Forward GPRS SUSPEND REQ from DCCH to PCU socket

As specified in 3GPP TS 03.60 Section 16.2.1 and 44.018 Section 3.4.15,
a Class B MS is sending a "RR GPRS SUSPEND REQ" via a DCCH to the BTS if
it wants to suspend GPRS services.  The BSS is now responsible to
somehow forward this to the SGSN.  As the Gs interface between BSC and
SGSN is both optional and doesn't have any provision to forward this
message, we have to send it over to the PCU so it can use regular BSSGP
signaling to inform the SGSN of the SUSPEND REQUEST.

This patch requires libosmocore Change-Id
I90113044460a6c511ced14f588876c4280d1cac7 for the related definition of
struct gsm48_gprs_susp_req.

Change-Id: I3c1af662c8f0d3d22da200638480f6ef05c3ed1f
Closes: OS#2249

4 files changed, 73 insertions, 9 deletions

diff --git a/include/osmo-bts/pcu_if.h b/include/osmo-bts/pcu_if.h
index 98efb570..6253c84c 100644
--- a/include/osmo-bts/pcu_if.h
+++ b/include/osmo-bts/pcu_if.h
@@ -15,6 +15,7 @@ int pcu_tx_rach_ind(struct gsm_bts *bts, int16_t qta, uint16_t ra, uint32_t fn,
 int pcu_tx_time_ind(uint32_t fn);
 int pcu_tx_pag_req(const uint8_t *identity_lv, uint8_t chan_needed);
 int pcu_tx_pch_data_cnf(uint32_t fn, uint8_t *data, uint8_t len);
+int pcu_tx_susp_req(struct gsm_lchan *lchan, uint32_t tlli, const uint8_t *ra_id, uint8_t cause);
 
 int pcu_sock_init(const char *path);
 void pcu_sock_exit(void);
diff --git a/include/osmo-bts/pcuif_proto.h b/include/osmo-bts/pcuif_proto.h
index b06077c3..144fba68 100644
--- a/include/osmo-bts/pcuif_proto.h
+++ b/include/osmo-bts/pcuif_proto.h
@@ -12,6 +12,7 @@
 #define PCU_IF_MSG_DATA_REQ	0x00	/* send data to given channel */
 #define PCU_IF_MSG_DATA_CNF	0x01	/* confirm (e.g. transmission on PCH) */
 #define PCU_IF_MSG_DATA_IND	0x02	/* receive data from given channel */
+#define PCU_IF_MSG_SUSP_REQ	0x03	/* BTS forwards GPRS SUSP REQ to PCU */
 #define PCU_IF_MSG_RTS_REQ	0x10	/* ready to send request */
 #define PCU_IF_MSG_DATA_CNF_DT	0x11	/* confirm (with direct tlli) */
 #define PCU_IF_MSG_RACH_IND	0x22	/* receive RACH */
@@ -171,6 +172,13 @@ struct gsm_pcu_if_pag_req {
 	uint8_t		identity_lv[9];
 } __attribute__ ((packed));
 
+/* BTS tells PCU about a GPRS SUSPENSION REQUEST received on DCCH */
+struct gsm_pcu_if_susp_req {
+	uint32_t	tlli;
+	uint8_t		ra_id[6];
+	uint8_t		cause;
+} __attribute__ ((packed));
+
 struct gsm_pcu_if {
 	/* context based information */
 	uint8_t		msg_type;	/* message type */
@@ -182,6 +190,7 @@ struct gsm_pcu_if {
 		struct gsm_pcu_if_data		data_cnf;
 		struct gsm_pcu_if_data_cnf_dt	data_cnf_dt;
 		struct gsm_pcu_if_data		data_ind;
+		struct gsm_pcu_if_susp_req	susp_req;
 		struct gsm_pcu_if_rts_req	rts_req;
 		struct gsm_pcu_if_rach_ind	rach_ind;
 		struct gsm_pcu_if_txt_ind	txt_ind;
diff --git a/src/common/pcu_sock.c b/src/common/pcu_sock.c
index 440f561d..d6946028 100644
--- a/src/common/pcu_sock.c
+++ b/src/common/pcu_sock.c
@@ -466,6 +466,23 @@ int pcu_tx_pch_data_cnf(uint32_t fn, uint8_t *data, uint8_t len)
 	return pcu_sock_send(&bts_gsmnet, msg);
 }
 
+/* forward data from a RR GPRS SUSPEND REQ towards PCU */
+int pcu_tx_susp_req(struct gsm_lchan *lchan, uint32_t tlli, const uint8_t *ra_id, uint8_t cause)
+{
+	struct msgb *msg;
+	struct gsm_pcu_if *pcu_prim;
+
+	msg = pcu_msgb_alloc(PCU_IF_MSG_SUSP_REQ, lchan->ts->trx->bts->nr);
+	if (!msg)
+		return -ENOMEM;
+	pcu_prim = (struct gsm_pcu_if *) msg->data;
+	pcu_prim->u.susp_req.tlli = tlli;
+	memcpy(pcu_prim->u.susp_req.ra_id, ra_id, sizeof(pcu_prim->u.susp_req.ra_id));
+	pcu_prim->u.susp_req.cause = cause;
+
+	return pcu_sock_send(&bts_gsmnet, msg);
+}
+
 static int pcu_rx_data_req(struct gsm_bts *bts, uint8_t msg_type,
 	const struct gsm_pcu_if_data *data_req)
 {
diff --git a/src/common/rsl.c b/src/common/rsl.c
index f93ca50d..5287201e 100644
--- a/src/common/rsl.c
+++ b/src/common/rsl.c
@@ -29,6 +29,7 @@
 #include <sys/types.h>
 #include <arpa/inet.h>
 
+#include <osmocom/core/byteswap.h>
 #include <osmocom/core/msgb.h>
 #include <osmocom/core/talloc.h>
 #include <osmocom/gsm/rsl.h>
@@ -36,6 +37,7 @@
 #include <osmocom/gsm/gsm0808.h>
 #include <osmocom/gsm/protocol/gsm_12_21.h>
 #include <osmocom/gsm/protocol/gsm_08_58.h>
+#include <osmocom/gsm/protocol/gsm_04_08.h>
 #include <osmocom/gsm/protocol/ipaccess.h>
 #include <osmocom/trau/osmo_ortp.h>
 
@@ -2557,32 +2559,35 @@ static inline int rsl_link_id_is_sacch(uint8_t link_id)
 		return 0;
 }
 
-static int rslms_is_meas_rep(struct msgb *msg)
+static int rslms_get_meas_msg_type(struct msgb *msg, bool rllh_link_id_is_sacch)
 {
 	struct abis_rsl_common_hdr *rh = msgb_l2(msg);
 	struct abis_rsl_rll_hdr *rllh;
 	struct gsm48_hdr *gh;
 
 	if ((rh->msg_discr & 0xfe) != ABIS_RSL_MDISC_RLL)
-		return 0;
+		return -1;
 
 	if (rh->msg_type != RSL_MT_UNIT_DATA_IND)
-		return 0;
+		return -2;
 
 	rllh = msgb_l2(msg);
-	if (rsl_link_id_is_sacch(rllh->link_id) == 0)
-		return 0;
+	if (rsl_link_id_is_sacch(rllh->link_id) != rllh_link_id_is_sacch)
+		return -3;
 
 	gh = msgb_l3(msg);
 	if (gh->proto_discr != GSM48_PDISC_RR)
-		return 0;
+		return -4;
+
+	return gh->msg_type;
+}
 
-	switch (gh->msg_type) {
+static int rslms_is_meas_rep(struct msgb *msg)
+{
+	switch (rslms_get_meas_msg_type(msg, 1)) {
 	case GSM48_MT_RR_MEAS_REP:
 	case GSM48_MT_RR_EXT_MEAS_REP:
 		return 1;
-	default:
-		break;
 	}
 
 	/* FIXME: this does not cover the Bter frame format and the associated
@@ -2591,6 +2596,36 @@ static int rslms_is_meas_rep(struct msgb *msg)
 	return 0;
 }
 
+static int rslms_is_gprs_susp_req(struct msgb *msg)
+{
+	return rslms_get_meas_msg_type(msg, 0) == GSM48_MT_RR_GPRS_SUSP_REQ;
+}
+
+/* TS 44.018 9.1.13b GPRS suspension request */
+static int handle_gprs_susp_req(struct msgb *msg)
+{
+	struct gsm48_hdr *gh = msgb_l3(msg);
+	struct gsm48_gprs_susp_req *gsr;
+	uint32_t tlli;
+	int rc;
+
+	if (!gh || msgb_l3len(msg) < sizeof(*gh)+sizeof(*gsr)) {
+		LOGP(DRSL, LOGL_NOTICE, "%s Short GPRS SUSPEND REQ received, ignoring\n", gsm_lchan_name(msg->lchan));
+		return -EINVAL;
+	}
+
+	gsr = (struct gsm48_gprs_susp_req *) gh->data;
+	tlli = osmo_ntohl(gsr->tlli);
+
+	LOGP(DRSL, LOGL_INFO, "%s Fwd GPRS SUSPEND REQ for TLLI=0x%08x to PCU\n",
+		gsm_lchan_name(msg->lchan), tlli);
+	rc = pcu_tx_susp_req(msg->lchan, tlli, gsr->ra_id, gsr->cause);
+
+	msgb_free(msg);
+
+	return rc;
+}
+
 static inline uint8_t ms_to2rsl(const struct gsm_lchan *lchan, const struct lapdm_entity *le)
 {
 	return (lchan->ms_t_offs >= 0) ? lchan->ms_t_offs : (lchan->p_offs - le->ta);
@@ -2731,6 +2766,8 @@ int lapdm_rll_tx_cb(struct msgb *msg, struct lapdm_entity *le, void *ctx)
 		rc = rsl_tx_meas_res(lchan, msgb_l3(msg), msgb_l3len(msg), le);
 		msgb_free(msg);
 		return rc;
+	} else if (rslms_is_gprs_susp_req(msg)) {
+		return handle_gprs_susp_req(msg);
 	} else {
 		LOGP(DRSL, LOGL_INFO, "%s Fwd RLL msg %s from LAPDm to A-bis\n",
 			gsm_lchan_name(lchan), rsl_msg_name(rh->msg_type));