netdev - Re: [PATCH net] tcp: do not restart timewait timer on rst reception

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Message-Id: <20180831.231132.2010294491856406070.davem@davemloft.net>
Date:   Fri, 31 Aug 2018 23:11:32 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     fw@...len.de
Cc:     netdev@...r.kernel.org, edumazet@...gle.com
Subject: Re: [PATCH net] tcp: do not restart timewait timer on rst reception

From: Florian Westphal <fw@...len.de>
Date: Thu, 30 Aug 2018 14:24:29 +0200

> RFC 1337 says:
>  ''Ignore RST segments in TIME-WAIT state.
>    If the 2 minute MSL is enforced, this fix avoids all three hazards.''
> 
> So with net.ipv4.tcp_rfc1337=1, expected behaviour is to have TIME-WAIT sk
> expire rather than removing it instantly when a reset is received.
> 
> However, Linux will also re-start the TIME-WAIT timer.
> 
> This causes connect to fail when tying to re-use ports or very long
> delays (until syn retry interval exceeds MSL).
...
> Without this patch, 'ss' shows restarts of tw timer and last packet is
> thus just another pure ack, more than one minute later.
> 
> This restores the original code from commit 283fd6cf0be690a83
> ("Merge in ANK networking jumbo patch") in netdev-vger-cvs.git .
> 
> For some reason the else branch was removed/lost in 1f28b683339f7
> ("Merge in TCP/UDP optimizations and [..]") and timer restart became
> unconditional.
> 
> Reported-by: Michal Tesar <mtesar@...hat.com>
> Signed-off-by: Florian Westphal <fw@...len.de>

Applied and thanks for the packet drill test case :-)