netdev - [PATCH] tcp: use rto_min value from socket in retransmits timeout

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Message-Id: <20210723093938.49354-1-zeil@yandex-team.ru>
Date:   Fri, 23 Jul 2021 12:39:38 +0300
From:   Dmitry Yakunin <zeil@...dex-team.ru>
To:     kafai@...com, edumazet@...gle.com, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Cc:     dmtrmonakhov@...dex-team.ru
Subject: [PATCH] tcp: use rto_min value from socket in retransmits timeout

Commit ca584ba07086 ("tcp: bpf: Add TCP_BPF_RTO_MIN for bpf_setsockopt")
adds ability to set rto_min value on socket less then default TCP_RTO_MIN.
But retransmits_timed_out() function still uses TCP_RTO_MIN and
tcp_retries{1,2} sysctls don't work properly for tuned socket values.

Fixes: ca584ba07086 ("tcp: bpf: Add TCP_BPF_RTO_MIN for bpf_setsockopt")
Signed-off-by: Dmitry Yakunin <zeil@...dex-team.ru>
Acked-by: Dmitry Monakhov <dmtrmonakhov@...dex-team.ru>
---
 net/ipv4/tcp_timer.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 20cf4a9..66c4b97 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -199,12 +199,13 @@ static unsigned int tcp_model_timeout(struct sock *sk,
  *  @boundary: max number of retransmissions
  *  @timeout:  A custom timeout value.
  *             If set to 0 the default timeout is calculated and used.
- *             Using TCP_RTO_MIN and the number of unsuccessful retransmits.
+ *             Using icsk_rto_min value from socket or RTAX_RTO_MIN from route
+ *             and the number of unsuccessful retransmits.
  *
  * The default "timeout" value this function can calculate and use
  * is equivalent to the timeout of a TCP Connection
  * after "boundary" unsuccessful, exponentially backed-off
- * retransmissions with an initial RTO of TCP_RTO_MIN.
+ * retransmissions with an initial RTO of icsk_rto_min or RTAX_RTO_MIN.
  */
 static bool retransmits_timed_out(struct sock *sk,
 				  unsigned int boundary,
@@ -217,7 +218,7 @@ static bool retransmits_timed_out(struct sock *sk,
 
 	start_ts = tcp_sk(sk)->retrans_stamp;
 	if (likely(timeout == 0)) {
-		unsigned int rto_base = TCP_RTO_MIN;
+		unsigned int rto_base = tcp_rto_min(sk);
 
 		if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
 			rto_base = tcp_timeout_init(sk);
-- 
2.7.4