zebra: keep seg6local information from 'show ipv6 route' consistent w…

…ith iproute2

Srv6 nexthop segments may not be set when configuring seg6local
attributes. This is the case for the following seg6local route:

Dump in vtysh, extract from 'show ipv6 route'
> B>* 2001:db8:1:1:1::/128 [20/0] is directly connected, vrf1, seg6local End.DT46 table 10, seg6 ::, weight 1, 00:02:10

Dump in iproute2, extract from 'ip -6 route show'
> 2001:db8:1:1:1:: nhid 22  encap seg6local action End.DT46 vrftable 10 dev vrf1 proto bgp metric 20 pref medium

As can be seen, the 'seg6 ::' nexthop segment is not visible on iproute2,
because it is not set. Do not display seg6 ipv6 nexthop when not set.

After:
> B>* 2001:db8:1:1:1::/128 [20/0] is directly connected, vrf1, seg6local End.DT46 table 10, weight 1, 00:02:10

Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com>

zebra/zebra_rnh.c

@@ -1538,7 +1538,9 @@ void show_route_nexthop_helper(struct vty *vty, const struct route_entry *re,
 				seg6local_action2str(
 					nexthop->nh_srv6->seg6local_action),
 				buf);
-		vty_out(vty, ", seg6 %pI6", &nexthop->nh_srv6->seg6_segs);
+		if (IPV6_ADDR_CMP(&nexthop->nh_srv6->seg6_segs, &in6addr_any))
+			vty_out(vty, ", seg6 %pI6",
+				&nexthop->nh_srv6->seg6_segs);
 	}
 
 	if (nexthop->weight)