netdev - Re: [PATCH net] udp: fix bcast packet reception

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Message-Id: <20171009.102918.193745106051263192.davem@davemloft.net>
Date:   Mon, 09 Oct 2017 10:29:18 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     pabeni@...hat.com
Cc:     netdev@...r.kernel.org, hannes@...essinduktion.org
Subject: Re: [PATCH net] udp: fix bcast packet reception

From: Paolo Abeni <pabeni@...hat.com>
Date: Mon,  9 Oct 2017 14:52:10 +0200

> The commit bc044e8db796 ("udp: perform source validation for
> mcast early demux") does not take into account that broadcast packets
> lands in the same code path and they need different checks for the
> source address - notably, zero source address are valid for bcast
> and invalid for mcast.
> 
> As a result, 2nd and later broadcast packets with 0 source address
> landing to the same socket are dropped. This breaks dhcp servers.
> 
> Since we don't have stringent performance requirements for ingress
> broadcast traffic, fix it by disabling UDP early demux such traffic.
> 
> Reported-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
> Fixes: bc044e8db796 ("udp: perform source validation for mcast early demux")
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>

Applied and queued up for -stable.