Merge pull request #16439 from louis-6wind/fix-ipv4-mapped-ipv6

bgpd: fixes for ipv4 mapped ipv6 address

bgpd/bgp_nht.c

@@ -351,7 +351,9 @@ int bgp_find_or_add_nexthop(struct bgp *bgp_route, struct bgp *bgp_nexthop,
 			}
 			return 0;
 		}
-
+		if (afi == AFI_IP6 && p.family == AF_INET)
+			/* IPv4 mapped IPv6 nexthop address */
+			afi = AFI_IP;
 		srte_color = bgp_attr_get_color(pi->attr);
 
 	} else if (peer) {
@@ -1078,14 +1080,25 @@ static int make_prefix(int afi, struct bgp_path_info *pi, struct prefix *p)
 							&ipv4);
 						p->u.prefix4 = ipv4;
 						p->prefixlen = IPV4_MAX_BITLEN;
+						p->family = AF_INET;
 					} else
 						p->u.prefix6 =
 							pi->attr->mp_nexthop_global;
 				} else
 					p->u.prefix6 =
 						pi->attr->mp_nexthop_local;
-			} else
+			} else {
-				p->u.prefix6 = pi->attr->mp_nexthop_global;
+				if (IS_MAPPED_IPV6(
+					    &pi->attr->mp_nexthop_global)) {
+					ipv4_mapped_ipv6_to_ipv4(&pi->attr->mp_nexthop_global,
+								 &ipv4);
+					p->u.prefix4 = ipv4;
+					p->prefixlen = IPV4_MAX_BITLEN;
+					p->family = AF_INET;
+				} else
+					p->u.prefix6 =
+						pi->attr->mp_nexthop_global;
+			}
 		}
 		break;
 	default:

bgpd/bgp_updgrp_packet.c

@@ -508,6 +508,9 @@ struct stream *bpacket_reformat_for_peer(struct bpacket *pkt,
 				gnh_modified = 1;
 			}
 		} else if (IN6_IS_ADDR_UNSPECIFIED(&v6nhglobal)) {
+			/* the UPDATE is originating from the local router.
+			 * Build the global nexthop.
+			 */
 			mod_v6nhg = &peer->nexthop.v6_global;
 			gnh_modified = 1;
 		} else if ((peer->sort == BGP_PEER_EBGP)
@@ -521,18 +524,32 @@ struct stream *bpacket_reformat_for_peer(struct bpacket *pkt,
 			 */
 			mod_v6nhg = &peer->nexthop.v6_global;
 			gnh_modified = 1;
+		} else if (IS_MAPPED_IPV6(&v6nhglobal) &&
+			   !IN6_IS_ADDR_LINKLOCAL(&peer->nexthop.v6_global)) {
+			/* prefer a IPv6 native global address over
+			 * an IPv4-mapped IPv6 address as nexthop when
+			 * forwarding UPDATEs.
+			 */
+			mod_v6nhg = &peer->nexthop.v6_global;
+			gnh_modified = 1;
 		}
 
 		if (peer->nexthop.v4.s_addr != INADDR_ANY &&
 		    (IN6_IS_ADDR_UNSPECIFIED(mod_v6nhg) ||
 		     (IN6_IS_ADDR_LINKLOCAL(mod_v6nhg) &&
-		      peer->connection->su.sa.sa_family == AF_INET6 &&
+		      ((peer->connection->su.sa.sa_family == AF_INET6 &&
-		      paf->afi == AFI_IP))) {
+			paf->afi == AFI_IP) ||
+		       (peer->connection->su.sa.sa_family == AF_INET &&
+			paf->afi == AFI_IP6))))) {
 			ipv4_to_ipv4_mapped_ipv6(mod_v6nhg, peer->nexthop.v4);
 			gnh_modified = 1;
 		}
 
 		if (IS_MAPPED_IPV6(&peer->nexthop.v6_global)) {
+			/* If the interface to the peer has no global IPv6
+			 * address, replace the nexthop in UPDATE with
+			 * the IPv4-mapped IPv6 address if any.
+			 */
 			mod_v6nhg = &peer->nexthop.v6_global;
 			gnh_modified = 1;
 		}

tests/topotests/bgp_nexthop_mp_ipv4_6/r2/bgp_ipv6_step2.json

@@ -6,6 +6,11 @@
         "bestpath": true,
         "path": "65100",
         "nexthops": [
+          {
+            "ip": "::ffff:ac10:1",
+            "afi": "ipv6",
+            "scope": "global"
+          },
           {
             "afi": "ipv6",
             "scope": "link-local",

tests/topotests/bgp_nexthop_mp_ipv4_6/r3/bgp_ipv6_step2.json

@@ -6,6 +6,11 @@
         "bestpath": true,
         "path": "65100",
         "nexthops": [
+          {
+            "ip": "::ffff:ac10:101",
+            "afi": "ipv6",
+            "scope": "global"
+          },
           {
             "afi": "ipv6",
             "scope": "link-local",