netdev - [PATCH v2 nf 1/4] netfilter: flowtable: fix excessive hw offload attempts after failure

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Message-Id: <20220509122616.65449-1-nbd@nbd.name>
Date:   Mon,  9 May 2022 14:26:13 +0200
From:   Felix Fietkau <nbd@....name>
To:     netdev@...r.kernel.org
Cc:     pablo@...filter.org, netfilter-devel@...r.kernel.org
Subject: [PATCH v2 nf 1/4] netfilter: flowtable: fix excessive hw offload attempts after failure

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.

Fixes: c07531c01d82 ("netfilter: flowtable: Remove redundant hw refresh bit")
Signed-off-by: Felix Fietkau <nbd@....name>
---
 net/netfilter/nf_flow_table_core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
index 3db256da919b..20b4a14e5d4e 100644
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -335,8 +335,10 @@ void flow_offload_refresh(struct nf_flowtable *flow_table,
 	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;
-- 
2.35.1