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authorEric Dumazet <edumazet@google.com>2019-09-26 15:42:51 -0700
committerDavid S. Miller <davem@davemloft.net>2019-09-27 20:42:24 +0200
commita41e8a88b06ee39fad4cb4a8ccf822563560a89c (patch)
tree4cb7c743f2425c421a5604ae6232843a4055c949 /net
parent174e23810cd3183dc2ca3f5166ef965a55eaaf54 (diff)
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 <edumazet@google.com> Reported-by: Yuchung Cheng <ycheng@google.com> Reported-by: Marek Majkowski <marek@cloudflare.com> Cc: Jon Maxwell <jmaxwell37@gmail.com> Link: https://marc.info/?l=linux-netdev&m=156940118307949&w=2 Acked-by: Jon Maxwell <jmaxwell37@gmail.com> Tested-by: Marek Majkowski <marek@cloudflare.com> Signed-off-by: Marek Majkowski <marek@cloudflare.com> Acked-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp_timer.c5
1 files 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))

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