netdev - Re: Get amount of fast retransmissions from TCP info

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CADVnQymNJeeA5F8+5gfxzVRcAEpq9DwipMMDGzp2vQnypH1QdQ@mail.gmail.com>
Date:   Wed, 3 May 2017 16:01:03 -0400
From:   Neal Cardwell <ncardwell@...gle.com>
To:     Lars Erik Storbukås <storbukas.dev@...il.com>
Cc:     Andreas Petlund <apetlund@...ula.no>,
        LKML <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>
Subject: Re: Get amount of fast retransmissions from TCP info

On Wed, May 3, 2017 at 3:47 PM, Lars Erik Storbukås
<storbukas.dev@...il.com> wrote:
> I also want to count the amount of ECN signals received. Do anyone
> have any input on where to place an ECN signal count?
>
> Is any of these locations a logical place to increase the ECN counter
> (which I've created in tcp_sock)? Both locations are in the
> tcp_input.c.
>
> /* In tcp_fastretrans_alert() */
> if (flag & FLAG_ECE) {
>     tp->prior_ssthresh = 0;
>     tp->ecn_count += 1; // ECN counter
> }

This approach sounds good to me.

> or
>
> /* In tcp_enter_recovery() */
> if (!tcp_in_cwnd_reduction(sk)) {
>     if (!ece_ack)
>         tp->prior_ssthresh = tcp_current_ssthresh(sk);
>     else
>        tp->ecn_count += 1; // ECN counter
>     tcp_init_cwnd_reduction(sk);
> }
> tcp_set_ca_state(sk, TCP_CA_Recovery);

This location would only count ECE marks we happened to get at the
moment we enter loss recovery.

neal