Re: routing link local addresses: where to put the scope id?

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

> The point I'm asking all this is that I'm investigating why ipf fails to 
> send TCP RSTs over link-local addresses. I've tracked this down as far as 
> that ipf6_fastroute() calls nd6_output() with a gateway route, causing 
> EHOSTUNREACH. My impression is that ipf_fastroute6() fails to tell the 
> routing routines about the LL scope -- I just don't know whether it should 
> do the KAME stuffing before calling  the routing routines or whether it 
> should call rtcache_setdst() with sin6_scope_id filled in?
Stuffing the scope into addr16[1] makes it work (for me).
I tested this on 7.1; I can't tell whether the pre-4.99.11 part is correct.

Shall I file a PR?

Index: ip_fil_netbsd.c
===================================================================
RCS file: /cvsroot/src/sys/external/bsd/ipf/netinet/ip_fil_netbsd.c,v
retrieving revision 1.11
diff -u -p -r1.11 ip_fil_netbsd.c
--- ip_fil_netbsd.c	25 Jul 2014 08:10:39 -0000	1.11
+++ ip_fil_netbsd.c	20 Jul 2017 13:04:22 -0000
@@ -1378,6 +1378,9 @@ ipf_fastroute6(struct mbuf *m0, struct m
 		sockaddr_in6_init(&u.dst6, &fdp->fd_ip6.in6, 0, 0, 0);
 	else
 		sockaddr_in6_init(&u.dst6, &fin->fin_fi.fi_dst.in6, 0, 0, 0);
+	/* KAME */
+	if (IN6_IS_ADDR_LINKLOCAL(&u.dst6.sin6_addr))
+		u.dst6.sin6_addr.s6_addr16[1] = htons(ifp->if_index);
 	dst = &u.dst;
 	rtcache_setdst(ro, dst);
 
@@ -1389,6 +1392,9 @@ ipf_fastroute6(struct mbuf *m0, struct m
 	dst6->sin6_family = AF_INET6;
 	dst6->sin6_len = sizeof(struct sockaddr_in6);
 	dst6->sin6_addr = fin->fin_fi.fi_dst.in6;
+	/* KAME */
+	if (IN6_IS_ADDR_LINKLOCAL(&dst6->sin6_addr))
+		dst6->sin6_addr.s6_addr16[1] = htons(ifp->if_index);
 
 	if (fdp != NULL) {
 		if (IP6_NOTZERO(&fdp->fd_ip6))
@@ -1407,15 +1413,6 @@ ipf_fastroute6(struct mbuf *m0, struct m
 		goto bad;
 	}
 
-	/* KAME */
-# if __NetBSD_Version__ >= 499001100
-	if (IN6_IS_ADDR_LINKLOCAL(&u.dst6.sin6_addr))
-		u.dst6.sin6_addr.s6_addr16[1] = htons(ifp->if_index);
-# else
-	if (IN6_IS_ADDR_LINKLOCAL(&dst6->sin6_addr))
-		dst6->sin6_addr.s6_addr16[1] = htons(ifp->if_index);
-# endif
-
 	{
 # if (__NetBSD_Version__ >= 106010000) && !defined(IN6_LINKMTU)
 		struct in6_ifextra *ife;