[Asterisk-Dev] DIAL_PRESERVE_CALLERID logic (Dial() option 'o')

[Kevin P. Fleming]

Thomas Andrews wrote:

> I was hunting down why my cid.cid_num kept on getting clobbered, and I
> discovered that someone had already solved my problem by introducing the
> DIAL_PRESERVE_CALLERID flag. The flag prevents cid_num from getting
> over-written with ${EXTEN}.
> 
> What I actually want to know is why anyone would *ever* want cid_num
> over-written with ${EXTEN} ?

Well.... this is a tricky situation. Look back in the archives around 
the time this was added to CVS, and you'll see lots of discussion 
related to it. Essentially, the change was made so that if the called 
channel gets parked/etc. when it returns to the parker it will have the 
correct (or at least close) CLID, instead of the parker's CLID. However, 
there are still many parts of this process that don't really work 
optimally, but it will take a significant rework of the CLID system to 
really do the job right.

I think a large number of system are run using the 'o' flag by default.