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abis_nm: fix ARFCN list encoding in Set Channel Attributes 

3GPP TS 12.21 defines coding of 'ARFCN List' attribute as follows:

  +---------------------------+--------------------+
  | Attribute Identifier      | 1st octet          |
  +---------------------------+--------------------+
  | Length                    | 2-3 octets         |
  +---------------------------+--------------------+
  | ARFCN1                    | 4-5 octets         |
  +---------------------------+--------------------+
  | ...                       | ...                |
  +---------------------------+--------------------+
  | ARFCNn                    | (n * 2 - 3) octets |
  +---------------------------+--------------------+

so this is basically TL16V, where L16 is the length of V.

In the Siemens dialect of OML coding rules are different though:

  +---------------------------+--------------------+
  | Attribute Identifier      | 1st octet          |
  +---------------------------+--------------------+
  | ARFCN count               | 2nd octet          |
  +---------------------------+--------------------+
  | ARFCN1                    | 4-5 octets         |
  +---------------------------+--------------------+
  | ...                       | ...                |
  +---------------------------+--------------------+
  | ARFCNn                    | (n * 2 - 2) octets |
  +---------------------------+--------------------+

so this is TCV, where C is the amount of ARFCNs in V.

This change fixes encoding of 'ARFCN List' for other dialects,
in particular encoding of the 'Length' field (1 vs 2 octets).
I verified the results in Wireshark (generic 3GPP TS 12.21
and ip.access dialect), everything looks good.

Change-Id: Iec1826f55459ac8e9355328a1a6bb0949874db60
Related: OS#4545
This commit is contained in:
Vadim Yanitskiy 2020-05-29 16:38:36 +07:00 committed by laforge
parent 1c963eb97d
commit 83e6e613a7
1 changed files with 28 additions and 11 deletions
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39
src/osmo-bsc/abis_nm.c
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@ -2019,26 +2019,43 @@ int abis_nm_set_channel_attr(struct gsm_bts_trx_ts *ts, uint8_t chan_comb)
msgb_tv_put(msg, NM_ATT_CHAN_COMB, chan_comb);
if (ts->hopping.enabled) {
unsigned int i;
uint8_t *len;
unsigned int i, n;
uint16_t *u16 = NULL;
uint8_t *u8 = NULL;
msgb_tv_put(msg, NM_ATT_HSN, ts->hopping.hsn);
msgb_tv_put(msg, NM_ATT_MAIO, ts->hopping.maio);
/* build the ARFCN list */
msgb_put_u8(msg, NM_ATT_ARFCN_LIST);
len = msgb_put(msg, 1);
*len = 0;
for (i = 0; i < ts->hopping.arfcns.data_len*8; i++) {
/* 3GPP TS 12.21 defines this IE as TL16V */
if (bts->type != GSM_BTS_TYPE_BS11)
u16 = (uint16_t *) msgb_put(msg, 2);
else /* ... but BS-11 wants TLV instead */
u8 = (uint8_t *) msgb_put(msg, 1);
/* build the ARFCN list from pre-computed bitmap */
for (i = 0, n = 0; i < ts->hopping.arfcns.data_len*8; i++) {
if (bitvec_get_bit_pos(&ts->hopping.arfcns, i)) {
msgb_put_u16(msg, i);
/* At least BS-11 wants a TLV16 here */
if (bts->type == GSM_BTS_TYPE_BS11)
*len += 1;
else
*len += sizeof(uint16_t);
n += 1;
}
}
/* BS-11 cannot handle more than 255 ARFCNs, because L is 8 bit.
* This is unlikely to happen, but better check than sorry... */
if (bts->type == GSM_BTS_TYPE_BS11 && n > 0xff) {
LOGPFOH(DNM, LOGL_ERROR, foh, "%s cannot handle %u (more than 255) "
"hopping channels\n", gsm_bts_name(bts), n);
msgb_free(msg);
return -EINVAL;
}
/* 3GPP TS 12.21 defines L as length of the V part (in octets) */
if (bts->type != GSM_BTS_TYPE_BS11)
*u16 = htons(n * sizeof(*u16));
else /* ... BS-11 wants the number of channels instead */
*u8 = n;
}
msgb_tv_put(msg, NM_ATT_TSC, gsm_ts_tsc(ts)); /* training sequence */
if (bts->type == GSM_BTS_TYPE_BS11)