On Mon, 2015-12-07 at 10:00 +0100, Per Hurtig wrote:
\
>  
> +static u32 tcp_unsent_pkts(const struct sock *sk)
> +{
> +     struct sk_buff *skb = tcp_send_head(sk);
> +     u32 pkts = 0;
> +
> +     if (skb)
> +             tcp_for_write_queue_from(skb, sk)
> +                     pkts += tcp_skb_pcount(skb);
> +
> +     return pkts;
> +}

write queue can be very big (consider GSO/TSO being off for example)

Parsing it just to implement later :

(tp->packets_out + tcp_unsent_pkts(sk) <
> +                         TCP_RTORESTART_THRESH)

is probably not very efficient.

I would rather implement a different helper, aborting the loop as soon
as the condition can not be met anymore.

> +
>  /* Restart timer after forward progress on connection.
>   * RFC2988 recommends to restart timer to now+rto.
>   */
> @@ -3027,6 +3040,17 @@ void tcp_rearm_rto(struct sock *sk)
>                        */
>                       if (delta > 0)
>                               rto = delta;
> +             } else if (icsk->icsk_pending == ICSK_TIME_RETRANS &&
> +                        (sysctl_tcp_timer_restart == 1 ||
> +                         sysctl_tcp_timer_restart == 3) &&
> +                        (tp->packets_out + tcp_unsent_pkts(sk) <
> +                         TCP_RTORESTART_THRESH)) {
> +                     struct sk_buff *skb = tcp_write_queue_head(sk);
> +                     const u32 rto_time_stamp = tcp_skb_timestamp(skb);
> +                     s32 delta = (s32)(tcp_time_stamp - rto_time_stamp);
> +
> +                     if (delta > 0 && rto > delta)
> +                             rto -= delta;
>               }
>               inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto,
>                                         TCP_RTO_MAX);


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