From: David Ahern <dsahern@gmail.com>
To: Mahesh Bandewar <maheshb@google.com>, Netdev <netdev@vger.kernel.org>
Cc: Eric Dumazet <edumazet@google.com>,
David Miller <davem@davemloft.net>,
Michael Chan <michael.chan@broadcom.com>,
Daniel Axtens <dja@axtens.net>,
Mahesh Bandewar <mahesh@bandewar.net>
Subject: Re: [PATCH next 0/3] blackhole device to invalidate dst
Date: Sat, 22 Jun 2019 09:35:53 -0600 [thread overview]
Message-ID: <5441f3f1-0672-fbb1-e875-7f8ceb68d719@gmail.com> (raw)
In-Reply-To: <20190622004519.89335-1-maheshb@google.com>
On 6/21/19 6:45 PM, Mahesh Bandewar wrote:
> When we invalidate dst or mark it "dead", we assign 'lo' to
> dst->dev. First of all this assignment is racy and more over,
> it has MTU implications.
>
> The standard dev MTU is 1500 while the Loopback MTU is 64k. TCP
> code when dereferencing the dst don't check if the dst is valid
> or not. TCP when dereferencing a dead-dst while negotiating a
> new connection, may use dst device which is 'lo' instead of
> using the correct device. Consider the following scenario:
>
Why doesn't the TCP code (or any code) check if a cached dst is valid?
That's the whole point of marking it dead - to tell users not to rely on
it.
next prev parent reply other threads:[~2019-06-22 15:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-22 0:45 [PATCH next 0/3] blackhole device to invalidate dst Mahesh Bandewar
2019-06-22 15:35 ` David Ahern [this message]
2019-06-23 23:01 ` Mahesh Bandewar (महेश बंडेवार)
2019-06-25 4:00 ` Michael Chan
2019-06-25 4:17 ` Mahesh Bandewar (महेश बंडेवार)
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