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Add GSMTAP encapsulation of RLP frames in CSD NT mode

In CSD (Circuit Switched Data) NT (Non-Transparent) mode, there
are RLP (Radio Link Protocol) frames inside the modified V.110.

wireshark alrady has a dissector for this, and we've introduced
a GSMTAP type for RLP some time ago.  So with this patch, we now
generate such GSMTAP RLP frames.

Change-Id: I6a258458822bcb3fe7290a9b9b3d104beecda219
---
M src/common/l1sap.c
1 file changed, 55 insertions(+), 3 deletions(-)

git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/24/35124/1

diff --git a/src/common/l1sap.c b/src/common/l1sap.c
index c599726..4b2ca02 100644
--- a/src/common/l1sap.c
+++ b/src/common/l1sap.c
@@ -1841,19 +1841,54 @@
 	return 1;
 }
 
-static void send_ul_rtp_packet_data(struct gsm_lchan *lchan, uint32_t fn,
+static void gsmtap_csd_ul(struct gsm_lchan *lchan, const struct ph_tch_param *tch_ind, const uint8_t *data, unsigned int data_len)
+{
+	struct gsm_bts_trx *trx = lchan->ts->trx;
+	struct gsmtap_inst *inst = trx->bts->gsmtap.inst;
+	if (!inst)
+		return;
+
+	if (lchan->csd_mode == LCHAN_CSD_M_NT) {
+		pbit_t buf[data_len/8+1];
+		int len = osmo_ubit2pbit_ext(buf, 0, data, 0, data_len, 1);
+		gsmtap_send_ex(inst, GSMTAP_TYPE_GSM_RLP, trx->arfcn | GSMTAP_ARFCN_F_UPLINK, lchan->ts->nr,
+				lchan->type == GSM_LCHAN_TCH_H ? GSMTAP_CHANNEL_TCH_H : GSMTAP_CHANNEL_TCH_F,
+				lchan->nr, tch_ind->fn, tch_ind->rssi, 0, buf, len);
+
+	}
+}
+
+static void gsmtap_csd_dl(struct gsm_lchan *lchan, const uint8_t *data, unsigned int data_len)
+{
+	struct gsm_bts_trx *trx = lchan->ts->trx;
+	struct gsmtap_inst *inst = trx->bts->gsmtap.inst;
+	if (!inst)
+		return;
+
+	if (lchan->csd_mode == LCHAN_CSD_M_NT) {
+		pbit_t buf[data_len/8+1];
+		int len = osmo_ubit2pbit_ext(buf, 0, data, 0, data_len, 1);
+		gsmtap_send_ex(inst, GSMTAP_TYPE_GSM_RLP, trx->arfcn, lchan->ts->nr,
+				lchan->type == GSM_LCHAN_TCH_H ? GSMTAP_CHANNEL_TCH_H : GSMTAP_CHANNEL_TCH_F,
+				lchan->nr, 0, 0, 0, buf, len);
+	}
+}
+
+static void send_ul_rtp_packet_data(struct gsm_lchan *lchan, const struct ph_tch_param *tch_ind,
 				    const uint8_t *data, uint16_t data_len)
 {
 	uint8_t rtp_pl[RFC4040_RTP_PLEN];
 	int rc;
 
+	gsmtap_csd_ul(lchan, tch_ind, data, data_len);
+
 	rc = csd_v110_rtp_encode(lchan, &rtp_pl[0], data, data_len);
 	if (rc < 0)
 		return;
 
 	osmo_rtp_send_frame_ext(lchan->abis_ip.rtp_socket,
 				&rtp_pl[0], sizeof(rtp_pl),
-				fn_ms_adj(fn, lchan),
+				fn_ms_adj(tch_ind->fn, lchan),
 				lchan->rtp_tx_marker);
 	/* Only clear the marker bit once we have sent a RTP packet with it */
 	lchan->rtp_tx_marker = false;
@@ -1987,7 +2022,7 @@
 				send_ul_rtp_packet_speech(lchan, fn, msg->data, msg->len);
 			break;
 		case RSL_CMOD_SPD_DATA:
-			send_ul_rtp_packet_data(lchan, fn, msg->data, msg->len);
+			send_ul_rtp_packet_data(lchan, tch_ind, msg->data, msg->len);
 			break;
 		case RSL_CMOD_SPD_SIGN:
 			return 0; /* drop stale TCH.ind */
@@ -2296,6 +2331,7 @@
 		int rc = csd_v110_rtp_decode(lchan, msg->tail,
 					     rtp_pl, rtp_pl_len);
 		if (rc > 0) {
+			gsmtap_csd_dl(lchan, msg->tail, rc);
 			msgb_put(msg, rc);
 		} else {
 			msgb_free(msg);

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