[Asterisk-Dev] how does asterisk choose which network interface to bind with?

[Liang Huang]

I am trying to port Asterisk 1.0.3 to an embeded system -- a router+adsl 
modem+wlan access point, which has many network interfaces, such as 
ppp0, eth0, l0, wlan0, br0..... When asterisk loads SIP channel module, 
it complains:

# asterisk -vvvcdg
.
.
.
  [res_agi.so] => (Asterisk Gateway Interface (AGI))
   == Registered application 'DeadAGI'
   == Registered application 'EAGI'
   == Registered application 'AGI'
  [chan_sip.so] => (Session Initiation Protocol (SIP))
Sep  8 12:41:19 WARNING[318]: chan_sip.c:8683 reload_config: Unable to 
get IP address for (none), SIP disabled
   == Registered application 'SIPDtmfMode'
  [chan_local.so] => (Local Proxy Channel)
.
.
.

Then I set SIP's binding address to 192.168.1.153, which is the IP 
address of "br0", and br0 is the network interface with which the 
embeded system provides its services: thttpd, telnetd, sshd. So I guess 
I should bind SIP channel module to this IP:

# asterisk -vvvcdg
.
.
  [res_agi.so] => (Asterisk Gateway Interface (AGI))
   == Registered application 'DeadAGI'
   == Registered application 'EAGI'
   == Registered application 'AGI'
  [chan_sip.so] => (Session Initiation Protocol (SIP))
   == SIP Listening on 192.168.1.153:5060
   == Using TOS bits 0
   == Registered application 'SIPDtmfMode'
  [chan_local.so] => (Local Proxy Channel)
.
.

It looks like it works this time, but the problem is that my SIP clients 
can't register on this asterisk server. Clients keep sending SIP 
registration packets to the server and get no response. I turned on SIP 
debug of the asterisk server, and there is no SIP message.

Could anyone give me some suggestions? or tell me which part of the code 
I should read to understand how asterisk register its services (like sip 
gateway) to the embeded system. (BTW, the embeded system is a linux mips 
system).

Thanks a lot~~~~

Best Regards,

Liang