zebra: correctly ignore multicast nl msgs

zebra does not care about _notifications_ from the kernel regarding
multicast routing;  we only use the MR netlink API to request stats from
the kernel by actively sending a RTM_GETROUTE.

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

diff --git a/zebra/rt_netlink.c b/zebra/rt_netlink.c
index ce06f1683df316ecb83cd2b3a02565ad44742f1d..2f9d0ac887a4ff29a0b4b25d148a3685320af161 100644 (file)
--- a/zebra/rt_netlink.c
+++ b/zebra/rt_netlink.c
@@ -1044,7 +1044,6 @@ static int netlink_route_change_read_multicast(struct nlmsghdr *h,
        struct rtmsg *rtm;
        struct rtattr *tb[RTA_MAX + 1];
        struct mcast_route_data *m;
-       struct mcast_route_data mr;
        int iif = 0;
        int count;
        int oif[256];
@@ -1053,12 +1052,8 @@ static int netlink_route_change_read_multicast(struct nlmsghdr *h,
        vrf_id_t vrf;
        int table;
 
-       if (mroute)
-               m = mroute;
-       else {
-               memset(&mr, 0, sizeof(mr));
-               m = &mr;
-       }
+       assert(mroute);
+       m = mroute;
 
        rtm = NLMSG_DATA(h);
 
@@ -1165,9 +1160,19 @@ int netlink_route_change(struct nlmsghdr *h, ns_id_t ns_id, int startup)
                return 0;
        }
 
-       if (!(rtm->rtm_family == AF_INET ||
-             rtm->rtm_family == AF_INET6 ||
-             rtm->rtm_family == RTNL_FAMILY_IPMR )) {
+       switch (rtm->rtm_family) {
+       case AF_INET:
+       case AF_INET6:
+               break;
+
+       case RTNL_FAMILY_IPMR:
+       case RTNL_FAMILY_IP6MR:
+               /* notifications on IPMR are irrelevant to zebra, we only care
+                * about responses to RTM_GETROUTE requests we sent.
+                */
+               return 0;
+
+       default:
                flog_warn(
                        EC_ZEBRA_UNKNOWN_FAMILY,
                        "Invalid address family: %u received from kernel route change: %s",
@@ -1193,10 +1198,14 @@ int netlink_route_change(struct nlmsghdr *h, ns_id_t ns_id, int startup)
                return -1;
        }
 
+       /* these are "magic" kernel-managed *unicast* routes used for
+        * outputting locally generated multicast traffic (which uses unicast
+        * handling on Linux because ~reasons~.
+        */
        if (rtm->rtm_type == RTN_MULTICAST)
-               netlink_route_change_read_multicast(h, ns_id, startup);
-       else
-               netlink_route_change_read_unicast(h, ns_id, startup);
+               return 0;
+
+       netlink_route_change_read_unicast(h, ns_id, startup);
        return 0;
 }