Re: [PATCH net] net: Avoid receiving packets with an l3mdev on unbound UDP sockets

[David Miller <davem@davemloft.net>]

From: David Ahern <dsa@cumulusnetworks.com>
Date: Mon, 30 Jan 2017 11:52:01 -0700

> On 1/26/17 11:02 AM, Robert Shearman wrote:
>> Packets arriving in a VRF currently are delivered to UDP sockets that
>> aren't bound to any interface. TCP defaults to not delivering packets
>> arriving in a VRF to unbound sockets. IP route lookup and socket
>> transmit both assume that unbound means using the default table and
>> UDP applications that haven't been changed to be aware of VRFs may not
>> function correctly in this case since they may not be able to handle
>> overlapping IP address ranges, or be able to send packets back to the
>> original sender if required.
>> 
>> So add a sysctl, udp_l3mdev_accept, to control this behaviour with it
>> being analgous to the existing tcp_l3mdev_accept, namely to allow a
>> process to have a VRF-global listen socket. Have this default to off
>> as this is the behaviour that users will expect, given that there is
>> no explicit mechanism to set unmodified VRF-unaware application into a
>> default VRF.
>> 
>> Signed-off-by: Robert Shearman <rshearma@brocade.com>
>> ---
>> I've targetted this for the net tree because I believe the expected
>> behaviour is different enough from the current behaviour to be
>> considered a bug. However, this should also apply to the net-next tree
>> as-is if this not deemed a bug.
> 
> Does not apply to net-next; collision in sysctl_net_ipv4.c
> 
> As for the code change, I have updated my unit tests and they all pass with this patch. Not sure why I marked my version as not working last November, but it is all good now.
> 
> Acked-by: David Ahern <dsa@cumulusnetworks.com>
> Tested-by: David Ahern <dsa@cumulusnetworks.com>

The conflict was easy enough to fix up, so I did it myself.

Applied to net-next, thanks.