Re: [PATCH] AT2 module UDH decoding

Paul Bagyenda wrote:

> Hi people,
> 
>  Just came across a small discrepancy between how the SMPP module  
> decodes MO SMS UDH and how the AT2 module does the same. (To be  
> precise, somebody was testing the incoming concatenation patch I  posted 
> earlier, and tripped on this.)
> 
>  The short story is that the SMPP module includes the header length  in 
> the decoded UDH, while the AT2 module does not. The fix is a one- liner 
> (not the cleanest I admit, but it works). Attached.

Hi Paul,

yep, confirmed... so this means:

smsc_at.c - decodes PDU into msg struct with pure UDH data in msg->sms.udhdata:
[...]
     /* if there is a UDH */
     udhlen = 0;
     if (udhi && len > 0) {
         udhlen = octstr_get_char(pdu, pos);
         pos++;
         if (udhlen + 1 > len)
             goto msg_error;
         udh = octstr_copy(pdu, pos, udhlen);
         pos += udhlen;
         len -= udhlen + 1;
     } else if (len <= 0) /* len < 0 is impossible, but sure is sure */
         udhi = 0;
[...]

smsc_smpp.c: - decodes PDU into msg struct with lengh byte in front:
[...]
     /*
      * Encode udh if udhi set
      * for reference see GSM03.40, section 9.2.3.24
      */
     if (pdu->u.deliver_sm.esm_class & ESM_CLASS_SUBMIT_UDH_INDICATOR) {
         int udhl;
         udhl = octstr_get_char(msg->sms.msgdata, 0) + 1;
         debug("bb.sms.smpp",0,"SMPP[%s]: UDH length read as %d",
               octstr_get_cstr(smpp->conn->id), udhl);
         if (udhl > octstr_len(msg->sms.msgdata)) {
             error(0, "SMPP[%s]: Mallformed UDH length indicator 0x%03x while 
message length "
                      "0x%03lx. Discarding MO message.", 
octstr_get_cstr(smpp->conn->id),
                      udhl, octstr_len(msg->sms.msgdata));
             *reason = SMPP_ESME_RINVESMCLASS;
             goto error;
         }
         msg->sms.udhdata = octstr_copy(msg->sms.msgdata, 0, udhl);
         octstr_delete(msg->sms.msgdata, 0, udhl);
     }
[...]

Now, at least I totally agree that we need to change something here, since the 
modules act different, and we expect the msg->sms.udhdata to have the same value 
regardless which "smsc type" it used.

So votes please if we should add the length byte in udhdata or not.

I'm +0 on adding the length byte in smsc_at.c code, hence applying Paul's patch.

Stipe

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