isrlgb at gmail.com
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 Posted: Tue Jun 02, 2015 5:19 pm Post subject: [asterisk-users] תשובה: Forward loop protection... |
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We could probably parse the rdnis field to see if it that hop is on the list
מאת: Kevin Larsen
נשלח: יום רביעי, 3 ביוני 2015 01:11
אל: Asterisk Users Mailing List - Non-Commercial Discussion
השב ל: Asterisk Users Mailing List - Non-Commercial Discussion
נושא: Re: [asterisk-users] Forward loop protection...
| Quote: | | Quote: | The loop checking is a bit more challenging than that. If Bob
forwards to Fred and Fred forwards to Sue, all is well when Bob and
Fred head out for a beer. A little later, we’re in deep doo-do0 when
Sue forwards to Bob.
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| Quote: | Could this possibly mean that any person who has CF set should never
be available as CF Destination. Simple db entry/check can have this done.
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That just goes to show that the problem can get complex pretty quickly. Using the original example above, it might be that you want to allow the Bob to Fred to Sue forwards, but only stop it if the Sue to Bob link is established, thus creating the loop. I wonder if you could do some kind of recursive check where you follow each forward and if you ever come back around to a number you have already checked you know there is a loop.
To reuse the example above, on the creation of the Bob to Fred forward, the database is checked to see if Fred has any forwards. He doesn't, so is at the end of the forwarding chain. Now Fred forwards to Sue. Again, she is at the end of the chain, so it is allowed. When Sue goes to forward to Bob, the check shows that Bob has a forward. Not a problem, but we create a temporary list that has Sue's number in it. Then we check the next stage of forwarding. Bob forwards to Fred. Fred's is checked against our temporary list and doesn't match, so we are still good. Bob's number is now added to the temporary list and we check the forward Fred has in place. Fred forward's to Sue. We check Sue's number against the temporary list and it does exist. Thus we have a loop detected and the forward can now be denied.
I am guessing with the recursion involved you might want to do the check outside of Asterisk and pass the result back in. I will also state that I have not had to do this deep checking in the past, so these are just some initial thoughts on how I would start approaching the problem. Of course, this also assumes that Bob, Fred, and Sue are all on the same phone system. If you don't have a shared database to look at, the problem just got harder indeed. |
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