Update kamailio.cfg to ring PBX longer than 16 seconds & support Sinch inbound calling

[danry25]

FusionPBX does not satisfy incoming calls with pbx_invite_timeout_aftertry getting triggered just after 3 rings, causing the current call to be rejected and the caller will generally reattempt, making a mess of your call log with many missed calls.

Added Sinch parsing on incoming SIP invites to remove values prefixed to the recipient's phone number that prevent Freeswitch from accepting calls.

[chelseatcarter]

Can one of the admins verify this patch?

[devopsec]

@danry25 thanks for submitting the PR.

The 16 seconds was chosen because it is within the 32 sec default INVITE timeout (RFC 3261 Timer B).
The current logic for inbound routes is tuned for that and will failover on any error to failover endpoint.

IMO there are better ways to handle this but users rely on that currently and it would be a major change to switch the default.

The better option is to simply change the timeout on your system, as it is configurable.

I do not mind the $ru parameter scrubbing on inbound calls but it would need some changes to make it in.
If you want to apply default transformations when the call is from a specific carrier, you need to filter on that carrier (i.e. IP or domain matching, etc..).
The better way to implement the parameter filtering would be a setting or group of settings on endpoint groups.