add vty-configurable loopback mode

this allows the BTS to loop-back any incoming data on a TCH

3 files changed, 83 insertions, 1 deletions

diff --git a/src/osmo-bts-sysmo/l1_if.c b/src/osmo-bts-sysmo/l1_if.c
index c11c0cd9..9b6100cc 100644
--- a/src/osmo-bts-sysmo/l1_if.c
+++ b/src/osmo-bts-sysmo/l1_if.c
@@ -375,7 +375,7 @@ static int handle_ph_readytosend_ind(struct femtol1_hdl *fl1,
 		if (!lchan)
 			break;
 
-		if (lchan->abis_ip.rtp_socket) {
+		if (!lchan->loopback && lchan->abis_ip.rtp_socket) {
 			osmo_rtp_socket_poll(lchan->abis_ip.rtp_socket);
 			/* FIXME: we _assume_ that we never miss TDMA
 			 * frames and that we always get to this point
diff --git a/src/osmo-bts-sysmo/sysmobts_vty.c b/src/osmo-bts-sysmo/sysmobts_vty.c
index c1bcfa71..fe035a40 100644
--- a/src/osmo-bts-sysmo/sysmobts_vty.c
+++ b/src/osmo-bts-sysmo/sysmobts_vty.c
@@ -344,6 +344,45 @@ DEFUN(set_tx_power, set_tx_power_cmd,
 	return CMD_SUCCESS;
 }
 
+DEFUN(loopback, loopback_cmd,
+	"trx <0-0> <0-7> loopback <0-1>",
+	TRX_STR
+	"Timeslot number\n"
+	"Set TCH loopback\n"
+	"Logical Channel Number\n")
+{
+	int trx_nr = atoi(argv[0]);
+	int ts_nr = atoi(argv[1]);
+	int lchan_nr = atoi(argv[2]);
+	struct gsm_bts_trx *trx = gsm_bts_trx_num(vty_bts, trx_nr);
+	struct gsm_bts_trx_ts *ts = &trx->ts[ts_nr];
+	struct gsm_lchan *lchan = &ts->lchan[lchan_nr];
+
+	lchan->loopback = 1;
+
+	return CMD_SUCCESS;
+}
+
+DEFUN(no_loopback, no_loopback_cmd,
+	"no trx <0-0> <0-7> loopback <0-1>",
+	NO_STR TRX_STR
+	"Timeslot number\n"
+	"Set TCH loopback\n"
+	"Logical Channel Number\n")
+{
+	int trx_nr = atoi(argv[0]);
+	int ts_nr = atoi(argv[1]);
+	int lchan_nr = atoi(argv[2]);
+	struct gsm_bts_trx *trx = gsm_bts_trx_num(vty_bts, trx_nr);
+	struct gsm_bts_trx_ts *ts = &trx->ts[ts_nr];
+	struct gsm_lchan *lchan = &ts->lchan[lchan_nr];
+
+	lchan->loopback = 0;
+
+	return CMD_SUCCESS;
+}
+
+
 void bts_model_config_write_bts(struct vty *vty, struct gsm_bts *bts)
 {
 }
@@ -381,6 +420,9 @@ int bts_model_vty_init(struct gsm_bts *bts)
 	install_element(ENABLE_NODE, &activate_lchan_cmd);
 	install_element(ENABLE_NODE, &set_tx_power_cmd);
 
+	install_element(ENABLE_NODE, &loopback_cmd);
+	install_element(ENABLE_NODE, &no_loopback_cmd);
+
 	install_element(TRX_NODE, &cfg_trx_clkcal_cmd);
 	install_element(TRX_NODE, &cfg_trx_clkcal_def_cmd);
 	install_element(TRX_NODE, &cfg_trx_clksrc_cmd);
diff --git a/src/osmo-bts-sysmo/tch.c b/src/osmo-bts-sysmo/tch.c
index a63910f8..c6c782fa 100644
--- a/src/osmo-bts-sysmo/tch.c
+++ b/src/osmo-bts-sysmo/tch.c
@@ -443,6 +443,10 @@ void bts_model_rtp_rx_cb(struct osmo_rtp_socket *rs, const uint8_t *rtp_pl,
 	DEBUGP(DRTP, "%s RTP IN: %s\n", gsm_lchan_name(lchan),
 		osmo_hexdump(rtp_pl, rtp_pl_len));
 
+	/* skip processing of incoming RTP frames if we are in loopback mode */
+	if (lchan->loopback)
+		return;
+
 	msg = l1p_msgb_alloc();
 	if (!msg) {
 		LOGP(DRTP, LOGL_ERROR, "%s: Failed to allocate Rx payload.\n",
@@ -538,6 +542,42 @@ int l1if_tch_rx(struct gsm_lchan *lchan, struct msgb *l1p_msg)
 	}
 	payload_len = data_ind->msgUnitParam.u8Size - 1;
 
+	if (lchan->loopback) {
+		GsmL1_Prim_t *rl1p;
+		GsmL1_PhDataReq_t *data_req;
+		GsmL1_MsgUnitParam_t *msu_param;
+
+		struct msgb *tmp;
+		int count = 0;
+
+		/* generate a new msgb from the paylaod */
+		rmsg = l1p_msgb_alloc();
+		if (!rmsg)
+			return -ENOMEM;
+
+		rl1p = msgb_l1prim(rmsg);
+		data_req = &rl1p->u.phDataReq;
+		msu_param = &data_req->msgUnitParam;
+
+		memcpy(msu_param->u8Buffer,
+			data_ind->msgUnitParam.u8Buffer,
+			data_ind->msgUnitParam.u8Size);
+		msu_param->u8Size = data_ind->msgUnitParam.u8Size;
+
+		/* make sure the queue doesn't get too long */
+		llist_for_each_entry(tmp, &lchan->dl_tch_queue, list)
+			count++;
+		while (count >= 1) {
+			tmp = msgb_dequeue(&lchan->dl_tch_queue);
+			msgb_free(tmp);
+			count--;
+		}
+
+		msgb_enqueue(&lchan->dl_tch_queue, rmsg);
+
+		return 0;
+	}
+
 	switch (payload_type) {
 	case GsmL1_TchPlType_Fr:
 #if defined(L1_HAS_EFR) && defined(USE_L1_RTP_MODE)