net/ipv6: need update peer route when modify metric

When we modify the route metric, the peer address's route need also
be updated. Before the fix:

+ ip addr add dev dummy1 2001:db8::1 peer 2001:db8::2 metric 60
+ ip -6 route show dev dummy1
2001:db8::1 proto kernel metric 60 pref medium
2001:db8::2 proto kernel metric 60 pref medium
+ ip addr change dev dummy1 2001:db8::1 peer 2001:db8::2 metric 61
+ ip -6 route show dev dummy1
2001:db8::1 proto kernel metric 61 pref medium
2001:db8::2 proto kernel metric 60 pref medium

After the fix:
+ ip addr change dev dummy1 2001:db8::1 peer 2001:db8::2 metric 61
+ ip -6 route show dev dummy1
2001:db8::1 proto kernel metric 61 pref medium
2001:db8::2 proto kernel metric 61 pref medium

Fixes: 8308f3ff ("net/ipv6: Add support for specifying metric of connected routes")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/addrconf.c

@@ -4586,12 +4586,14 @@ inet6_rtm_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh,
 }
 
 static int modify_prefix_route(struct inet6_ifaddr *ifp,
-			       unsigned long expires, u32 flags)
+			       unsigned long expires, u32 flags,
+			       bool modify_peer)
 {
 	struct fib6_info *f6i;
 	u32 prio;
 
-	f6i = addrconf_get_prefix_route(&ifp->addr, ifp->prefix_len,
+	f6i = addrconf_get_prefix_route(modify_peer ? &ifp->peer_addr : &ifp->addr,
+					ifp->prefix_len,
 					ifp->idev->dev, 0, RTF_DEFAULT, true);
 	if (!f6i)
 		return -ENOENT;
@@ -4602,7 +4604,8 @@ static int modify_prefix_route(struct inet6_ifaddr *ifp,
 		ip6_del_rt(dev_net(ifp->idev->dev), f6i);
 
 		/* add new one */
-		addrconf_prefix_route(&ifp->addr, ifp->prefix_len,
+		addrconf_prefix_route(modify_peer ? &ifp->peer_addr : &ifp->addr,
+				      ifp->prefix_len,
 				      ifp->rt_priority, ifp->idev->dev,
 				      expires, flags, GFP_KERNEL);
 	} else {
@@ -4678,7 +4681,7 @@ static int inet6_addr_modify(struct inet6_ifaddr *ifp, struct ifa6_config *cfg)
 		int rc = -ENOENT;
 
 		if (had_prefixroute)
-			rc = modify_prefix_route(ifp, expires, flags);
+			rc = modify_prefix_route(ifp, expires, flags, false);
 
 		/* prefix route could have been deleted; if so restore it */
 		if (rc == -ENOENT) {
@@ -4686,6 +4689,15 @@ static int inet6_addr_modify(struct inet6_ifaddr *ifp, struct ifa6_config *cfg)
 					      ifp->rt_priority, ifp->idev->dev,
 					      expires, flags, GFP_KERNEL);
 		}
+
+		if (had_prefixroute && !ipv6_addr_any(&ifp->peer_addr))
+			rc = modify_prefix_route(ifp, expires, flags, true);
+
+		if (rc == -ENOENT && !ipv6_addr_any(&ifp->peer_addr)) {
+			addrconf_prefix_route(&ifp->peer_addr, ifp->prefix_len,
+					      ifp->rt_priority, ifp->idev->dev,
+					      expires, flags, GFP_KERNEL);
+		}
 	} else if (had_prefixroute) {
 		enum cleanup_prefix_rt_t action;
 		unsigned long rt_expires;