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tcp: disable Fast Open on timeouts after handshake 

Some middle-boxes black-hole the data after the Fast Open handshake
(https://www.ietf.org/proceedings/94/slides/slides-94-tcpm-13.pdf).
The exact reason is unknown. The work-around is to disable Fast Open
temporarily after multiple recurring timeouts with few or no data
delivered in the established state.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Christoph Paasch <cpaasch@apple.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yuchung Cheng 2015-11-18 18:17:30 -08:00 committed by David S. Miller
parent 0db19b8504
commit 0e45f4da59
1 changed files with 12 additions and 0 deletions
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12
net/ipv4/tcp_timer.c
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@ -176,6 +176,18 @@ static int tcp_write_timeout(struct sock *sk)
syn_set = true;
} else {
if (retransmits_timed_out(sk, sysctl_tcp_retries1, 0, 0)) {
/* Some middle-boxes may black-hole Fast Open _after_
* the handshake. Therefore we conservatively disable
* Fast Open on this path on recurring timeouts with
* few or zero bytes acked after Fast Open.
*/
if (tp->syn_data_acked &&
tp->bytes_acked <= tp->rx_opt.mss_clamp) {
tcp_fastopen_cache_set(sk, 0, NULL, true, 0);
if (icsk->icsk_retransmits == sysctl_tcp_retries1)
NET_INC_STATS_BH(sock_net(sk),
LINUX_MIB_TCPFASTOPENACTIVEFAIL);
}
/* Black hole detection */
tcp_mtu_probing(icsk, sk);