ip6mr: Add API for default_rule fib

Add the ability to discern whether a given FIB rule notification relates
to the default rule inserted when registering ip6mr or a different one.

Would later be used by drivers wishing to offload ipv6 multicast routes
but unable to offload rules other than the default one.

Signed-off-by: Yuval Mintz <[e-mail]>
Signed-off-by: Ido Schimmel <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/mroute6.h

···
 #include <net/net_namespace.h>
 #include <uapi/linux/mroute6.h>
 #include <linux/mroute_base.h>
+#include <net/fib_rules.h>
 
 #ifdef CONFIG_IPV6_MROUTE
 static inline int ip6_mroute_opt(int opt)
···
 static inline void ip6_mr_cleanup(void)
 {
 	return;
+}
+#endif
+
+#ifdef CONFIG_IPV6_MROUTE_MULTIPLE_TABLES
+bool ip6mr_rule_default(const struct fib_rule *rule);
+#else
+static inline bool ip6mr_rule_default(const struct fib_rule *rule)
+{
+	return true;
 }
 #endif
 

net/ipv6/ip6mr.c

···
 {
 	return fib_rules_seq_read(net, RTNL_FAMILY_IP6MR);
 }
+
+bool ip6mr_rule_default(const struct fib_rule *rule)
+{
+	return fib_rule_matchall(rule) && rule->action == FR_ACT_TO_TBL &&
+	       rule->table == RT6_TABLE_DFLT && !rule->l3mdev;
+}
+EXPORT_SYMBOL(ip6mr_rule_default);
 #else
 #define ip6mr_for_each_table(mrt, net) \
 	for (mrt = net->ipv6.mrt6; mrt; mrt = NULL)