handover,sysmobts: Handle handover in the sysmobts code

When the lchan was activated for handover configure it to wait
for a RACH burst. On release make sure to always release the
RACH SAPI (in case it has been allocated). On the first frame
inform handover.c about it and forward the received access burst
to the handover layer.

Using an E71 it was possible to make a handover for SDCCH and
TCH/F from a nanoBTS but also from itself to itself. The vty
commands of OpenBSC and the silent-call have been used for that.
I didn't verify audio handling so far.

1 files changed, 26 insertions, 0 deletions

diff --git a/src/osmo-bts-sysmo/l1_if.c b/src/osmo-bts-sysmo/l1_if.c
index 32da5d9f..bdd06f0d 100644
--- a/src/osmo-bts-sysmo/l1_if.c
+++ b/src/osmo-bts-sysmo/l1_if.c
@@ -47,6 +47,7 @@
 #include <osmo-bts/paging.h>
 #include <osmo-bts/measurement.h>
 #include <osmo-bts/pcu_if.h>
+#include <osmo-bts/handover.h>
 
 #include <sysmocom/femtobts/superfemto.h>
 #include <sysmocom/femtobts/gsml1prim.h>
@@ -705,6 +706,9 @@ static int handle_ph_data_ind(struct femtol1_hdl *fl1, GsmL1_PhDataInd_t *data_i
 			     data_ind->msgUnitParam.u8Size));
 	dump_meas_res(LOGL_DEBUG, &data_ind->measParam);
 
+	if (lchan->ho.active == HANDOVER_WAIT_FRAME)
+		handover_frame(lchan);
+
 	switch (data_ind->sapi) {
 	case GsmL1_Sapi_Sacch:
 		radio_link_timeout(lchan, (data_ind->msgUnitParam.u8Size == 0));
@@ -819,11 +823,26 @@ static int check_acc_delay(GsmL1_PhRaInd_t *ra_ind, struct gsm_bts_role_bts *bts
 	return *acc_delay <= btsb->max_ta;
 }
 
+static int handle_handover(struct gsm_lchan *lchan, struct gsm_bts_role_bts *btsb,
+				GsmL1_PhRaInd_t *ra_ind)
+{
+	uint8_t acc_delay;
+	if (!check_acc_delay(ra_ind, btsb, &acc_delay)) {
+		LOGP(DHO, LOGL_INFO, "%s ignoring RACH request %u > max_ta(%u)\n",
+			gsm_lchan_name(lchan), acc_delay, btsb->max_ta);
+		return 0;
+	}
+
+	handover_rach(lchan, ra_ind->msgUnitParam.u8Buffer[0], acc_delay);
+	return 0;
+}
+
 static int handle_ph_ra_ind(struct femtol1_hdl *fl1, GsmL1_PhRaInd_t *ra_ind)
 {
 	struct gsm_bts_trx *trx = fl1->priv;
 	struct gsm_bts *bts = trx->bts;
 	struct gsm_bts_role_bts *btsb = bts->role;
+	struct gsm_lchan *lchan;
 	struct osmo_phsap_prim pp;
 	struct lapdm_channel *lc;
 	uint8_t acc_delay;
@@ -836,6 +855,13 @@ static int handle_ph_ra_ind(struct femtol1_hdl *fl1, GsmL1_PhRaInd_t *ra_ind)
 	if (ra_ind->measParam.fLinkQuality < fl1->min_qual_rach)
 		return 0;
 
+	/*
+	 * Check if this is a handover
+	 */
+	lchan = l1if_hLayer_to_lchan(trx, ra_ind->hLayer2);
+	if (lchan && lchan->ho.active == HANDOVER_ENABLED)
+		return handle_handover(lchan, btsb, ra_ind);
+
 	/* increment number of RACH slots with valid RACH burst */
 	if (trx == bts->c0)
 		btsb->load.rach.access++;