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diff --git a/doc/ulogd.sgml b/doc/ulogd.sgml new file mode 100644 index 0000000..c019c63 --- /dev/null +++ b/doc/ulogd.sgml @@ -0,0 +1,449 @@ +<!doctype linuxdoc system> + +<!-- $Id$ --> + +<article> + +<title>ULOGD - the Userspace Logging Daemon</title> +<author>Harald Welte <laforge@gnumonks.org></author> +<date>Revision $Revision$, $Date$</date> + +<abstract> +This is the documentation for <tt>ulogd</tt>, the Userspace logging daemon. +ulogd makes use of the Linux >= 2.4.x packet filter subsystem (iptables) and +the ULOG target for iptables. +</abstract> + +<toc> + +<sect>DESIGN + +<sect1>CONCEPT +<p> +I want to provide a flexible, almost universal logging daemon for my netfilter +ULOG target. It is not optimized in any way, the goal is to keep as simple as +possible. These are my thoughts about how the architecture which is most +capable of doing that: +<p> +<descrip> +<tag>Interpreter plugins</tag> +It should be possible to add plugins / runtime modules for new protocols, etc. +For example the standard logging daemon provides source-ip, dest-ip, +source-port, dest-port, etc. Logging for various other protocols (GRE, +IPsec, ...) may be implemented as modules. + +<tag>Output plugins</tag> +... describe how and where to put the information gained by logging plugins. +The easiest way is to build a line per packet and fprint it to a file. +Some people might want to log into a SQL database or want an output +conforming to the intrusion detection systems communication draft from the +IETF. + +</descrip> + +<sect1>DETAILS +<p> +The major clue is providing a framework which is as flexible as possible. +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. +<p> +Rusty advised me to use some kind of type-key-value triples, which is in fact +what I implemented. +<p> +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 revisions: +<itemize> +<item>Not a single dynamic allocation in the core during runtime. +Everything is pre-allocated at start of ulogd to provide the highest +possible throughput. +<item>Hash tables in addition to the linked lists. Linked lists are only +traversed if we really want to access each element of the list. +</itemize> + +<sect>INSTALLATION +<p> +<sect1>Linux kernel +<p> +First you will need a recent 2.4.x kernel. If you have a kernel >= +2.4.18-pre8, it already has the kernel support for ULOG (ipt_ULOG.o). +<p> +If you have an older kernel version (between 2.4.0 and 2.4.18-pre6), you +can use the patch-o-matic system of netfilter/iptables, as described in +the following section. + +<sect1>ipt_ULOG from netfilter/iptables patch-o-matic +<p> +You only need to read this chapter if you have a 2.4.x kernel <= +2.4.18-pre6. +<p> +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 <URL URL="http://www.netfilter.org/">. +<p> +To run patch-o-matic, just type +<tscreen><verb> +make patch-o-matic +</verb></tscreen> +in the userspace directory of netfilter CVS. + +<sect1>ulogd +<sect2>Recompiling the source +<p> +Download the ulogd package from <URL URL="http://ftp.netfilter.org/pub/ulogd/"> and +untar it. +<p> +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'. +<p> +To compile and install the program, call 'make install'. + +<sect2>Using a precompiled package +<p> +I also provide a SRPM, which should compile on almost any rpm-based distribution. It is available at <URL URL="http://ftp.netfilter.org/pub/ulogd/"> +<p> +Just download the package and do the usual 'rpm --rebuild <file>'. + +<sect>Configuration +<sect1>iptables ULOG target +<sect2>Quick Setup +<p> +Just add rules using the ULOG target to your firewalling chain. A very basic +example: +<tscreen><verb> +iptables -A FORWARD -j ULOG --ulog-nlgroup 32 --ulog-prefix foo +</verb></tscreen> +<p> +To increase logging performance, try to use the +<tscreen><verb> +--ulog-qthreshold N +</verb></tscreen> +option (where 1 < N <= 50). The number you specify is the amount of packets +batched together in one multipart netlink message. If you set this to 20, the +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. +<p> +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. +<sect2>ULOG target reference +<p> +<descrip> +<tag>--ulog-nlgroup N</tag> +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. +<tag>--ulog-cprange N</tag> +Copyrange. This works like the 'snaplen' parameter 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 <tt>0</tt> +<tag>--ulog-qthreshold N</tag> +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. +<tag>--ulog-prefix STRING</tag> +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. +</descrip> + +<sect2>ipt_ULOG module parameters +<p> +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: +<descrip> +<tag>nlbufsiz N</tag> +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. +<tag>flushtimeout N</tag> +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. +</descrip> +Example: +<tscreen><verb> +modprobe ipt_ULOG nlbufsiz=65535 flushtimeout=100 +</verb></tscreen> +This would use a buffer size of 64k and a flushtimeout of 100 clockticks (1 second on x86). + +<sect1>ulogd +<p> +ulogd is what this is all about, so let's describe it's configuration... +<sect2>ulogd configfile syntax reference +<p> +All configurable parameters of ulogd are in the configfile, typically located +at '/etc/ulogd.conf'. +<p> +The following configuration parameters are available: +<descrip> +<tag>nlgroup</tag> +The netlink multicast group, which ulgogd should bind to. This is the same as +given with the '--ulog-nlgroup' option to iptables. +<tag>logfile</tag> +The main logfile, where ulogd reports any errors, warnings and other unexpected conditions. Apart from a regular filename, the following special values can be used; ``syslog'' to log via the unix syslog(3) mechanism. ``stdout'' to log to stdout. +<tag>loglevel</tag> +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. +<tag>plugin</tag> +This option is followed by a filename of a ulogd plugin, which ulogd shold load +upon initialization. This option may appear more than once. +<tag>rmem</tag> +Size of the netlink socket receive memory. You should set this to at least the +size of the kernel buffer (nlbufsiz parameter of the ipt_ULOG module). Please +note that there is a maximum limit in /proc/sys/net/core/rmem_max which you +cannot exceed by increasing the ``rmem'' parameter. You may need to raise the +system-wide maximum limit before. +<tag>bufsize</tag> +Size of the receive buffer. You should set this to at least the socket receive buffer (rmem). +</descrip> +<sect2>ulogd commandline option reference +<p> +Apart from the configfile, there are a couple of commandline options to ulogd: +<descrip> +<tag>-h --help</tag> +Print a help message about the commandline options. +<tag>-V --version</tag> +Print version information about ulogd. +<tag>-d --daemon</tag> +For off into daemon mode. Unless you are debugging, you will want to use this +most of the time. +<tag>-c --configfile</tag> +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. +</descrip> + +<sect>Available plugins +<p> +It is important to understand that ulogd without plugins does nothing. It will receive packets, and do nothing with them. +<p> +There are two kinds of plugins, interpreter and output plugins. Interpreter +plugins parse the packet, output plugins write the interpreted information to +some logfile/database/... + +<sect1>Interpreter plugins +<p> +ulogd comes with the following interpreter plugins: +<sect2>ulogd_BASE.so +<p> +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. +<sect2>ulogd_PWSNIFF.so +<p> +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. +<sect2>ulogd_LOCAL.so +<p> +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. + +<sect1>Output plugins +<p> +ulogd comes with the following output plugins: + +<sect2>ulogd_OPRINT.so +<p> +A very simple output module, dumping all packets in the format +<tscreen><verb> +===>PACKET BOUNDARY +key=value +key=value +... +===>PACKET BOUNDARY +... +</verb></tscreen> +to a file. The only useful application is debugging. +<p>The module defines the following configuration directives: +<descrip> +<tag>dumpfile</tag> +The filename where it should log to. The default is +<tt>/var/log/ulogd.pktlog</tt> +</descrip> + +<sect2>ulogd_LOGEMU.so +<p> +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. +<p> +The module defines the following configuration directives: +<descrip> +<tag>file</tag>The filename where it should log to. The default is +<tt>/var/log/ulogd.syslogemu</tt> +<tag>sync</tag>Set 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 <tt>0</tt> +</descrip> + +<sect2>ulogd_MYSQL.so +<p> +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) + +<p> +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 easily select which information you want +to log - just by the layout of the table. + +<p> +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. + +<p> +You may want to have a look at the file '<tt>doc/mysql.table</tt>' 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. + +<p> +The module defines the following configuration directives: +<descrip> +<tag>table</tag> +Name of the table to which ulogd should log. +<tag>ldb</tag> +Name of the mysql database. +<tag>host</tag> +Name of the mysql database host. +<tag>port</tag> +TCP port number of mysql database server. +<tag>user</tag> +Name of the mysql user. +<tag>pass</tag> +Password for mysql. +</descrip> + +<sect2>ulogd_PGSQL.so +<p> +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) + +<p> +The plugin automagically inserts the data into the configured table; It +connects to pgsql 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 easily select which information you want +to log - just by the layout of the table. + +<p> +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. + +<p> +You may want to have a look at the file '<tt>doc/mysql.table</tt>' 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. + +<p> +The module defines the following configuration directives: +<descrip> +<tag>table</tag> +Name of the table to which ulogd should log. +<tag>db</tag> +Name of the database. +<tag>host</tag> +Name of the mysql database host. +<tag>port</tag> +TCP port number of database server. +<tag>user</tag> +Name of the sql user. +<tag>pass</tag> +Password for sql user. +</descrip> + +<sect2>ulogd_PCAP.so +<p> +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: +<descrip> +<tag>file</tag> +The filename where it should log to. The default is: +<tt>/var/log/ulogd.pcap</tt> +<tag>sync</tag> +Set this to <tt>1</tt> 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 <tt>0</tt> +</descrip> + +<sect2>ulogd_SQLITE3.so +<p> +An output plugin for logging into a SQLITE v3 database. This is only compiled +if you have the sqlite libraries installed, and the configure script was able to +detect them. (that is: --with-sqlite3 was specified for ./configure) + +<p> +The plugin automagically inserts the data into the configured table; It +opens the sqlite db 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 easily select which information you want +to log - just by the layout of the table. + +<p> +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. + +<p> +You may want to have a look at the file '<tt>doc/sqlite3.table</tt>' 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. + +<p> +The module defines the following configuration directives: +<descrip> +<tag>table</tag> +Name of the table to which ulogd should log. +<tag>db</tag> +Name of the database. +<tag>buffer</tag> +Size of the sqlite buffer. +</descrip> +</sect2> + +<sect2>ulogd_SYSLOG.so +<p> +An output plugin that really logs via syslogd. Lines will look exactly like printed with traditional LOG target. + +<p> +The module defines the following configuration directives: +<descrip> +<tag>facility</tag> +The syslog facility (LOG_DAEMON, LOG_KERN, LOG_LOCAL0 .. LOG_LOCAL7, LOG_USER) +<tag>level</tag> +The syslog level (LOG_EMERG, LOG_ALERT, LOG_CRIT, LOG_ERR, LOG_WARNING, LOG_NOTICE, LOG_INFO, LOG_DEBUG) +</descrip> +</sect2> + +<sect> QUESTIONS / COMMENTS +<p> +All comments / questions / ... are appreciated. +<p> +Just drop me a note to laforge@gnumonks.org +<p> +Please note also that there is now a mailinglist, ulogd@lists.gnumonks.org. +You can subscribe at +<URL URL="http://lists.gnumonks.org/mailman/listinfo/ulogd/">. +<p> +The preferred method for reporting bugs is the netfilter bugzilla system, +available at <URL URL="http://bugzilla.netfilter.org/">. + +</article> |