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authorYuchung Cheng <ycheng@google.com>2013-10-29 10:09:05 -0700
committerDavid S. Miller <davem@davemloft.net>2013-10-29 22:50:41 -0400
commitc968601d174739cb1e7100c95e0eb3d2f7e91bc9 (patch)
treeba4605fa37ed4d0a8f47bd49c3cb53929285ebf3 /net/ipv4/tcp_metrics.c
parentaa58d9813d9d236ca12f921d90634ee1dc2bcc24 (diff)
downloadlinux-stericsson-c968601d174739cb1e7100c95e0eb3d2f7e91bc9.tar.gz
tcp: temporarily disable Fast Open on SYN timeout
Fast Open currently has a fall back feature to address SYN-data being dropped but it requires the middle-box to pass on regular SYN retry after SYN-data. This is implemented in commit aab487435 ("net-tcp: Fast Open client - detecting SYN-data drops") However some NAT boxes will drop all subsequent packets after first SYN-data and blackholes the entire connections. An example is in commit 356d7d8 "netfilter: nf_conntrack: fix tcp_in_window for Fast Open". The sender should note such incidents and fall back to use the regular TCP handshake on subsequent attempts temporarily as well: after the second SYN timeouts the original Fast Open SYN is most likely lost. When such an event recurs Fast Open is disabled based on the number of recurrences exponentially. Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_metrics.c')
-rw-r--r--net/ipv4/tcp_metrics.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 4a2a84110dfb..2ab09cbae74d 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -671,8 +671,9 @@ void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
struct tcp_fastopen_metrics *tfom = &tm->tcpm_fastopen;
write_seqlock_bh(&fastopen_seqlock);
- tfom->mss = mss;
- if (cookie->len > 0)
+ if (mss)
+ tfom->mss = mss;
+ if (cookie && cookie->len > 0)
tfom->cookie = *cookie;
if (syn_lost) {
++tfom->syn_loss;