How to Enable IPtables TRACE Target on Debian Squeeze (6)

I am trying to use the TRACE target of IPtables but I can't seem to get any trace information logged. I want to use what is described here: Debugger for Iptables.

From the iptables man for TRACE:

   This target marks packes so that the kernel will log every  rule  which
   match  the  packets  as  those traverse the tables, chains, rules. (The
   ipt_LOG or ip6t_LOG module is required for the  logging.)  The  packets
   are   logged   with   the   string   prefix:  "TRACE:  tablename:chain-
   name:type:rulenum " where type can be "rule" for plain  rule,  "return"
   for  implicit  rule at the end of a user defined chain and "policy" for
   the policy of the built in chains.
   It can only be used in the raw table.

I use the following rule: iptables -A PREROUTING -t raw -p tcp -j TRACE but nothing is appended either in /var/log/syslog or /var/log/kern.log!

Is there another step missing? Am I looking in the wrong place?

edit

Even though I can't find log entries, the TRACE target seems to be set up correctly since the packet counters get incremented:

# iptables -L -v -t raw
Chain PREROUTING (policy ACCEPT 193 packets, 63701 bytes)
 pkts bytes target     prot opt in     out     source               destination
  193 63701 TRACE      tcp  --  any    any     anywhere             anywhere

Chain OUTPUT (policy ACCEPT 178 packets, 65277 bytes)
 pkts bytes target     prot opt in     out     source               destination

edit 2

The rule iptables -A PREROUTING -t raw -p tcp -j LOG does print packet information to /var/log/syslog... Why doesn't TRACE work?


Run:

modprobe ipt_LOG

That fixed it for me.


Seems like (i.e. works for me) with new kernel this is needed (for IPv4):

modprobe nf_log_ipv4
sysctl net.netfilter.nf_log.2=nf_log_ipv4

credits:

  • https://www.centos.org/forums/viewtopic.php?f=47&t=54411
  • upvoting other answers as they gave me important hints