2022-01-24 17:19:12

by kai zhang

Subject: [PATCH] net: fix duplicate logs of iptables TRACE target

Below configuration, mangle,filter and security tables have no rule:

There are 5 logs for incoming ssh packet:

kernel: [ 7018.727278] TRACE: raw:PREROUTING:policy:2 IN=enp9s0 ...
kernel: [ 7018.727304] TRACE: mangle:PREROUTING:policy:1 IN=enp9s0 ...
kernel: [ 7018.727327] TRACE: mangle:INPUT:policy:1 IN=enp9s0 ...
kernel: [ 7018.727343] TRACE: filter:INPUT:policy:1 IN=enp9s0 ...
kernel: [ 7018.727359] TRACE: security:INPUT:policy:1 IN=enp9s0 ...

Signed-off-by: kai zhang <[email protected]>
---
net/ipv4/netfilter/ip_tables.c | 4 +++-
net/ipv6/netfilter/ip6_tables.c | 4 +++-
2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 2ed7c58b4..5f0e6096e 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -304,9 +304,11 @@ ipt_do_table(void *priv,

#if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE)
/* The packet is traced: log it */
- if (unlikely(skb->nf_trace))
+ if (unlikely(skb->nf_trace)) {
trace_packet(state->net, skb, hook, state->in,
state->out, table->name, private, e);
+ nf_reset_trace(skb);
+ }
#endif
/* Standard target? */
if (!t->u.kernel.target->target) {
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 2d816277f..ae842a835 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -327,9 +327,11 @@ ip6t_do_table(void *priv, struct sk_buff *skb,

#if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE)
/* The packet is traced: log it */
- if (unlikely(skb->nf_trace))
+ if (unlikely(skb->nf_trace)) {
trace_packet(state->net, skb, hook, state->in,
state->out, table->name, private, e);
+ nf_reset_trace(skb);
+ }
#endif
/* Standard target? */
if (!t->u.kernel.target->target) {
--
2.30.2

2022-01-24 18:04:37

by Florian Westphal

Subject: Re: [PATCH] net: fix duplicate logs of iptables TRACE target

kai zhang <[email protected]> wrote:
> Below configuration, mangle,filter and security tables have no rule:
>
> There are 5 logs for incoming ssh packet:
>
> kernel: [ 7018.727278] TRACE: raw:PREROUTING:policy:2 IN=enp9s0 ...
> kernel: [ 7018.727304] TRACE: mangle:PREROUTING:policy:1 IN=enp9s0 ...
> kernel: [ 7018.727327] TRACE: mangle:INPUT:policy:1 IN=enp9s0 ...
> kernel: [ 7018.727343] TRACE: filter:INPUT:policy:1 IN=enp9s0 ...
> kernel: [ 7018.727359] TRACE: security:INPUT:policy:1 IN=enp9s0 ...

Thats correct and exactly whats supposed to happen.

> #if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE)
> /* The packet is traced: log it */
> - if (unlikely(skb->nf_trace))
> + if (unlikely(skb->nf_trace)) {
> trace_packet(state->net, skb, hook, state->in,
> state->out, table->name, private, e);
> + nf_reset_trace(skb);
> + }

This breaks the long established behavior of TRACE,
we don't want users to have to TRACE tables individually which may also
be hard when nat is involved.