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authorEric Dumazet <edumazet@google.com>2024-06-14 15:06:15 +0200
committerJakub Kicinski <kuba@kernel.org>2024-06-18 02:50:39 +0200
commit9e046bb111f13461d3f9331e24e974324245140e (patch)
treecf7f45e9a5b5aa77111b6c6a5bcd2063353f56f7 /net/ipv4
parentnetrom: Fix a memory leak in nr_heartbeat_expiry() (diff)
downloadlinux-9e046bb111f13461d3f9331e24e974324245140e.tar.xz
linux-9e046bb111f13461d3f9331e24e974324245140e.zip
tcp: clear tp->retrans_stamp in tcp_rcv_fastopen_synack()
Some applications were reporting ETIMEDOUT errors on apparently good looking flows, according to packet dumps. We were able to root cause the issue to an accidental setting of tp->retrans_stamp in the following scenario: - client sends TFO SYN with data. - server has TFO disabled, ACKs only SYN but not payload. - client receives SYNACK covering only SYN. - tcp_ack() eats SYN and sets tp->retrans_stamp to 0. - tcp_rcv_fastopen_synack() calls tcp_xmit_retransmit_queue() to retransmit TFO payload w/o SYN, sets tp->retrans_stamp to "now", but we are not in any loss recovery state. - TFO payload is ACKed. - we are not in any loss recovery state, and don't see any dupacks, so we don't get to any code path that clears tp->retrans_stamp. - tp->retrans_stamp stays non-zero for the lifetime of the connection. - after first RTO, tcp_clamp_rto_to_user_timeout() clamps second RTO to 1 jiffy due to bogus tp->retrans_stamp. - on clamped RTO with non-zero icsk_retransmits, retransmits_timed_out() sets start_ts from tp->retrans_stamp from TFO payload retransmit hours/days ago, and computes bogus long elapsed time for loss recovery, and suffers ETIMEDOUT early. Fixes: a7abf3cd76e1 ("tcp: consider using standard rtx logic in tcp_rcv_fastopen_synack()") CC: stable@vger.kernel.org Co-developed-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Co-developed-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Link: https://lore.kernel.org/r/20240614130615.396837-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/ipv4')
-rw-r--r--net/ipv4/tcp_input.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9c04a9c8be9d..01d208e0eef3 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6296,6 +6296,7 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
skb_rbtree_walk_from(data)
tcp_mark_skb_lost(sk, data);
tcp_xmit_retransmit_queue(sk);
+ tp->retrans_stamp = 0;
NET_INC_STATS(sock_net(sk),
LINUX_MIB_TCPFASTOPENACTIVEFAIL);
return true;