From: David Miller <davem@davemloft.net>
To: ilpo.jarvinen@helsinki.fi
Cc: ncardwell@google.com, netdev@vger.kernel.org,
nanditad@google.com, ycheng@google.com, therbert@google.com
Subject: Re: [PATCH 3/5] tcp: use SACKs and DSACKs that arrive on ACKs below snd_una
Date: Sun, 27 Nov 2011 18:57:29 -0500 (EST) [thread overview]
Message-ID: <20111127.185729.461507155117180287.davem@davemloft.net> (raw)
In-Reply-To: <alpine.DEB.2.00.1111170344580.1205@melkinpaasi.cs.helsinki.fi>
From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Thu, 17 Nov 2011 03:52:37 +0200 (EET)
> On Wed, 16 Nov 2011, Neal Cardwell wrote:
>
>> The bug: When the ACK field is below snd_una (which can happen when
>> ACKs are reordered), senders ignored DSACKs (preventing undo) and did
>> not call tcp_fastretrans_alert, so they did not increment
>> prr_delivered to reflect newly-SACKed sequence ranges, and did not
>> call tcp_xmit_retransmit_queue, thus passing up chances to send out
>> more retransmitted and new packets based on any newly-SACKed packets.
>>
>> The change: When the ACK field is below snd_una (the "old_ack" goto
>> label), call tcp_fastretrans_alert to allow undo based on any
>> newly-arrived DSACKs and try to send out more packets based on
>> newly-SACKed packets.
>>
>> Other patches in this series will provide other changes that are
>> necessary to fully fix this problem.
>>
>> Signed-off-by: Neal Cardwell <ncardwell@google.com>
...
> Acked-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Applied to net-next.
> ...unrelated to the fix, I realized that FRTO is not fully thought through
> in this old ACK case, also its RFC seems to lack considerations on what to
> do in such case. ...I'll need to think the FRTO stuff a bit more.
Every feature added to TCP beginning with timestamps has not been well
thought out wrt. reordering. :-)
next prev parent reply other threads:[~2011-11-27 23:57 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-16 18:58 [PATCH 1/5] tcp: make is_dupack a parameter to tcp_fastretrans_alert() Neal Cardwell
2011-11-16 18:58 ` [PATCH 2/5] tcp: use DSACKs that arrive when packets_out is 0 Neal Cardwell
2011-11-17 1:34 ` Ilpo Järvinen
2011-11-27 23:55 ` David Miller
2011-11-16 18:58 ` [PATCH 3/5] tcp: use SACKs and DSACKs that arrive on ACKs below snd_una Neal Cardwell
2011-11-17 1:52 ` Ilpo Järvinen
2011-11-27 23:57 ` David Miller [this message]
2011-11-16 18:58 ` [PATCH 4/5] tcp: allow undo from reordered DSACKs Neal Cardwell
2011-11-17 5:18 ` Ilpo Järvinen
2011-11-17 20:49 ` Neal Cardwell
2011-11-22 12:44 ` Ilpo Järvinen
2011-11-27 23:58 ` David Miller
2011-11-28 17:31 ` Neal Cardwell
2011-12-12 12:05 ` [PATCH 1/1] tcp: fix spurious undos in CA_Open Ilpo Järvinen
2011-12-12 19:40 ` Neal Cardwell
2011-12-14 8:57 ` Ilpo Järvinen
2011-12-18 18:23 ` Neal Cardwell
2011-11-16 18:58 ` [PATCH 5/5] tcp: skip cwnd moderation in TCP_CA_Open in tcp_try_to_open Neal Cardwell
2011-11-17 5:14 ` Ilpo Järvinen
2011-11-19 21:08 ` Neal Cardwell
2011-11-20 8:38 ` Ilpo Järvinen
2011-11-21 22:57 ` Yuchung Cheng
2011-11-22 11:47 ` Ilpo Järvinen
2011-11-28 0:01 ` David Miller
2011-11-28 17:35 ` Neal Cardwell
2011-11-28 20:33 ` Yuchung Cheng
2011-11-29 10:33 ` Ilpo Järvinen
2011-11-20 10:19 ` Alexander Zimmermann
2011-11-17 1:23 ` [PATCH 1/5] tcp: make is_dupack a parameter to tcp_fastretrans_alert() Ilpo Järvinen
2011-11-27 23:55 ` David Miller
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