$Revision: 1488 $
$Date: 2007-01-11 19:05:13 +0200 (Thu, 11 Jan 2007) $
User's Guide
Overview
This module is designed to be used at intermediate sip proxies like loadbalancers in front of
registrars and proxies. It provides functions for inserting a Path header including a parameter for
passing forward the received-&uri; of a registration to the next hop. It also provides a mechanism
for evaluating this parameter in subsequent requests and to set the destination &uri; according to it.
Path insertion for registrations
For registrations in a scenario like [UAC] -> [P1] -> [REG]
,
the "path" module can be used at the intermediate proxy P1 to insert a Path
header into the message before forwarding it to the registrar REG. Two functions
can be used to achieve this:
add_path(...) adds a Path header in the form of
Path: <sip:1.2.3.4;lr>
to the message using the address
of the outgoing interface. A port is only added if it's not the default
port 5060.
If a username is passed to the function, it is also included in the Path
&uri;, like Path: <sip:username@1.2.3.4;lr>
.
add_path_received(...) also add a Path header in the
same form as above, but also adds a parameter indicating the received-&uri;
of the message, like
Path: <sip:1.2.3.4;received=sip:2.3.4.5:1234;lr>
. This
is especially useful if the proxy does NAT detection and wants to pass
the NAT'ed address to the registrar.
If the function is called with a username, it's included in the Path &uri; too.
Outbound routing to NAT'ed UACs
If the NAT'ed address of an UAC is passed to the registrar, the registrar routes back
subsequent requests using the Path header of the registration as Route header of the
current request. If the intermediate proxy had inserted a Path header including the
received
parameter during the registration, this parameter will show up
in the Route header of the new request as well, allowing the intermediate proxy to route
to this address instead of the one propagated in the Route &uri; for tunneling through NAT.
This behaviour can be activated by setting the module parameter use_received
.
Dependencies
&ser; Modules
The following modules must be loaded before this module:
The "rr" module is needed for outbound routing according to the received
parameter.
External Libraries or Applications
The following libraries or applications must be installed before
running &ser; with this module loaded:
None.
Exported Parameters
<varname>use_received</varname> (int)
If set to 1, the received
parameter of the first Route &uri; is evaluated and
used as destination-&uri; if present.
Default value is 0.
Set <varname>use_received</varname> parameter
...
modparam("path", "use_received", 1)
...
Exported Functions
<function moreinfo="none">add_path()</function>
This function is used to insert a Path header in the form
Path: <sip:1.2.3.4;lr>
, where 1.2.3.4
is the address
of the outgoing interface.
This function can be used from REQUEST_ROUTE.
<function>add_path</function> usage
...
if (!add_path()) {
sl_send_reply("503", "Internal Path Error");
...
};
...
<function moreinfo="none">add_path(user)</function>
This function adds a Path header in the form
Path: <sip:user@1.2.3.4;lr>
.
Meaning of the parameters is as follows:
user - The username to be inserted as user part.
This function can be used from REQUEST_ROUTE.
<function>add_path(user)</function> usage
...
if (!add_path("loadbalancer")) {
sl_send_reply("503", "Internal Path Error");
...
};
...
<function moreinfo="none">add_path_received()</function>
This function adds a Path header in the form
Path: <sip:1.2.3.4;received=sip:2.3.4.5:1234;lr>
, setting it's own
outgoing address as domain-part, and the address the request has been received from as
received-parameter.
This function can be used from REQUEST_ROUTE.
<function>add_path_received()</function> usage
...
if (!add_path_received()) {
sl_send_reply("503", "Internal Path Error");
...
};
...
<function moreinfo="none">add_path_received(user)</function>
This function adds a Path header in the form
Path: <sip:user@1.2.3.4;received=sip:2.3.4.5:1234;lr>
, setting
'user' as username part of address, it's own
outgoing address as domain-part, and the address the request has been received from as
received-parameter.
This function can be used from REQUEST_ROUTE.
<function>add_path_received(user)</function> usage
...
if (!add_path_received("inbound")) {
sl_send_reply("503", "Internal Path Error");
...
};
...