Subject: Re: [PATCH net-next 3/4] ipv4: Use probe_size to check write queue data length

From: Fan Du <[email-masked]>
Date: Wed, 18 Mar 2015 09:37:05 +0800

于 2015年03月10日 20:26, John Heffner 写道:
> NACK.  From RFC4821:
>
>     In addition, the timely loss detection algorithms in most protocols
>     have pre-conditions that SHOULD be satisfied before sending a probe.
>     For example, TCP Fast Retransmit is not robust unless there are
>     sufficient segments following a probe; that is, the sender SHOULD
>     have enough data queued and sufficient receiver window to send the
>     probe plus at least Tcprexmtthresh [RFC2760] additional segments.
>     This restriction may inhibit probing in some protocol states, such as
>     too close to the end of a connection, or when the window is too
>     small.
>

Thanks for pointing this out for me.

My limit understanding is the extra segments is used to trigger fast retransmit,
and the conditions is the count of duplicate ack. Then why needs an extra one more
segment here besides 'reordering' segment to trigger this?

size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
                                             ^^^
btw, any comments for the rest of patches?

-- 
天下英雄出我辈，一入江湖岁月催。
鸿图霸业谈笑间，不胜人生一场醉。
提剑跨骑挥鬼雨，白骨如山鸟惊飞。
尘世如潮人如水，只叹江湖几人回。

来，干了这碗酒，接着解BUG!