Table of Contents:
V. Command Line Arguments
*NOTE* This document may very will be inaccurate, if at all possible
you should refer to
for authoritative information.
1. Dot.conf (required)
Dot.conf is used to handle the configuration data and is
required for PacketBL to operate. It can be obtained from:
Dot.conf uses "Apache-style" configuration files so logical
hierarchal configuration files can be used.
2. iptables (required)
Iptables' library "ipq" (IP Queuing library) is required, it
provides the necessary hooks to allow PacketBL to accept
packets from the QUEUE target and process them.
3. FireDNS (optional)
FireDNS is a library that queries all configured nameservers in
parallel and once it gets an answer from one of them reports
this. It can make name resolution MUCH faster, especially when
a configured nameserver is unreachable or down.
1. PacketBL uses a GNU autoconf style `configure' script for
configuration. To invoke this script run the `configure' script
within the top-level source directory, for example:
There are a few options that can be passed to the `configure' script
that will affect the way PacketBL is built (in addition to the
standard autoconf `configure' script options):
This option will enable the experimental caching
mechanism. This may introduce unexpected problems.
If you encounter any problems you should post a bug
report to the PacketBL mailing list (for details, see
This option will cause PacketBL to use FireDNS's name
resolution routines when testing IPs against DNS RBLs.
Read above for more information on FireDNS.
This option will enable the experimental statistic
gathering code, which will require an extra thread to
handle incoming connections to a UNIX domain socket.
This option allows one to specify the path to the UNIX
domain socket that is used for communications between
the PacketBL daemon and the "packetbl_getstat" process.
Default is /tmp/.packetbl.sock.
1. The configuration file (packetbl.conf) is in "Apache-style" format.
An example configuration file might look something like this:
2. Explanation of configuration elements:
This element begins the HOST section of the
configuration. You must define your Blacklists DNS
RBLs and Whitelist addresses in the HOST section.
b. BlackListBL dnsbl.sorbs.net
The "BlackListBL" element defines a DNS RBL which is
checked to determine whether or not packets are
dropped. This particular example configures
"dnsbl.sorbs.net" as an RBL to use.
c. WhiteList 127.0.0.0/8
The "WhiteList" element defines a range in (CIDR
format) of IP address to always accept and never check
the configured "BlackListBL" elements. You should
usually leave at least "127.0.0.0/8" there for safety.
d. FallthroughAccept yes
The "FallthroughAccept" element tells PacketBL how to
handle packets that are neither listed in a configured
DNS RBL ("BlackListBL" element) nor match a configured
whitelist ("WhiteList" element). Usually you should
leave this as "yes" (the default).
e. AllowNonPort25 no
The "AllowNonPort25" element controls whether or not
PacketBL will examine packets that are passed it that
do not have a "Destination Port" of 25 (SMTP). This
is probably not something you want, leaving it "no"
is safe. Enabling this and mis-configuring your
iptables configuration could cause a LOT of load on the
configured DNS RBLs and may cause you to lose access to
f. AllowNonSyn no
The "AllowNonSyn" element controls whether or not
PacketBL will examine packets that are passed it that
do not have the SYN flag set (i.e, incoming TCP
connections). This is probably not something you want,
leaving it "no" is safe. Enabling this and
mis-configuring your iptables configuration could cause
a LOT of load on the configured DNS RBLs and may cause
you to lose access to them!
g. DryRun no
The "DryRun" element controls whether or not PacketBL
actually rejects (DROPs) the packets that match a
configured DNS RBL. Setting this to "yes" will cause
all packets to be ACCEPTed. The default is "no"
which causes normal operation.
h. CacheSize 8192
The "CacheSize" element determines the size of the
cache (in entries, not bytes or bits) if cache has
been enabled at compile time. A setting of "0" causes
caching to be disabled. The largest reasonable value
is currently 21675, anything above that will be wasted.
i. CacheTTL 3600
The "CacheTTL" element determines the length of time
(in seconds) that cached entries are considered valid.
Once an entry is looked up through a configured DNS RBL
it will not need to be looked up again until after its
"Time To Live" has been exceeded.
j. LogFacility daemon
The "LogFacility" element controls which syslog facility
PacketBL sends its information to. The default is
probably fine for most people.
k. Quiet no
The "Quiet" element controls whether PacketBL writes
a message to syslog() every time it accepts or rejects
a packet. The safe choice (and default) is "no"
meaning that PacketBL writes a message to syslog about
V. COMMAND LINE ARGUMENTS
1. PacketBL supports a minimal number of command line arguments, since
most configuration should be done in the configuration file (see
previous section). The following is a complete list of supported
command line arguments:
The "-q" option causes PacketBL to be quiet, it is
identical to setting "Quiet" to "yes" in the
The "-V" option causes PacketBL to print out its
version number and other relevant information to
standard output and exit successfully.
Command line arguments always override their configuration file
counter-parts where appropriate. Unknown command line arguments
cause PacketBL to terminate in error immediately at startup.