zebra: evpn: not coerce VTEP IP to IPv4 in nh_list

In L3 BGP-EVPN, if there are both IPv4 and IPv6 routes in the VPN, zebra
maintains two instances of `struct zebra_neigh` object: one with IPv4
address of the nexthop, and another with IPv6 address that is an IPv4
mapped to IPv6, but only one intance of `struct zebra_mac` object, that
contains a list of nexthop addresses that use this mac.

The code in `zebra_vxlan` module uses the fact that the list is empty as
the indication that the `zebra_mac` object is unused, and needs to be
dropped. However, preexisting code used nexthop address converted to
IPv4 notation for the element of this list. As a result, when two
`zebra_neigh` objects, one IPv4 and one IPv6-mapped-IPv4 were linked to
the `zebra_mac` object, only one element was added to the list.
Consequently, when one of the two `zebra_neigh` objects was dropped, the
only element in the list was removed, making it empty, and `zebra_mac`
object was dropped, and neigbrour cache elements uninstalled from the
kernel.

As a result, after the last route in _one_ family was removed from a
remote vtep, all remaining routes in the _other_ family became
unreachable, because RMAC of the vtep was removed.

This commit makes `zebra_mac` use uncoerced IP address of the `zebra_neigh`
object for the entries in the `nh_list`. This way, `zebra_mac` object no
longer loses track of `zebra_neigh` objects that need it.

Bug-URL: https://github.com/FRRouting/frr/issues/16340
Signed-off-by: Eugene Crosser <crosser@average.org>

diff --git a/zebra/zebra_vxlan.c b/zebra/zebra_vxlan.c
index b8c11e186a7b9dd0b49de494b7305b1c13dc3c8f..f1ae42e32043be4e478b8cc2868e81f76593a987 100644 (file)
--- a/zebra/zebra_vxlan.c
+++ b/zebra/zebra_vxlan.c
@@ -1356,6 +1356,18 @@ static int zl3vni_remote_rmac_add(struct zebra_l3vni *zl3vni,
 {
        struct zebra_mac *zrmac = NULL;
        struct ipaddr *vtep = NULL;
+       struct ipaddr ipv4_vtep;
+
+       /* vtep_ip may be v4 or v6-mapped-v4. But zrmac->fwd_info
+        * can only contain v4 version. So convert if needed
+        */
+       memset(&ipv4_vtep, 0, sizeof(ipv4_vtep));
+       ipv4_vtep.ipa_type = IPADDR_V4;
+       if (vtep_ip->ipa_type == IPADDR_V6)
+               ipv4_mapped_ipv6_to_ipv4(&vtep_ip->ipaddr_v6,
+                                        &(ipv4_vtep.ipaddr_v4));
+       else
+               IPV4_ADDR_COPY(&(ipv4_vtep.ipaddr_v4), &vtep_ip->ipaddr_v4);
 
        zrmac = zl3vni_rmac_lookup(zl3vni, rmac);
        if (!zrmac) {
@@ -1369,7 +1381,7 @@ static int zl3vni_remote_rmac_add(struct zebra_l3vni *zl3vni,
                        return -1;
                }
                memset(&zrmac->fwd_info, 0, sizeof(zrmac->fwd_info));
-               zrmac->fwd_info.r_vtep_ip = vtep_ip->ipaddr_v4;
+               zrmac->fwd_info.r_vtep_ip = ipv4_vtep.ipaddr_v4;
 
                vtep = XCALLOC(MTYPE_EVPN_VTEP, sizeof(struct ipaddr));
                memcpy(vtep, vtep_ip, sizeof(struct ipaddr));
@@ -1383,14 +1395,14 @@ static int zl3vni_remote_rmac_add(struct zebra_l3vni *zl3vni,
                /* install rmac in kernel */
                zl3vni_rmac_install(zl3vni, zrmac);
        } else if (!IPV4_ADDR_SAME(&zrmac->fwd_info.r_vtep_ip,
-                                  &vtep_ip->ipaddr_v4)) {
+                                  &(ipv4_vtep.ipaddr_v4))) {
                if (IS_ZEBRA_DEBUG_VXLAN)
                        zlog_debug(
                                "L3VNI %u Remote VTEP change(%pI4 -> %pIA) for RMAC %pEA",
                                zl3vni->vni, &zrmac->fwd_info.r_vtep_ip,
                                vtep_ip, rmac);
 
-               zrmac->fwd_info.r_vtep_ip = vtep_ip->ipaddr_v4;
+               zrmac->fwd_info.r_vtep_ip = ipv4_vtep.ipaddr_v4;
 
                vtep = XCALLOC(MTYPE_EVPN_VTEP, sizeof(struct ipaddr));
                memcpy(vtep, vtep_ip, sizeof(struct ipaddr));
@@ -1410,36 +1422,29 @@ static void zl3vni_remote_rmac_del(struct zebra_l3vni *zl3vni,
                                   struct zebra_mac *zrmac,
                                   struct ipaddr *vtep_ip)
 {
-       struct ipaddr ipv4_vtep;
-
        if (!zl3vni_nh_lookup(zl3vni, vtep_ip)) {
-               memset(&ipv4_vtep, 0, sizeof(ipv4_vtep));
-               ipv4_vtep.ipa_type = IPADDR_V4;
-               if (vtep_ip->ipa_type == IPADDR_V6)
-                       ipv4_mapped_ipv6_to_ipv4(&vtep_ip->ipaddr_v6,
-                                                &ipv4_vtep.ipaddr_v4);
-               else
-                       memcpy(&(ipv4_vtep.ipaddr_v4), &vtep_ip->ipaddr_v4,
-                              sizeof(struct in_addr));
-
                /* remove nh from rmac's list */
-               l3vni_rmac_nh_list_nh_delete(zl3vni, zrmac, &ipv4_vtep);
-               /* delete nh is same as current selected, fall back to
-                * one present in the list
-                */
-               if (IPV4_ADDR_SAME(&zrmac->fwd_info.r_vtep_ip,
-                                  &ipv4_vtep.ipaddr_v4) &&
-                   listcount(zrmac->nh_list)) {
+               l3vni_rmac_nh_list_nh_delete(zl3vni, zrmac, vtep_ip);
+               /* If there are remaining entries, use IPv4 from one */
+               if (listcount(zrmac->nh_list)) {
                        struct ipaddr *vtep;
+                       struct ipaddr ipv4_vtep;
 
                        vtep = listgetdata(listhead(zrmac->nh_list));
-                       zrmac->fwd_info.r_vtep_ip = vtep->ipaddr_v4;
+                       memset(&ipv4_vtep, 0, sizeof(ipv4_vtep));
+                       ipv4_vtep.ipa_type = IPADDR_V4;
+                       if (vtep->ipa_type == IPADDR_V6)
+                               ipv4_mapped_ipv6_to_ipv4(&vtep->ipaddr_v6,
+                                                        &(ipv4_vtep.ipaddr_v4));
+                       else
+                               IPV4_ADDR_COPY(&(ipv4_vtep.ipaddr_v4),
+                                              &vtep->ipaddr_v4);
+                       zrmac->fwd_info.r_vtep_ip = ipv4_vtep.ipaddr_v4;
                        if (IS_ZEBRA_DEBUG_VXLAN)
-                               zlog_debug(
-                                       "L3VNI %u Remote VTEP nh change(%pIA -> %pI4) for RMAC %pEA",
-                                       zl3vni->vni, &ipv4_vtep,
-                                       &zrmac->fwd_info.r_vtep_ip,
-                                       &zrmac->macaddr);
+                               zlog_debug("L3VNI %u Remote VTEP nh change(%pIA -> %pI4) for RMAC %pEA",
+                                          zl3vni->vni, vtep_ip,
+                                          &zrmac->fwd_info.r_vtep_ip,
+                                          &zrmac->macaddr);
 
                        /* install rmac in kernel */
                        zl3vni_rmac_install(zl3vni, zrmac);
@@ -2531,7 +2536,6 @@ void zebra_vxlan_evpn_vrf_route_add(vrf_id_t vrf_id, const struct ethaddr *rmac,
                                    const struct prefix *host_prefix)
 {
        struct zebra_l3vni *zl3vni = NULL;
-       struct ipaddr ipv4_vtep;
 
        zl3vni = zl3vni_from_vrf(vrf_id);
        if (!zl3vni || !is_l3vni_oper_up(zl3vni))
@@ -2547,24 +2551,10 @@ void zebra_vxlan_evpn_vrf_route_add(vrf_id_t vrf_id, const struct ethaddr *rmac,
        svd_remote_nh_add(zl3vni, vtep_ip, rmac, host_prefix);
 
        /*
-        * if the remote vtep is a ipv4 mapped ipv6 address convert it to ipv4
-        * address. Rmac is programmed against the ipv4 vtep because we only
-        * support ipv4 tunnels in the h/w right now
-        */
-       memset(&ipv4_vtep, 0, sizeof(ipv4_vtep));
-       ipv4_vtep.ipa_type = IPADDR_V4;
-       if (vtep_ip->ipa_type == IPADDR_V6)
-               ipv4_mapped_ipv6_to_ipv4(&vtep_ip->ipaddr_v6,
-                                        &(ipv4_vtep.ipaddr_v4));
-       else
-               memcpy(&(ipv4_vtep.ipaddr_v4), &vtep_ip->ipaddr_v4,
-                      sizeof(struct in_addr));
-
-       /*
-        * add the rmac - remote rmac to be installed is against the ipv4
+        * add the rmac - remote rmac to be installed is against the
         * nexthop address
         */
-       zl3vni_remote_rmac_add(zl3vni, rmac, &ipv4_vtep);
+       zl3vni_remote_rmac_add(zl3vni, rmac, vtep_ip);
 }
 
 /* handle evpn vrf route delete */