From: Eric Dumazet <edumazet@google.com>
Date: Mon, 30 Sep 2019 15:44:44 -0700
Subject: tcp: adjust rto_base in retransmits_timed_out()
Git-commit: 3256a2d6ab1f71f9a1bd2d7f6f18eb8108c48d17
Patch-mainline: 5.4-rc2
References: bnc#1151927 5.3.5
The cited commit exposed an old retransmits_timed_out() bug
which assumed it could call tcp_model_timeout() with
TCP_RTO_MIN as rto_base for all states.
But flows in SYN_SENT or SYN_RECV state uses a different
RTO base (1 sec instead of 200 ms, unless BPF choses
another value)
This caused a reduction of SYN retransmits from 6 to 4 with
the default /proc/sys/net/ipv4/tcp_syn_retries value.
Fixes: a41e8a88b06e ("tcp: better handle TCP_USER_TIMEOUT in SYN_SENT state")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Marek Majkowski <marek@cloudflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
net/ipv4/tcp_timer.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -198,8 +198,13 @@ static bool retransmits_timed_out(struct
return false;
start_ts = tcp_sk(sk)->retrans_stamp;
- if (likely(timeout == 0))
- timeout = tcp_model_timeout(sk, boundary, TCP_RTO_MIN);
+ if (likely(timeout == 0)) {
+ unsigned int rto_base = TCP_RTO_MIN;
+
+ if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
+ rto_base = tcp_timeout_init(sk);
+ timeout = tcp_model_timeout(sk, boundary, rto_base);
+ }
return (s32)(tcp_time_stamp(tcp_sk(sk)) - start_ts - timeout) >= 0;
}