netdev - Re: [PATCH net] net: vxlan: fix crash when interface is created with no group

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Date:	Fri, 21 Mar 2014 05:22:06 -0600
From:	David Stevens <dlstevens@...ibm.com>
To:	Mike Rapoport <mike.rapoport@...ellosystems.com>
Cc:	David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] net: vxlan: fix crash when interface is created with no
 group

-----Mike Rapoport <mike.rapoport@...ellosystems.com> wrote: -----

>Checking skb->protocol will drop ARP requests. What about using
>ip_hdr(skb)->version?

Mike, ip_hdr() here is the outer packet, so it's got to be a UDP packet--
we just don't know if it's UDP/IP or UDP/IPv6 when it is bound to INADDR_ANY,
since both can be delivered. It could use version in this case, because
both possible protocols have version in the same place, but I think it's
more correct to use the MAC layer protocol rather than relying on the
fact that IPv4 and IPv6 have "version" in the same spot. "It could be ARP"
would be the argument for NOT using the version in places where it really
could be ARP, even though that isn't the case here.

vxlan_rcv() is only called for VXLAN encapsulated packets sent to the bound
UDP port.

So, if "vs->family" holds the one we want to support, we can't just blindly
assume the received packet is IPv4, for example, and start accessing
IPv4 fields, because it could be an IPv6 packet. We have to check the
packet type too. And if it's not the one we bound to, drop it.

That's what the code snippet I outlined is trying to do.

                                         +-DLS

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