ipv4: Add support to rtable for ipv6 gateway

Add support for an IPv6 gateway to rtable. Since a gateway is either
IPv4 or IPv6, make it a union with rt_gw4 where rt_gw_family decides
which address is in use.

When dumping the route data, encode an ipv6 nexthop using RTA_VIA.
Signed-off-by: David Ahern <dsahern@gmail.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c

@@ -318,6 +318,9 @@ mlxsw_sp_span_gretap4_route(const struct net_device *to_dev,
 	*saddrp = fl4.saddr;
 	if (rt->rt_gw_family == AF_INET)
 		*daddrp = rt->rt_gw4;
+	/* can not offload if route has an IPv6 gateway */
+	else if (rt->rt_gw_family == AF_INET6)
+		dev = NULL;
 
 out:
 	ip_rt_put(rt);

include/net/route.h

@@ -60,7 +60,10 @@ struct rtable {
 	int			rt_iif;
 
 	/* Info on neighbour */
-	__be32			rt_gw4;
+	union {
+		__be32		rt_gw4;
+		struct in6_addr	rt_gw6;
+	};
 
 	/* Miscellaneous cached information */
 	u32			rt_mtu_locked:1,

net/ipv4/route.c

@@ -1535,14 +1535,20 @@ static void rt_set_nexthop(struct rtable *rt, __be32 daddr,
 
 	if (fi) {
 		struct fib_nh_common *nhc = FIB_RES_NHC(*res);
-		struct fib_nh *nh = container_of(nhc, struct fib_nh, nh_common);
+		struct fib_nh *nh;
 
-		if (nh->fib_nh_gw4 && nh->fib_nh_scope == RT_SCOPE_LINK) {
-			rt->rt_gw4 = nh->fib_nh_gw4;
-			rt->rt_gw_family = AF_INET;
+		if (nhc->nhc_gw_family && nhc->nhc_scope == RT_SCOPE_LINK) {
+			rt->rt_gw_family = nhc->nhc_gw_family;
+			/* only INET and INET6 are supported */
+			if (likely(nhc->nhc_gw_family == AF_INET))
+				rt->rt_gw4 = nhc->nhc_gw.ipv4;
+			else
+				rt->rt_gw6 = nhc->nhc_gw.ipv6;
 		}
+
 		ip_dst_init_metrics(&rt->dst, fi->fib_metrics);
 
+		nh = container_of(nhc, struct fib_nh, nh_common);
 #ifdef CONFIG_IP_ROUTE_CLASSID
 		rt->dst.tclassid = nh->nh_tclassid;
 #endif
@@ -2600,6 +2606,8 @@ struct dst_entry *ipv4_blackhole_route(struct net *net, struct dst_entry *dst_or
 		rt->rt_gw_family = ort->rt_gw_family;
 		if (rt->rt_gw_family == AF_INET)
 			rt->rt_gw4 = ort->rt_gw4;
+		else if (rt->rt_gw_family == AF_INET6)
+			rt->rt_gw6 = ort->rt_gw6;
 
 		INIT_LIST_HEAD(&rt->rt_uncached);
 	}
@@ -2679,8 +2687,21 @@ static int rt_fill_info(struct net *net, __be32 dst, __be32 src,
 			goto nla_put_failure;
 	}
 	if (rt->rt_gw_family == AF_INET &&
-	    nla_put_in_addr(skb, RTA_GATEWAY, rt->rt_gw4))
+	    nla_put_in_addr(skb, RTA_GATEWAY, rt->rt_gw4)) {
 		goto nla_put_failure;
+	} else if (rt->rt_gw_family == AF_INET6) {
+		int alen = sizeof(struct in6_addr);
+		struct nlattr *nla;
+		struct rtvia *via;
+
+		nla = nla_reserve(skb, RTA_VIA, alen + 2);
+		if (!nla)
+			goto nla_put_failure;
+
+		via = nla_data(nla);
+		via->rtvia_family = AF_INET6;
+		memcpy(via->rtvia_addr, &rt->rt_gw6, alen);
+	}
 
 	expires = rt->dst.expires;
 	if (expires) {

net/ipv4/xfrm4_policy.c

@@ -100,6 +100,8 @@ static int xfrm4_fill_dst(struct xfrm_dst *xdst, struct net_device *dev,
 	xdst->u.rt.rt_gw_family = rt->rt_gw_family;
 	if (rt->rt_gw_family == AF_INET)
 		xdst->u.rt.rt_gw4 = rt->rt_gw4;
+	else if (rt->rt_gw_family == AF_INET6)
+		xdst->u.rt.rt_gw6 = rt->rt_gw6;
 	xdst->u.rt.rt_pmtu = rt->rt_pmtu;
 	xdst->u.rt.rt_mtu_locked = rt->rt_mtu_locked;
 	INIT_LIST_HEAD(&xdst->u.rt.rt_uncached);

net/mpls/mpls_iptunnel.c

@@ -141,8 +141,9 @@ static int mpls_xmit(struct sk_buff *skb)
 		if (rt->rt_gw_family == AF_INET)
 			err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt->rt_gw4,
 					 skb);
-		else
-			err = -EAFNOSUPPORT;
+		else if (rt->rt_gw_family == AF_INET6)
+			err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt->rt_gw6,
+					 skb);
 	} else if (rt6) {
 		if (ipv6_addr_v4mapped(&rt6->rt6i_gateway)) {
 			/* 6PE (RFC 4798) */