pimd, pim6d: clarify RFC5549 MRIB nexthop handling

The entire `case NEXTHOP_TYPE_IPV6_IFINDEX:` block here was a bit of a
tripwire to stumble over, since there was no indication at all that this
concerns RFC5549 nexthop handling.  So it got mis-adapted for PIM IPv6
support.

Clarify this a whole bunch that this is for v4-over-v6 nexthop mangling,
and nothing else.

This should really also use neighbor's secondary address lists for the
lookup, but that is probably going to break compatibility with other
boxes that don't include v6 addrs in v4 hellos and needs further
machinery to do properly, so for now just leave a breadcrumb.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

diff --git a/pimd/pim_nht.c b/pimd/pim_nht.c
index 94dcfb826558ee85cc8da4423f53907719623948..6845838b65e87f727016d362a431681e770ed245 100644 (file)
--- a/pimd/pim_nht.c
+++ b/pimd/pim_nht.c
@@ -696,9 +696,7 @@ int pim_parse_nexthop_update(ZAPI_CALLBACK_ARGS)
        int i;
        struct pim_rpf rpf;
        struct pim_nexthop_cache *pnc = NULL;
-       struct pim_neighbor *nbr = NULL;
        struct interface *ifp = NULL;
-       struct interface *ifp1 = NULL;
        struct vrf *vrf = vrf_lookup_by_id(vrf_id);
        struct pim_instance *pim;
        struct zapi_route nhr;
@@ -739,11 +737,6 @@ int pim_parse_nexthop_update(ZAPI_CALLBACK_ARGS)
                for (i = 0; i < nhr.nexthop_num; i++) {
                        nexthop = nexthop_from_zapi_nexthop(&nhr.nexthops[i]);
                        switch (nexthop->type) {
-                       case NEXTHOP_TYPE_IPV4:
-                       case NEXTHOP_TYPE_IPV4_IFINDEX:
-                       case NEXTHOP_TYPE_IPV6:
-                       case NEXTHOP_TYPE_BLACKHOLE:
-                               break;
                        case NEXTHOP_TYPE_IFINDEX:
                                /*
                                 * Connected route (i.e. no nexthop), use
@@ -760,31 +753,44 @@ int pim_parse_nexthop_update(ZAPI_CALLBACK_ARGS)
                                        pnc->rpf.rpf_addr.u.prefix6;
 #endif
                                break;
-                       case NEXTHOP_TYPE_IPV6_IFINDEX:
+#if PIM_IPV == 4
+                       /* RFC5549 IPv4-over-IPv6 nexthop handling:
+                        * if we get an IPv6 nexthop in IPv4 PIM, hunt down a
+                        * PIM neighbor and use that instead.
+                        */
+                       case NEXTHOP_TYPE_IPV6_IFINDEX: {
+                               struct interface *ifp1 = NULL;
+                               struct pim_neighbor *nbr = NULL;
+
                                ifp1 = if_lookup_by_index(nexthop->ifindex,
                                                          pim->vrf->vrf_id);
 
                                if (!ifp1)
                                        nbr = NULL;
                                else
+                                       /* FIXME: should really use nbr's
+                                        * secondary address list here
+                                        */
                                        nbr = pim_neighbor_find_if(ifp1);
+
                                /* Overwrite with Nbr address as NH addr */
                                if (nbr)
-#if PIM_IPV == 4
                                        nexthop->gate.ipv4 = nbr->source_addr;
-#else
-                                       nexthop->gate.ipv6 = nbr->source_addr;
-#endif
-                               else {
+                               else
                                        // Mark nexthop address to 0 until PIM
                                        // Nbr is resolved.
-#if PIM_IPV == 4
                                        nexthop->gate.ipv4 = PIMADDR_ANY;
+
+                               break;
+                       }
 #else
-                                       nexthop->gate.ipv6 = PIMADDR_ANY;
+                       case NEXTHOP_TYPE_IPV6_IFINDEX:
 #endif
-                               }
-
+                       case NEXTHOP_TYPE_IPV6:
+                       case NEXTHOP_TYPE_IPV4:
+                       case NEXTHOP_TYPE_IPV4_IFINDEX:
+                       case NEXTHOP_TYPE_BLACKHOLE:
+                               /* nothing to do for the other nexthop types */
                                break;
                        }