From: Yuchung Cheng <ycheng@google.com>
To: Neal Cardwell <ncardwell@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 10:56:54 -0700 [thread overview]
Message-ID: <CAK6E8=dXS7cbjxp=GwmH_JROOFvU_Yp9YnTn0diHT5A4WWkhQQ@mail.gmail.com> (raw)
In-Reply-To: <CADVnQynJVvFesFYp68N5kzCJJD3-NXPZUUMfkg8m=or4eaLzMQ@mail.gmail.com>
On Tue, Oct 8, 2013 at 7:05 AM, Neal Cardwell <ncardwell@google.com> wrote:
> 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.
Sounds good. Let me do more tests then I will submit a bug fix.
>
> neal
prev parent reply other threads:[~2013-10-08 17:57 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
2013-10-08 17:56 ` Yuchung Cheng [this message]
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