Filter element parameters

The following table shows which element parameters are supported by which filter, and whether they are optional ($\circ$) or required ($\bullet$):

Parameter	route	rsvp
ah	.	$\circ$
dport	.	$\circ$
dst	.	$\bullet$
esp	.	$\circ$
from	$\circ$	.
fromif	$\circ$	.
ipproto	.	$\circ$
order	$\circ$	.
sport	.	$\circ$
src	.	$\circ$
to	$\circ$	.

Elements of fw and tcindex have no parameters and have therefore been omitted from the above table.

Units and meaning of parameters we haven't already described in the filter section:

Parameter	Unit	Description
ah	integer	SPI in AH header [RFC2402]
dport	port	Destination port number
dst	host	Destination IP address
esp	integer	SPI in ESP header [RFC2406]
from	integer	Incoming realm
fromif	string	Incoming interface name
ipproto	IP protocol	Transport layer protocol
sport	port	Source port number
src	host	Source IP address
to	integer	Outgoing realm

The units ``host'', ``port'', and ``IP protocol'' are special: the value can either be an integer, or a string containing the name of a host, a service, or a transport-layer protocol, respectively. If a name is given, tcc invokes the corresponding resolver function of the host to obtain the numeric value.