kern/75121: Wrong behaviour of IFF_LINK2 bit in 6in6 gifs?

[Gleb Smirnoff]

The following reply was made to PR kern/75121; it has been noted by GNATS.

From: Gleb Smirnoff <glebius at freebsd.org>
To: Antonio Tapiador del Dujo <atapiador at dit.upm.es>
Cc: FreeBSD-gnats-submit at freebsd.org
Subject: Re: kern/75121: Wrong behaviour of IFF_LINK2 bit in 6in6 gifs?
Date: Tue, 18 Jan 2005 13:57:51 +0300

   Antonio,
 
 On Wed, Dec 15, 2004 at 07:22:00PM +0100, Antonio Tapiador del Dujo wrote:
 A> >Description:
 A> I'm researching on IPv6 multihoming.
 A> I need a generic 6in6 tunnel interface that accepts packets from any source, so I tried with the IFF_LINK2 as said in gif(4), but it didn't work.
 A> Looking at the code, I found out the address checks are done regardless of the IFF_LINK2 (netinet6/in6_gif.c, line 318)
 A> Shouldn't these checks take into account the IFF_LINK2?
 A> Moving them inside the next if works as I expected.
 
 No they shouldn't. Perhaps you have some misconfiguration with your tunnels.
 If you have tunnel configured as X <-> Y on machine A, then you MUST have
 tunnel configured Y <-> X on machine B. This is requirement for gif protocol.
 Otherwise you will have odd and undefined behavior, when multiple tunnels
 terminate on one box.
 
 The IFF_LINK2 means that incoming tunnel packets may come from interface
 different to interface we use for sending out tunnel packets.
 
 If you don't mind, I close the PR.
 
 -- 
 Totus tuus, Glebius.
 GLEBIUS-RIPN GLEB-RIPE