Re: Unable to decode PDU for SMS-STATUS-REPORT

[Philippe Nunes <philippe.nunes@linux.intel.com>]

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Hi,

On 06/25/2012 06:20 PM, Audric Schiltknecht wrote:
> On Mon, 25 Jun 2012 18:10:36 +0200, Audric Schiltknecht wrote:
>> Hi guys.
>>
>> I'm having troubles with delivery reports.
>>
>> When I send a message with the property "UseDeliveryReports" set to
>> "true",
>> I can get the delivery report from the GSM modem, but ofono is unable
>> to decode it:
>>
>> ofonod[677]: SMS: < \r\n+CDS:
>>
>> 32\r\n07913386094000F006DB0A810011223344216052714081802160527140228000\r\n
>>
>> ofonod[677]: drivers/atmodem/sms.c:at_cds_notify() Got new
>> Status-Report PDU via CDS:
>> 07913386094000F006DB0A810011223344216052714081802160527140228000, 32
>> ofonod[677]: src/sms.c:ofono_sms_status_notify() len 32 tpdu len 32
>> ofonod[677]: Unable to decode PDU
>>
>> The PDU is valid, since I can decode it using some online tool.
>>
>> It seems that sms_decode does not correctly handle the SMSCC part
>> (913386094000F0),
>> and tries to decode it as the sender address, which obviously fails.
>
>
> Digging a little further in the code, I found that the sms_decode()
> function is responsible
> of decoding the SMSC part of the PDU. However, this is done if tpdu_len
> < len, which is not the case,
> since both of them equal to 32.
>
> If I correctly understand, 'tpdu' is returned by the modem in the +CDS
> notification.
> Here, its value is 32, which is correct as shown in the logs.
> 'len' is calculated in the decode_hex_own_buffer() function called in
> the +CDS notification callback.
> Here, its value also is 32, and I do not see how it could not be that.
>
> Any help to point out my mistake(s) will be appreciated ;)
>

As pointed by Denis, the length given by the CDS notification should be 
the length of the TPDU part (PDU without SMSC). In your case, this value 
should be 24 and not 32.

07913386094000F0 | 06DB0A810011223344216052714081802160527140228000
----------------   ------------------------------------------------
SMSC (8 octets)  |           TPDU (24 octets)

decode_hex_own_buffer() function returns the length of the PDU 
(including the SMSC). In your case, this value is indeed 32.

So, you're facing definitely with an incorrect modem behavior.
Regards,

Philippe.