pimd: Fix PIM6 MLD VRF support (use recvmsg() pktinfo)

When receiving MLD messages, prefer pktinfo over msghdr.msg_name for
determining the source interface. The latter is just the VRF master
interface in case of VRF and we need the true interface the packet was
received on instead.

Signed-off-by: Martin Buck <mb-tmp-tvguho.pbz@gromit.dyndns.org>
(cherry picked from commit 374c8dc4dbc8a560036fecdfb3213f690099b869)

diff --git a/pimd/pim6_mld.c b/pimd/pim6_mld.c
index a39d182990bf5c97c0a30b23bac3c05a387a2753..e258a52dc5f8a3e4bf395e1a0fe9ec09b2f9ffcf 100644 (file)
--- a/pimd/pim6_mld.c
+++ b/pimd/pim6_mld.c
@@ -1665,18 +1665,6 @@ static void gm_t_recv(struct event *t)
                goto out_free;
        }
 
-       struct interface *ifp;
-
-       ifp = if_lookup_by_index(pkt_src->sin6_scope_id, pim->vrf->vrf_id);
-       if (!ifp || !ifp->info)
-               goto out_free;
-
-       struct pim_interface *pim_ifp = ifp->info;
-       struct gm_if *gm_ifp = pim_ifp->mld;
-
-       if (!gm_ifp)
-               goto out_free;
-
        for (cmsg = CMSG_FIRSTHDR(mh); cmsg; cmsg = CMSG_NXTHDR(mh, cmsg)) {
                if (cmsg->cmsg_level != SOL_IPV6)
                        continue;
@@ -1695,6 +1683,21 @@ static void gm_t_recv(struct event *t)
                }
        }
 
+       /* Prefer pktinfo as that also works in case of VRF */
+       ifindex_t ifindex = pktinfo ? pktinfo->ipi6_ifindex
+                                   : pkt_src->sin6_scope_id;
+       struct interface *ifp;
+
+       ifp = if_lookup_by_index(ifindex, pim->vrf->vrf_id);
+       if (!ifp || !ifp->info)
+               goto out_free;
+
+       struct pim_interface *pim_ifp = ifp->info;
+       struct gm_if *gm_ifp = pim_ifp->mld;
+
+       if (!gm_ifp)
+               goto out_free;
+
        if (!pktinfo || !hoplimit) {
                zlog_err(log_ifp(
                        "BUG: packet without IPV6_PKTINFO or IPV6_HOPLIMIT"));