Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Linus Lüssing <> | Subject | [PATCH net-next v2] netfilter: ebtables: avoid resetting limit rule state | Date | Sun, 9 Dec 2018 07:14:05 +0100 |
| |
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
This also aligns the behavior to "xtables-nft-multi ebtables" which uses nft_limit instead of ebt_limit. In tests nft_limit did not suffer from this issue and rate limited to 650 just fine.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
---
Changelog v2:
- Adjusted commit message (adjusted title, added test results with nft_limit for comparison) - Excluded rate limiting variables from zeroing when passed to userspace by increasing .usersize. This became necessary with 4.11 / commit ec2318904965 ("xtables: extend matches and targets with .usersize") - Retested with 4.20-rc4 and current net-next/master (83af01ba1c2d)
v1 was:
"[net-next] bridge: ebtables: Avoid resetting limit rule state" -> https://lore.kernel.org/patchwork/patch/854802/ --- net/bridge/netfilter/ebt_limit.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/net/bridge/netfilter/ebt_limit.c b/net/bridge/netfilter/ebt_limit.c index 165b9d678cf1..2cf9861c3bce 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)) { @@ -105,7 +109,7 @@ static struct xt_match ebt_limit_mt_reg __read_mostly = { .match = ebt_limit_mt, .checkentry = ebt_limit_mt_check, .matchsize = sizeof(struct ebt_limit_info), - .usersize = offsetof(struct ebt_limit_info, prev), + .usersize = sizeof(struct ebt_limit_info), #ifdef CONFIG_COMPAT .compatsize = sizeof(struct ebt_compat_limit_info), #endif -- 2.11.0
| ![\](/images/icornerr.gif) |