mwan - Multiwan scripts supporting policy based traffic forwarding

** Abstract **

mwan is a set of scripts triggered by interface hotplug events supporting
policy based routing for both local sourced and forwarded traffic flows.

** Features **

Multiwan package provides an UCI configuration interface that abstracts
iptables and ip rule systems to provide a simplified configuration model
that fits for policy based routing.

UCI Multiwan maps interfaces into policies; the configured interface
identifies the rt_table parameter in the UCI network section which
specifies the routing table to be used. Triggered by interface hotplug
events a rule will be inserted in the routing policy database by means
of the iproute2 utility for each policy.

UCI Multiwan identifies traffic flows by means of rule and host sections.

An UCI rule section contains traffic parameters and a reference to a policy.
Traffic rules will translate into iptables rules in the mangle table; meaning
a mark will be applied on the packet.

An UCI host section contains an absolute appplication path and a reference to
a policy. Host sections translate into a database file which is inspected by a
preloader utility which wraps the socket call. In case of application match a
mark is set via the socket mark option in the preloader utility.

Based on the packet mark a routing table will be selected; depending on the
traffic destination and the rules in the routing table the outgoing physical
interface will be selected.

** OpenWRT firmware integration **

Multiwan can be integrated in OpenWRT as a package. The Makefile currenly puts
under "Network" and the submenu "IP Addresses and Names" when doing make menuconfig.

** Configuration **

mwan uses /etc/config/mwan as UCI configuration file and requires by default
a globals section


Sections of type policy

Option		Type	Default			Description
interface	string	<name of UCI section>	Logical OpenWRT interface
last_resort	string	unreachable		Action to be executed when no match
		[unreachable|blackhole|continue] in the routing table


Sections of type rule

Option		Type	Default			Description
src		string				Match logical OpenWrt interface
						as source
src_ip		string				Match source IP address
dest_ip		string				Match destination IP address
proto		number				Match protocol
		or name
src_port	port or	range			Match source port or source port range
dest_port	port or	range			Match destination port or destination
						port range
icmp_type	icmp type or number		Match icmp type
string		string				String pattern to match against
hex-string	string				Hexadecimal string to match against
algo		string	bm			Name of matching algorithm to use
		[bm|kmp]
from_offset	number	0			Offset to start match search
to_offset	number	65535			Offset to end match search
icase		bool	0			Ignore case sensitive match
policy		string	<name of UCI section>	Policy section

Except for the parameters policy, icase, to_offset, from_offset, algo all other
parameters can be preceded by the negation char '!'

Sections of type host (static leases)
Option		Type	Default			Description
path		list				Match listed applications
arg		string				Match on part of application's
						command line argument
policy		string	<name of UCI section>	Policy section