1.3.1. OpenSER Modules

The following modules must be loaded before this module:

• usrloc module - only if the NATed contacts are to be pinged.

1.3.2. External Libraries or Applications

The following libraries or applications must be installed before running OpenSER with this module loaded:

• None.

1.4.1. natping_interval (integer)

Period of time in seconds between sending the NAT pings to all currently registered UAs to keep their NAT bindings alive. Value of 0 disables this functionality.

Enabling the NAT pinging functionality will force the module to bind itself to USRLOC module.

Default value is 0.

...
modparam("nathelper", "natping_interval", 10)
...

1.4.2. ping_nated_only (integer)

If this variable is set then only contacts that have "behind_NAT" flag in user location database set will get ping.

Default value is 0.

...
modparam("nathelper", "ping_nated_only", 1)
...

1.4.3. received_avp (str)

The name of the Attribute-Value-Pair (AVP) used to store the URI containing the received IP, port, and protocol. The URI is created by fix_nated_register function of nathelper module and the attribute is then used by the registrar to store the received parameters. Do not forget to change the value of corresponding parameter in registrar module if you change the value of this parameter.

You must set this parameter if you use "fix_nated_register". In such case you must set the parameter with same name of "registrar" module to same value.

Default value is "NULL" (disabled).

...
modparam("nathelper", "received_avp", "$avp(i:42)")
...

1.4.4. rtpproxy_sock (string)

Socket used to connect to RTPProxy. It may specify a UNIX socket or an IPv4/IPv6 UDP socket.

Default value is "unix:/var/run/rtpproxy.sock".

...
modparam("nathelper", "rtpproxy_sock", "udp:localhost:12221")
...

1.4.5. rtpproxy_disable (integer)

If true (set to a non 0 value), the RTPProxy support will be disabled - no connection to it will be established.

Default value is "0 (false)".

...
modparam("nathelper", "rtpproxy_disable", 1)
...

1.4.6. rtpproxy_disable_tout (integer)

Once RTPProxy was found unreachable and marked as disable, nathelper will not attempt to establish communication to RTPProxy for rtpproxy_disable_tout seconds.

Default value is "60".

...
modparam("nathelper", "rtpproxy_disable_tout", 20)
...

1.4.7. rtpproxy_tout (integer)

Timeout value in waiting for reply from RTPProxy.

Default value is "1".

...
modparam("nathelper", "rtpproxy_tout", 2)
...

1.4.8. rtpproxy_retr (integer)

How many times nathelper should retry to send and receive after timeout was generated.

Default value is "5".

...
modparam("nathelper", "rtpproxy_retr", 2)
...

1.4.9. force_socket (string)

Socket to be forced in communicating to RTPProxy. It makes sense only for UDP communication. If no one specified, the OS will choose.

Default value is "NULL".

...
modparam("nathelper", "force_socket", "localhost:33333")
...

1.4.10. sipping_bflag (integer)

What branch flag should be used by the module to identify NATed contacts for which it should perform NAT ping via a SIP request instead if dummy UDP package.

Default value is -1 (disabled).

...
modparam("nathelper", "sipping_bflag", 7)
...

1.4.11. sipping_from (string)

The parameter sets the SIP URI to be used in generating the SIP requests for NAT ping purposes. To enable the SIP request pinging feature, you have to set this parameter. The SIP request pinging will be used only for requests marked so.

Default value is "NULL".

...
modparam("nathelper", "sipping_from", "sip:pinger@siphub.net")
...

1.4.12. sipping_method (string)

The parameter sets the SIP method to be used in generating the SIP requests for NAT ping purposes.

Default value is "OPTIONS".

...
modparam("nathelper", "sipping_method", "INFO")
...

1.4.13. nortpproxy_str (string)

The parameter sets the SDP attribute used by nathelper to mark the packet SDP informations have already been mangled.

If empty string, no marker will be added or checked.

The string must be a complete SDP line, including the EOH (\r\n).

Default value is "a=nortpproxy:yes\r\n".

...
modparam("nathelper", "nortpproxy_str", "a=sdpmangled:yes\r\n")
...

1.5.1. fix_nated_contact()

Rewrites Contact HF to contain request's source address:port.

This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, BRANCH_ROUTE.

...
if (search("User-Agent: Cisco ATA.*") {fix_nated_contact();};
...

1.5.2. fix_nated_sdp(flags [, ip_address])

Alters the SDP information in orer to facilitate NAT traversal. What changes to be performed may be controled via the "flags" paramter.

Meaning of the parameters is as follows:

• flags - the value may be a bitwise OR of the following flags:

  • 0x01 - adds "a=direction:active" SDP line;

  • 0x02 - rewrite media IP address (c=) with source address of the message or the provided IP address (the provide IP address take precedence over the source address).

  • 0x04 - adds "a=nortpproxy:yes" SDP line;

  • 0x08 - rewrite IP from origin description (o=) with source address of the message or the provided IP address (the provide IP address take precedence over the source address).

• ip_address - IP to be used for rewritting SDP. If not specified, the received signalling IP will be used. The parameter allows pseudo-variables usage. NOTE: For the IP to be used, you need to use 0x02 or 0x08 flags, otherwise it will have no effect.

This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE.

...
if (search("User-Agent: Cisco ATA.*") {fix_nated_sdp("3");};
...

1.5.3. force_rtp_proxy([flags [, ip_address]])

Rewrites SDP body to ensure that media is passed through an RTP proxy. It can have optional parameters to force additional features. If ip_address is provided, it will be used to replace the one in SDP.

Meaning of the parameters is as follows:

• flags - flags to turn on some features.

  • a - flags that UA from which message is received doesn't support symmetric RTP.

  • l - force "lookup", that is, only rewrite SDP when corresponding session is already exists in the RTP proxy. Only makes sense for SIP requests, replies are always processed in "lookup" mode.

  • i - flags that message is received from UA in the LAN (internal network). Only makes sense when RTP proxy is running in the bridge mode.

  • e - flags that message is received from UA in the WAN (external network). Only makes sense when RTP proxy is running in the bridge mode.

  • f - instructs nathelper to ignore marks inserted by another nathelper in transit to indicate that the session is already goes through another proxy. Allows creating chain of proxies.

  • r - flags that IP address in SDP should be trusted. Without this flag, nathelper ignores address in the SDP and uses source address of the SIP message as media address which is passed to the RTP proxy.

  • o - flags that IP from the origin description (o=) should be also changed.

  • c - flags to change the session-level SDP connection (c=) IP if media-description also includes connection information.

  • s - flags to swap creation with confirmation between requests and replies. By default, a request creates the RTP session and a reply confirms it. If swapped, a reply will create the RTP session and a request will confirm it.

• ip_address - new SDP IP address.

This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE.

...
if (search("User-Agent: Cisco ATA.*") {force_rtp_proxy();};
if (src_ip=1.2.3.4) {force_rtp_proxy("i");};
if (search("User-Agent: Cisco ATA.*") {force_rtp_proxy("","1.2.3.4");};
...

1.5.4. unforce_rtp_proxy()

Tears down the RTPProxy session for the current call.

This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE.

...
unforce_rtp_proxy();
...

1.5.5. add_rcv_param([flag]),

Add received parameter to Contact header fields or Contact URI. The parameter will contain URI created from the source IP, port, and protocol of the packet containing the SIP message. The parameter can be then processed by another registrar, this is useful, for example, when replicating register messages using t_replicate function to another registrar.

Meaning of the parameters is as follows:

• flag - flags to indicate if the parameter should be added to Contact URI or Contact header. If the flag is non-zero, the parameter will be added to the Contact URI. If not used or equal to zero, the parameter will go to the Contact header.

This function can be used from REQUEST_ROUTE.

...
add_rcv_param(); # add the parameter to the Contact header
....
add_rcv_param("1"); # add the paramter to the Contact URI
...

1.5.6. fix_nated_register()

The function creates a URI consisting of the source IP, port, and protocol and stores the URI in an Attribute-Value-Pair. The URI will be appended as "received" parameter to Contact in 200 OK and registrar will store it in the user location database.

This function can be used from REQUEST_ROUTE.

...
fix_nated_register();
...

1.5.7. nat_uac_test(flags)

Tries to guess if client's request originated behind a nat. The parameter determines what heuristics is used.

Meaning of the flags is as follows:

• 1 - Contact header field is searched for occurrence of RFC1918 addresses.

• 2 - the "received" test is used: address in Via is compared against source IP address of signaling

• 4 - Top Most VIA is searched for occurrence of RFC1918 addresses

• 8 - SDP is searched for occurrence of RFC1918 addresses

• 16 - test if the source port is different from the port in Via

All flags can be bitwise combined, the test returns true if any of the tests identified a NAT.

This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE.