BGP : Fix for nexthop as IPv4 mapped IPv6 address

1. Added a macro to validate the IPv4 Mapped IPv6 address.
2. Modifications done for bgp receive and while sending updates
   for IPv4 Mapped IPv6 address as nexthop.
3. Modifications done for installing IPv4 Mapped IPv6 address as nexthop
   in RIB.
4. Minor correction done in fpm while sending the routes for
   nexthop as IPv4 Mapped IPv6 address.

Signed-off-by: Kaushik <kaushik@niralnetworks.com>

bgpd/bgp_nht.c

@@ -146,6 +146,11 @@ int bgp_find_or_add_nexthop(struct bgp *bgp_route, struct bgp *bgp_nexthop,
 			afi = BGP_ATTR_NEXTHOP_AFI_IP6(pi->attr) ? AFI_IP6
 								 : AFI_IP;
 
+		/* Validation for the ipv4 mapped ipv6 nexthop. */
+		if (IS_MAPPED_IPV6(&pi->attr->mp_nexthop_global)) {
+			afi = AFI_IP;
+		}
+
 		/* This will return true if the global IPv6 NH is a link local
 		 * addr */
 		if (make_prefix(afi, pi, &p) < 0)
@@ -533,6 +538,7 @@ static int make_prefix(int afi, struct bgp_path_info *pi, struct prefix *p)
 				    : 0;
 	struct bgp_dest *net = pi->net;
 	const struct prefix *p_orig = bgp_dest_get_prefix(net);
+	struct in_addr ipv4;
 
 	if (p_orig->family == AF_FLOWSPEC) {
 		if (!pi->peer)
@@ -548,8 +554,15 @@ static int make_prefix(int afi, struct bgp_path_info *pi, struct prefix *p)
 			p->u.prefix4 = p_orig->u.prefix4;
 			p->prefixlen = p_orig->prefixlen;
 		} else {
-			p->u.prefix4 = pi->attr->nexthop;
-			p->prefixlen = IPV4_MAX_BITLEN;
+			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;
+			} else {
+				p->u.prefix4 = pi->attr->nexthop;
+				p->prefixlen = IPV4_MAX_BITLEN;
+			}
 		}
 		break;
 	case AFI_IP6:

bgpd/bgp_updgrp_packet.c

@@ -574,6 +574,18 @@ struct stream *bpacket_reformat_for_peer(struct bpacket *pkt,
 			gnh_modified = 1;
 		}
 
+		if (IN6_IS_ADDR_UNSPECIFIED(mod_v6nhg)) {
+			if (peer->nexthop.v4.s_addr) {
+				ipv4_to_ipv4_mapped_ipv6(mod_v6nhg,
+						peer->nexthop.v4);
+			}
+		}
+
+		if (IS_MAPPED_IPV6(&peer->nexthop.v6_global)) {
+			mod_v6nhg = &peer->nexthop.v6_global;
+			gnh_modified = 1;
+		}
+
 		if (nhlen == BGP_ATTR_NHLEN_IPV6_GLOBAL_AND_LL
 		    || nhlen == BGP_ATTR_NHLEN_VPNV6_GLOBAL_AND_LL) {
 			stream_get_from(&v6nhlocal, s, offset_nhlocal,

lib/ipaddr.h

@@ -93,6 +93,13 @@ static inline char *ipaddr2str(const struct ipaddr *ip, char *buf, int size)
 	return buf;
 }
 
+#define IS_MAPPED_IPV6(A)					\
+	((A)->s6_addr32[0] == 0x00000000			\
+	? ((A)->s6_addr32[1] == 0x00000000			\
+		? (ntohl((A)->s6_addr32[2]) == 0xFFFF ? 1 : 0)	\
+		: 0)						\
+		: 0)
+
 /*
  * Convert IPv4 address to IPv4-mapped IPv6 address which is of the
  * form ::FFFF:<IPv4 address> (RFC 4291). This IPv6 address can then

zebra/rt_netlink.c

@@ -1051,14 +1051,17 @@ static bool _netlink_route_add_gateway_info(uint8_t route_family,
 				 bytelen + 2))
 			return false;
 	} else {
-		if (gw_family == AF_INET) {
-			if (!nl_attr_put(nlmsg, req_size, RTA_GATEWAY,
-					 &nexthop->gate.ipv4, bytelen))
-				return false;
-		} else {
-			if (!nl_attr_put(nlmsg, req_size, RTA_GATEWAY,
-					 &nexthop->gate.ipv6, bytelen))
-				return false;
+		if (!(nexthop->rparent
+		      && IS_MAPPED_IPV6(&nexthop->rparent->gate.ipv6))) {
+			if (gw_family == AF_INET) {
+				if (!nl_attr_put(nlmsg, req_size, RTA_GATEWAY,
+						 &nexthop->gate.ipv4, bytelen))
+					return false;
+			} else {
+				if (!nl_attr_put(nlmsg, req_size, RTA_GATEWAY,
+						 &nexthop->gate.ipv6, bytelen))
+					return false;
+			}
 		}
 	}
 

zebra/zebra_fpm_netlink.c

@@ -364,6 +364,7 @@ static int netlink_route_info_encode(struct netlink_route_info *ri,
 	struct rtattr *nest, *inner_nest;
 	struct rtnexthop *rtnh;
 	struct vxlan_encap_info_t *vxlan;
+	struct in6_addr ipv6;
 
 	struct {
 		struct nlmsghdr n;
@@ -423,8 +424,15 @@ static int netlink_route_info_encode(struct netlink_route_info *ri,
 		nhi = &ri->nhs[0];
 
 		if (nhi->gateway) {
-			nl_attr_put(&req->n, in_buf_len, RTA_GATEWAY,
-				    nhi->gateway, bytelen);
+			if (nhi->type == NEXTHOP_TYPE_IPV4_IFINDEX
+			    && ri->af == AF_INET6) {
+				ipv4_to_ipv4_mapped_ipv6(&ipv6,
+							 nhi->gateway->ipv4);
+				nl_attr_put(&req->n, in_buf_len, RTA_GATEWAY,
+					    &ipv6, bytelen);
+			} else
+				nl_attr_put(&req->n, in_buf_len, RTA_GATEWAY,
+					    nhi->gateway, bytelen);
 		}
 
 		if (nhi->if_index) {

zebra/zebra_nhg.c

@@ -1775,6 +1775,7 @@ static int nexthop_active(afi_t afi, struct route_entry *re,
 	struct interface *ifp;
 	rib_dest_t *dest;
 	struct zebra_vrf *zvrf;
+	struct in_addr ipv4;
 
 	if ((nexthop->type == NEXTHOP_TYPE_IPV4)
 	    || nexthop->type == NEXTHOP_TYPE_IPV6)
@@ -1835,13 +1836,23 @@ static int nexthop_active(afi_t afi, struct route_entry *re,
 		return 0;
 	}
 
+	/* Validation for ipv4 mapped ipv6 nexthop. */
+	if (IS_MAPPED_IPV6(&nexthop->gate.ipv6)) {
+		afi = AFI_IP;
+	}
+
 	/* Make lookup prefix. */
 	memset(&p, 0, sizeof(struct prefix));
 	switch (afi) {
 	case AFI_IP:
 		p.family = AF_INET;
 		p.prefixlen = IPV4_MAX_PREFIXLEN;
-		p.u.prefix4 = nexthop->gate.ipv4;
+		if (IS_MAPPED_IPV6(&nexthop->gate.ipv6)) {
+			ipv4_mapped_ipv6_to_ipv4(&nexthop->gate.ipv6, &ipv4);
+			p.u.prefix4 = ipv4;
+		} else {
+			p.u.prefix4 = nexthop->gate.ipv4;
+		}
 		break;
 	case AFI_IP6:
 		p.family = AF_INET6;