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LAPDm: Reject (release) establishment on DCCH, SAPI 0 without L3 payload 

If the channel is activated for immediate assignment, the initial data
link establishment on main signaling link with SAPI 0 must have L3
infomation included in the SABM message. If this is not the case,
release the data link without notifying BSC.

Related: OS#5971
Change-Id: I6819b51a876b8743c2d4a04165b7900723a1631c
This commit is contained in:
Andreas Eversberg 2023-11-21 14:26:43 +01:00
parent bc6cc67115
commit 647b8d0978
2 changed files with 22 additions and 0 deletions
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2
include/osmo-bts/lchan.h
View File

@ -208,6 +208,8 @@ struct gsm_lchan {
uint8_t sapis_dl[23];
uint8_t sapis_ul[23];
struct lapdm_channel lapdm_ch;
/* It is required to have L3 info with DL establishment. */
bool l3_info_estab;
struct llist_head dl_tch_queue;
unsigned int dl_tch_queue_len;
struct {

20
src/common/rsl.c
View File

@ -1907,6 +1907,9 @@ static int rsl_rx_chan_activ(struct msgb *msg)
reactivation = true;
}
/* If Activation Type is IMMEDIATE ASSIGNMENT, we expect L3 info with establishment. */
lchan->l3_info_estab = (type == RSL_ACT_INTRA_IMM_ASS);
if (!reactivation && lchan->state != LCHAN_S_NONE) {
LOGPLCHAN(lchan, DRSL, LOGL_ERROR, "error: lchan is not available, but in state: %s.\n",
gsm_lchans_name(lchan->state));
@ -3831,6 +3834,23 @@ int lapdm_rll_tx_cb(struct msgb *msg, struct lapdm_entity *le, void *ctx)
msg->trx = lchan->ts->trx;
msg->lchan = lchan;
/* If DL estabishment on main signaling link and SAPI 0 with L3 info is expected. */
if (lchan->l3_info_estab && rh->msg_type == RSL_MT_EST_IND) {
struct abis_rsl_rll_hdr *rllh = msgb_l2(msg);
if ((rllh->link_id & 0xc7) == 0) {
/* Reject initial establishment without L3 info. */
if (msgb_l2len(msg) == sizeof(struct abis_rsl_rll_hdr)) {
LOGPLCHAN(lchan, DRSL, LOGL_ERROR, "RLL EST IND without contention resolution.\n");
/* Release normally, re-use the msgb. */
rh->msg_type = RSL_MT_REL_REQ;
msgb_tv_put(msg, RSL_IE_RELEASE_MODE, RSL_REL_NORMAL);
return rsl_rx_rll(lchan->ts->trx, msg);
}
/* Re-estabishment without contention resoltuion is allowed. */
lchan->l3_info_estab = false;
}
}
/* If this is a Measurement Report, then we simply ignore it,
* because it has already been processed in l1sap_ph_data_ind(). */
if (rslms_is_meas_rep(msg)) {