Changes between Version 75 and Version 76 of FAQ

Timestamp:

Aug 14, 2009 9:07:34 AM (15 years ago)

Author:

bennylp

Comment:

--

FAQ

@@ -851 +851 @@
 
 
-
+=== My machine has multiple NICs (multihomed) and PJSIP chooses the wrong IP interface === #multihomed
+
+If the machine is multihomed (such as when VPN is used), PJSIP will use the following logic to determine which IP address is used for the Contact and Via header.
+
+First of all, by default PJSIP binds sockets to INADDR_ANY (0.0.0.0), so it will be able to send and receive to/from any destinations configured in the system.
+
+An IP address will be choosen by using [http://www.pjsip.org/pjlib/docs/html/group__pj__addr__resolve.htm#g410b1bd02dcabf108b129e95368beef4 pj_gethostip()] function. Since version 1.2 this function selects which IP interface to use based on a scoring algorithm as follows:
+  - add 1 to the score of the IP that is resolved from gethostbyname(gethostname())
+  - add 2 to the score of the IP that is used as the default interface
+  - add 1 to the score of all interfaces from the interface enumeration. 
+  - add the end of the algorithm, choose interface with the highest score
+
+(Note: please see ticket #800 for the algorithm used on PJSIP version older than 1.2)
+
+This IP address then will be used in the Contact and Via header of the outgoing request
+
+If REGISTER is used, then this is becoming less of an issue. PJSUA-LIB will inspect the 200/OK response, check if the IP/port number seen by the server match the IP/port that we use in Contact, and if they're not the same, PJSUA-LIB will update the registration by sending un-REGISTER and new REGISTER with a new Contact. This new Contact then will be used for subsequent requests generated on behalf of the account.