abis_rsl: Send the IMMEDIATE Assignment after the Channel Ack.

The Channel Activate might be sent to a different TRX than the
Immediate Assignment. So we need to make sure that the channel
is activated before we send the immediate assignment for the RACH.

Another reason for that is according to GSM 08.58 we should take
the frame number from the activate and use it for the starting
time inside the immediate assignment message. We obviously do not
do this yet.

The code assumes that the BTS will either respond with a CHAN ACK
or a CHAN NACK if not the lchan will remain in the request state.

1 files changed, 40 insertions, 13 deletions

diff --git a/openbsc/src/abis_rsl.c b/openbsc/src/abis_rsl.c
index 266cb17cf..6a905d252 100644
--- a/openbsc/src/abis_rsl.c
+++ b/openbsc/src/abis_rsl.c
@@ -42,11 +42,15 @@
 #include <openbsc/rtp_proxy.h>
 #include <osmocore/rsl.h>
 
+#include <osmocore/talloc.h>
+
 #define RSL_ALLOC_SIZE		1024
 #define RSL_ALLOC_HEADROOM	128
 
 #define MAX(a, b) (a) >= (b) ? (a) : (b)
 
+static int rsl_send_imm_assignment(struct gsm_lchan *lchan);
+
 static u_int8_t mdisc_by_msgtype(u_int8_t msg_type)
 {
 	/* mask off the transparent bit ? */
@@ -795,6 +799,13 @@ static int rsl_rx_chan_act_ack(struct msgb *msg)
 			gsm_lchans_name(msg->lchan->state));
 	rsl_lchan_set_state(msg->lchan, LCHAN_S_ACTIVE);
 
+	if (msg->lchan->rqd_ref) {
+		rsl_send_imm_assignment(msg->lchan);
+		talloc_free(msg->lchan->rqd_ref);
+		msg->lchan->rqd_ref = NULL;
+		msg->lchan->rqd_ta = 0;
+	}
+
 	dispatch_signal(SS_LCHAN, S_LCHAN_ACTIVATE_ACK, msg->lchan);
 
 	return 0;
@@ -1139,14 +1150,11 @@ static int rsl_rx_chan_rqd(struct msgb *msg)
 {
 	struct gsm_bts *bts = msg->trx->bts;
 	struct abis_rsl_dchan_hdr *rqd_hdr = msgb_l2(msg);
-	u_int8_t buf[GSM_MACBLOCK_LEN];
-	struct gsm48_imm_ass *ia = (struct gsm48_imm_ass *) buf;
 	struct gsm48_req_ref *rqd_ref;
 	enum gsm_chan_t lctype;
 	enum gsm_chreq_reason_t chreq_reason;
 	struct gsm_lchan *lchan;
 	u_int8_t rqd_ta;
-	int ret;
 
 	u_int16_t arfcn;
 	u_int8_t ts_number, subch;
@@ -1185,6 +1193,17 @@ static int rsl_rx_chan_rqd(struct msgb *msg)
 		     gsm_lchans_name(lchan->state));
 	rsl_lchan_set_state(lchan, LCHAN_S_ACT_REQ);
 
+	/* save the RACH data as we need it after the CHAN ACT ACK */
+	lchan->rqd_ref = talloc_zero(bts, struct gsm48_req_ref);
+	if (!lchan->rqd_ref) {
+		LOGP(DRSL, LOGL_ERROR, "Failed to allocate gsm48_req_ref.\n");
+		lchan_free(lchan);
+		return -ENOMEM;
+	}
+
+	memcpy(lchan->rqd_ref, rqd_ref, sizeof(*rqd_ref));
+	lchan->rqd_ta = rqd_ta;
+
 	ts_number = lchan->ts->nr;
 	arfcn = lchan->ts->trx->arfcn;
 	subch = lchan->nr;
@@ -1194,8 +1213,23 @@ static int rsl_rx_chan_rqd(struct msgb *msg)
 	lchan->bs_power = 0; /* 0dB reduction, output power = Pn */
 	lchan->rsl_cmode = RSL_CMOD_SPD_SIGN;
 	lchan->tch_mode = GSM48_CMODE_SIGN;
+
+	/* FIXME: Start another timer or assume the BTS sends a ACK/NACK? */
 	rsl_chan_activate_lchan(lchan, 0x00, rqd_ta, 0);
 
+	DEBUGP(DRSL, "%s Activating ARFCN(%u) SS(%u) lctype %s "
+		"r=%s ra=0x%02x\n", gsm_lchan_name(lchan), arfcn, subch,
+		gsm_lchant_name(lchan->type), gsm_chreq_name(chreq_reason),
+		rqd_ref->ra);
+	return 0;
+}
+
+static int rsl_send_imm_assignment(struct gsm_lchan *lchan)
+{
+	struct gsm_bts *bts = lchan->ts->trx->bts;
+	u_int8_t buf[GSM_MACBLOCK_LEN];
+	struct gsm48_imm_ass *ia = (struct gsm48_imm_ass *) buf;
+
 	/* create IMMEDIATE ASSIGN 04.08 messge */
 	memset(ia, 0, sizeof(*ia));
 	/* we set ia->l2_plen once we know the length of the MA below */
@@ -1205,8 +1239,8 @@ static int rsl_rx_chan_rqd(struct msgb *msg)
 	gsm48_lchan2chan_desc(&ia->chan_desc, lchan);
 
 	/* use request reference extracted from CHAN_RQD */
-	memcpy(&ia->req_ref, rqd_ref, sizeof(ia->req_ref));
-	ia->timing_advance = rqd_ta;
+	memcpy(&ia->req_ref, lchan->rqd_ref, sizeof(ia->req_ref));
+	ia->timing_advance = lchan->rqd_ta;
 	if (!lchan->ts->hopping.enabled) {
 		ia->mob_alloc_len = 0;
 	} else {
@@ -1215,20 +1249,13 @@ static int rsl_rx_chan_rqd(struct msgb *msg)
 	}
 	ia->l2_plen = GSM48_LEN2PLEN(sizeof(*ia) + ia->mob_alloc_len);
 
-	DEBUGP(DRSL, "%s Activating ARFCN(%u) SS(%u) lctype %s "
-		"r=%s ra=0x%02x\n", gsm_lchan_name(lchan), arfcn, subch,
-		gsm_lchant_name(lchan->type), gsm_chreq_name(chreq_reason),
-		rqd_ref->ra);
-
 	/* Start timer T3101 to wait for GSM48_MT_RR_PAG_RESP */
 	lchan->T3101.cb = t3101_expired;
 	lchan->T3101.data = lchan;
 	bsc_schedule_timer(&lchan->T3101, bts->network->T3101, 0);
 
 	/* send IMMEDIATE ASSIGN CMD on RSL to BTS (to send on CCCH to MS) */
-	ret = rsl_imm_assign_cmd(bts, sizeof(*ia)+ia->mob_alloc_len, (u_int8_t *) ia);
-
-	return ret;
+	return rsl_imm_assign_cmd(bts, sizeof(*ia)+ia->mob_alloc_len, (u_int8_t *) ia);
 }
 
 /* MS has requested a channel on the RACH */