Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 0e45f4da authored by Yuchung Cheng's avatar Yuchung Cheng Committed by David S. Miller
Browse files

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: default avatarYuchung Cheng <ycheng@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reported-by: default avatarChristoph Paasch <cpaasch@apple.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0db19b85

net/ipv4/tcp_timer.c

+12 −0
Original line number Diff line number Diff line
@@ -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);