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gsm/lapdm: Fix UI frames from BTS->MS have length (B4 format) 

This is part of a set of commit to fix LAPDm to handle datalink
connection on ACCH (SAPI 3)

This is required to transfer SMS on SACCH of TCH/f or SDCCH/8 (4).

Written-by: Andreas Eversberg <jolly@eversberg.eu>
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
This commit is contained in:
Andreas.Eversberg 2011-11-06 20:46:30 +01:00 committed by Harald Welte
parent f1f80de007
commit 816e178e99
1 changed files with 11 additions and 7 deletions
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18
src/gsm/lapdm.c
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@ -520,8 +520,10 @@ static int l2_ph_data_ind(struct msgb *msg, struct lapdm_entity *le,
if (mctx.link_id & 0x40) {
/* It was received from network on SACCH */
/* If sent by BTS, lapdm_fmt must be B4 */
if (le->mode == LAPDM_MODE_MS) {
/* If UI on SACCH sent by BTS, lapdm_fmt must be B4 */
if (le->mode == LAPDM_MODE_MS
&& LAPDm_CTRL_is_U(msg->l2h[3])
&& LAPDm_CTRL_U_BITS(msg->l2h[3]) == 0) {
mctx.lapdm_fmt = LAPDm_FMT_B4;
n201 = N201_B4;
LOGP(DLLAPD, LOGL_INFO, "fmt=B4\n");
@ -802,6 +804,8 @@ static int rslms_rx_rll_est_req(struct msgb *msg, struct lapdm_datalink *dl)
/* L3 requests transfer of unnumbered information */
static int rslms_rx_rll_udata_req(struct msgb *msg, struct lapdm_datalink *dl)
{
struct lapdm_entity *le = dl->entity;
int ui_bts = (le->mode == LAPDM_MODE_BTS);
struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
uint8_t chan_nr = rllh->chan_nr;
uint8_t link_id = rllh->link_id;
@ -828,9 +832,9 @@ static int rslms_rx_rll_udata_req(struct msgb *msg, struct lapdm_datalink *dl)
msg->l3h = (uint8_t *) TLVP_VAL(&tv, RSL_IE_L3_INFO);
length = TLVP_LEN(&tv, RSL_IE_L3_INFO);
/* check if the layer3 message length exceeds N201 */
if (length + 5 > 23) { /* FIXME: do we know the channel N201? */
if (length + 4 + !ui_bts > 23) {
LOGP(DLLAPD, LOGL_ERROR, "frame too large: %d > N201(%d) "
"(discarding)\n", length + 5, 23);
"(discarding)\n", length, 18 + ui_bts);
msgb_free(msg);
return -EIO;
}
@ -844,13 +848,13 @@ static int rslms_rx_rll_udata_req(struct msgb *msg, struct lapdm_datalink *dl)
msg->tail = msg->data + length;
/* Push L1 + LAPDm header on msgb */
msg->l2h = msgb_push(msg, 2 + 3);
msg->l2h = msgb_push(msg, 4 + !ui_bts);
msg->l2h[0] = le->tx_power;
msg->l2h[1] = le->ta;
msg->l2h[2] = LAPDm_ADDR(LAPDm_LPD_NORMAL, sapi, dl->dl.cr.loc2rem.cmd);
msg->l2h[3] = LAPDm_CTRL_U(LAPDm_U_UI, 0);
msg->l2h[4] = LAPDm_LEN(length);
// FIXME: short L2 header support
if (!ui_bts)
msg->l2h[4] = LAPDm_LEN(length);
/* Tramsmit */
return tx_ph_data_enqueue(dl, msg, chan_nr, link_id, 23);