kernel: fix flow offload issues with pppoe

sync xt_FLOWOFFLOAD code with latest version of nft_flow_offload

Signed-off-by: Felix Fietkau <nbd@nbd.name>
(cherry-picked from commit 726ef8ba2dbe4d4a693c4d9300bc69e234e6d67d)

1 files changed, 27 insertions, 0 deletions

diff --git a/target/linux/generic/pending-5.10/704-00-netfilter-flowtable-fix-excessive-hw-offload-attempt.patch b/target/linux/generic/pending-5.10/704-00-netfilter-flowtable-fix-excessive-hw-offload-attempt.patch
new file mode 100644
index 0000000000..c15f090f71
--- /dev/null
+++ b/target/linux/generic/pending-5.10/704-00-netfilter-flowtable-fix-excessive-hw-offload-attempt.patch
@@ -0,0 +1,27 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Fri, 6 May 2022 12:37:23 +0200
+Subject: [PATCH] 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.
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/netfilter/nf_flow_table_core.c
++++ b/net/netfilter/nf_flow_table_core.c
+@@ -331,8 +331,10 @@ 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;