bpf: Handle ipv6 gateway in bpf_ipv4_fib_lookup

Update bpf_ipv4_fib_lookup to handle an ipv6 gateway.
Signed-off-by: NDavid Ahern <dsahern@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/filter.c

@@ -4639,15 +4639,26 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 		return BPF_FIB_LKUP_RET_UNSUPP_LWT;
 
 	dev = nhc->nhc_dev;
-	if (nhc->nhc_gw_family)
-		params->ipv4_dst = nhc->nhc_gw.ipv4;
 
 	params->rt_metric = res.fi->fib_priority;
 
 	/* xdp and cls_bpf programs are run in RCU-bh so
 	 * rcu_read_lock_bh is not needed here
 	 */
-	neigh = __ipv4_neigh_lookup_noref(dev, (__force u32)params->ipv4_dst);
+	if (likely(nhc->nhc_gw_family != AF_INET6)) {
+		if (nhc->nhc_gw_family)
+			params->ipv4_dst = nhc->nhc_gw.ipv4;
+
+		neigh = __ipv4_neigh_lookup_noref(dev,
+						 (__force u32)params->ipv4_dst);
+	} else {
+		struct in6_addr *dst = (struct in6_addr *)params->ipv6_dst;
+
+		params->family = AF_INET6;
+		*dst = nhc->nhc_gw.ipv6;
+		neigh = __ipv6_neigh_lookup_noref_stub(dev, dst);
+	}
+
 	if (!neigh)
 		return BPF_FIB_LKUP_RET_NO_NEIGH;