From: Florian Westphal <fw@strlen.de>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Florian Westphal <fw@strlen.de>,
David Miller <davem@davemloft.net>,
netdev <netdev@vger.kernel.org>,
Yuchung Cheng <ycheng@google.com>
Subject: Re: [PATCH v2 net] tcp: randomize timestamps on syncookies
Date: Fri, 5 May 2017 11:36:30 +0200 [thread overview]
Message-ID: <20170505093630.GA3233@breakpoint.cc> (raw)
In-Reply-To: <1493950957.7796.36.camel@edumazet-glaptop3.roam.corp.google.com>
Eric Dumazet <eric.dumazet@gmail.com> wrote:
> From: Eric Dumazet <edumazet@google.com>
>
> Whole point of randomization was to hide server uptime, but an attacker
> can simply start a syn flood and TCP generates 'old style' timestamps,
> directly revealing server jiffies value.
>
> Also, TSval sent by the server to a particular remote address vary
> depending on syncookies being sent or not, potentially triggering PAWS
> drops for innocent clients.
>
> Lets implement proper randomization, including for SYNcookies.
Thanks a lot Eric, this works for me (I also tested ipv6 this time ;) )
Minor nit:
net/ipv4/tcp_ipv4.c:154:6: warning: unused variable 'seq' [-Wunused-variable]
Other than this:
Reviewed-by: Florian Westphal <fw@strlen.de>
Tested-by: Florian Westphal <fw@strlen.de>
next prev parent reply other threads:[~2017-05-05 9:36 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-04 22:02 [PATCH net] tcp: randomize timestamps on syncookies Eric Dumazet
2017-05-05 0:24 ` Florian Westphal
2017-05-05 0:32 ` Florian Westphal
2017-05-05 1:59 ` Eric Dumazet
2017-05-05 2:22 ` [PATCH v2 " Eric Dumazet
2017-05-05 9:36 ` Florian Westphal [this message]
2017-05-05 13:46 ` Eric Dumazet
2017-05-05 13:56 ` [PATCH v3 " Eric Dumazet
2017-05-05 16:00 ` David Miller
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