[RESEND]tc-flower not worked when configured dst_port and src_port range in one rule.

Hi, all.

recently met an issue: tc-flower not worked when configured dst_port
and src_port range in one rule.

detailed like this:
$ tc qdisc add dev ens38 ingress
$ tc filter add dev ens38 ingress protocol ip flower ip_proto udp \
  dst_port 5000 src_port 2000-3000 action drop

I try to find the root cause in kernel source code:
1. FLOW_DISSECTOR_KEY_PORTS and FLOW_DISSECTOR_KEY_PORTS_RANGE flag of
mask->dissector were set
in fl_classify from flow_dissector.c.
2. then skb_flow_dissect -> __skb_flow_dissect -> __skb_flow_dissect_ports.
3. FLOW_DISSECTOR_KEY_PORTS handled and FLOW_DISSECTOR_KEY_PORTS_RANGE
not handled
in __skb_flow_dissect_ports, so tp_range.tp.src was 0 here expected
the actual skb source port.

By the way, __skb_flow_bpf_to_target function may has the same issue.

Please help confirm and fix it, thank you.

source code of __skb_flow_dissect_ports in flow_dissector.c as below:

static void
__skb_flow_dissect_ports(const struct sk_buff *skb,
struct flow_dissector *flow_dissector,
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;

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;

if (dissector_ports == FLOW_DISSECTOR_KEY_MAX)
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);
}

Best regards.

On Fri, Feb 14, 2025 at 05:00:30PM +0800, Qiang Zhang wrote:

Hi, all.

recently met an issue: tc-flower not worked when configured dst_port
and src_port range in one rule.

detailed like this:
$ tc qdisc add dev ens38 ingress
$ tc filter add dev ens38 ingress protocol ip flower ip_proto udp \
  dst_port 5000 src_port 2000-3000 action drop

I try to find the root cause in kernel source code:
1. FLOW_DISSECTOR_KEY_PORTS and FLOW_DISSECTOR_KEY_PORTS_RANGE flag of
mask->dissector were set
in fl_classify from flow_dissector.c.
2. then skb_flow_dissect -> __skb_flow_dissect -> __skb_flow_dissect_ports.
3. FLOW_DISSECTOR_KEY_PORTS handled and FLOW_DISSECTOR_KEY_PORTS_RANGE
not handled
in __skb_flow_dissect_ports, so tp_range.tp.src was 0 here expected
the actual skb source port.

By the way, __skb_flow_bpf_to_target function may has the same issue.

Please help confirm and fix it, thank you.

Thanks for your analysis and report!

I think you are right, please try the following patch. I tested it by
myself and I am working on a selftest to cover this case.

---

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 5db41bf2ed93..c33af3ef0b79 100644
--- a/net/core/flow_dissector.c
+++ b/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