From 97b201a37fa0ef58dea35086001d2f6a3c3a494c Mon Sep 17 00:00:00 2001 From: laforge Date: Wed, 5 Mar 2003 22:46:04 +0000 Subject: big documenttion update, bring docs in sync with reality --- doc/ulogd.sgml | 231 +++++++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 192 insertions(+), 39 deletions(-) (limited to 'doc') diff --git a/doc/ulogd.sgml b/doc/ulogd.sgml index f8d95ec..e8bbeb6 100644 --- a/doc/ulogd.sgml +++ b/doc/ulogd.sgml @@ -1,17 +1,17 @@ - +
ULOGD - the Userspace Logging Daemon Harald Welte <laforge@gnumonks.org> -Revision $Revision: 1.6 $, $Date: 2002/06/13 12:56:16 $ +Revision $Revision: 1.7 $, $Date: 2003/02/08 12:21:36 $ This is the documentation for ulogd, the Userspace logging daemon. -ulogd makes use of the Linux 2.4 firewalling subsystem (netfilter) and the -ULOG target for netfilter. +ulogd makes use of the Linux >= 2.4.x packet filter subsystem (iptables) and +the ULOG target for iptables @@ -48,15 +48,12 @@ Nobody knows what strange network protocols are out there :) Flexibility depends on the communication between the output of the logging plugins and input of the output plugins.

-Rusty advised me to use some kind of type-key-value triples, but I think -this is the total overkill and is too complicated for me to implement it -in a reasonable short period of time. (3 hours later) Hmm... Rusty finally -convinced me to use linked lists of type-key-value triples - and it wasn't -that difficult. +Rusty advised me to use some kind of type-key-value triples, which is in fact +what I implemented.

-Another issue is, of course, performance. Up to ulogd 0.3, ulogd did several +One issue is, of course, performance. Up to ulogd 0.3, ulogd did several linked list iterations and about 30 malloc() calls _per packet_. This -changed with the new 0.9 revision: +changed with the new >= 0.9 revisions: Not a single dynamic allocation in the core during runtime. Everything is pre-allocated at start of ulogd to provide the highest @@ -84,7 +81,7 @@ You only need to read this chapter if you have a 2.4.x kernel <= In order to put the ipt_ULOG module into your kernel source,you need the latest iptables package, or even better: the latest CVS snapshot. A description how to obtain this is provided on the netfilter -homepage . +homepage .

To run patch-o-matic, just type @@ -95,7 +92,7 @@ in the userspace directory of netfilter CVS. ulogd Recompiling the source

-Download the ulogd package from and +Download the ulogd package from and untar it.

If you want to build ulogd with MySQL support, type './configure --with-mysql'. You may also have to specify the path of the mysql libraries using '--with-mysql=path'. To build ulogd without MySQL support, just use './configure'. @@ -104,17 +101,18 @@ To compile and install the program, call 'make install'. Using a precompiled package

-I also provide a SRPM, which should compile on almost any rpm-based distribution. It is available at +I also provide a SRPM, which should compile on almost any rpm-based distribution. It is available at

Just download the package and do the usual 'rpm --rebuild <file>'. Configuration -netfilter +iptables ULOG target +Quick Setup

Just add rules using the ULOG target to your firewalling chain. A very basic example: -iptables -A FORWARD -j ULOG --ulog-nlgroup 32 --prefix foo +iptables -A FORWARD -j ULOG --ulog-nlgroup 32 --ulog-prefix foo

To increase logging performance, try to use the @@ -127,36 +125,133 @@ kernel schedules ulogd only once every 20 packets. All 20 packets are then processed by ulogd. This reduces the number of context switches between kernel and userspace.

-Of course you can combine the ULOG target with the different netfilter match modules. -For a more detailed description, have a look at the netfilter HOWTO's, available on -the netfilter homepage. +Of course you can combine the ULOG target with the different netfilter match +modules. For a more detailed description, have a look at the netfilter +HOWTO's, available on the netfilter homepage. +ULOG target reference +

+ +--ulog-nlgroup N +The number of the netlink multicast group to which ULOG'ed packets are sent. +You will have to use the same group number in the ULOG target and ulogd in +order to make logging work. +--ulog-cprange N +Copyrange. This works like the 'snaplen' paramter of tcpdump. You can specify +a number of bytes up to which the packet is copied. If you say '40', you will +receive the first fourty bytes of every packet. Leave it to '0' +--ulog-qthreshold N +Queue threshold. If a packet is matched by the iptables rule, and already N +packets are in the queue, the queue is flushed to userspace. You can use this +to implement a policy like: Use a big queue in order to gain high performance, +but still have certain packets logged immediately to userspace. +--ulog-prefix STRING +A string that is associated with every packet logged by this rule. You can use +this option to later tell from which rule the packet was logged. + + +ipt_ULOG module parameters +

+The ipt_ULOG kernel module has a couple of module loadtime parameters which can +(and should) be tuned to accomodate the needs of the application: + +nlbufsiz N +Netlink buffer size. A buffer of the specified size N is allocated for every +netlink group that is used. Please note that due to restrictions of the kernel +memory allocator, we cannot have a buffer size > 128kBytes. Larger buffer +sizes increase the performance, since less kernel/userspace context switches +are needed for the same amount of packets. The backside of this performance +gain is a potentially larger delay. The default value is 4096 bytes, which is +quite small. +flushtimeout N +The flushtimeout determines, after how many clock ticks (on alpha: 1ms, on +x86 and most other platforms: 10ms time units) the buffer/queue is to be +flushed, even if it is not full. This can be used to have the advantage of a +large buffer, but still a finite maximum delay introduced. The default value +is set to 10 seconds. + +Example: + +modprobe ipt_ULOG nlbufsiz=65535 flushtimeout=100 + +This would use a buffer size of 64k and a flushtimeout of 100 clockticks (1 second on x86). ulogd

-All configurable parameters of ulogd are in the configfile '/etc/ulogd.conf' +ulogd is what this is all about, so let's describe it's configuration... +ulogd configfile syntax reference +

+All configurable parameters of ulogd are in the configfile, typically located +at '/etc/ulogd.conf'.

The following configuration parameters are available: nlgroup -The netlink multicast group, which ulgogd should bind to. This is the same as given with the '--ulog-nlgroup' option to iptables. +The netlink multicast group, which ulgogd should bind to. This is the same as +given with the '--ulog-nlgroup' option to iptables. logfile The main logfile, where ulogd reports any errors, warnings and other unexpected conditions. loglevel -This specifies, how verbose the logging to logfile is. Currently defined loglevels are: 1=debug information, 3=informational messages, 5=noticable exceptional conditions, 7=error conditions, 8=fatal errors, program abort. +This specifies, how verbose the logging to logfile is. Currently defined +loglevels are: 1=debug information, 3=informational messages, 5=noticable +exceptional conditions, 7=error conditions, 8=fatal errors, program abort. plugin -This option is followed by a filename of a ulogd plugin, which ulogd shold load upon initialization. This option may appear more than once. +This option is followed by a filename of a ulogd plugin, which ulogd shold load +upon initialization. This option may appear more than once. +bufsize +Size of the receive buffer. You should set this to at least the size of the +kernel buffer (nlbufsiz parameter of the ipt_ULOG module). + +ulogd commandline option reference +

+Apart from the configfile, there are a couple of commandline options to ulogd: + +-h --help +Print a help message about the commandline options. +-V --version +Print version information about ulogd. +-d --daemon +For off into daemon mode. Unless you are debugging, you will want to use this +most of the time. +-c --configfile +Using this commandline option, an alternate config file can be used. This is +important if multiple instances of ulogd are to be run on a single machine. Available plugins

-ulogd comes with the following plugins: - -ulogd_BASE.so -Basic interpreter plugin for nfmark, timestamp, mac address, ip header, tcp header, udp header, icmp header, ah/esp header. -ulogd_PWSNIFF.so -Example interpreter plugin to log plaintext passwords as used with FTP and POP3. Don't blame me for writing this plugin! The protocols are inherently insecure, and there are a lot of other tools for sniffing passwords... it's just an example. -ulogd_OPRINT.so +It is important to understand that ulogd without plugins does nothing. It will receive packets, and do nothing with them. +

+There are two kinds of plugins, interpreter and output plugins. Interpreter +plugins parse the packet, output plugin write the interpreted information to +some logfile/database/... + +Interpreter plugins +

+ulogd comes with the following interpreter plugins: +ulogd_BASE.so +

+Basic interpreter plugin for nfmark, timestamp, mac address, ip header, tcp +header, udp header, icmp header, ah/esp header... Most people will want to load +this very important plugin. +ulogd_PWSNIFF.so +

+Example interpreter plugin to log plaintext passwords as used with FTP and +POP3. Don't blame me for writing this plugin! The protocols are inherently +insecure, and there are a lot of other tools for sniffing passwords... it's +just an example. +ulogd_LOCAL.so +

+This is a 'virtual interpreter'. It doesn't really return any information on +the packet itself, rather the local system time and hostname. Please note that +the time is the time at the time of logging, not the packets receive time. + +Output plugins +

+ulogd comes with the following output plugins: + +ulogd_OPRINT.so +

A very simple output module, dumping all packets in the format ===>PACKET BOUNDARY @@ -166,25 +261,30 @@ key=value ===>PACKET BOUNDARY ... -to a file. +to a file. The only useful application is debugging.

The module defines the following configuration directives: dumpfile -The filename where it should log to. The default is /var/log/ulogd.pktlog +The filename where it should log to. The default is +/var/log/ulogd.pktlog -ulogd_LOGEMU.so -An output module which tries to emulate the old syslog-based LOG targed as far as possible. Logging is done to a textfile instead of syslog, though. +ulogd_LOGEMU.so +

+An output module which tries to emulate the old syslog-based LOG targed as far +as possible. Logging is done to a seperate textfile instead of syslog, though.

The module defines the following configuration directives: -syslogfileThe filename where it should log to. The default is /var/log/ulogd.syslogemu - - -syslogsyncSet this to 1 if you want to have your logfile written synchronously. This may reduce performance, but makes your log-lines appear immediately. The default is 0 +syslogfileThe filename where it should log to. The default is +/var/log/ulogd.syslogemu +syslogsyncSet this to 1 if you want to have your logfile written +synchronously. This may reduce performance, but makes your log-lines appear +immediately. The default is 0 -ulogd_MYSQL.so +ulogd_MYSQL.so +

An output plugin for logging into a mysql database. This is only compiled if you have the mysql libraries installed, and the configure script was able to detect them. (that is: --with-mysql was specified for ./configure)

@@ -217,7 +317,57 @@ Name of the mysql user Password for mysql +ulogd_PGSQL.so +

+An output plugin for logging into a postgresql database. This is only compiled +if you have the mysql libraries installed, and the configure script was able to +detect them. (that is: --with-pgsql was specified for ./configure)

+ +The plugin automagically inserts the data into the configured table; It +connects to mysql during the startup phase of ulogd and obtains a list of the +columns in the table. Then it tries to resolve the column names against keys of +interpreter plugins. This way you can easly select which information you want +to log - just by the layout of the table.

+ +If, for example, your table contains a field called 'ip_saddr', ulogd will +resolve this against the key 'ip.saddr' and put the ip address as 32bit +unsigned integer into the table.

+ +You may want to have a look at the file 'doc/mysql.table' as an +example table including fields to log all keys from ulogd_BASE.so. Just delete +the fields you are not interested in, and create the table.

+ +The module defines the following configuration directives: + +pgsqltable +Name of the table to which ulogd should log +pgsqldb +Name of the mysql database +pgsqlhost +Name of the mysql database host +pgsqluser +Name of the mysql user +pgsqlpass +Password for mysql + + +ulogd_PCAP.so +

+An output plugin that can be used to generate libpcap-style packet logfiles. +This can be useful for later analysing the packet log with tools like tcpdump +or ethereal. + +The module defines the following configuration directives: + +pcapfile +The filename where it should log to. The default is: +/var/log/ulogd.pcap +pcapsync +Set this to 1 if you want to have your pcap logfile written +synchronously. This may reduce performance, but makes your packets appear +immediately in the file on disk. The default is 0 + QUESTIONS / COMMENTS

All comments / questions / ... are appreciated. @@ -227,5 +377,8 @@ Just drop me a note to laforge@gnumonks.org Please note also that there is now a mailinglist, ulogd@lists.gnumonks.org. You can subscribe at +

+The preferred method for reporting bugs is the netfilter bugzilla system, +available at .

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