This is a note to let you know that I've just added the patch titled
tcp: disable Fast Open on timeouts after handshake
to the 4.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tcp-disable-fast-open-on-timeouts-after-handshake.patch
and it can be found in the queue-4.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Fri Dec 11 11:38:35 EST 2015
From: Yuchung Cheng <ycheng@xxxxxxxxxx>
Date: Wed, 18 Nov 2015 18:17:30 -0800
Subject: tcp: disable Fast Open on timeouts after handshake
From: Yuchung Cheng <ycheng@xxxxxxxxxx>
[ Upstream commit 0e45f4da5981895e885dd72fe912a3f8e32bae73 ]
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@xxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reported-by: Christoph Paasch <cpaasch@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv4/tcp_timer.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -176,6 +176,18 @@ static int tcp_write_timeout(struct sock
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);
Patches currently in stable-queue which might be from ycheng@xxxxxxxxxx are
queue-4.2/tcp-disable-fast-open-on-timeouts-after-handshake.patch
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