Re: [PATCH 0/4] Prevent UDP tunnels from operating on garbage socket

[David Miller <davem@davemloft.net>]

From: David Miller <davem@davemloft.net>
Date: Mon, 06 Apr 2015 12:41:14 -0400 (EDT)

> Tom if you are saying that skb->sk should be reset to the tunnel
> socket, that doesn't work and is completely broken.

Thinking some more, I think what you are missing is that deeper in the
ipv4/ipv6 transmit call chain we do things like sk_mc_loop() etc. on
the socket and we cannot just do it on skb->sk.

To make that work correctly we must pass the tunnel socket down
through the ipv4/ipv6 packet output paths, via netfilter hooks
if necessary.

I am also really disappointed with the call signature of the udp
tunnel send paths.  You have to be honest with yourself and agree
that something with 11 arguments is not a well designed interface.

Now that hopefully you can see that the socket is actually required,
can possibly use that to trim the function signature down for
udp_tunnel{,6}_xmit_skb()?

Worst case, make a "struct udp_tunnel_state" just like I made a "struct
nf_hook_state" for the netfilter hooks.

Thanks.