Log MARK value

Log MARK value

[julien vehent]

Hi There,

I'm trying to debug some rules and would like to LOG the mark value
assigned to a packet.
The LOG target doesn't give this information, even in debug level. I
tried ULOG but apparently it's the same thing.
/proc/net/ip_conntrack shows a "mark" field that stays at zero,
whatever I change in my rules.

I found a commit from Patrick McHardy on this subject :
http://kerneltrap.org/mailarchive/git-commits-head/2008/4/19/1508664

Has this been commited yet ? If yes, how can I use it ?
My current kernel version is Linux 2.6.18-6-686.

The test rule : iptables -t mangle -A INPUT -p tcp --dport 22 -j MARK
--set-mark 0x5

What's seen on the system :

arael:/proc/net# cat ip_conntrack|grep dport=22
tcp      6 431999 ESTABLISHED src=[IP SRC] dst=[IP DST] sport=3874
dport=22 packets=2585 bytes=165320 src=[IP SRC] dst=[IP DST]  sport=22
dport=3874 packets=2483 bytes=637896 [ASSURED] mark=0 use=1

arael:/proc/net# iptables -L -v -t mangle
Chain INPUT (policy ACCEPT 1074K packets, 448M bytes)
 pkts bytes target     prot opt in     out     source               destination
  360 27348 MARK       tcp  --  any    any     anywhere
anywhere            tcp dpt:ssh MARK set 0x5

arael:/proc/net# tail -n 1 /var/log/syslog
Jul 18 20:27:07 arael kernel: IN=eth0 OUT=
MAC=00:0c:29:f8:19:1a:00:15:60:98:aa:6b:08:00 SRC=[IP SRC] DST=[IP
DST] LEN=92 TOS=0x00 PREC=0x00 TTL=128 ID=21023 DF PROTO=TCP SPT=3874
DPT=22 WINDOW=63732 RES=0x00 ACK PSH URGP=0


Regards,
Julien

Re: Log MARK value

[Brian Austin - Standard Universal]

julien vehent wrote:
> Hi There,
>
> I'm trying to debug some rules and would like to LOG the mark value
> assigned to a packet.
> The LOG target doesn't give this information, even in debug level. I
> tried ULOG but apparently it's the same thing.
> /proc/net/ip_conntrack shows a "mark" field that stays at zero,
> whatever I change in my rules.
>
> I found a commit from Patrick McHardy on this subject :
> http://kerneltrap.org/mailarchive/git-commits-head/2008/4/19/1508664
>
> Has this been commited yet ? If yes, how can I use it ?
> My current kernel version is Linux 2.6.18-6-686.
>
> The test rule : iptables -t mangle -A INPUT -p tcp --dport 22 -j MARK
> --set-mark 0x5
>
> What's seen on the system :
>
> arael:/proc/net# cat ip_conntrack|grep dport=22
> tcp      6 431999 ESTABLISHED src=[IP SRC] dst=[IP DST] sport=3874
> dport=22 packets=2585 bytes=165320 src=[IP SRC] dst=[IP DST]  sport=22
> dport=3874 packets=2483 bytes=637896 [ASSURED] mark=0 use=1
>
> arael:/proc/net# iptables -L -v -t mangle
> Chain INPUT (policy ACCEPT 1074K packets, 448M bytes)
>  pkts bytes target     prot opt in     out     source               destination
>   360 27348 MARK       tcp  --  any    any     anywhere
> anywhere            tcp dpt:ssh MARK set 0x5
>
> arael:/proc/net# tail -n 1 /var/log/syslog
> Jul 18 20:27:07 arael kernel: IN=eth0 OUT=
> MAC=00:0c:29:f8:19:1a:00:15:60:98:aa:6b:08:00 SRC=[IP SRC] DST=[IP
> DST] LEN=92 TOS=0x00 PREC=0x00 TTL=128 ID=21023 DF PROTO=TCP SPT=3874
> DPT=22 WINDOW=63732 RES=0x00 ACK PSH URGP=0
>
>
> Regards,
> Julien
> --
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>   
you need to save the mark for it to appear in the ip_conntrack list.

	iptables -t mangle -A INPUT -p tcp --dport 22 -j MARK --set-mark 0x5
	iptables -t mangle -A INPUT -p tcp --dport 22 -j CONNMARK --save-mark

you need patch and compile kernel source to see it in syslog

patch net/ipv4/netfilter/ipt_LOG.c like this... 

@@ -56,6 +56,8 @@
        printk("SRC=%u.%u.%u.%u DST=%u.%u.%u.%u ",
               NIPQUAD(ih->saddr), NIPQUAD(ih->daddr));

+       printk("FWMARK=%u ", (unsigned int)skb->mark);
+
        /* Max length: 46 "LEN=65535 TOS=0xFF PREC=0xFF TTL=255 ID=65535 " */
        printk("LEN=%u TOS=0x%02X PREC=0x%02X TTL=%u ID=%u ",
               ntohs(ih->tot_len), ih->tos & IPTOS_TOS_MASK,
 
regards

b