net: Properly update v4 routes with v6 nexthop

When creating a v4 route that uses a v6 nexthop from a nexthop group.
Allow the kernel to properly send the nexthop as v6 via the RTA_VIA
attribute.

Broken behavior:

$ ip nexthop add via fe80::9 dev eth0
$ ip nexthop show
id 1 via fe80::9 dev eth0 scope link
$ ip route add 4.5.6.7/32 nhid 1
$ ip route show
default via 10.0.2.2 dev eth0
4.5.6.7 nhid 1 via 254.128.0.0 dev eth0
10.0.2.0/24 dev eth0 proto kernel scope link src 10.0.2.15
$

Fixed behavior:

$ ip nexthop add via fe80::9 dev eth0
$ ip nexthop show
id 1 via fe80::9 dev eth0 scope link
$ ip route add 4.5.6.7/32 nhid 1
$ ip route show
default via 10.0.2.2 dev eth0
4.5.6.7 nhid 1 via inet6 fe80::9 dev eth0
10.0.2.0/24 dev eth0 proto kernel scope link src 10.0.2.15
$

v2, v3: Addresses code review comments from David Ahern

Fixes: dcb1ecb50edf (“ipv4: Prepare for fib6_nh from a nexthop object”)
Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 977cfd09..85bcd97 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -5333,7 +5333,7 @@ static int rt6_fill_node_nexthop(struct sk_buff *skb, struct nexthop *nh,
 		if (!mp)
 			goto nla_put_failure;
 
-		if (nexthop_mpath_fill_node(skb, nh))
+		if (nexthop_mpath_fill_node(skb, nh, AF_INET6))
 			goto nla_put_failure;
 
 		nla_nest_end(skb, mp);
@@ -5341,7 +5341,7 @@ static int rt6_fill_node_nexthop(struct sk_buff *skb, struct nexthop *nh,
 		struct fib6_nh *fib6_nh;
 
 		fib6_nh = nexthop_fib6_nh(nh);
-		if (fib_nexthop_info(skb, &fib6_nh->nh_common,
+		if (fib_nexthop_info(skb, &fib6_nh->nh_common, AF_INET6,
 				     flags, false) < 0)
 			goto nla_put_failure;
 	}
@@ -5470,13 +5470,14 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
 			goto nla_put_failure;
 
 		if (fib_add_nexthop(skb, &rt->fib6_nh->nh_common,
-				    rt->fib6_nh->fib_nh_weight) < 0)
+				    rt->fib6_nh->fib_nh_weight, AF_INET6) < 0)
 			goto nla_put_failure;
 
 		list_for_each_entry_safe(sibling, next_sibling,
 					 &rt->fib6_siblings, fib6_siblings) {
 			if (fib_add_nexthop(skb, &sibling->fib6_nh->nh_common,
-					    sibling->fib6_nh->fib_nh_weight) < 0)
+					    sibling->fib6_nh->fib_nh_weight,
+					    AF_INET6) < 0)
 				goto nla_put_failure;
 		}
 
@@ -5493,7 +5494,7 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
 
 		rtm->rtm_flags |= nh_flags;
 	} else {
-		if (fib_nexthop_info(skb, &rt->fib6_nh->nh_common,
+		if (fib_nexthop_info(skb, &rt->fib6_nh->nh_common, AF_INET6,
 				     &nh_flags, false) < 0)
 			goto nla_put_failure;