netfilter: flowtable: fetch stats only if flow is still alive

Do not fetch statistics if flow has expired since it might not in
hardware anymore. After this update, remove the FLOW_OFFLOAD_HW_DYING
check from nf_flow_offload_stats() since this flag is never set on.

Fixes: c29f74e0 ("netfilter: nf_flow_table: hardware offload support")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: wenxu <wenxu@ucloud.cn>

net/netfilter/nf_flow_table_core.c

@@ -348,9 +348,6 @@ static void nf_flow_offload_gc_step(struct flow_offload *flow, void *data)
 {
 	struct nf_flowtable *flow_table = data;
 
-	if (flow->flags & FLOW_OFFLOAD_HW)
-		nf_flow_offload_stats(flow_table, flow);
-
 	if (nf_flow_has_expired(flow) || nf_ct_is_dying(flow->ct) ||
 	    (flow->flags & (FLOW_OFFLOAD_DYING | FLOW_OFFLOAD_TEARDOWN))) {
 		if (flow->flags & FLOW_OFFLOAD_HW) {
@@ -361,6 +358,8 @@ static void nf_flow_offload_gc_step(struct flow_offload *flow, void *data)
 		} else {
 			flow_offload_del(flow_table, flow);
 		}
+	} else if (flow->flags & FLOW_OFFLOAD_HW) {
+		nf_flow_offload_stats(flow_table, flow);
 	}
 }
 

net/netfilter/nf_flow_table_offload.c

@@ -784,8 +784,7 @@ void nf_flow_offload_stats(struct nf_flowtable *flowtable,
 	__s32 delta;
 
 	delta = nf_flow_timeout_delta(flow->timeout);
-	if ((delta >= (9 * NF_FLOW_TIMEOUT) / 10) ||
-	    flow->flags & FLOW_OFFLOAD_HW_DYING)
+	if ((delta >= (9 * NF_FLOW_TIMEOUT) / 10))
 		return;
 
 	offload = kzalloc(sizeof(struct flow_offload_work), GFP_ATOMIC);