netdev - Re: [PATCH] fix pushed_seq in keepalive / zero window probe timer

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Date:	Mon, 22 Aug 2011 21:41:04 +0800
From:	Li Yu <raise.sail@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	davem@...emloft.net, ilpo.jarvinen@...sinki.fi
Subject: Re: [PATCH] fix pushed_seq in keepalive / zero window probe timer

2011/8/22 Eric Dumazet <eric.dumazet@...il.com>:
> Le lundi 22 août 2011 à 14:57 +0800, Li Yu a écrit :
>> In tcp_write_wakeup(), we may split the probe segment since send window or mss is larger than it.
>> so I think that we should update tp->pushed_seq after tcp_fragment(), is it right? thanks.
>>
>
> I am not sure what you want to fix.
>
> Fact is the skb has the TCPHDR_PSH, even if tcp_transmit_skb() (or
> tcp_fragment()) is/are not able to clone/split it.
>
>

Indeed, you are right. The goal of this patch is to fix tp->pushed_seq
may point to unsent byte seq number.

>> Signed-off-by: Li Yu <raise.sail@...il.com>
>> CC: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
>> CC: David S. Miller <davem@...emloft.net>
>> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
>> index 882e0b0..659a71f 100644
>> --- a/net/ipv4/tcp_output.c
>> +++ b/net/ipv4/tcp_output.c
>> @@ -2784,9 +2784,6 @@ int tcp_write_wakeup(struct sock *sk)
>>               unsigned int mss = tcp_current_mss(sk);
>>               unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
>>
>> -             if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
>> -                     tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
>> -
>>               /* We are probing the opening of a window
>>                * but the window size is != 0
>>                * must have been a result SWS avoidance ( sender )
>> @@ -2803,8 +2800,11 @@ int tcp_write_wakeup(struct sock *sk)
>>               TCP_SKB_CB(skb)->flags |= TCPHDR_PSH;
>>               TCP_SKB_CB(skb)->when = tcp_time_stamp;
>>               err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
>> -             if (!err)
>> +             if (!err) {
>>                       tcp_event_new_data_sent(sk, skb);
>> +                     if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
>> +                             tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
>> +             }
>>               return err;
>>       } else {
>>               if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
>>
>> --
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>
>
>
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