[OpenSIPS-Users] Why does OpenSIPS replies "408" when getting "ICMP udp port XXXX unreachable" ?

[Iñaki Baz Castillo]

Hi, if OpenSIPS routes a request via UDP to SERVER_IP:SERVER_PORT and receives 
a ICMP error:

  ICMP SERVER_IP udp port SERVER_PORT unreachable

then OpenSIPS remains retransmiting the request (until transaction timer 
expires and so). After that it generates a 408 response.

I wonder why. Some firewalls are configured to drop UDP requests, so in case 
there is no application listening in UDP 5060, then the request is dropped 
and OpenSIPS retransmissions are justified.

But if the server replies an ICMP error, OpenSIPS should understand that the 
destination is unreachable (it's nothing listening in that port), so IMHO 
OpenSIPS whould generate an internal "network error" that would become 
a "503" according to RFC 3261, o a "477" according to the OpenSIPS behaviour 
when failing sending a request via TCP.

Am I wrong?


-- 
Iñaki Baz Castillo