Hi all,
I'm looking at USSD message generation in openbsc, and would like to move a bit of msg generation to libosmocore.
However, in libosmocore's gsm0480.c I already find an implementation that seems to do the same, yet with some differences I'm not sure how to deal with.
The function originally in openbsc: gsm0480_send_releaseComplete()
On the iu branch, I've moved the msg generation to gsm0480_gen_releaseComplete() This should rather go to libosmocore.
There I already find gsm0480_create_ussd_resp()
The openbsc variants are rather shorter. Is it incomplete/incorrect?? Is the libosmocore gsm0480_create_ussd_resp() just bloat for this case??
For convenience, let me paste the code:
openbsc's Release Complete, very lean:
struct msgb *gsm0480_gen_releaseComplete(void) { struct msgb *msg;
msg = gsm48_msgb_alloc_name("GSM 04.08 USSD REL COMPL"); if (!msg) return NULL;
gsm0480_l3hdr_push(msg, GSM48_PDISC_NC_SS, GSM0480_MTYPE_RELEASE_COMPLETE); return msg; }
Note that the above does not set a direction flag nor trans_id in the proto_discr, like libosmocore's gsm0480_create_ussd_resp() does; neither do I understand the purpose of all the constant "code/id" TLs and wrapping:
struct msgb *gsm0480_create_ussd_resp(uint8_t invoke_id, uint8_t trans_id, const char *text) { struct msgb *msg; uint8_t *ptr8; int response_len;
msg = msgb_alloc_headroom(1024, 128, "GSM 04.80"); if (!msg) return NULL;
/* First put the payload text into the message */ ptr8 = msgb_put(msg, 0); gsm_7bit_encode_n_ussd(ptr8, msgb_tailroom(msg), text, &response_len); msgb_put(msg, response_len);
/* Then wrap it as an Octet String */ msgb_wrap_with_TL(msg, ASN1_OCTET_STRING_TAG);
/* Pre-pend the DCS octet string */ msgb_push_TLV1(msg, ASN1_OCTET_STRING_TAG, 0x0F);
/* Then wrap these as a Sequence */ msgb_wrap_with_TL(msg, GSM_0480_SEQUENCE_TAG);
/* Pre-pend the operation code */ msgb_push_TLV1(msg, GSM0480_OPERATION_CODE, GSM0480_OP_CODE_PROCESS_USS_REQ);
/* Wrap the operation code and IA5 string as a sequence */ msgb_wrap_with_TL(msg, GSM_0480_SEQUENCE_TAG);
/* Pre-pend the invoke ID */ msgb_push_TLV1(msg, GSM0480_COMPIDTAG_INVOKE_ID, invoke_id);
/* Wrap this up as a Return Result component */ msgb_wrap_with_TL(msg, GSM0480_CTYPE_RETURN_RESULT);
/* Wrap the component in a Facility message */ msgb_wrap_with_TL(msg, GSM0480_IE_FACILITY);
/* And finally pre-pend the L3 header */ gsm0480_l3hdr_push(msg, GSM48_PDISC_NC_SS | trans_id | (1<<7) /* TI direction = 1 */, GSM0480_MTYPE_RELEASE_COMPLETE); return msg; }
Thanks for any insights!
~N