ipv4: fib_rules: Add port mask matching

Extend IPv4 FIB rules to match on source and destination ports using a
mask. Note that the mask is only set when not matching on a range.

Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20250217134109.311176-4-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/fib_rules.h

@@ -148,6 +148,17 @@ static inline bool fib_rule_port_inrange(const struct fib_rule_port_range *a,
 		ntohs(port) <= a->end;
 }
 
+static inline bool fib_rule_port_match(const struct fib_rule_port_range *range,
+				       u16 port_mask, __be16 port)
+{
+	if ((range->start ^ ntohs(port)) & port_mask)
+		return false;
+	if (!port_mask && fib_rule_port_range_set(range) &&
+	    !fib_rule_port_inrange(range, port))
+		return false;
+	return true;
+}
+
 static inline bool fib_rule_port_range_valid(const struct fib_rule_port_range *a)
 {
 	return a->start != 0 && a->end != 0 && a->end < 0xffff &&

net/ipv4/fib_rules.c

@@ -201,12 +201,12 @@ INDIRECT_CALLABLE_SCOPE int fib4_rule_match(struct fib_rule *rule,
 	if (rule->ip_proto && (rule->ip_proto != fl4->flowi4_proto))
 		return 0;
 
-	if (fib_rule_port_range_set(&rule->sport_range) &&
-	    !fib_rule_port_inrange(&rule->sport_range, fl4->fl4_sport))
+	if (!fib_rule_port_match(&rule->sport_range, rule->sport_mask,
+				 fl4->fl4_sport))
 		return 0;
 
-	if (fib_rule_port_range_set(&rule->dport_range) &&
-	    !fib_rule_port_inrange(&rule->dport_range, fl4->fl4_dport))
+	if (!fib_rule_port_match(&rule->dport_range, rule->dport_mask,
+				 fl4->fl4_dport))
 		return 0;
 
 	return 1;