[GPRS] BSSGP/SGSN: Implement Gb-Interface Paging

We now have a function that generates BSSGP PS and CS paging request.

It is called from the libgtp code when we receive a GTP packet from
the GGSN for a MM context that is in SUSPEND state.  We then issue
a PS paging request to the Cell with the BVCI where the last RA update
was being performed.

TODO: We still don't enqueue the GTP packet (and transmit it on paging
complete), and we don't rate-limit the paging requests, i.e. every GTP packet
will trigger another paging request.

We probably also need some kind of logic that marks the phone as UNREGISTERED
if it doesn't respond to paging requests for some time.

2 files changed, 90 insertions, 0 deletions

diff --git a/openbsc/include/openbsc/gprs_bssgp.h b/openbsc/include/openbsc/gprs_bssgp.h
index 9eaf989a..e432cf75 100644
--- a/openbsc/include/openbsc/gprs_bssgp.h
+++ b/openbsc/include/openbsc/gprs_bssgp.h
@@ -199,6 +199,33 @@ static inline int bssgp_tlv_parse(struct tlv_parsed *tp, uint8_t *buf, int len)
 	return tlv_parse(tp, &tvlv_att_def, buf, len, 0, 0);
 }
 
+enum bssgp_paging_mode {
+	BSSGP_PAGING_PS,
+	BSSGP_PAGING_CS,
+};
+
+enum bssgp_paging_scope {
+	BSSGP_PAGING_BSS_AREA,		/* all cells in BSS */
+	BSSGP_PAGING_LOCATION_AREA,	/* all cells in LA */
+	BSSGP_PAGING_ROUTEING_AREA,	/* all cells in RA */
+	BSSGP_PAGING_BVCI,		/* one cell */
+};
+
+struct bssgp_paging_info {
+	enum bssgp_paging_mode mode;
+	enum bssgp_paging_scope scope;
+	struct gprs_ra_id raid;
+	uint16_t bvci;
+	const char *imsi;
+	uint32_t *ptmsi;
+	uint16_t drx_params;
+	uint8_t qos[3];
+};
+
+/* Send a single GMM-PAGING.req to a given NSEI/NS-BVCI */
+int gprs_bssgp_tx_paging(uint16_t nsei, uint16_t ns_bvci,
+			 struct bssgp_paging_info *pinfo);
+
 /* gprs_bssgp_vty.c */
 int gprs_bssgp_vty_init(void);
 
diff --git a/openbsc/src/gprs/gprs_bssgp.c b/openbsc/src/gprs/gprs_bssgp.c
index c7c49d4b..f27e3a7e 100644
--- a/openbsc/src/gprs/gprs_bssgp.c
+++ b/openbsc/src/gprs/gprs_bssgp.c
@@ -787,3 +787,66 @@ int gprs_bssgp_tx_dl_ud(struct msgb *msg, struct sgsn_mm_ctx *mmctx)
 
 	return gprs_ns_sendmsg(bssgp_nsi, msg);
 }
+
+/* Send a single GMM-PAGING.req to a given NSEI/NS-BVCI */
+int gprs_bssgp_tx_paging(uint16_t nsei, uint16_t ns_bvci,
+			 struct bssgp_paging_info *pinfo)
+{
+	struct msgb *msg = bssgp_msgb_alloc();
+	struct bssgp_normal_hdr *bgph =
+			(struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
+	uint16_t drx_params = htons(pinfo->drx_params);
+	uint8_t mi[10];
+	int imsi_len = gsm48_generate_mid_from_imsi(mi, pinfo->imsi);
+	uint8_t ra[6];
+
+	if (imsi_len < 2)
+		return -EINVAL;
+
+	msgb_nsei(msg) = nsei;
+	msgb_bvci(msg) = ns_bvci;
+
+	if (pinfo->mode == BSSGP_PAGING_PS)
+		bgph->pdu_type = BSSGP_PDUT_PAGING_PS;
+	else
+		bgph->pdu_type = BSSGP_PDUT_PAGING_CS;
+	/* IMSI */
+	msgb_tvlv_put(msg, BSSGP_IE_IMSI, imsi_len-2, mi+2);
+	/* DRX Parameters */
+	msgb_tvlv_put(msg, BSSGP_IE_DRX_PARAMS, 2,
+			(uint8_t *) &drx_params);
+	/* Scope */
+	switch (pinfo->scope) {
+	case BSSGP_PAGING_BSS_AREA:
+		{
+			uint8_t null = 0;
+			msgb_tvlv_put(msg, BSSGP_IE_BSS_AREA_ID, 1, &null);
+		}
+		break;
+	case BSSGP_PAGING_LOCATION_AREA:
+		gsm48_construct_ra(ra, &pinfo->raid);
+		msgb_tvlv_put(msg, BSSGP_IE_LOCATION_AREA, 4, ra);
+		break;
+	case BSSGP_PAGING_ROUTEING_AREA:
+		gsm48_construct_ra(ra, &pinfo->raid);
+		msgb_tvlv_put(msg, BSSGP_IE_ROUTEING_AREA, 6, ra);
+		break;
+	case BSSGP_PAGING_BVCI:
+		{
+			uint16_t bvci = htons(pinfo->bvci);
+			msgb_tvlv_put(msg, BSSGP_IE_BVCI, 2, (uint8_t *)&bvci);
+		}
+		break;
+	}
+	/* QoS profile mandatory for PS */
+	if (pinfo->mode == BSSGP_PAGING_PS)
+		msgb_tvlv_put(msg, BSSGP_IE_QOS_PROFILE, 3, pinfo->qos);
+
+	/* Optional (P-)TMSI */
+	if (pinfo->ptmsi) {
+		uint32_t ptmsi = htonl(*pinfo->ptmsi);
+		msgb_tvlv_put(msg, BSSGP_IE_TMSI, 4, (uint8_t *) &ptmsi);
+	}
+
+	return gprs_ns_sendmsg(bssgp_nsi, msg);
+}