[asterisk-dev] T38 Passthrough in chan_sip.c

[George Pajari]

Olle E Johansson wrote:
>
> 18 mar 2006 kl. 09.01 skrev George Pajari:
>
>> I'm trying to figure out why the T38 passthrough code generates 
>> warnings of the form "The other side of the bridge don't have udptl 
>> struct" and my investigations of the code suggest that the udptl 
>> structure is not allocated because the SIP channel does not have the 
>> flag SIP_PAGE2_T38SUPPORT_UDPTL set.
>>
>> But SIP_PAGE2_T38SUPPORT_UDPTL is defined with value 0:
>>
>> #define SIP_PAGE2_T38SUPPORT_UDPTL      (0 << 15)
>>
>> so how can this flag ever be set?
>>
>> Will not the test:
>>
>> ast_test_flag(&p->t38.t38support, SIP_PAGE2_T38SUPPORT_UDPTL)
>>
>> always be false?
> Too early in the morning...

I don't think so.

> That flag is the first flag, bit 0 of an allocation of three bits. We 
> use that
> many times if you look at lines above.

But you use SIP_PAGE2_T38SUPPORT_UDPTL as a bit mask yet the expression 
(0 << 15)  has no bits set. So  ast_test_flag(&p->t38.t38support, 
SIP_PAGE2_T38SUPPORT_UDPTL) must always be false regardless of the value 
of the t38support flag variable.

> For some reason, the receiving end of the call doesn't have the bit set.

It can never have the bit set as there is no bit set in the 
SIP_PAGE2_T38SUPPORT_UDPTL define. Hence the section of the code that 
"sets" this flag:

ast_set_flag(&global_flags_page2, SIP_PAGE2_T38SUPPORT_UDPTL);

has no effect on global_flags_page2 because SIP_PAGE2_T38SUPPORT_UDPTL == 0

> Do sip show peer on that peer and see if it has support enabled.

What, exactly, do you mean by "support enabled". If you mean "T38 pt 
UDPTL" in the "sip show peer" output, then this can never be Yes as 
explained above.

-- 
George Pajari, netVOICE communications    604 484 VOIP (484 8647 x102)
Open Source VoIP/Telephony Specialists  1 877 NET VOIP (638 8647 x102)
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