[asterisk-users] How to set externip in sip.conf automatically?

[Larry Alkoff]

John Marvin wrote:
> Larry Alkoff wrote:
>> As stated in the original post, when I entter the IP with an editor 
>> directly into sip.conf calls work just fine but I am looking for a way 
>> to have that done _automatically_.
>>
>> The Asterisk - Future of Telephony book says it is possible for 
>> Asterisk to access a Linux environment variable containing the IP 
>> information in the form of "${ENV{variable}}.
>>
>> It doesn't seem to work.  I am asking how to make it work.
>>
> 
> Actually, I don't think you read his response carefully enough. He was 
> giving you a method of doing it automatically.
> 
> But first, lets dismiss the environment variable solution. I haven't 
> played with using environment variables in Asterisk, so I can't help you 
> there. But I do know about environment variables in general, and you 
> cannot use them to solve your problem. Environment variables are not 
> "global", i.e. if you change one it does not effect the value in all 
> currently running programs. The "environment" (all of the environment 
> variables and their values) is inherited from the parent process (it is 
> passed in by the kernel on the new processes stack when the process 
> first starts). After that, only the process itself can change its own 
> values in order to pass on a changed value to a child (but again, only 
> when that child process is started, i.e. a parent cannot affect the 
> environment of an already running child process). In summary, you can't 
> change the values of Asterisk's environment variables after Asterisk has 
> already started. The values that Asterisk sees are the values that it 
> inherited from its parent process, i.e. most likely the rc scripts that 
> started Asterisk when you first booted the machine.
> 
> Now, back to the solution proposed by Brad. He was in effect proposing 
> that you dynamically change sip.conf. However, parsing a rewriting 
> sip.conf automatically is kind of ugly, but luckily Asterisk supports 
> #include. So, he suggested that you can periodically generate a file 
> with a single line in it, i.e. "externip=xx.xx.xx.xx" and then use 
> #include in your sip.conf to include it (i.e. sip.conf doesn't have to 
> ever change). The final part of the solution is to make Asterisk reread 
> sip.conf (and the included dynamically created file at the same time). 
> You can do that with:
> 
>     asterisk -rx "sip reload"
> 
> which you can put into the same cron job that you currently are using to 
> refresh /etc/myip.
> 
> John

John you are quite correct about Brad's solution and I have to thank you 
both.  I thought again about Brad's post last night in bed - where I do 
my best work <g>.

The #include route is indeed a way to go.

In the meantime, I've found more about externhost which was implemented 
in Asterisk 1.20+.

I put a line in sip.conf of
externhost=myhost.dyndns.org
with a refresh of 6 hours against the default of 10 seconds ala
externrefresh=21600

This seems to be working nicely but, if there are problems, I'll change 
to #include.

You are also correct that environmental variables will not refresh until 
the Asterisk shell is reloaded - hopefully not often!

It would still be nice to be able to access shell variables from within 
the CLI and particularly frustrating since the "Asterisk - Future of 
Telephony" mentions a specific method on page 92.  Perhaps they got the 
syntax wrong.  I certainly would like a better connection between the 
shell and CLI.

Thanks for your explanation and I apologize for not realizing that 
Brad's suggestion was spot on.

Larry


-- 
Larry Alkoff N2LA - Austin TX
Using Thunderbird on Linux