netdev - Re: [PATCH v2 1/1] tcp: fixing TLP's FIN recovery

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Date:	Thu, 12 Jun 2014 10:36:42 -0700
From:	Nandita Dukkipati <nanditad@...gle.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Per Hurtig <per.hurtig@....se>, panweiping3@...il.com,
	Netdev <netdev@...r.kernel.org>,
	Anna Brunström <anna.brunstrom@....se>,
	mohammad.rajiullah@....se, Neal Cardwell <ncardwell@...gle.com>,
	sergei.shtylyov@...entembedded.com
Subject: Re: [PATCH v2 1/1] tcp: fixing TLP's FIN recovery

On Thu, Jun 12, 2014 at 8:28 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Thu, 2014-06-12 at 17:08 +0200, Per Hurtig wrote:
>> Fix to a problem observed when losing a FIN segment that does not
>> contain data.  In such situations, TLP is unable to recover from
>> *any* tail loss and instead adds at least PTO ms to the
>> retransmission process, i.e., RTO = RTO + PTO.
>>
>> Signed-off-by: Per Hurtig <per.hurtig@....se>
>> ---
>>  net/ipv4/tcp_output.c | 4 +---
>>  1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
>> index ad7549f..819bf0c 100644
>> --- a/net/ipv4/tcp_output.c
>> +++ b/net/ipv4/tcp_output.c
>> @@ -2131,9 +2131,7 @@ void tcp_send_loss_probe(struct sock *sk)
>>       if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
>>               goto rearm_timer;
>>
>> -     /* Probe with zero data doesn't trigger fast recovery. */
>> -     if (skb->len > 0)
>> -             err = __tcp_retransmit_skb(sk, skb);
>> +     err = __tcp_retransmit_skb(sk, skb);
>>
>>       /* Record snd_nxt for loss detection. */
>>       if (likely(!err))
>
> Thanks a lot Per
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Acked-by: Nandita Dukkipati <nanditad@...gle.com>

Thanks Per and Eric. This is nice addition that makes TLP more useful
for tail losses.
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