nathelper Module
     __________________________________________________________

   Table of Contents

   1. Admin Guide

        1.1. Overview
        1.2. NAT pinging types
        1.3. Dependencies

              1.3.1. OpenSIPS Modules
              1.3.2. External Libraries or Applications

        1.4. Exported Parameters

              1.4.1. natping_interval (integer)
              1.4.2. ping_nated_only (integer)
              1.4.3. natping_partitions (integer)
              1.4.4. natping_socket (string)
              1.4.5. received_avp (str)
              1.4.6. force_socket (string)
              1.4.7. sipping_bflag (string)
              1.4.8. remove_on_timeout_bflag (string)
              1.4.9. sipping_latency_flag (string)
              1.4.10. sipping_ignore_rpl_codes (CSV string)
              1.4.11. sipping_from (string)
              1.4.12. sipping_method (string)
              1.4.13. nortpproxy_str (string)
              1.4.14. natping_tcp (integer)
              1.4.15. oldip_skip (string)
              1.4.16. ping_threshold (int)
              1.4.17. max_pings_lost (int)
              1.4.18. cluster_id (integer)
              1.4.19. cluster_sharing_tag (string)

        1.5. Exported Functions

              1.5.1. fix_nated_contact([uri_params])
              1.5.2. fix_nated_sdp(flags [, ip_address [,
                      sdp_fields]])

              1.5.3. add_rcv_param([flag]),
              1.5.4. fix_nated_register()
              1.5.5. nat_uac_test(flags)

        1.6. Exported MI Functions

              1.6.1. nh_enable_ping

   2. Frequently Asked Questions
   3. Contributors

        3.1. By Commit Statistics
        3.2. By Commit Activity

   4. Documentation

        4.1. Contributors

   List of Tables

   3.1. Top contributors by DevScore^(1), authored commits^(2) and
          lines added/removed^(3)

   3.2. Most recently active contributors^(1) to this module

   List of Examples

   1.1. Set natping_interval parameter
   1.2. Set ping_nated_only parameter
   1.3. Set natping_partitions parameter
   1.4. Set natping_socket parameter
   1.5. Set received_avp parameter
   1.6. Set force_socket parameter
   1.7. Set sipping_bflag parameter
   1.8. Set remove_on_timeout_bflag parameter
   1.9. Set sipping_latency_flag parameter
   1.10. Set sipping_ignore_rpl_codes parameter
   1.11. Set sipping_from parameter
   1.12. Set sipping_method parameter
   1.13. Set nortpproxy_str parameter
   1.14. Set natping_tcp parameter
   1.15. Set oldip_skip parameter
   1.16. Set ping_threshold parameter
   1.17. Set max_pings_lost parameter
   1.18. Set cluster_id parameter
   1.19. Set cluster_sharing_tag parameter
   1.20. fix_nated_contact usage
   1.21. fix_nated_sdp usage
   1.22. add_rcv_paramer usage
   1.23. fix_nated_register usage
   1.24. nh_enable_ping usage

Chapter 1. Admin Guide

1.1. Overview

   This is a module to help with NAT traversal. In particular, it
   helps symmetric UAs that don't advertise they are symmetric and
   are not able to determine their public address.
   fix_nated_contact rewrites Contact header field with request's
   source address:port pair. fix_nated_sdp adds the active
   direction indication to SDP (flag 0x01) and updates source IP
   address too (flag 0x02).

   Since version 2.2, stateful ping(only SIP Pings) for nathelper
   is available. This allows you to remove contacts from usrloc
   location table when max_pings_lost pings are not responded to,
   each ping having a response timeout of ping_threshold seconds.
   In order to have this functionality, contacts must have
   remove_on_timeout_bflag flag set when inserted into the
   location table.

   Works with multipart messages that contain an SDP part, but not
   with multi-layered multipart messages.

1.2. NAT pinging types

   Currently, the nathelper module supports two types of NAT
   pings:
     * UDP package - 4 bytes (zero filled) UDP packages are sent
       to the contact address.
          + Advantages: low bandwitdh traffic, easy to generate by
            OpenSIPS;
          + Disadvantages: unidirectional traffic through NAT
            (inbound - from outside to inside); As many NATs do
            update the bind timeout only on outbound traffic, the
            bind may expire and closed.
     * SIP request - a stateless SIP request is sent to the
       contact address.
          + Advantages: bidirectional traffic through NAT, since
            each PING request from OpenSIPS (inbound traffic) will
            force the SIP client to generate a SIP reply (outbound
            traffic) - the NAT bind will be surely kept open.
            Since version 2.2, one can also choose to remove
            contacts from the location table if a certain
            threshold is detected.
          + Disadvantages: higher bandwitdh traffic, more
            expensive (as time) to generate by OpenSIPS;

1.3. Dependencies

1.3.1. OpenSIPS Modules

   The following modules must be loaded before this module:
     * usrloc module - only if the NATed contacts are to be
       pinged.
     * clusterer - only if "cluster_id" option is enabled.

1.3.2. External Libraries or Applications

   The following libraries or applications must be installed
   before running OpenSIPS with this module loaded:
     * None.

1.4. Exported Parameters

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.

Note

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

   Default value is 0.

   Example 1.1. Set natping_interval parameter
...
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.

   Example 1.2. Set ping_nated_only parameter
...
modparam("nathelper", "ping_nated_only", 1)
...

1.4.3. natping_partitions (integer)

   How many partitions/chunks to be used for sending the pingings.
   One partition means sending all pingings together. Two
   partitions means to send half pings and second half at a time.

   Default value is 1.

   Example 1.3. Set natping_partitions parameter
...
modparam("nathelper", "natping_partitions", 4)
...

1.4.4. natping_socket (string)

   Spoof the natping's source-ip to this address. Works only for
   IPv4.

   Default value is NULL.

   Example 1.4. Set natping_socket parameter
...
modparam("nathelper", "natping_socket", "192.168.1.1:5006")
...

1.4.5. 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.

Note

   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).

   Example 1.5. Set received_avp parameter
...
modparam("nathelper", "received_avp", "$avp(received)")
...

1.4.6. force_socket (string)

   Sending socket to be used for pinging contacts without local
   socket information (the local socket information may be lost
   during a restart or contact replication). If no one specified,
   OpenSIPS will choose the first listening interface matching the
   destination protocol and AF family.

   Default value is “NULL”.

   Example 1.6. Set force_socket parameter
...
modparam("nathelper", "force_socket", "localhost:33333")
...

1.4.7. sipping_bflag (string)

   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 NULL (disabled).

   Example 1.7. Set sipping_bflag parameter
...
modparam("nathelper", "sipping_bflag", "SIPPING_ENABLE")
...

1.4.8. remove_on_timeout_bflag (string)

   What branch flag to be used in order to activate usrloc contact
   removal when the ping_threshold is exceeded.

   Default value is NULL (disabled).

   Example 1.8. Set remove_on_timeout_bflag parameter
...
modparam("nathelper", "remove_on_timeout_bflag", "SIPPING_RTO")
...

1.4.9. sipping_latency_flag (string)

   The branch flag which will be used in order to enable contact
   pinging latency computation and reporting via the usrloc
   E_UL_LATENCY_UPDATE event.

   Default value is NULL (disabled).

   Example 1.9. Set sipping_latency_flag parameter
...
modparam("nathelper", "sipping_latency_flag", "SIPPING_CALC_LATENCY")
...

1.4.10. sipping_ignore_rpl_codes (CSV string)

   A comma-separated list of SIP reply status codes to contact
   pings which are to be discarded. This may be useful for
   "full-sharing" user location topologies, where the location
   nodes are not directly facing the UAs, hence the intermediary
   SIP component may generate replies to offline contact ping
   attempts (e.g. 408 - Request Timeout) -- such ping replies
   should be ignored.

   Default value is "NULL" (all reply status codes are accepted).

   Example 1.10. Set sipping_ignore_rpl_codes parameter
...
modparam("nathelper", "sipping_ignore_rpl_codes", "408, 480, 404")
...

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”.

   Example 1.11. Set sipping_from parameter
...
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”.

   Example 1.12. Set sipping_method parameter
...
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.

Note

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

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

   Example 1.13. Set nortpproxy_str parameter
...
modparam("nathelper", "nortpproxy_str", "a=sdpmangled:yes\r\n")
...

1.4.14. natping_tcp (integer)

   If the flag is set, TCP/TLS clients will also be pinged with
   SIP OPTIONS messages.

   Default value is 0 (not set).

   Example 1.14. Set natping_tcp parameter
...
modparam("nathelper", "natping_tcp", 1)
...

1.4.15. oldip_skip (string)

   Parameter which specifies whether old media ip and old origin
   ip shall be put in the sdp body. The parameter has two values :
   'o' ("a=oldoip" field shall be skipped) and 'c' ("a=oldcip"
   field shall be skipped).

   Default value is 0 (not set).

   Example 1.15. Set oldip_skip parameter
...
modparam("nathelper", "oldip_skip", "oc")
...

1.4.16. ping_threshold (int)

   If a contact does not respond in ping_threshold seconds since
   the ping has been sent, the contact shall be removed after
   max_pings_lost unresponded pings.

   Default value is 3 (seconds).

   Example 1.16. Set ping_threshold parameter
...
modparam("nathelper", "ping_threshold", 10)
...

1.4.17. max_pings_lost (int)

   Number of unresponded pings after which the contact shall be
   removed from the location table.

   Default value is 3 (pings).

   Example 1.17. Set max_pings_lost parameter
...
modparam("nathelper", "max_pings_lost", 5)
...

1.4.18. cluster_id (integer)

   The ID of the cluster the module is part of. The clustering
   support is used by the nathelper module for controlling the
   pinging process. When part of a cluster of multiple nodes, the
   nodes can agree upon which node is the one responsible for
   pinging.

   The clustering with sharing tag support may be used to control
   which node in the cluster will perform the pinging/probing to
   the contacts. See the cluster_sharing_tag option.

   For more info on how to define and populate a cluster (with
   OpenSIPS nodes) see the "clusterer" module.

   Default value is “0 (none)”.

   Example 1.18. Set cluster_id parameter
...
# Be part of cluster ID 9
modparam("nathelper", "cluster_id", 9)
...

1.4.19. cluster_sharing_tag (string)

   The name of the sharing tag (as defined per clusterer modules)
   to control which node is responsible for perform pinging of the
   contacts. If defined, only the node with active status of this
   tag will perform the pinging.

   The cluster_id must be defined for this option to work.

   This is an optional parameter. If not set, all the nodes in the
   cluster will individually do the pinging.

   Default value is “empty (none)”.

   Example 1.19. Set cluster_sharing_tag parameter
...
# only the node with the active "vip" sharing tag will perform pinging
modparam("nathelper", "cluster_id", 9)
modparam("nathelper", "cluster_sharing_tag", "vip")
...

1.5. Exported Functions

1.5.1.  fix_nated_contact([uri_params])

   Rewrites the URI Contact HF to contain request's source
   address:port. If a list of URI parameter is provided, it will
   be added to the modified contact;

   IMPORTANT NOTE: Changes made by this function shall not be seen
   in the async resume route. So make sure you call it in all the
   resume routes where you need the contact fixed.

   Parameters:
     * uri_params (string, optional)

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

   Example 1.20. fix_nated_contact usage
...
if (search("User-Agent: Cisco ATA.*") {
    fix_nated_contact(";ata=cisco");
} else {
    fix_nated_contact();
}
...

1.5.2.  fix_nated_sdp(flags [, ip_address [, sdp_fields]])

   Alters the SDP information in orer to facilitate NAT traversal.
   What changes to be performed may be controled via the “flags”
   parameter. Since version 1.12 the name of the old ip fields are
   "a=oldoip" for old origin ip and "a=oldcip" for old meda ip.

   Meaning of the parameters is as follows:
     * flags (int) - 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
            provided IP address takes 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 provided IP address takes precedence over
            the source address).
          + 0x10 - force rewrite of null media IP and/or origin IP
            address. Without this flag, null IPs are left
            untouched.
     * ip_address (string, optional) - IP to be used for rewriting
       SDP. If not specified, the received signalling IP will be
       used. NOTE: For the IP to be used, you need to use 0x02 or
       0x08 flags, otherwise it will have no effect.
     * sdp_fields (string, optional) - SDP field(s) to be appended
       to SDP. Note: Each SDP field must be preceded by "\r\n".

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

   Example 1.21. fix_nated_sdp usage
...
# Add "a=direction:active" SDP line
# Rewrite media IP (c= line)
# Add extra "a=x-attr1" SDP line
# Add extra "a=x-attr2" SDP line
if (search("User-Agent: Cisco ATA.*")
    {fix_nated_sdp(3,,"\r\na=x-attr1\r\na=x-attr2");};
...

1.5.3.  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 (int, optional) - 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.

   Example 1.22. add_rcv_paramer usage
...
add_rcv_param(); # add the parameter to the Contact header
....
add_rcv_param(1); # add the parameter to the Contact URI
...

1.5.4.  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.

   Example 1.23. fix_nated_register usage
...
fix_nated_register();
...

1.5.5.  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 (int) parameter is as follows:
     * 1 - Contact header field is searched for occurrence of
       RFC1918 / RFC6598 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 /
       RFC6598 addresses
     * 8 - SDP is searched for occurrence of RFC1918 / RFC6598
       addresses
     * 16 - test if the source port is different from the port in
       Via
     * 32 - address in Contact is compared against source IP
       address of signaling
     * 64 - Port in Contact is compared against source port of
       signaling

   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.

1.6. Exported MI Functions

1.6.1. nh_enable_ping

   Gets or sets the natpinging status.

   Parameters:
     * status (optional) - if not provided the function returns
       the current natping status. Otherwise, enables natping if
       parameter value greater than 0 or disables natping if
       parameter value is 0.

   Example 1.24. nh_enable_ping usage
...
$ opensips-cli -x mi nh_enable_ping
Status:: 1
$
$ opensips-cli -x mi nh_enable_ping 0
$
$ opensips-cli -x mi nh_enable_ping
Status:: 0
$
...

Chapter 2. Frequently Asked Questions

   2.1.

       Where can I find more about OpenSIPS?

       Take a look at https://opensips.org/.

   2.2.

       Where can I post a question about this module?

       First at all check if your question was already answered on one
       of our mailing lists:
         * User Mailing List -
           http://lists.opensips.org/cgi-bin/mailman/listinfo/users
         * Developer Mailing List -
           http://lists.opensips.org/cgi-bin/mailman/listinfo/devel

       E-mails regarding any stable OpenSIPS release should be sent to
       <users@lists.opensips.org> and e-mails regarding development
       versions should be sent to <devel@lists.opensips.org>.

       If you want to keep the mail private, send it to
       <users@lists.opensips.org>.

   2.3.

       How can I report a bug?

       Please follow the guidelines provided at:
       https://github.com/OpenSIPS/opensips/issues.

Chapter 3. Contributors

3.1. By Commit Statistics

   Table 3.1. Top contributors by DevScore^(1), authored
   commits^(2) and lines added/removed^(3)
     Name DevScore Commits Lines ++ Lines --
   1. Bogdan-Andrei Iancu (@bogdan-iancu) 151 119 2036 862
   2. Maksym Sobolyev (@sobomax) 146 39 3533 4766
   3. Liviu Chircu (@liviuchircu) 42 33 397 274
   4. Ionut Ionita (@ionutrazvanionita) 40 15 1598 627
   5. Razvan Crainea (@razvancrainea) 32 26 149 240
   6. Daniel-Constantin Mierla (@miconda) 22 17 142 124
   7. Anca Vamanu 22 4 1602 185
   8. Jan Janak (@janakj) 21 11 780 129
   9. Andrei Pelinescu-Onciul 20 17 121 110
   10. Jiri Kuthan (@jiriatipteldotorg) 18 10 764 47

   All remaining contributors: Ancuta Onofrei, Ovidiu Sas
   (@ovidiusas), Vlad Patrascu (@rvlad-patrascu), Andrei Dragus,
   Vlad Paiu (@vladpaiu), Henning Westerholt (@henningw), Dan
   Pascu (@danpascu), Christophe Sollet (@csollet), Marcus Hunger,
   Klaus Darilion, Sergio Gutierrez, Nils Ohlmeier, Emmanuel Buu,
   Carsten Bock, Shlomi Gutman, Jeremie Le Hen, Bayan Towfiq,
   Laurent Schweizer, Jasper Hafkenscheid, Konstantin Bokarius,
   John Riordan, Peter Lemenkov (@lemenkov), Walter Doekes
   (@wdoekes), Elena-Ramona Modroiu, Edson Gellert Schubert.

   (1) DevScore = author_commits + author_lines_added /
   (project_lines_added / project_commits) + author_lines_deleted
   / (project_lines_deleted / project_commits)

   (2) including any documentation-related commits, excluding
   merge commits. Regarding imported patches/code, we do our best
   to count the work on behalf of the proper owner, as per the
   "fix_authors" and "mod_renames" arrays in
   opensips/doc/build-contrib.sh. If you identify any
   patches/commits which do not get properly attributed to you,
   please submit a pull request which extends "fix_authors" and/or
   "mod_renames".

   (3) ignoring whitespace edits, renamed files and auto-generated
   files

3.2. By Commit Activity

   Table 3.2. Most recently active contributors^(1) to this module
                      Name                   Commit Activity
   1.  Bogdan-Andrei Iancu (@bogdan-iancu) Nov 2003 - May 2020
   2.  Liviu Chircu (@liviuchircu)         Jan 2013 - Mar 2020
   3.  Jasper Hafkenscheid                 Mar 2020 - Mar 2020
   4.  Razvan Crainea (@razvancrainea)     Dec 2010 - Sep 2019
   5.  Dan Pascu (@danpascu)               May 2019 - May 2019
   6.  Vlad Patrascu (@rvlad-patrascu)     May 2017 - Apr 2019
   7.  Peter Lemenkov (@lemenkov)          Jun 2018 - Jun 2018
   8.  Shlomi Gutman                       Mar 2018 - Mar 2018
   9.  Ovidiu Sas (@ovidiusas)             Sep 2010 - Feb 2018
   10. Ionut Ionita (@ionutrazvanionita)   Nov 2014 - Nov 2016

   All remaining contributors: Walter Doekes (@wdoekes),
   Christophe Sollet (@csollet), Vlad Paiu (@vladpaiu), Maksym
   Sobolyev (@sobomax), Anca Vamanu, John Riordan, Emmanuel Buu,
   Andrei Dragus, Sergio Gutierrez, Klaus Darilion,
   Daniel-Constantin Mierla (@miconda), Konstantin Bokarius, Edson
   Gellert Schubert, Henning Westerholt (@henningw), Ancuta
   Onofrei, Marcus Hunger, Carsten Bock, Jeremie Le Hen, Laurent
   Schweizer, Bayan Towfiq, Andrei Pelinescu-Onciul, Elena-Ramona
   Modroiu, Jiri Kuthan (@jiriatipteldotorg), Jan Janak (@janakj),
   Nils Ohlmeier.

   (1) including any documentation-related commits, excluding
   merge commits

Chapter 4. Documentation

4.1. Contributors

   Last edited by: Jasper Hafkenscheid, Liviu Chircu
   (@liviuchircu), Vlad Patrascu (@rvlad-patrascu), Razvan Crainea
   (@razvancrainea), Bogdan-Andrei Iancu (@bogdan-iancu), Peter
   Lemenkov (@lemenkov), Ovidiu Sas (@ovidiusas), Ionut Ionita
   (@ionutrazvanionita), Walter Doekes (@wdoekes), Christophe
   Sollet (@csollet), Vlad Paiu (@vladpaiu), Maksym Sobolyev
   (@sobomax), Anca Vamanu, Andrei Dragus, Sergio Gutierrez, Klaus
   Darilion, Daniel-Constantin Mierla (@miconda), Konstantin
   Bokarius, Edson Gellert Schubert, Carsten Bock, Ancuta Onofrei,
   Marcus Hunger, Jeremie Le Hen, Bayan Towfiq, Elena-Ramona
   Modroiu, Jan Janak (@janakj), Jiri Kuthan (@jiriatipteldotorg).

   Documentation Copyrights:

   Copyright © 2018 VoIP Embedded, Inc.

   Copyright © 2003-2008 Sippy Software, Inc.

   Copyright © 2005 Voice Sistem SRL
