flow_dissector: Fix handling of mixed port and port-range keys

This patch fixes a bug in TC flower filter where rules combining a
specific destination port with a source port range weren't working
correctly.

The specific case was when users tried to configure rules like:

tc filter add dev ens38 ingress protocol ip flower ip_proto udp \
dst_port 5000 src_port 2000-3000 action drop

The root cause was in the flow dissector code. While both
FLOW_DISSECTOR_KEY_PORTS and FLOW_DISSECTOR_KEY_PORTS_RANGE flags
were being set correctly in the classifier, the __skb_flow_dissect_ports()
function was only populating one of them: whichever came first in
the enum check. This meant that when the code needed both a specific
port and a port range, one of them would be left as 0, causing the
filter to not match packets as expected.

Fix it by removing the either/or logic and instead checking and
populating both key types independently when they're in use.

Fixes: 8ffb055 ("cls_flower: Fix the behavior using port ranges with hw-offload")
Reported-by: Qiang Zhang <dtzq01@gmail.com>
Closes: https://lore.kernel.org/netdev/CAPx+-5uvFxkhkz4=j_Xuwkezjn9U6kzKTD5jz4tZ9msSJ0fOJA@mail.gmail.com/
Cc: Yoshiki Komachi <komachi.yoshiki@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20250218043210.732959-2-xiyou.wangcong@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: congwang

net/core/flow_dissector.c

@@ -853,23 +853,30 @@ __skb_flow_dissect_ports(const struct sk_buff *skb,
 			 void *target_container, const void *data,
 			 int nhoff, u8 ip_proto, int hlen)
 {
-	enum flow_dissector_key_id dissector_ports = FLOW_DISSECTOR_KEY_MAX;
-	struct flow_dissector_key_ports *key_ports;
+	struct flow_dissector_key_ports_range *key_ports_range = NULL;
+	struct flow_dissector_key_ports *key_ports = NULL;
+	__be32 ports;
 
 	if (dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_PORTS))
-		dissector_ports = FLOW_DISSECTOR_KEY_PORTS;
-	else if (dissector_uses_key(flow_dissector,
-				    FLOW_DISSECTOR_KEY_PORTS_RANGE))
-		dissector_ports = FLOW_DISSECTOR_KEY_PORTS_RANGE;
+		key_ports = skb_flow_dissector_target(flow_dissector,
+						      FLOW_DISSECTOR_KEY_PORTS,
+						      target_container);
 
-	if (dissector_ports == FLOW_DISSECTOR_KEY_MAX)
+	if (dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_PORTS_RANGE))
+		key_ports_range = skb_flow_dissector_target(flow_dissector,
+							    FLOW_DISSECTOR_KEY_PORTS_RANGE,
+							    target_container);
+
+	if (!key_ports && !key_ports_range)
 		return;
 
-	key_ports = skb_flow_dissector_target(flow_dissector,
-					      dissector_ports,
-					      target_container);
-	key_ports->ports = __skb_flow_get_ports(skb, nhoff, ip_proto,
-						data, hlen);
+	ports = __skb_flow_get_ports(skb, nhoff, ip_proto, data, hlen);
+
+	if (key_ports)
+		key_ports->ports = ports;
+
+	if (key_ports_range)
+		key_ports_range->tp.ports = ports;
 }
 
 static void