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/integer)
              1.4.8. remove_on_timeout_bflag (string/integer)
              1.4.9. sipping_latency_flag (string/integer)
              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)

        1.5. 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_interval parameter
   1.15. Set natping_interval parameter
   1.16. Set ping_threshold parameter
   1.17. Set ping_threshold parameter
   1.18. fix_nated_contact usage
   1.19. fix_nated_sdp usage
   1.20. add_rcv_paramer usage
   1.21. fix_nated_register usage
   1.22. 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.

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/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.

   WARNING: Setting INT flags is deprecated! Use quoted strings
   instead!

   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/integer)

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

   WARNING: Setting INT flags is deprecated! Use quoted strings
   instead!

   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/integer)

   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_interval 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 natping_interval 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 ping_threshold parameter
...
modparam("nathelper", "max_pings_lost", 5)
...

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.

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

   Example 1.18. 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 - 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).
          + 0x10 - force rewrite of null media IP and/or origin IP
            address. Without this flag, null IPs are left
            untouched.
     * ip_address - IP to be used for rewriting 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.
     * sdp_fields - 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 1.19. 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 - 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 1.20. 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 1.21. 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 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

   Enables natping if parameter value greater than 0. Disables
   natping if parameter value is 0. With no parameter, it returns
   the current natping status.

   The function may takean optional parameter (for set operations)
   - a number in decimal format.

   Example 1.22. nh_enable_ping usage
...
$ opensipsctl fifo nh_enable_ping
Status:: 1
$
$ opensipsctl fifo nh_enable_ping 0
$
$ opensipsctl fifo nh_enable_ping
Status:: 0
$
...

Chapter 2. Frequently Asked Questions

   2.1.

       Where can I find more about OpenSIPS?

       Take a look at http://www.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. Maksym Sobolyev (@sobomax) 153 39 3533 4766
   2. Bogdan-Andrei Iancu (@bogdan-iancu) 141 111 1815 784
   3. Ionut Ionita (@ionutrazvanionita) 40 15 1598 627
   4. Liviu Chircu (@liviuchircu) 36 27 386 249
   5. Razvan Crainea (@razvancrainea) 29 22 143 236
   6. Daniel-Constantin Mierla (@miconda) 22 17 142 124
   7. Jan Janak (@janakj) 21 11 780 129
   8. Anca Vamanu 21 4 1602 185
   9. Andrei Pelinescu-Onciul 20 17 121 110
   10. Ovidiu Sas (@ovidiusas) 18 13 110 173

   All remaining contributors: Jiri Kuthan (@jiriatipteldotorg),
   Ancuta Onofrei, Andrei Dragus, Vlad Paiu (@vladpaiu), Henning
   Westerholt (@henningw), Christophe Sollet (@csollet), Marcus
   Hunger, Vlad Patrascu (@rvlad-patrascu), Klaus Darilion, Sergio
   Gutierrez, Nils Ohlmeier, Emmanuel Buu, Carsten Bock, Shlomi
   Gutman, Jeremie Le Hen, Bayan Towfiq, Laurent Schweizer,
   Konstantin Bokarius, John Riordan, 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.  Liviu Chircu (@liviuchircu)         Jan 2013 - Aug 2018
   2.  Razvan Crainea (@razvancrainea)     Dec 2010 - Jul 2018
   3.  Bogdan-Andrei Iancu (@bogdan-iancu) Nov 2003 - Jun 2018
   4.  Shlomi Gutman                       Mar 2018 - Mar 2018
   5.  Ovidiu Sas (@ovidiusas)             Sep 2010 - Feb 2018
   6.  Vlad Patrascu (@rvlad-patrascu)     May 2017 - Aug 2017
   7.  Ionut Ionita (@ionutrazvanionita)   Nov 2014 - Nov 2016
   8.  Walter Doekes (@wdoekes)            May 2014 - May 2014
   9.  Christophe Sollet (@csollet)        Dec 2009 - Oct 2013
   10. Vlad Paiu (@vladpaiu)               Aug 2010 - Jun 2012

   All remaining contributors: 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: Liviu Chircu (@liviuchircu), Bogdan-Andrei
   Iancu (@bogdan-iancu), Ovidiu Sas (@ovidiusas), Ionut Ionita
   (@ionutrazvanionita), Razvan Crainea (@razvancrainea), 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).

   doc copyrights:

   Copyright © 2018 VoIP Embedded, Inc.

   Copyright © 2003-2008 Sippy Software, Inc.

   Copyright © 2005 Voice Sistem SRL
