net: ipv6: Compare lwstate in detecting duplicate nexthops

Lennert reported a failure to add different mpls encaps in a multipath
route:

  $ ip -6 route add 1234::/16 \
        nexthop encap mpls 10 via fe80::1 dev ens3 \
        nexthop encap mpls 20 via fe80::1 dev ens3
  RTNETLINK answers: File exists

The problem is that the duplicate nexthop detection does not compare
lwtunnel configuration. Add it.

Fixes: 19e42e45 ("ipv6: support for fib route lwtunnel encap attributes")
Signed-off-by: David Ahern <dsahern@gmail.com>
Reported-by: João Taveira Araújo <joao.taveira@gmail.com>
Reported-by: Lennert Buytenhek <buytenh@wantstofly.org>
Acked-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Tested-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip6_route.h

@@ -22,6 +22,7 @@ struct route_info {
 #include <net/flow.h>
 #include <net/ip6_fib.h>
 #include <net/sock.h>
+#include <net/lwtunnel.h>
 #include <linux/ip.h>
 #include <linux/ipv6.h>
 #include <linux/route.h>
@@ -232,4 +233,11 @@ static inline struct in6_addr *rt6_nexthop(struct rt6_info *rt,
 		return daddr;
 }
 
+static inline bool rt6_duplicate_nexthop(struct rt6_info *a, struct rt6_info *b)
+{
+	return a->dst.dev == b->dst.dev &&
+	       a->rt6i_idev == b->rt6i_idev &&
+	       ipv6_addr_equal(&a->rt6i_gateway, &b->rt6i_gateway) &&
+	       !lwtunnel_cmp_encap(a->dst.lwtstate, b->dst.lwtstate);
+}
 #endif

net/ipv6/ip6_fib.c

@@ -786,10 +786,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
 				goto next_iter;
 			}
 
-			if (iter->dst.dev == rt->dst.dev &&
-			    iter->rt6i_idev == rt->rt6i_idev &&
-			    ipv6_addr_equal(&iter->rt6i_gateway,
-					    &rt->rt6i_gateway)) {
+			if (rt6_duplicate_nexthop(iter, rt)) {
 				if (rt->rt6i_nsiblings)
 					rt->rt6i_nsiblings = 0;
 				if (!(iter->rt6i_flags & RTF_EXPIRES))

net/ipv6/route.c

@@ -3036,17 +3036,11 @@ static int ip6_route_info_append(struct list_head *rt6_nh_list,
 				 struct rt6_info *rt, struct fib6_config *r_cfg)
 {
 	struct rt6_nh *nh;
-	struct rt6_info *rtnh;
 	int err = -EEXIST;
 
 	list_for_each_entry(nh, rt6_nh_list, next) {
 		/* check if rt6_info already exists */
-		rtnh = nh->rt6_info;
-
-		if (rtnh->dst.dev == rt->dst.dev &&
-		    rtnh->rt6i_idev == rt->rt6i_idev &&
-		    ipv6_addr_equal(&rtnh->rt6i_gateway,
-				    &rt->rt6i_gateway))
+		if (rt6_duplicate_nexthop(nh->rt6_info, rt))
 			return err;
 	}