skbuff: Release nfct refcount on napi stolen or re-used skbs

When multiple SKBs are merged to a new skb under napi GRO,
or SKB is re-used by napi, if nfct was set for them in the
driver, it will not be released while freeing their stolen
head state or on re-use.

Release nfct on napi's stolen or re-used SKBs, and
in gro_list_prepare, check conntrack metadata diff.

Fixes: 5c6b9460 ("net/mlx5e: CT: Handle misses after executing CT action")
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -6008,6 +6008,18 @@ static void gro_list_prepare(const struct list_head *head,
 			diffs = memcmp(skb_mac_header(p),
 				       skb_mac_header(skb),
 				       maclen);
+
+		diffs |= skb_get_nfct(p) ^ skb_get_nfct(skb);
+
+		if (!diffs) {
+			struct tc_skb_ext *skb_ext = skb_ext_find(skb, TC_SKB_EXT);
+			struct tc_skb_ext *p_ext = skb_ext_find(p, TC_SKB_EXT);
+
+			diffs |= (!!p_ext) ^ (!!skb_ext);
+			if (!diffs && unlikely(skb_ext))
+				diffs |= p_ext->chain ^ skb_ext->chain;
+		}
+
 		NAPI_GRO_CB(p)->same_flow = !diffs;
 	}
 }
@@ -6270,6 +6282,7 @@ static void napi_reuse_skb(struct napi_struct *napi, struct sk_buff *skb)
 	skb_shinfo(skb)->gso_type = 0;
 	skb->truesize = SKB_TRUESIZE(skb_end_offset(skb));
 	skb_ext_reset(skb);
+	nf_reset_ct(skb);
 
 	napi->skb = skb;
 }

net/core/skbuff.c

@@ -943,6 +943,7 @@ void __kfree_skb_defer(struct sk_buff *skb)
 
 void napi_skb_free_stolen_head(struct sk_buff *skb)
 {
+	nf_reset_ct(skb);
 	skb_dst_drop(skb);
 	skb_ext_put(skb);
 	napi_skb_cache_put(skb);