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

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Message-ID: <5508D6C1.2020302@gmail.com>
Date:	Wed, 18 Mar 2015 09:37:05 +0800
From:	Fan Du <fengyuleidian0615@...il.com>
To:	John Heffner <johnwheffner@...il.com>
CC:	Fan Du <fan.du@...el.com>, David Miller <davem@...emloft.net>,
	Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 3/4] ipv4: Use probe_size to check write queue
 data length

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?

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来，干了这碗酒，接着解BUG!
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