[Asterisk-Users] Caller ID with BT CD50

[Tony Hoyle]

Tony Hoyle wrote:

> That's the way the code is written (which is why you have 3 values in 
> the dring entry I think).  There's an assumption in the code that it has 
> 3 rings to compare with.
> 
Actually it's worse than that...  there is actually no terminator in the code.

It's looking for a distinct pattern of <ring>,<ring>,<short ring> and it 
terminates after <short ring>.  If you never get that theoretically it'll 
never terminate (and scrawl already the stack, memory etc. which isn't a good 
thing for an app running in the root context!!!).

The standard ring BT pattern I see is 367,247,217,96 (which is actually 
120,30,121, but the numbers are cumulative).  The 96 causes a break out of the 
loop after the 3rd ring.  If the 4th ring was >200 it would be a buffer 
overrun (this could be caused easily by, for example, two short rings followed 
by a long one).

So what I *suspect* is happening is this:

1. The code is working as written, but isn't really suitable for the UK... it 
will work though (you'll have to specify all 3 dring values though).
2. The 4th ring on your second number is actually causing a buffer overrun and 
corrupting asterisk... you're lucky it doesn't crash :)

I've changed the patch to fix the buffer overrun, plus a hack to only look for 
the dring values you specify, thus:

(just after the ++receivedRingT):

       if(receivedRingT==3)
          break; /* More than 3 rings would overrun our test buffer */

     /* If all 3 dring values are zero, then there's nothing left to detect */
       for (counter=0; counter < 3; counter++) {
            if (p->drings.ringnum[counter].ring[receivedRingT])
                break;
        }
        if (counter == 3)
            break;

In my case if I specify dring1=367,0,0 it'll stop trying to detect after the 
first ring.

Not sure I like all the hardcoded numbers for number of drings etc...  that's 
another patch though :)

Tony

-- 
Te audire no possum. Musa sapientum fixa est in aure.

Tony Hoyle <tmh at nodomain.org>  Key ID: 104D/4F4B6917 2003-09-13
Fingerprint: 063C AFB4 3026 F724 0AA2  02B8 E547 470E 4F4B 6917