable *rt = skb_rtable(skb);
struct net *net = dev_net(rt->dst.dev);
struct flowi4 fl4;
struct sock *sk;
struct inet_sock *inet;
__be32 daddr;
if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb))
return;
sk = icmp_xmit_lock(net);
if (sk == NULL)
return;
inet = inet_sk(sk);
icmp_param->data.icmph.checksum = 0;
inet->tos = ip_hdr(skb)->tos;
daddr = ipc.addr = ip_hdr(skb)->saddr;
ipc.opt = NULL;
ipc.tx_flags = 0;
if (icmp_param->replyopts.opt.opt.optlen) {
ipc.opt = &icmp_param->replyopts.opt;
if (ipc.opt->opt.srr)
daddr = icmp_param->replyopts.opt.opt.faddr;
}
memset(&fl4, 0, sizeof(fl4));
fl4.daddr = daddr;
fl4.saddr = rt->rt_spec_dst;
fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
fl4.flowi4_proto = IPPROTO_ICMP;
security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
rt = ip_route_output_key(net, &fl4);
if (IS_ERR(rt))
goto out_unlock;
if (icmpv4_xrlim_allow(net, rt, icmp_param->data.icmph.type,
icmp_param->data.icmph.code))
icmp_push_reply(icmp_param, &fl4, &ipc, &rt);
ip_rt_put(rt);
out_unlock:
icmp_xmit_unlock(sk);
}
static struct rtable *icmp_route_lookup(struct net *net,
struct flowi4 *fl4,
struct sk_buff *skb_in,
const struct iphdr *iph,
__be32 saddr, u8 tos,
int type, int code,
struct icmp_bxm *param)
{
struct rtable *rt, *rt2;
int err;
memset(fl4, 0, sizeof(*fl4));
fl4->daddr = (param->replyopts.opt.opt.srr ?
param->replyopts.opt.opt.faddr : iph->saddr);
fl4->saddr = saddr;
fl4->flowi4_tos = RT_TOS(tos);
fl4->flowi4_proto = IPPROTO_ICMP;
fl4->fl4_icmp_type = type;
fl4->fl4_icmp_code = code;
security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4));
rt = __ip_route_output_key(net, fl4);
if (IS_ERR(rt))
return rt;
/* No need to clone since we're just using its address. */
rt2 = rt;
rt = (struct rtable *) xfrm_lookup(net, &rt->dst,
flowi4_to_flowi(fl4), NULL, 0);
if (!IS_ERR(rt)) {
if (rt != rt2)
return rt;
} else if (PTR_ERR(rt) == -EPERM) {
rt = NULL;
} else
return rt;
err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(fl4), AF_INET);
if (err)
goto relookup_failed;
if (inet_addr_type(net, fl4->saddr) == RTN_LOCAL) {
rt2 = __ip_route_output_key(net, fl4);
if (IS_ERR(rt2))
err = PTR_ERR(rt2);
} else {
struct flowi4 fl4_2 = {};
unsigned long orefdst;
fl4_2.daddr = fl4->saddr;
rt2 = ip_route_output_key(net, &fl4_2);
if (IS_ERR(rt2)) {
err = PTR_ERR(rt2);
goto relookup_failed;
}
/* Ugh! */
orefdst = skb_in->_skb_refdst; /* save old refdst */
err = ip_route_input(skb_in, fl4->daddr, fl4->saddr,
RT_TOS(tos), rt2->dst.dev);
dst_release(&rt2->dst);
rt2 = skb_rtable(skb_in);
skb_in->_skb_refdst = orefdst; /* restore old refdst */
}
if (err)
goto relookup_failed;
rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst,
flowi4_to_flowi(fl4), NULL,
XFRM_LOOKUP_ICMP);
if (!IS_ERR(rt2)) {
dst_release(&rt->dst);
rt = rt2;
} else if (PTR_ERR(rt2) == -EPERM) {
if (rt)
dst_release(&rt->dst);
return rt2;
} else {
err = PTR_ERR(rt2);
goto relookup_failed;
}
return rt;
relookup_failed:
if (rt)
return rt;
return ERR_PTR(err);
}
/*
* Send an ICMP message in response to a situation
*
* RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header.
* MAY send more (we do).
* MUST NOT change this header information.
* MUST NOT reply to a multicast/broadcast IP address.
* MUST NOT reply to a multicast/broadcast MAC address.
* MUST reply to only the first fragment.
*/
void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
{
struct iphdr *iph;
int room;
struct icmp_bxm icmp_param;
struct rtable *rt = skb_rtable(skb_in);
struct ipcm_cookie ipc;
struct flowi4 fl4;
__be32 saddr;
u8 tos;
struct net *net;
struct sock *sk;
if (!rt)
goto out;
net = dev_net(rt->dst.dev);
/*
* Find the original header. It is expected to be valid, of course.
* Check this, icmp_send is called from the most obscure devices
* sometimes.
*/
iph = ip_hdr(skb_in);
if ((u8 *)iph < skb_in->head ||
(skb_in->network_header + sizeof(*iph)) > skb_in->tail)
goto out;
/*
* No replies to physical multicast/broadcast
*/
if (skb_in->pkt_type != PACKET_HOST)
goto out;
/*
* Now check at the protocol level
*/
if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
goto out;
/*
* Only reply to fragment 0. We byte re-order the constant
* mask for efficiency.
*/
if (iph->frag_off & htons(IP_OFFSET))
goto out;
/*
* If we send an ICMP error to an ICMP error a mess would result..
*/
if (icmp_pointers[type].error) {
/*
* We are an error, check if we are replying to an
* ICMP error
*/
if (iph->protocol == IPPROTO_ICMP) {
u8 _inner_type, *itp;
itp = skb_header_pointer(skb_in,
skb_network_header(skb_in) +
(iph->ihl << 2) +
offsetof(struct icmphdr,
type) -
skb_in->data,
sizeof(_inner_type),
&_inner_type);
if (itp == NULL)
goto out;
/*
* Assume any unknown ICMP type is an error. This
* isn't specified by the RFC, but think about it..
*/
if (*itp > NR_ICMP_TYPES ||
icmp_pointers[*itp].error)
goto out;
}
}
sk = icmp_xmit_lock(net);
if (sk == NULL)
return;
/*
* Construct source address and options.
*/
saddr = iph->daddr;
if (!(rt->rt_flags & RTCF_LOCAL)) {
struct net_device *dev = NULL;
rcu_read_lock();
if (rt_is_input_route(rt) &&
net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr)
dev = dev_get_by_index_rcu(net, rt->rt_iif);
if (dev)
saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK);
else
saddr = 0;
rcu_read_unlock();
}
tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) |
IPTOS_PREC_INTERNETCONTROL) :
iph->tos;
if (ip_options_echo(&icmp_param.replyopts.opt.opt, skb_in))
goto out_unlock;
/*
* Prepare data for ICMP header.
*/
icmp_param.data.icmph.type = type;
icmp_param.data.icmph.code = code;
icmp_param.data.icmph.un.gateway = info;
icmp_param.data.icmph.checksum = 0;
icmp_param.skb = skb_in;
icmp_param.offset = skb_network_offset(skb_in);
inet_sk(sk)->tos = tos;
ipc.addr = iph->saddr;
ipc.opt = &icmp_param.replyopts.opt;
ipc.tx_flags = 0;
rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos,
type, code, &icmp_param);
if (IS_ERR(rt))
goto out_unlock;
if (!icmpv4_xrlim_allow(net, rt, type, code))
goto ende;
/* RFC says return as much as we can without exceeding 576 bytes. */
room = dst_mtu(&rt->dst);
if (room > 576)
room = 576;
room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
room -= sizeof(struct icmphdr);
icmp_param.data_len = skb_in->len - icmp_param.offset;
if (icmp_param.data_len > room)
icmp_param.data_len = room;
icmp_param.head_len = sizeof(struct icmphdr);
icmp_push_reply(&icmp_param, &fl4, &ipc, &rt);
ende:
ip_rt_put(rt);
out_unlock:
icmp_xmit_unlock(sk);
out:;
}
EXPORT_SYMBOL(icmp_send);
/*
* Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH.
*/
static void icmp_unreach(struct sk_buff *skb)
{
const struct iphdr *iph;
struct icmphdr *icmph;
int hash, protocol;
const struct net_protocol *ipprot;
u32 info = 0;
struct net *net;
net = dev_net(skb_dst(skb)->dev);
/*
* Incomplete header ?
* Only checks for the IP header, there should be an
* additional check for longer headers in upper levels.
*/
if (!pskb_may_pull(skb, sizeof(struct iphdr)))
goto out_err;
icmph = icmp_hdr(skb);
iph = (const struct iphdr *)skb->data;
if (iph->ihl < 5) /* Mangled header, drop. */
goto out_err;
if (icmph->type == ICMP_DEST_UNREACH) {
switch (icmph->code & 15) {
case ICMP_NET_UNREACH:
case ICMP_HOST_UNREACH:
case ICMP_PROT_UNREACH:
case ICMP_PORT_UNREACH:
break;
case ICMP_FRAG_NEEDED:
if (ipv4_config.no_pmtu_disc) {
LIMIT_NETDEBUG(KERN_INFO "ICMP: %pI4: fragmentation needed and DF set.\n",
&iph->daddr);
} else {
info = ip_rt_frag_needed(net, iph,
ntohs(icmph->un.frag.mtu),
skb->dev);
if (!info)
goto out;
}
break;
case ICMP_SR_FAILED:
LIMIT_NETDEBUG(KERN_INFO "ICMP: %pI4: Source Route Failed.\n",
&iph->daddr);
break;
default:
break;
}
if (icmph->code > NR_ICMP_UNREACH)
goto out;
} else if (icmph->type == ICMP_PARAMETERPROB)
info = ntohl(icmph->un.gateway) >> 24;
/*
* Throw it at our lower layers
*
* RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
* header.
* RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
* transport layer.
* RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
* transport layer.
*/
/*
* Check the other end isn't violating RFC 1122. Some routers send
* bogus responses to broadcast frames. If you see this message
* first check your netmask matches at both ends, if it does then
* get the other vendor to fix their kit.
*/
if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses &&
inet_addr_type(net, iph->daddr) == RTN_BROADCAST) {
if (net_ratelimit())
printk(KERN_WARNING "%pI4 sent an invalid ICMP "
"type %u, code %u "
"error to a broadcast: %pI4 on %s\n",
&ip_hdr(skb)->saddr,
icmph->type, icmph->code,
&iph->daddr,
skb->dev->name);
goto out;
}
/* Checkin full IP header plus 8 bytes of protocol to
* avoid additional coding at protocol handlers.
*/
if (!pskb_may_pull(skb, iph->ihl * 4 + 8))
goto out;
iph = (const struct iphdr *)skb->data;
protocol = iph->protocol;
/*
* Deliver ICMP message to raw sockets. Pretty useless feature?
*/
raw_icmp_error(skb, protocol, info);
hash = protocol & (MAX_INET_PROTOS - 1);
rcu_read_lock();
ipprot = rcu_dereference(inet_protos[hash]);
if (ipprot && ipprot->err_handler)
ipprot->err_handler(skb, info);
rcu_read_unlock();
out:
return;
out_err:
ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
goto out;
}
/*
* Handle ICMP_REDIRECT.
*/
static void icmp_redirect(struct sk_buff *skb)
{
const struct iphdr *iph;
if (skb->len < sizeof(struct iphdr))
goto out_err;
/*
* Get the copied header of the packet that caused the redirect
*/
if (!pskb_may_pull(skb, sizeof(struct iphdr)))
goto out;
iph = (const struct iphdr *)skb->data;
switch (icmp_hdr(skb)->code & 7) {
case ICMP_REDIR_NET:
case ICMP_REDIR_NETTOS:
/*
* As per RFC recommendations now handle it as a host redirect.
*/
case ICMP_REDIR_HOST:
case ICMP_REDIR_HOSTTOS:
ip_rt_redirect(ip_hdr(skb)->saddr, iph->daddr,
icmp_hdr(skb)->un.gateway,
iph->saddr, skb->dev);
break;
}
/* Ping wants to see redirects.
* Let's pretend they are errors of sorts... */
if (iph->protocol == IPPROTO_ICMP &&
iph->ihl >= 5 &&
pskb_may_pull(skb, (iph->ihl<<2)+8)) {
ping_err(skb, icmp_hdr(skb)->un.gateway);
}
out:
return;
out_err:
ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS);
goto out;
}
/*
* Handle ICMP_ECHO ("ping") requests.
*
* RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
* requests.
* RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
* included in the reply.
* RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
* echo requests, MUST have default=NOT.
* See also WRT handling of options once they are done and working.
*/
static void icmp_echo(struct sk_buff *skb)
{
struct net *net;
net = dev_net(skb_dst(skb)->dev);
if (!net->ipv4.sysctl_icmp_echo_ignore_all) {
struct icmp_bxm icmp_param;
icmp_param.data.icmph = *icmp_hdr(skb);
icmp_param.data.icmph.type = ICMP_ECHOREPLY;
icmp_param.skb = skb;
icmp_param.offset = 0;
icmp_param.data_len = skb->len;
icmp_param.head_len = sizeof(struct icmphdr);
icmp_reply(&icmp_param, skb);
}
}
/*
* Handle ICMP Timestamp requests.
* RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
* SHOULD be in the kernel for minimum random latency.
* MUST be accurate to a few minutes.
* MUST be updated at least at 15Hz.
*/
static void icmp_timestamp(struct sk_buff *skb)
{
struct timespec tv;
struct icmp_bxm icmp_param;
/*
* Too short.
*/
if (skb->len < 4)
goto out_err;
/*
* Fill in the current time as ms since midnight UT:
*/
getnstimeofday(&tv);
icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC +
tv.tv_nsec / NSEC_PER_MSEC);
icmp_param.data.times[2] = icmp_param.data.times[1];
if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4))
BUG();
icmp_param.data.icmph = *icmp_hdr(skb);
icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY;
icmp_param.data.icmph.code = 0;
icmp_param.skb = skb;
icmp_param.offset = 0;
icmp_param.data_len = 0;
icmp_param.head_len = sizeof(struct icmphdr) + 12;
icmp_reply(&icmp_param, skb);
out:
return;
out_err:
ICMP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
goto out;
}
/*
* Handle ICMP_ADDRESS_MASK requests. (RFC950)
*
* RFC1122 (3.2.2.9). A host MUST only send replies to
* ADDRESS_MASK requests if it's been configured as an address mask
* agent. Receiving a request doesn't constitute implicit permission to
* act as one. Of course, implementing this correctly requires (SHOULD)
* a way to turn the functionality on and off. Another one for sysctl(),
* I guess. -- MS
*
* RFC1812 (4.3.3.9). A router MUST implement it.
* A router SHOULD have switch turning it on/off.
* This switch MUST be ON by default.
*
* Gratuitous replies, zero-source replies are not implemented,
* that complies with RFC. DO NOT implement them!!! All the idea
* of broadcast addrmask replies as specified in RFC950 is broken.
* The problem is that it is not uncommon to have several prefixes
* on one physical interface. Moreover, addrmask agent can even be
* not aware of existing another prefixes.
* If source is zero, addrmask agent cannot choose correct prefix.
* Gratuitous mask announcements suffer from the same problem.
* RFC1812 explains it, but still allows to use ADDRMASK,
* that is pretty silly. --ANK
*
* All these rules are so bizarre, that I removed kernel addrmask
* support at all. It is wrong, it is obsolete, nobody uses it in
* any case. --ANK
*
* Furthermore you can do it with a usermode address agent program
* anyway...
*/
static void icmp_address(struct sk_buff *skb)
{
#if 0
if (net_ratelimit())
printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n");
#endif
}
/*
* RFC1812 (4.3.3.9). A router SHOULD listen all replies, and complain
* loudly if an inconsistency is found.
* called with rcu_read_lock()
*/
static void icmp_address_reply(struct sk_buff *skb)
{
struct rtable *rt = skb_rtable(skb);
struct net_device *dev = skb->dev;
struct in_device *in_dev;
struct in_ifaddr *ifa;
if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC))
return;
in_dev = __in_dev_get_rcu(dev);
if (!in_dev)
return;
if (in_dev->ifa_list &&
IN_DEV_LOG_MARTIANS(in_dev) &&
IN_DEV_FORWARD(in_dev)) {
__be32 _mask, *mp;
mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask);
BUG_ON(mp == NULL);
for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) {
if (*mp == ifa->ifa_mask &&
inet_ifa_match(ip_hdr(skb)->saddr, ifa))
break;
}
if (!ifa && net_ratelimit()) {
printk(KERN_INFO "Wrong address mask %pI4 from %s/%pI4\n",
mp, dev->name, &ip_hdr(skb)->saddr);
}
}
}
static void icmp_discard(struct sk_buff *skb)
{
}
/*
* Deal with incoming ICMP packets.
*/
int icmp_rcv(struct sk_buff *skb)
{
struct icmphdr *icmph;
struct rtable *rt = skb_rtable(skb);
struct net *net = dev_net(rt->dst.dev);
if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
struct sec_path *sp = skb_sec_path(skb);
int nh;
if (!(sp && sp->xvec[sp->len - 1]->props.flags &
XFRM_STATE_ICMP))
goto drop;
if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
goto drop;
nh = skb_network_offset(skb);
skb_set_network_header(skb, sizeof(*icmph));
if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb))
goto drop;
skb_set_network_header(skb, nh);
}
ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS);
switch (skb->ip_summed) {
case CHECKSUM_COMPLETE:
if (!csum_fold(skb->csum))
break;
/* fall through */
case CHECKSUM_NONE:
skb->csum = 0;
if (__skb_checksum_complete(skb))
goto error;
}
if (!pskb_pull(skb, sizeof(*icmph)))
goto error;
icmph = icmp_hdr(skb);
ICMPMSGIN_INC_STATS_BH(net, icmph->type);
/*
* 18 is the highest 'known' ICMP type. Anything else is a mystery
*
* RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently
* discarded.
*/
if (icmph->type > NR_ICMP_TYPES)
goto error;
/*
* Parse the ICMP message
*/
if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
/*
* RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
* silently ignored (we let user decide with a sysctl).
* RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
* discarded if to broadcast/multicast.
*/
if ((icmph->type == ICMP_ECHO ||
icmph->type == ICMP_TIMESTAMP) &&
net->ipv4.sysctl_icmp_echo_ignore_broadcasts) {
goto error;
}
if (icmph->type != ICMP_ECHO &&
icmph->type != ICMP_TIMESTAMP &&
icmph->type != ICMP_ADDRESS &&
icmph->type != ICMP_ADDRESSREPLY) {
goto error;
}
}
icmp_pointers[icmph->type].handler(skb);
drop:
kfree_skb(skb);
return 0;
error:
ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
goto drop;
}
/*
* This table is the definition of how we handle ICMP.
*/
static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
[ICMP_ECHOREPLY] = {
.handler = ping_rcv,
},
[1] = {
.handler = icmp_discard,
.error = 1,
},
[2] = {
.handler = icmp_discard,
.error = 1,
},
[ICMP_DEST_UNREACH] = {
.handler = icmp_unreach,
.error = 1,
},
[ICMP_SOURCE_QUENCH] = {
.handler = icmp_unreach,
.error = 1,
},
[ICMP_REDIRECT] = {
.handler = icmp_redirect,
.error = 1,
},
[6] = {
.handler = icmp_discard,
.error = 1,
},
[7] = {
.handler = icmp_discard,
.error = 1,
},
[ICMP_ECHO] = {
.handler = icmp_echo,
},
[9] = {
.handler = icmp_discard,
.error = 1,
},
[10] = {
.handler = icmp_discard,
.error = 1,
},
[ICMP_TIME_EXCEEDED] = {
.handler = icmp_unreach,
.error = 1,
},
[ICMP_PARAMETERPROB] = {
.handler = icmp_unreach,
.error = 1,
},
[ICMP_TIMESTAMP] = {
.handler = icmp_timestamp,
},
[ICMP_TIMESTAMPREPLY] = {
.handler = icmp_discard,
},
[ICMP_INFO_REQUEST] = {
.handler = icmp_discard,
},
[ICMP_INFO_REPLY] = {
.handler = icmp_discard,
},
[ICMP_ADDRESS] = {
.handler = icmp_address,
},
[ICMP_ADDRESSREPLY] = {
.handler = icmp_address_reply,
},
};
static void __net_exit icmp_sk_exit(struct net *net)
{
int i;
for_each_possible_cpu(i)
inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]);
kfree(net->ipv4.icmp_sk);
net->ipv4.icmp_sk = NULL;
}
static int __net_init icmp_sk_init(struct net *net)
{
int i, err;
net->ipv4.icmp_sk =
kzalloc(nr_cpu_ids * sizeof(struct sock *), GFP_KERNEL);
if (net->ipv4.icmp_sk == NULL)
return -ENOMEM;
for_each_possible_cpu(i) {
struct sock *sk;
err = inet_ctl_sock_create(&sk, PF_INET,
SOCK_RAW, IPPROTO_ICMP, net);
if (err < 0)
goto fail;
net->ipv4.icmp_sk[i] = sk;
/* Enough space for 2 64K ICMP packets, including
* sk_buff struct overhead.
*/
sk->sk_sndbuf =
(2 * ((64 * 1024) + sizeof(struct sk_buff)));
/*
* Speedup sock_wfree()
*/
sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
}
/* Control parameters for ECHO replies. */
net->ipv4.sysctl_icmp_echo_ignore_all = 0;
net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
/* Control parameter - ignore bogus broadcast responses? */
net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
/*
* Configurable global rate limit.
*
* ratelimit defines tokens/packet consumed for dst->rate_token
* bucket ratemask defines which icmp types are ratelimited by
* setting it's bit position.
*
* default:
* dest unreachable (3), source quench (4),
* time exceeded (11), parameter problem (12)
*/
net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
net->ipv4.sysctl_icmp_ratemask = 0x1818;
net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
return 0;
fail:
for_each_possible_cpu(i)
inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]);
kfree(net->ipv4.icmp_sk);
return err;
}
static struct pernet_operations __net_initdata icmp_sk_ops = {
.init = icmp_sk_init,
.exit = icmp_sk_exit,
};
int __init icmp_init(void)
{
return register_pernet_subsys(&icmp_sk_ops);
}
Reference in New Issue View Git Blame Copy Permalink