Subject: [PATCH] netfilter: flowtable: fix excessive hw offload attempts after failure
From: Felix Fietkau <[email-masked]>
Date: Fri, 6 May 2022 12:37:23 +0200

If a flow cannot be offloaded, the code currently repeatedly tries again as
quickly as possible, which can significantly increase system load.
Fix this by limiting flow timeout update and hardware offload retry to once
per second.

Signed-off-by: Felix Fietkau <[email-masked]>
---

--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -318,8 +318,10 @@ void flow_offload_refresh(struct nf_flow
 	u32 timeout;
 
 	timeout = nf_flowtable_time_stamp + flow_offload_get_timeout(flow);
-	if (READ_ONCE(flow->timeout) != timeout)
+	if (timeout - READ_ONCE(flow->timeout) > HZ)
 		WRITE_ONCE(flow->timeout, timeout);
+	else
+		return;
 
 	if (likely(!nf_flowtable_hw_offload(flow_table)))
 		return;