net/sched: flow_dissector: Fix matching on zone id for invalid conns

If ct rejects a flow, it removes the conntrack info from the skb.
act_ct sets the post_ct variable so the dissector will see this case
as an +tracked +invalid state, but the zone id is lost with the
conntrack info.

To restore the zone id on such cases, set the last executed zone,
via the tc control block, when passing ct, and read it back in the
dissector if there is no ct info on the skb (invalid connection).

Fixes: 7baf2429 ("net/sched: cls_flower add CT_FLAGS_INVALID flag support")
Signed-off-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/skbuff.h

@@ -1380,7 +1380,7 @@ skb_flow_dissect_ct(const struct sk_buff *skb,
 		    struct flow_dissector *flow_dissector,
 		    void *target_container,
 		    u16 *ctinfo_map, size_t mapsize,
-		    bool post_ct);
+		    bool post_ct, u16 zone);
 void
 skb_flow_dissect_tunnel_info(const struct sk_buff *skb,
 			     struct flow_dissector *flow_dissector,

include/net/pkt_sched.h

@@ -198,6 +198,7 @@ struct tc_skb_cb {
 
 	u16 mru;
 	bool post_ct;
+	u16 zone; /* Only valid if post_ct = true */
 };
 
 static inline struct tc_skb_cb *tc_skb_cb(const struct sk_buff *skb)

net/core/flow_dissector.c

@@ -238,7 +238,7 @@ void
 skb_flow_dissect_ct(const struct sk_buff *skb,
 		    struct flow_dissector *flow_dissector,
 		    void *target_container, u16 *ctinfo_map,
-		    size_t mapsize, bool post_ct)
+		    size_t mapsize, bool post_ct, u16 zone)
 {
 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
 	struct flow_dissector_key_ct *key;
@@ -260,6 +260,7 @@ skb_flow_dissect_ct(const struct sk_buff *skb,
 	if (!ct) {
 		key->ct_state = TCA_FLOWER_KEY_CT_FLAGS_TRACKED |
 				TCA_FLOWER_KEY_CT_FLAGS_INVALID;
+		key->ct_zone = zone;
 		return;
 	}
 

net/sched/act_ct.c

@@ -1049,6 +1049,7 @@ static int tcf_ct_act(struct sk_buff *skb, const struct tc_action *a,
 	skb_push_rcsum(skb, nh_ofs);
 
 	tc_skb_cb(skb)->post_ct = true;
+	tc_skb_cb(skb)->zone = p->zone;
 out_clear:
 	if (defrag)
 		qdisc_skb_cb(skb)->pkt_len = skb->len;

net/sched/cls_flower.c

@@ -311,6 +311,7 @@ static int fl_classify(struct sk_buff *skb, const struct tcf_proto *tp,
 {
 	struct cls_fl_head *head = rcu_dereference_bh(tp->root);
 	bool post_ct = tc_skb_cb(skb)->post_ct;
+	u16 zone = tc_skb_cb(skb)->zone;
 	struct fl_flow_key skb_key;
 	struct fl_flow_mask *mask;
 	struct cls_fl_filter *f;
@@ -328,7 +329,7 @@ static int fl_classify(struct sk_buff *skb, const struct tcf_proto *tp,
 		skb_flow_dissect_ct(skb, &mask->dissector, &skb_key,
 				    fl_ct_info_to_flower_map,
 				    ARRAY_SIZE(fl_ct_info_to_flower_map),
-				    post_ct);
+				    post_ct, zone);
 		skb_flow_dissect_hash(skb, &mask->dissector, &skb_key);
 		skb_flow_dissect(skb, &mask->dissector, &skb_key,
 				 FLOW_DISSECTOR_F_STOP_BEFORE_ENCAP);