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@@ -0,0 +1,79 @@ +Userspace logging facility for netfilter / linux 2.4 +$Id$ + +===> IDEA + +This packages is intended for passing packets from the kernel to userspace +to do some logging there. It should work like that: + +- Register a target called ULOG with netfilter +- if the target is hit: + - send the packet out using netlink multicast facility + - return NF_ACCEPT immediately + +We don't have to enqueue packets, just send them out as datagrams. If the +user process isn't fast enough this isn't our problem. + +More than one logging daemon may listen to the netlink multicast address. + +===> CONTENTS + +The package is consisting out of three parts: + +1. Netfilter target ipt_ULOG +This is the kernel module which does the kernel part of packet passing to +the userspace. This module is inserted on demand through the netfilter +subsystem as soon as You add a rule with the target ULOG to any chain. + +2. iptables plugin (libipt_ULOG.so) +This is a plugin for the netfilter configuration tool iptables. Just put +it to /usr/local/lib/iptables and it is loaded on demand from iptables. + +3. Ulog library (libipulog.a) +Just a little library like libipq.a which provides a convenient way to +write userspace logging daemons. The functions provided are described +in the source code, a small demo program (ulog_test) is also included. + +4. ulogd daemon (ulogd) +A sophisticated logging daemon which uses libipulog. The daemon provides +an easy to use plugin interface to write additional packet interpreters and +output targets. Example plugins (interpreter: ip, tcp, icmp output: simple +logging to a file) are included. + +===> USAGE + +Just apply the kernel patch and enable the kernel config option +CONFIG_IP_NF_TARGET_ULOG in the netfilter subsection of the network options. +Then recompile the kernel or just recompile the netfilter modules using +'make modules SUBDIRS=net/ipv4/netfilter'. +Next step is installing the module using 'make modules_install' + +To use the iptables plugin, copy libipt_ULOG.so to /usr/local/lib/iptables + +Now You are ready to go. You may now insert logging rules to every chain. +To see the full syntax, type 'iptables -j ULOG -h' + +===> EXAMPLES + +At first a simple example, which passes every outgoing packet to the +userspace logging, using netlink multicast group 3. + +iptables -A OUTPUT -j ULOG --ulog-nlgroup 3 + +A more advanced one, passing all incoming tcp packets with destination +port 80 to the userspace logging daemon listening on netlink multicast +group 32. All packets get tagged with the ulog prefix "inp" + +iptables -A INPUT -j ULOG -p tcp --dport 80 --ulog-nlgroup 32 --ulog-prefix inp + +In the latest Version (0.2) I added another parameter (--ulog-cprange). +Using this parameter You are able to specify how much octets of the +packet should be copied from the kernel to userspace. +Setting --ulog-cprange to 0 does always copy the whole packet. Default is 0 + +===> COPYRIGHT + CREDITS + +The code is (C) 2000 by Harald Welte <laforge@sunbeam.franken.de> + +Credits to Rusty Russel, James Morris, Marc Boucher and all the other +netfilter hackers. |