[PATCH net] tcp: clear tp->retrans_stamp in tcp_finish_connect()

[PATCH net] tcp: clear tp->retrans_stamp in tcp_finish_connect()

[Eric Dumazet]

tcp_connect() does :

     tp->retrans_stamp = tcp_time_stamp(tp);

When 3WHS completes, we need to clear retrans_stamp otherwise
various things can break.

This bug became more visible after commit b701a99e431d ("tcp: Add
tcp_clamp_rto_to_user_timeout() helper to improve accuracy"), but
predates git history.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
---
 net/ipv4/tcp_input.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a9d9555a973fed4e3562a57d1a2cdadfef40dae4..6c1c79a34ea0b694d0259b3f39ac1481b81dac5a 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5680,6 +5680,7 @@ void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
 	 * packet.
 	 */
 	tp->lsndtime = tcp_jiffies32;
+	tp->retrans_stamp = 0;
 
 	if (sock_flag(sk, SOCK_KEEPOPEN))
 		inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
-- 
2.20.0.405.gbc1bbc6f85-goog

Re: [PATCH net] tcp: clear tp->retrans_stamp in tcp_finish_connect()

[Neal Cardwell]

On Wed, Dec 19, 2018 at 4:50 PM Eric Dumazet <edumazet@google.com> wrote:
>
> tcp_connect() does :
>
>      tp->retrans_stamp = tcp_time_stamp(tp);
>
> When 3WHS completes, we need to clear retrans_stamp otherwise
> various things can break.
>
> This bug became more visible after commit b701a99e431d ("tcp: Add
> tcp_clamp_rto_to_user_timeout() helper to improve accuracy"), but
> predates git history.
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
> ---

Acked-by: Neal Cardwell <ncardwell@google.com>

Thanks!

neal

Re: [PATCH net] tcp: clear tp->retrans_stamp in tcp_finish_connect()

[Eric Dumazet]

On 12/19/2018 01:50 PM, Eric Dumazet wrote:
> tcp_connect() does :
> 
>      tp->retrans_stamp = tcp_time_stamp(tp);
> 
> When 3WHS completes, we need to clear retrans_stamp otherwise
> various things can break.
> 
> This bug became more visible after commit b701a99e431d ("tcp: Add
> tcp_clamp_rto_to_user_timeout() helper to improve accuracy"), but
> predates git history.
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Acked-by: Soheil Hassas Yeganeh <soheil@google.com>


David please disregard this patch. tp->retrans_stamp is already cleared
in tcp_clean_rtx_queue() when the SYN packet is removed from rtx queue.

Thanks.

Re: [PATCH net] tcp: clear tp->retrans_stamp in tcp_finish_connect()

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 19 Dec 2018 15:27:19 -0800

> On 12/19/2018 01:50 PM, Eric Dumazet wrote:
>> tcp_connect() does :
>> 
>>      tp->retrans_stamp = tcp_time_stamp(tp);
>> 
>> When 3WHS completes, we need to clear retrans_stamp otherwise
>> various things can break.
>> 
>> This bug became more visible after commit b701a99e431d ("tcp: Add
>> tcp_clamp_rto_to_user_timeout() helper to improve accuracy"), but
>> predates git history.
>> 
>> Signed-off-by: Eric Dumazet <edumazet@google.com>
>> Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
> 
> 
> David please disregard this patch. tp->retrans_stamp is already cleared
> in tcp_clean_rtx_queue() when the SYN packet is removed from rtx queue.

Ok.