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ipv4: Create probe timer for tcp PMTU as per RFC4821

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As per RFC4821 7.3.  Selecting Probe Size, a probe timer should
be armed once probing has converged. Once this timer expired,
probing again to take advantage of any path PMTU change. The
recommended probing interval is 10 minutes per RFC1981. Probing
interval could be sysctled by sysctl_tcp_probe_interval.

Eric Dumazet suggested to implement pseudo timer based on 32bits
jiffies tcp_time_stamp instead of using classic timer for such
rare event.

Signed-off-by: Fan Du <fan.du@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Fan Du 2015-03-06 11:18:24 +08:00 committed by David S. Miller
parent 6b58e0a5f3
commit 05cbc0db03
7 changed files with 51 additions and 2 deletions
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2
include/net/inet_connection_sock.h
View File

@ -126,6 +126,8 @@ struct inet_connection_sock {
/* Information on the current probe. */
int probe_size;
u32 probe_timestamp;
} icsk_mtup;
u32 icsk_ca_priv[16];
u32 icsk_user_timeout;

1
include/net/netns/ipv4.h
View File

@ -88,6 +88,7 @@ struct netns_ipv4 {
int sysctl_tcp_mtu_probing;
int sysctl_tcp_base_mss;
int sysctl_tcp_probe_threshold;
u32 sysctl_tcp_probe_interval;
struct ping_group_range ping_group_range;

3
include/net/tcp.h
View File

@ -67,6 +67,9 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
/* The least MTU to use for probing */
#define TCP_BASE_MSS 1024
/* probing interval, default to 10 minutes as per RFC4821 */
#define TCP_PROBE_INTERVAL 600
/* Specify interval when tcp mtu probing will stop */
#define TCP_PROBE_THRESHOLD 8

7
net/ipv4/sysctl_net_ipv4.c
View File

@ -890,6 +890,13 @@ static struct ctl_table ipv4_net_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec,
},
{
.procname = "tcp_probe_interval",
.data = &init_net.ipv4.sysctl_tcp_probe_interval,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{ }
};

1
net/ipv4/tcp_ipv4.c
View File

@ -2461,6 +2461,7 @@ static int __net_init tcp_sk_init(struct net *net)
net->ipv4.sysctl_tcp_ecn = 2;
net->ipv4.sysctl_tcp_base_mss = TCP_BASE_MSS;
net->ipv4.sysctl_tcp_probe_threshold = TCP_PROBE_THRESHOLD;
net->ipv4.sysctl_tcp_probe_interval = TCP_PROBE_INTERVAL;
return 0;
fail:

38
net/ipv4/tcp_output.c
View File

@ -1354,6 +1354,8 @@ void tcp_mtup_init(struct sock *sk)
icsk->icsk_af_ops->net_header_len;
icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
icsk->icsk_mtup.probe_size = 0;
if (icsk->icsk_mtup.enabled)
icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
}
EXPORT_SYMBOL(tcp_mtup_init);
@ -1828,6 +1830,31 @@ send_now:
return false;
}
static inline void tcp_mtu_check_reprobe(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
struct net *net = sock_net(sk);
u32 interval;
s32 delta;
interval = net->ipv4.sysctl_tcp_probe_interval;
delta = tcp_time_stamp - icsk->icsk_mtup.probe_timestamp;
if (unlikely(delta >= interval * HZ)) {
int mss = tcp_current_mss(sk);
/* Update current search range */
icsk->icsk_mtup.probe_size = 0;
icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
sizeof(struct tcphdr) +
icsk->icsk_af_ops->net_header_len;
icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
/* Update probe time stamp */
icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
}
}
/* Create a new MTU probe if we are ready.
* MTU probe is regularly attempting to increase the path MTU by
* deliberately sending larger packets. This discovers routing
@ -1870,9 +1897,16 @@ static int tcp_mtu_probe(struct sock *sk)
icsk->icsk_mtup.search_low) >> 1);
size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
/* When misfortune happens, we are reprobing actively,
* and then reprobe timer has expired. We stick with current
* probing process by not resetting search range to its orignal.
*/
if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
interval < max(1, net->ipv4.sysctl_tcp_probe_threshold)) {
/* TODO: set timer for probe_converge_event */
interval < net->ipv4.sysctl_tcp_probe_threshold) {
/* Check whether enough time has elaplased for
* another round of probing.
*/
tcp_mtu_check_reprobe(sk);
return -1;
}

1
net/ipv4/tcp_timer.c
View File

@ -107,6 +107,7 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
if (net->ipv4.sysctl_tcp_mtu_probing) {
if (!icsk->icsk_mtup.enabled) {
icsk->icsk_mtup.enabled = 1;
icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
} else {
struct net *net = sock_net(sk);