netdev - Re: [PATCH net] tcp: purge write queue upon RST

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Message-Id: <20180228.114240.1711766040670948234.davem@davemloft.net>
Date:   Wed, 28 Feb 2018 11:42:40 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     soheil.kdev@...il.com
Cc:     netdev@...r.kernel.org, edumazet@...gle.com, willemb@...gle.com,
        soheil@...gle.com, ycheng@...gle.com, ncardwell@...gle.com
Subject: Re: [PATCH net] tcp: purge write queue upon RST

From: Soheil Hassas Yeganeh <soheil.kdev@...il.com>
Date: Tue, 27 Feb 2018 18:32:18 -0500

> From: Soheil Hassas Yeganeh <soheil@...gle.com>
> 
> When the connection is reset, there is no point in
> keeping the packets on the write queue until the connection
> is closed.
> 
> RFC 793 (page 70) and RFC 793-bis (page 64) both suggest
> purging the write queue upon RST:
> https://tools.ietf.org/html/draft-ietf-tcpm-rfc793bis-07
> 
> Moreover, this is essential for a correct MSG_ZEROCOPY
> implementation, because userspace cannot call close(fd)
> before receiving zerocopy signals even when the connection
> is reset.
> 
> Fixes: f214f915e7db ("tcp: enable MSG_ZEROCOPY")
> Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>
> Reviewed-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
> Signed-off-by: Neal Cardwell <ncardwell@...gle.com>

This is one of those "yeah, why have we been doing this all of
this time?" kind of situation.

Let's hope there isn't some subtle side effect, but indeed this
current behavior is broken for MSG_ZEROCOPY.

Applied and queued up for -stable, thanks!