From: Florian Westphal <fw@strlen.de>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Miller <davem@davemloft.net>,
netdev <netdev@vger.kernel.org>, Florian Westphal <fw@strlen.de>,
Neal Cardwell <ncardwell@google.com>,
Yuchung Cheng <ycheng@google.com>
Subject: Re: [PATCH net-next] tcp: syncookies: extend validity range
Date: Thu, 14 May 2015 23:45:44 +0200 [thread overview]
Message-ID: <20150514214544.GF6179@breakpoint.cc> (raw)
In-Reply-To: <1431638816.27831.80.camel@edumazet-glaptop2.roam.corp.google.com>
Eric Dumazet <eric.dumazet@gmail.com> wrote:
> From: Eric Dumazet <edumazet@google.com>
>
> Now we allow storing more request socks per listener, we might
> hit syncookie mode less often and hit following bug in our stack :
>
> When we send a burst of syncookies, then exit this mode,
> tcp_synq_no_recent_overflow() can return false if the ACK packets coming
> from clients are coming three seconds after the end of syncookie
> episode.
Heh. Indeed. This dates back to original from 1997...
> This is a way too strong requirement and conflicts with rest of
> syncookie code which allows ACK to be aged up to 2 minutes.
>
> Perfectly valid ACK packets are dropped just because clients might be
> in a crowded wifi environment or on another planet.
>
> So let's fix this, and also change tcp_synq_overflow() to not
> dirty a cache line for every syncookie we send, as we are under attack.
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
> As this is an old bug, I chose net-next tree.
Looks great, thanks Eric!
Acked-by: Florian Westphal <fw@strlen.de>
next prev parent reply other threads:[~2015-05-14 21:45 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-14 21:26 [PATCH net-next] tcp: syncookies: extend validity range Eric Dumazet
2015-05-14 21:45 ` Florian Westphal [this message]
2015-05-15 0:12 ` Yuchung Cheng
2015-05-15 2:33 ` David Miller
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