net: Set rtm_table to RT_TABLE_COMPAT for ipv6 for tables > 255

Set rtm_table to RT_TABLE_COMPAT for ipv6 for tables > 255 to
keep legacy software happy. This is similar to what was done for
ipv4 in commit 709772e ("net: Fix routing tables with
id > 255 for legacy software").

Signed-off-by: Kalash Nainwal <kalash@arista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/route.c

@@ -4665,7 +4665,7 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
 		table = rt->fib6_table->tb6_id;
 	else
 		table = RT6_TABLE_UNSPEC;
-	rtm->rtm_table = table;
+	rtm->rtm_table = table < 256 ? table : RT_TABLE_COMPAT;
 	if (nla_put_u32(skb, RTA_TABLE, table))
 		goto nla_put_failure;