ipv6: fib_rules: Check if rule is a default rule

As explained in commit 3c71006d ("ipv4: fib_rules: Check if rule is
a default rule"), drivers supporting IPv6 FIB offload need to be able to
sanitize the rules they don't support and potentially flush their
tables.

Add an IPv6 helper to check if a FIB rule is a default rule.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip6_fib.h

@@ -295,6 +295,7 @@ int ipv6_route_open(struct inode *inode, struct file *file);
 #ifdef CONFIG_IPV6_MULTIPLE_TABLES
 int fib6_rules_init(void);
 void fib6_rules_cleanup(void);
+bool fib6_rule_default(const struct fib_rule *rule);
 #else
 static inline int               fib6_rules_init(void)
 {
@@ -304,5 +305,9 @@ static inline void              fib6_rules_cleanup(void)
 {
 	return ;
 }
+static inline bool fib6_rule_default(const struct fib_rule *rule)
+{
+	return true;
+}
 #endif
 #endif

net/ipv6/fib6_rules.c

@@ -29,6 +29,26 @@ struct fib6_rule {
 	u8			tclass;
 };
 
+static bool fib6_rule_matchall(const struct fib_rule *rule)
+{
+	struct fib6_rule *r = container_of(rule, struct fib6_rule, common);
+
+	if (r->dst.plen || r->src.plen || r->tclass)
+		return false;
+	return fib_rule_matchall(rule);
+}
+
+bool fib6_rule_default(const struct fib_rule *rule)
+{
+	if (!fib6_rule_matchall(rule) || rule->action != FR_ACT_TO_TBL ||
+	    rule->l3mdev)
+		return false;
+	if (rule->table != RT6_TABLE_LOCAL && rule->table != RT6_TABLE_MAIN)
+		return false;
+	return true;
+}
+EXPORT_SYMBOL_GPL(fib6_rule_default);
+
 struct dst_entry *fib6_rule_lookup(struct net *net, struct flowi6 *fl6,
 				   int flags, pol_lookup_t lookup)
 {