netdev.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Neal Cardwell <ncardwell@google.com>
To: Yuchung Cheng <ycheng@google.com>
Cc: dormando <dormando@rydia.net>,
	Michele Baldessari <michele@acksyn.org>,
	Russell King - ARM Linux <linux@arm.linux.org.uk>,
	netdev <netdev@vger.kernel.org>,
	Nandita Dukkipati <nanditad@google.com>
Subject: Re: IPv6 kernel warning
Date: Tue, 8 Oct 2013 10:05:51 -0400	[thread overview]
Message-ID: <CADVnQynJVvFesFYp68N5kzCJJD3-NXPZUUMfkg8m=or4eaLzMQ@mail.gmail.com> (raw)
In-Reply-To: <CAK6E8=czoej81t=-J=gjjyQiGVbZ0qiNKBbeRVSWYtweXfSRNQ@mail.gmail.com>

On Mon, Oct 7, 2013 at 3:51 PM, Yuchung Cheng <ycheng@google.com> wrote:
> I suspect tcp_process_tlp_ack() should not revert state to Open
> directly, but calling tcp_try_keep_open() instead, similar to all the
> undo processing in the tcp_fastretrans_alert(): after
> tcp_end_cwnd_reduction(), the process (E) falls back to check other
> stats before moving to CA_Open.
>
>
> index 9c62257..9012b42 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -3314,7 +3314,7 @@ static void tcp_process_tlp_ack(struct sock *sk, u32 ack,
>                         tcp_init_cwnd_reduction(sk, true);
>                         tcp_set_ca_state(sk, TCP_CA_CWR);
>                         tcp_end_cwnd_reduction(sk);
> -                       tcp_set_ca_state(sk, TCP_CA_Open);
> +                       tcp_try_keep_open(sk);
>                         NET_INC_STATS_BH(sock_net(sk),
>                                          LINUX_MIB_TCPLOSSPROBERECOVERY);
>                 }

Yes, nice catch! This looks good to me. My testing confirms that this
definitely fixes a bug when this code fires and there are segments
SACKed out. Since it will stay in CA_Disorder if there are outstanding
retransmissions, I bet it will also fix the WARN_ON(tp->retrans_out !=
0) in state TCP_CA_Open that people are seeing.

neal

  parent reply	other threads:[~2013-10-08 14:05 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-09-20 13:11 IPv6 kernel warning Russell King - ARM Linux
2013-09-20 16:08 ` Michele Baldessari
2013-09-20 16:40   ` Yuchung Cheng
2013-10-07 18:13     ` dormando
2013-10-07 19:51       ` Yuchung Cheng
2013-10-07 19:56         ` dormando
2013-10-07 20:00           ` Yuchung Cheng
2013-10-07 20:15             ` dormando
2013-10-08 18:24             ` dormando
2013-10-08 20:53               ` Yuchung Cheng
2013-10-09 17:33                 ` Yuchung Cheng
2013-10-09 18:48                   ` dormando
2013-10-11 18:15                     ` dormando
2013-10-08 14:05         ` Neal Cardwell [this message]
2013-10-08 17:56           ` Yuchung Cheng

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CADVnQynJVvFesFYp68N5kzCJJD3-NXPZUUMfkg8m=or4eaLzMQ@mail.gmail.com' \
    --to=ncardwell@google.com \
    --cc=dormando@rydia.net \
    --cc=linux@arm.linux.org.uk \
    --cc=michele@acksyn.org \
    --cc=nanditad@google.com \
    --cc=netdev@vger.kernel.org \
    --cc=ycheng@google.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).