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kernel: bridge: ebtables: Avoid resetting limit rule state

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This is needed for the Gluon ARP limiter to work without hiccups in
traffic.

Link: https://patchwork.ozlabs.org/patch/841210/
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
This commit is contained in:
Linus Lüssing 2017-11-26 05:20:59 +01:00 committed by Christof Schulze
parent b98956e47e
commit 66d4cdf466
1 changed files with 63 additions and 0 deletions
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patches/lede/0061-kernel-bridge-ebtables-Avoid-resetting-limit-rule-state.patch Normal file
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@ -0,0 +1,63 @@
From: Linus Lüssing <linus.luessing@c0d3.blue>
Date: Sun, 26 Nov 2017 05:19:21 +0100
Subject: kernel: bridge: ebtables: Avoid resetting limit rule state
Link: https://patchwork.ozlabs.org/patch/841210/
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
diff --git a/target/linux/generic/patches-4.4/121-bridge-ebtables-Avoid-resetting-limit-rule-state.patch b/target/linux/generic/patches-4.4/121-bridge-ebtables-Avoid-resetting-limit-rule-state.patch
new file mode 100644
index 0000000000000000000000000000000000000000..417fdd75e543ebb6a3fdd56cb97fc83324eeb104
--- /dev/null
+++ b/target/linux/generic/patches-4.4/121-bridge-ebtables-Avoid-resetting-limit-rule-state.patch
@@ -0,0 +1,50 @@
+From 535097827e437bfa1906ed3210e6504750f4342b Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Linus=20L=C3=BCssing?= <linus.luessing@c0d3.blue>
+Date: Sat, 25 Nov 2017 00:36:13 +0100
+Subject: [PATCH] bridge: ebtables: Avoid resetting limit rule state
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+So far any changes with ebtables will reset the state of limit rules,
+leading to spikes in traffic. This is especially noticeable if changes
+are done frequently, for instance via a daemon.
+
+This patch fixes this by bailing out from (re)setting if the limit
+rule was initialized before.
+
+When sending packets every 250ms for 600s, with a
+"--limit 1/sec --limit-burst 50" rule and a command like this
+in the background:
+
+$ ebtables -N VOIDCHAIN
+$ while true; do ebtables -F VOIDCHAIN; sleep 30; done
+
+The results are:
+
+Before: ~1600 packets
+After: 650 packets
+
+Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
+---
+ net/bridge/netfilter/ebt_limit.c | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+diff --git a/net/bridge/netfilter/ebt_limit.c b/net/bridge/netfilter/ebt_limit.c
+index 61a9f1be1263..f74b48633feb 100644
+--- a/net/bridge/netfilter/ebt_limit.c
++++ b/net/bridge/netfilter/ebt_limit.c
+@@ -69,6 +69,10 @@ static int ebt_limit_mt_check(const struct xt_mtchk_param *par)
+ {
+ struct ebt_limit_info *info = par->matchinfo;
+
++ /* Do not reset state on unrelated table changes */
++ if (info->prev)
++ return 0;
++
+ /* Check for overflow. */
+ if (info->burst == 0 ||
+ user2credits(info->avg * info->burst) < user2credits(info->avg)) {
+--
+2.11.0
+