  ULOGD - the Userspace Logging Daemon
  Harald Welte <laforge@gnumonks.org>
  Revision $Revision: 5846 $, $Date: 2005-07-12 17:33:23 +0200
  (Tue, 12 Jul 2005) $

  This is the documentation for ulogd, the Userspace logging daemon.
  ulogd makes use of the Linux >= 2.4.x packet filter subsystem (ipta-
  bles) and the ULOG target for iptables.
  ______________________________________________________________________

  Table of Contents


  1. DESIGN
     1.1 CONCEPT
     1.2 DETAILS

  2. INSTALLATION
     2.1 Linux kernel
     2.2 ipt_ULOG from netfilter/iptables patch-o-matic
     2.3 ulogd
        2.3.1 Recompiling the source
        2.3.2 Using a precompiled package

  3. Configuration
     3.1 iptables ULOG target
        3.1.1 Quick Setup
        3.1.2 ULOG target reference
        3.1.3 ipt_ULOG module parameters
     3.2 ulogd
        3.2.1 ulogd configfile syntax reference
        3.2.2 ulogd commandline option reference

  4. Available plugins
     4.1 Interpreter plugins
        4.1.1 ulogd_BASE.so
        4.1.2 ulogd_PWSNIFF.so
        4.1.3 ulogd_LOCAL.so
     4.2 Output plugins
        4.2.1 ulogd_OPRINT.so
        4.2.2 ulogd_LOGEMU.so
        4.2.3 ulogd_MYSQL.so
        4.2.4 ulogd_PGSQL.so
        4.2.5 ulogd_PCAP.so
        4.2.6 ulogd_SQLITE3.so
        4.2.7 ulogd_SYSLOG.so

  5. QUESTIONS / COMMENTS


  ______________________________________________________________________

  [1m1.  DESIGN[0m

  [1m1.1.  CONCEPT[0m

  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:


     [1mInterpreter plugins[0m
        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.


     [1mOutput plugins[0m
        ... 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.



  [1m1.2.  DETAILS[0m

  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.

  Rusty advised me to use some kind of type-key-value triples, which is
  in fact what I implemented.

  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:

  o  Not a single dynamic allocation in the core during runtime.
     Everything is pre-allocated at start of ulogd to provide the
     highest possible throughput.

  o  Hash tables in addition to the linked lists. Linked lists are only
     traversed if we really want to access each element of the list.


  [1m2.  INSTALLATION[0m


  [1m2.1.  Linux kernel[0m

  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).

  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.


  [1m2.2.  ipt_ULOG from netfilter/iptables patch-o-matic[0m

  You only need to read this chapter if you have a 2.4.x kernel <=
  2.4.18-pre6.

  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
  <http://www.netfilter.org/>.

  To run patch-o-matic, just type


       make patch-o-matic



  in the userspace directory of netfilter CVS.


  [1m2.3.  ulogd[0m

  [1m2.3.1.  Recompiling the source[0m

  Download the ulogd package from  <http://ftp.netfilter.org/pub/ulogd/>
  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'.

  To compile and install the program, call 'make install'.


  [1m2.3.2.  Using a precompiled package[0m

  I also provide a SRPM, which should compile on almost any rpm-based
  distribution. It is available at
  <http://ftp.netfilter.org/pub/ulogd/>

  Just download the package and do the usual 'rpm --rebuild <file>'.


  [1m3.  Configuration[0m

  [1m3.1.  iptables ULOG target[0m

  [1m3.1.1.  Quick Setup[0m

  Just add rules using the ULOG target to your firewalling chain. A very
  basic example:


       iptables -A FORWARD -j ULOG --ulog-nlgroup 32 --ulog-prefix foo



  To increase logging performance, try to use the


       --ulog-qthreshold N



  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.

  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.

  [1m3.1.2.  ULOG target reference[0m


     [1m--ulog-nlgroup N[0m
        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.

     [1m--ulog-cprange N[0m
        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 0

     [1m--ulog-qthreshold N[0m
        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.

     [1m--ulog-prefix STRING[0m
        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.


  [1m3.1.3.  ipt_ULOG module parameters[0m

  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:

     [1mnlbufsiz N[0m
        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.

     [1mflushtimeout N[0m
        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 clock-
  ticks (1 second on x86).


  [1m3.2.  ulogd[0m

  ulogd is what this is all about, so let's describe it's
  configuration...

  [1m3.2.1.  ulogd configfile syntax reference[0m

  All configurable parameters of ulogd are in the configfile, typically
  located at '/etc/ulogd.conf'.
  The following configuration parameters are available:

     [1mnlgroup[0m
        The netlink multicast group, which ulgogd should bind to. This
        is the same as given with the '--ulog-nlgroup' option to
        iptables.

     [1mlogfile[0m
        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.

     [1mloglevel[0m
        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.

     [1mplugin[0m
        This option is followed by a filename of a ulogd plugin, which
        ulogd shold load upon initialization. This option may appear
        more than once.

     [1mrmem[0m
        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.

     [1mbufsize[0m
        Size of the receive buffer. You should set this to at least the
        socket receive buffer (rmem).

  [1m3.2.2.  ulogd commandline option reference[0m

  Apart from the configfile, there are a couple of commandline options
  to ulogd:

     [1m-h --help[0m
        Print a help message about the commandline options.

     [1m-V --version[0m
        Print version information about ulogd.

     [1m-d --daemon[0m
        For off into daemon mode.  Unless you are debugging, you will
        want to use this most of the time.

     [1m-c --configfile[0m
        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.


  [1m4.  Available plugins[0m

  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 plugins write the
  interpreted information to some logfile/database/...

  [1m4.1.  Interpreter plugins[0m

  ulogd comes with the following interpreter plugins:

  [1m4.1.1.  ulogd_BASE.so[0m

  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.

  [1m4.1.2.  ulogd_PWSNIFF.so[0m

  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.

  [1m4.1.3.  ulogd_LOCAL.so[0m

  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.


  [1m4.2.  Output plugins[0m

  ulogd comes with the following output plugins:


  [1m4.2.1.  ulogd_OPRINT.so[0m

  A very simple output module, dumping all packets in the format


       ===>PACKET BOUNDARY
       key=value
       key=value
       ...
       ===>PACKET BOUNDARY
       ...



  to a file.  The only useful application is debugging.

  The module defines the following configuration directives:

     [1mdumpfile[0m
        The filename where it should log to. The default is
        /var/log/ulogd.pktlog


  [1m4.2.2.  ulogd_LOGEMU.so[0m

  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:

     [1mfile[0m
        The filename where it should log to. The default is
        /var/log/ulogd.syslogemu

     [1msync[0m
        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 0


  [1m4.2.3.  ulogd_MYSQL.so[0m

  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)


  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.


  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:

     [1mtable[0m
        Name of the table to which ulogd should log.

     [1mldb[0m
        Name of the mysql database.

     [1mhost[0m
        Name of the mysql database host.

     [1mport[0m
        TCP port number of mysql database server.

     [1muser[0m
        Name of the mysql user.

     [1mpass[0m
        Password for mysql.


  [1m4.2.4.  ulogd_PGSQL.so[0m

  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 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.


  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:

     [1mtable[0m
        Name of the table to which ulogd should log.

     [1mdb [22mName of the database.

     [1mhost[0m
        Name of the mysql database host.

     [1mport[0m
        TCP port number of database server.

     [1muser[0m
        Name of the sql user.

     [1mpass[0m
        Password for sql user.


  [1m4.2.5.  ulogd_PCAP.so[0m

  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:

     [1mfile[0m
        The filename where it should log to.  The default is:
        /var/log/ulogd.pcap

     [1msync[0m
        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


  [1m4.2.6.  ulogd_SQLITE3.so[0m

  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)


  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.


  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/sqlite3.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:

     [1mtable[0m
        Name of the table to which ulogd should log.

     [1mdb [22mName of the database.

     [1mbuffer[0m
        Size of the sqlite buffer.

  [1m4.2.7.  ulogd_SYSLOG.so[0m

  An output plugin that really logs via syslogd. Lines will look exactly
  like printed with traditional LOG target.


  The module defines the following configuration directives:

     [1mfacility[0m
        The syslog facility (LOG_DAEMON, LOG_KERN, LOG_LOCAL0 ..
        LOG_LOCAL7, LOG_USER)

     [1mlevel[0m
        The syslog level (LOG_EMERG, LOG_ALERT, LOG_CRIT, LOG_ERR,
        LOG_WARNING, LOG_NOTICE, LOG_INFO, LOG_DEBUG)

  [1m5.  QUESTIONS / COMMENTS[0m

  All comments / questions / ... are appreciated.

  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
  <http://lists.gnumonks.org/mailman/listinfo/ulogd/>.


  The preferred method for reporting bugs is the netfilter bugzilla
  system, available at  <http://bugzilla.netfilter.org/>.



