From a41e8a88b06ee39fad4cb4a8ccf822563560a89c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 26 Sep 2019 15:42:51 -0700 Subject: [PATCH] tcp: better handle TCP_USER_TIMEOUT in SYN_SENT state Yuchung Cheng and Marek Majkowski independently reported a weird behavior of TCP_USER_TIMEOUT option when used at connect() time. When the TCP_USER_TIMEOUT is reached, tcp_write_timeout() believes the flow should live, and the following condition in tcp_clamp_rto_to_user_timeout() programs one jiffie timers : remaining = icsk->icsk_user_timeout - elapsed; if (remaining <= 0) return 1; /* user timeout has passed; fire ASAP */ This silly situation ends when the max syn rtx count is reached. This patch makes sure we honor both TCP_SYNCNT and TCP_USER_TIMEOUT, avoiding these spurious SYN packets. Fixes: b701a99e431d ("tcp: Add tcp_clamp_rto_to_user_timeout() helper to improve accuracy") Signed-off-by: Eric Dumazet Reported-by: Yuchung Cheng Reported-by: Marek Majkowski Cc: Jon Maxwell Link: https://marc.info/?l=linux-netdev&m=156940118307949&w=2 Acked-by: Jon Maxwell Tested-by: Marek Majkowski Signed-off-by: Marek Majkowski Acked-by: Yuchung Cheng Signed-off-by: David S. Miller --- net/ipv4/tcp_timer.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index dbd9d2d0ee63..40de2d2364a1 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -210,7 +210,7 @@ static int tcp_write_timeout(struct sock *sk) struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_sock *tp = tcp_sk(sk); struct net *net = sock_net(sk); - bool expired, do_reset; + bool expired = false, do_reset; int retry_until; if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { @@ -242,9 +242,10 @@ static int tcp_write_timeout(struct sock *sk) if (tcp_out_of_resources(sk, do_reset)) return 1; } + } + if (!expired) expired = retransmits_timed_out(sk, retry_until, icsk->icsk_user_timeout); - } tcp_fastopen_active_detect_blackhole(sk, expired); if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG)) -- 2.25.1