Date: Thu, 17 May 2012 15:13:08 -0700 From: prabhakar lakhera <prabhakar.lakhera@gmail.com> To: freebsd-net@freebsd.org Subject: Re: How to set the IPv6 linklocal scope id for an interface? Message-ID: <CALg%2BrhVNXmor3JSAYmOVG%2BnSEdbJBU15N6AnGxmNUFn81vXx8g@mail.gmail.com> In-Reply-To: <CALg%2BrhVakDqBQdnvwYOsHFNKOo-6dsM2-nk5fGztt7E004hAMA@mail.gmail.com> References: <CALg%2BrhVakDqBQdnvwYOsHFNKOo-6dsM2-nk5fGztt7E004hAMA@mail.gmail.com>
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Removing the hyperlinks (these seem to get appended by gmail:
Hi,
Is there any way for the administrator to set an interface's scope if
for link local scope?
I see that in6_domifattach calls=A0scope6_ifattach which sets the
interface local scope and link local scope for the interface equal to
the ifp index.
scope6_ifattach(struct ifnet *ifp)
{
=A0 =A0 =A0 .....
=A0 =A0 =A0 .....
=A0 =A0 =A0 =A0 /*
=A0 =A0 =A0 =A0 =A0* XXX: IPV6_ADDR_SCOPE_xxx macros are not standard.
=A0 =A0 =A0 =A0 =A0* Should we rather hardcode here?
=A0 =A0 =A0 =A0 =A0*/
=A0 =A0 =A0 =A0 sid->s6id_list[IPV6_ADDR_SCOPE_INTFACELOCAL] =3D ifp->if_in=
dex;
=A0 =A0 =A0 =A0 sid->s6id_list[IPV6_ADDR_SCOPE_LINKLOCAL] =3D ifp->if_index=
;
=A0 =A0 =A0 .....
=A0 =A0 =A0 .....
}
I am trying to avoid the following:
Here's the problem. I have two interfaces A and B on same link. Both
learn RA for the link. One of these is used to add a default route
entry in the routing table. Lets say default router entry for A is
picked, we have the following default route entry:
destination: ::/0
gw: =A0 =A0 =A0 =A0 =A0 =A0 fe80:<A's link local scope id embedded>::<ident=
ifier>
route_ifp: =A0 =A0 A
I used IPv6 address hosted on interface B to send a packet to
destination X and I got back a neighbor redirect from gw destined for
B for X.
However the redirect is dropped. Below is the code from
icmp6_redirect_input that fails a check:
2346
2347 gw6 =3D &(((struct sockaddr_in6
*)rt->rt_gateway)->sin6_addr);
2348 if (bcmp(&src6, gw6, sizeof(struct in6_addr)) !=3D 0)=
{
2349 nd6log((LOG_ERR,
2350 "ICMP6 redirect rejected; "
2351 "not equal to gw-for-src=3D%s (must be sa=
me): "
2352 "%s\n",
2353 ip6_sprintf(ip6buf, gw6),
2354 icmp6_redirect_diag(&src6, &reddst6,
&redtgt6)));
2355 RTFREE_LOCKED(rt);
2356 goto bad;
2357 }
src6 is the router's LLA but since it's received on B, it's embedded
with B's link scope embedded id. So we end up comparing:
=A0 fe80:<A's link local scope id embedded>::<identifier> with
=A0 fe80:<B's link local scope id embedded>::<identifier>
Since ids are different the comparison fails and the redirect is dropped.
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