.\"	$NetBSD: ippool.5,v 1.3 2012/07/22 14:27:51 darrenr Exp $
.\"
.TH IPPOOL 5
.SH NAME
ippool, ippool.conf \- IP Pool file format
.SH DESCRIPTION
The file ippool.conf is used with ippool(8) to configure address pools for
use with ipnat(8) and ipf(8).
.PP
There are four different types of address pools that can be configured
through ippool.conf. The various types are presented below with a brief
description of how they are used:
.HP
dstlist
.IP
destination list - is a collection of IP addresses with an optional
network interface name that can be used with either redirect (rdr) rules
in ipnat.conf(5) or as the destination in ipf.conf(5) for policy based
routing.
.HP
group-map
.IP
group maps - support the srcgrpmap and dstgrpmap call functions in
ipf.conf(5) by providing a list of addresses or networks rule group
numbers to start processing them with.
.HP
hash
.IP
hash tables - provide the means for performing a very efficient
lookup address or network when there is expected to be only one
exact match. These are best used with more static sets of addresses
so they can be sized optimally.
.HP
pool
.IP
address pools - are an alternative to hash tables that can perform just
as well in most circumstances. In addition, the address pools allow for
heirarchical matching, so it is possible to define a subnet as matching
but then exclude specific addresses from it.
.SS
Evolving Configuration
.PP
Over time the configuration syntax used by ippool.conf(5) has evolved.
Originally the syntax used was more verbose about what a particular
value was being used for, for example:
.PP
.nf
table role = ipf type = tree number = 100
        { 1.1.1.1/32; !2.2.0.0/16; 2.2.2.0/24; ef00::5/128; };
.fi
.PP
The IP pool configuration file is used for defining a single object that
contains a reference to multiple IP address/netmask pairs.  A pool may consist
of a mixture of netmask sizes, from 0 to 32.
.PP
At this point in time, only IPv4 addressing is supported.
.SH OVERVIEW
.PP
The IP pool configuration file provides for defining two different mechanisms
for improving speed in matching IP addresses with rules.
The first,
.B table
, defines a lookup
.I table
to provide a single reference in a
filter rule to multiple targets and the second,
.B group-map
, provides a mechanism to target multiple groups from a single filter line.
.PP
The
.B group-map
command can only be used with filter rules that use the
.B call
command to invoke either
.B fr_srcgrpmap
or
.B fr_dstgrpmap
, to use the source or destination address,
respectively, for determining which filter group to jump to next for
continuation of filter packet processing.
.SH POOL TYPES
.PP
Two storage formats are provided: hash tables and tree structure.  The hash
table is intended for use with objects all containing the same netmask or a
few different sized netmasks of non-overlapping address space and the tree
is designed for being able to support exceptions to a covering mask, in
addition to normal searching as you would do with a table.  It is not possible
to use the tree data storage type with
.B group-map
configuration entries.
.SH POOL ROLES
.PP
When a pool is defined in the configuration file, it must have an associated
role.  At present the only supported role is
.B ipf.
Future development will see futher expansion of their use by other sections
of IPFilter code.
.SH EXAMPLES
The following examples show how the pool configuration file is used with
the ipf configuration file to enhance the ability for the ipf configuration
file to be succinct in meaning.
.TP
1
The first example shows how a filter rule makes reference to a specific
pool for matching of the source address.
.nf
pool ipf/tree (name "100";)
	{ 1.1.1.1/32; !2.2.0.0/16; 2.2.2.0/24; ef00::5/128; };
.fi
.PP
Both of the above examples produce the same configuration in the kernel
for use with ipf.conf(5).
.PP
Newer options for use in ippool.conf(5) will only be offered in the new
configuration syntax and all output using "ippool -l" will also be in the
new configuration syntax.
.SS
IPFilter devices and pools
.PP
To cater to different administration styles, ipool.conf(5) allows you to
tie a pool to a specific role in IPFilter. The recognised role names are:
.HP
ipf
.IP
pools defined for role "ipf" are available for use with all rules that are
found in ipf.conf(5) except for auth rules.
.HP
nat
.IP
pools defined for role "nat" are available for use with all rules that are
found in ipnat.conf(5).
.HP
auth
.IP
pools defined for role "auth" are available only for use with "auth" rules
that are found in ipf.conf(5) 
.HP
all
.IP
pools that are defined for the "all" role are available to all types of
rules, be they NAT rules in ipnat.conf(5) or firewall rules in ipf.conf(5).
.SH Address Pools
.PP
An address pool can be used in ipf.conf(5) and ipnat.conf(5) for matching
the source or destination address of packets. They can be referred to either
by name or number and can hold an arbitrary number of address patterns to
match.
.PP
An address pool is considered to be a "tree type". In the older configuration
style, it was necessary to have "type=tree" in ippool.conf(5). In the new
style configuration, it follows the IPFilter device with which the pool
is being configured.
Now it is the default if left out.
.PP
For convenience, both IPv4 and IPv6 addresses can be stored in the same
address pool. It should go without saying that either type of packet can
only ever match an entry in a pool that is of the same address family.
.PP
The address pool searches the list of addresses configured for the best
match. The "best match" is considered to be the match that has the highest
number of bits set in the mask. Thus if both 2.2.0.0/16 and 2.2.2.0/24 are
present in an address pool, the addres 2.2.2.1 will match 2.2.2.0/24 and
2.2.1.1 will match 2.2.0.0/16. The reason for this is to allow exceptions
to be added through the use of negative matching. In the following example,
the pool contains "2.2.0.0/16" and "!2.2.2.0/24", meaning that all packets
that match 2.2.0.0/16, except those that match 2.2.2.0/24, will be considered
as a match for this pool.
.PP
.nf
table role = ipf type = tree number = 100
        { 1.1.1.1/32; 2.2.0.0/16; !2.2.2.0/24; ef00::5/128; };
.fi
.PP
The prior example is the older file format. The declaration that
defines the pool itself has been updated and can now be expressed
as below:
.PP
.nf
pool ipf/tree (name "100";)
	{ 1.1.1.1/32; !2.2.0.0/16; 2.2.2.0/24; ef00::5/128; };
.fi
.PP
If the role and table type are left out, such as in the exmaple below,
the default is to make the table available to all aspects of IPFilter
and for the storage type to be "tree".
.PP
.nf
pool (name "100";)
	{ 1.1.1.1/32; !2.2.0.0/16; 2.2.2.0/24; ef00::5/128; };
.fi
.PP
For the sake of clarity and to aid in managing large numbers of addresses
inside address pools, it is possible to specify a location to load the
addresses from. To do this simply use a "file://" URL where you would
specify an actual IP address.
.PP
.nf
pool ipf/tree (name rfc1918;) { file:///etc/ipf/rfc1918; };
.fi
.PP
The contents of the file might look something like this:
.PP
.nf
# RFC 1918 networks
10.0.0.0/8
!127.0.0.0/8
172.16.0.0/12
192.168.0.0/24
.fi
.PP
In this example, the inclusion of the line "!127.0.0.0/8" is, strictly
speaking not correct and serves only as an example to show that negative
matching is also supported in this file.
.PP
Another format that ippool(8) recognises for input from a file is that
from whois servers. In the following example, output from a query to a
WHOIS server for information about which networks are associated with
the name "microsoft" has been saved in a file named "ms-networks".
There is no need to modify the output from the whois server, so using
either the whois command or dumping data directly from it over a TCP
connection works perfectly file as input.
.PP
.nf
pool ipf/tree (name microsoft;) { whois file "/etc/ipf/ms-networks"; };
.fi
.PP
And to then block all packets to/from networks defined in that file,
a rule like this might be used:
.PP
.nf
block in from pool/microsoft to any
.fi
.PP
Note that there are limitations on the output returned by whois servers
so be aware that their output may not be 100% perfect for your goal.
.SH Destination Lists
.PP
Destination lists are provided for use primarily with NAT redirect rules
(rdr). Their purpose is to allow more sophisticated methods of selecting
which host to send traffic to next than the simple round-robin technique
that is present with with "round-robin" rules in ipnat.conf(5).
.PP
When building a list of hosts to use as a redirection list, it is
necessary to list each host to be used explicitly. Expressing a
collection of hosts as a range or a subnet is not supported. With each
address it is also possible to specify a network interface name. The
network interface name is ignored by NAT when using destination lists.
The network itnerface name is currently only used with policy based
routing (use of "to"/"dup-to" in ipf.conf(5)).
.PP
Unlike the other directives that can be expressed in this file, destination
lists must be written using the new configuration syntax. Each destination
list must have a name associated with it and a next hop selection policy.
Some policies have further options. The currently available selection
policies are:
.HP
round-robin
.IP
steps through the list of hosts configured with the destination list
one by one
.HP
random
.IP
the next hop is chosen by random selection from the list available
.HP
src-hash
.IP
a hash is made of the source address components of the packet
(address and port number) and this is used to select which
next hop address is used
.HP
dst-hash
.IP
a hash is made of the destination address components of the packet
(address and port number) and this is used to select which
next hop address is used
.HP
hash
.IP
a hash is made of all the address components in the packet
(addresses and port numbers) and this is used to select which
next hop address is used
.HP
weighted
.IP
selecting a weighted policy for destination selection needs further
clarification as to what type of weighted selection will be used.
The sub-options to a weighted policy are:
.RS
.HP
connection
.IP
the host that has received the least number of connections is selected
to be the next hop. When all hosts have the same connection count,
the last one used will be the next address selected.
.RE
.PP
The first example here shows 4 destinations that are used with a
round-robin selection policy. 
.PP
.nf
pool nat/dstlist (name servers; policy round-robin;)
        { 1.1.1.2; 1.1.1.4; 1.1.1.5; 1.1.1.9; };
.fi
.PP
In the following example, the destination is chosen by whichever has
had the least number of connections. By placing the interface name
with each address and saying "all/dstlist", the destination list can
be used with both ipnat.conf(5) and ipf.conf(5).
.PP
.nf
pool all/dstlist (name servers; policy weighted connection;)
        { bge0:1.1.1.2; bge0:1.1.1.4; bge1:1.1.1.5; bge1:1.1.1.9; };
.fi
.SH Group maps
.PP
Group maps are provided to allow more efficient processing of packets
where there are a larger number of subnets and groups of rules for those
subnets. Group maps are used with "call" rules in ipf.conf(5) that
use the "srcgrpmap" and "dstgrpmap" functions.
.PP
A group map declaration must mention which group is the default group
for all matching addresses to be applied to. Then inside the list of
addresses and networks for the group, each one may optionally have
a group number associated with it. A simple example like this, where
the first two entries would map to group 2020 but 5.0.0.0/8 sends
rule processing to group 2040.
.PP
.nf
group-map out role = ipf number = 2010 group = 2020
        { 2.2.2.2/32; 4.4.0.0/16; 5.0.0.0/8, group = 2040; };
.fi
.PP
An example that outlines the real purpose of group maps is below,
where each one of the 12 subnets is mapped to a different group
number. This might be because each subnet has its own policy and
rather than write a list of twelve rules in ipf.conf(5) that match
the subnet and branch off with a head statement, a single rule can
be used with this group map to achieve the same result.
.PP
.nf
group-map ( name "2010"; in; )
    { 192.168.1.0/24, group = 10010; 192.168.2.0/24, group = 10020;
      192.168.3.0/24, group = 10030; 192.168.4.0/24, group = 10040;
      192.168.5.0/24, group = 10050; 192.168.6.0/24, group = 10060;
      192.168.7.0/24, group = 10070; 192.168.8.0/24, group = 10080;
      192.168.9.0/24, group = 10090; 192.168.10.0/24, group = 10100;
      192.168.11.0/24, group = 10110; 192.168.12.0/24, group = 10120;
    };
.fi
.PP
The limitation with group maps is that only the source address or the
destination address can be used to map the packet to the starting group,
not both, in your ipf.conf(5) file.
.SH Hash Tables
.PP
The hash table is operationally similar to the address pool. It is
used as a store for a collection of address to match on, saving the
need to write a lengthy list of rules. As with address pools, searching
will attempt to find the best match - an address specification with the
largest contiguous netmask.
.PP
Hash tables are best used where the list of addresses, subnets and
networks is relatively static, which is something of a contrast to
the address pool that can work with either static or changing
address list sizes.
.PP
Further work is still needed to have IPFilter correctly size and tune
the hash table to optimise searching. The goal is to allow for small to
medium sized tables to achieve close to O(1) for either a positive or
negative match, in contrast to the address pool, which is O(logn).
.PP
The following two examples build the same table in the kernel, using
the old configuration format (first) and the new one (second).
.PP
.nf
table role=all type=hash name=servers size=5
        { 1.1.1.2/32; 1.1.1.3/32; 11.23.44.66/32; };

pool all/hash (name servers; size 5;)
	{ 1.1.1.2; 1.1.1.3; 11.23.44.66; };
.fi
.SH FILES
/dev/iplookup
.br
/etc/ippool.conf
.br
/etc/hosts
.SH SEE ALSO
ippool(8), hosts(5), ipf(5), ipf(8), ipnat(8)