Expand VTY option which controls use of TCH for signalling

For statistical clarity and site tuning, it is sometimes
desirable to completely disable the use of TCH for signaling.

In the existing version of this VTY command, there is no way to
accomplish this. We can only restrict TCH for signaling non-voice
related actions.

This patch deprecates 'allow-tch-for-signalling (0|1)' and
adds 'tch-signalling-policy (never|emergency|voice|always)' to
provide more options.

Change-Id: I4459941ddad4e4a3bec8409b180d9a23a735e640

5 files changed, 82 insertions, 22 deletions

diff --git a/include/osmocom/bsc/bts.h b/include/osmocom/bsc/bts.h
index 66cf68f02..a26bdbd2c 100644
--- a/include/osmocom/bsc/bts.h
+++ b/include/osmocom/bsc/bts.h
@@ -259,6 +259,13 @@ enum bts_attribute {
 	TRX_PHY_VERSION,
 };
 
+enum bts_tch_signalling_policy {
+	BTS_TCH_SIGNALLING_NEVER,
+	BTS_TCH_SIGNALLING_EMERG,
+	BTS_TCH_SIGNALLING_VOICE,
+	BTS_TCH_SIGNALLING_ALWAYS,
+};
+
 struct vty;
 
 struct gsm_bts_model {
@@ -514,9 +521,8 @@ struct gsm_bts {
 	 * interference reported in RSL Resource Indication. */
 	bool chan_alloc_avoid_interf;
 
-	/* When true (default), TCH can be allocated to serve
-	 * non-voicecall-related signalling services when SDCCHs are exhausted */
-	bool chan_alloc_allow_tch_for_signalling;
+	/* If SDCCHs are exhausted, when can we use TCH for signalling purposes. */
+	enum bts_tch_signalling_policy chan_alloc_tch_signalling_policy;
 
 	enum neigh_list_manual_mode neigh_list_manual_mode;
 	/* parameters from which we build SYSTEM INFORMATION */
diff --git a/src/osmo-bsc/abis_rsl.c b/src/osmo-bsc/abis_rsl.c
index d37fac8e2..f6215d954 100644
--- a/src/osmo-bsc/abis_rsl.c
+++ b/src/osmo-bsc/abis_rsl.c
@@ -2178,7 +2178,11 @@ void abis_rsl_chan_rqd_queue_poll(struct gsm_bts *bts)
 	 * in the code below, all other channel requests will get an SDCCH first
 	 * (if possible). */
 
-	if (gsm_chreq_reason_is_voicecall(rqd->reason) || bts->chan_alloc_allow_tch_for_signalling) {
+	if (bts->chan_alloc_tch_signalling_policy == BTS_TCH_SIGNALLING_ALWAYS ||
+	    (bts->chan_alloc_tch_signalling_policy == BTS_TCH_SIGNALLING_VOICE &&
+	     gsm_chreq_reason_is_voicecall(rqd->reason)) ||
+	    (bts->chan_alloc_tch_signalling_policy == BTS_TCH_SIGNALLING_EMERG &&
+	     rqd->reason == GSM_CHREQ_REASON_EMERG)) {
 		if (!lchan) {
 			LOG_BTS(bts, DRSL, LOGL_NOTICE, "CHAN RQD[%s]: no resources for %s 0x%x, retrying with %s\n",
 				get_value_string(gsm_chreq_descs, rqd->reason), gsm_lchant_name(GSM_LCHAN_SDCCH),
diff --git a/src/osmo-bsc/bts.c b/src/osmo-bsc/bts.c
index d0adb2a3f..89895ca3b 100644
--- a/src/osmo-bsc/bts.c
+++ b/src/osmo-bsc/bts.c
@@ -295,7 +295,7 @@ struct gsm_bts *gsm_bts_alloc(struct gsm_network *net, struct gsm_bts_sm *bts_sm
 	bts->neigh_list_manual_mode = NL_MODE_AUTOMATIC;
 	bts->early_classmark_allowed_3g = true; /* 3g Early Classmark Sending controlled by bts->early_classmark_allowed param */
 	bts->si_unused_send_empty = true;
-	bts->chan_alloc_allow_tch_for_signalling = true;
+	bts->chan_alloc_tch_signalling_policy = BTS_TCH_SIGNALLING_ALWAYS;
 	bts->si_common.cell_sel_par.cell_resel_hyst = 2; /* 4 dB */
 	bts->si_common.cell_sel_par.rxlev_acc_min = 0;
 	bts->si_common.si2quater_neigh_list.arfcn = bts->si_common.data.earfcn_list;
diff --git a/src/osmo-bsc/bts_vty.c b/src/osmo-bsc/bts_vty.c
index ba4215aaf..2ae9d9bf1 100644
--- a/src/osmo-bsc/bts_vty.c
+++ b/src/osmo-bsc/bts_vty.c
@@ -565,6 +565,31 @@ DEFUN_ATTR(cfg_bts_chan_alloc_interf,
 	return CMD_SUCCESS;
 }
 
+DEFUN_ATTR(cfg_bts_chan_alloc_tch_signalling_policy,
+	   cfg_bts_chan_alloc_tch_signalling_policy_cmd,
+	   "channel allocator tch-signalling-policy (never|emergency|voice|always)",
+	   "Channel Allocator\n" "Channel Allocator\n"
+	   "Configure when TCH/H or TCH/F channels can be used to serve signalling if SDCCHs are exhausted\n"
+	   "Never allow TCH for signalling purposes\n"
+	   "Only allow TCH for signalling purposes when establishing an emergency call\n"
+	   "Allow TCH for signalling purposes when establishing any voice call\n"
+	   "Always allow TCH for signalling purposes (default)\n",
+	   CMD_ATTR_IMMEDIATE)
+{
+	struct gsm_bts *bts = vty->index;
+
+	if (!strcmp(argv[0], "never"))
+		bts->chan_alloc_tch_signalling_policy = BTS_TCH_SIGNALLING_NEVER;
+	else if (!strcmp(argv[0], "emergency"))
+		bts->chan_alloc_tch_signalling_policy = BTS_TCH_SIGNALLING_EMERG;
+	else if (!strcmp(argv[0], "voice"))
+		bts->chan_alloc_tch_signalling_policy = BTS_TCH_SIGNALLING_VOICE;
+	else
+		bts->chan_alloc_tch_signalling_policy = BTS_TCH_SIGNALLING_ALWAYS;
+
+	return CMD_SUCCESS;
+}
+
 DEFUN_ATTR(cfg_bts_chan_alloc_allow_tch_for_signalling,
 	   cfg_bts_chan_alloc_allow_tch_for_signalling_cmd,
 	   "channel allocator allow-tch-for-signalling (0|1)",
@@ -572,14 +597,16 @@ DEFUN_ATTR(cfg_bts_chan_alloc_allow_tch_for_signalling,
 	   "Configure whether TCH/H or TCH/F channels can be used to serve non-call-related signalling if SDCCHs are exhausted\n"
 	   "Forbid use of TCH for non-call-related signalling purposes\n"
 	   "Allow use of TCH for non-call-related signalling purposes (default)\n",
-	   CMD_ATTR_IMMEDIATE)
+	   CMD_ATTR_IMMEDIATE|CMD_ATTR_DEPRECATED)
 {
 	struct gsm_bts *bts = vty->index;
 
+	vty_out(vty, "%% 'allow-tch-for-signalling' is deprecated, use 'tch-signalling-policy' instead.%s", VTY_NEWLINE);
+
 	if (!strcmp(argv[0], "0"))
-		bts->chan_alloc_allow_tch_for_signalling = false;
+		bts->chan_alloc_tch_signalling_policy = BTS_TCH_SIGNALLING_VOICE;
 	else
-		bts->chan_alloc_allow_tch_for_signalling = true;
+		bts->chan_alloc_tch_signalling_policy = BTS_TCH_SIGNALLING_ALWAYS;
 
 	return CMD_SUCCESS;
 }
@@ -4185,8 +4212,12 @@ static void config_write_bts_single(struct vty *vty, struct gsm_bts *bts)
 		VTY_NEWLINE);
 	if (bts->chan_alloc_avoid_interf)
 		vty_out(vty, "  channel allocator avoid-interference 1%s", VTY_NEWLINE);
-	if (!bts->chan_alloc_allow_tch_for_signalling)
-		vty_out(vty, "  channel allocator allow-tch-for-signalling 0%s", VTY_NEWLINE);
+	if (bts->chan_alloc_tch_signalling_policy == BTS_TCH_SIGNALLING_NEVER)
+		vty_out(vty, "  channel allocator tch-signalling-policy never%s", VTY_NEWLINE);
+	else if (bts->chan_alloc_tch_signalling_policy == BTS_TCH_SIGNALLING_EMERG)
+		vty_out(vty, "  channel allocator tch-signalling-policy emergency%s", VTY_NEWLINE);
+	else if (bts->chan_alloc_tch_signalling_policy == BTS_TCH_SIGNALLING_VOICE)
+		vty_out(vty, "  channel allocator tch-signalling-policy voice%s", VTY_NEWLINE);
 	vty_out(vty, "  rach tx integer %u%s",
 		bts->si_common.rach_control.tx_integer, VTY_NEWLINE);
 	vty_out(vty, "  rach max transmission %u%s",
@@ -4509,6 +4540,7 @@ int bts_vty_init(void)
 	install_element(BTS_NODE, &cfg_bts_oml_e1_tei_cmd);
 	install_element(BTS_NODE, &cfg_bts_challoc_cmd);
 	install_element(BTS_NODE, &cfg_bts_chan_alloc_interf_cmd);
+	install_element(BTS_NODE, &cfg_bts_chan_alloc_tch_signalling_policy_cmd);
 	install_element(BTS_NODE, &cfg_bts_chan_alloc_allow_tch_for_signalling_cmd);
 	install_element(BTS_NODE, &cfg_bts_rach_tx_integer_cmd);
 	install_element(BTS_NODE, &cfg_bts_rach_max_trans_cmd);
diff --git a/tests/osmo-bsc.vty b/tests/osmo-bsc.vty
index ace21dfb3..f2af32bca 100644
--- a/tests/osmo-bsc.vty
+++ b/tests/osmo-bsc.vty
@@ -166,18 +166,20 @@ OsmoBSC(config-net-bts)# channel ?
   allocator  Channel Allocator
 
 OsmoBSC(config-net-bts)# channel allocator ?
-  ascending                 Allocate Timeslots and Transceivers in ascending order
-  descending                Allocate Timeslots and Transceivers in descending order
-  avoid-interference        Configure whether reported interference levels from RES IND are used in channel allocation
-  allow-tch-for-signalling  Configure whether TCH/H or TCH/F channels can be used to serve non-call-related signalling if SDCCHs are exhausted
+  ascending              Allocate Timeslots and Transceivers in ascending order
+  descending             Allocate Timeslots and Transceivers in descending order
+  avoid-interference     Configure whether reported interference levels from RES IND are used in channel allocation
+  tch-signalling-policy  Configure when TCH/H or TCH/F channels can be used to serve signalling if SDCCHs are exhausted
 
 OsmoBSC(config-net-bts)# channel allocator avoid-interference ?
   0  Ignore interference levels (default). Always assign lchans in a deterministic order.
   1  In channel allocation, prefer lchans with less interference.
 
-OsmoBSC(config-net-bts)# channel allocator allow-tch-for-signalling ?
-  0  Forbid use of TCH for non-call-related signalling purposes
-  1  Allow use of TCH for non-call-related signalling purposes (default)
+OsmoBSC(config-net-bts)# channel allocator tch-signalling-policy ?
+  never      Never allow TCH for signalling purposes
+  emergency  Only allow TCH for signalling purposes when establishing an emergency call
+  voice      Allow TCH for signalling purposes when establishing any voice call
+  always     Always allow TCH for signalling purposes (default)
 
 OsmoBSC(config-net-bts)# show running-config
 ... !channel allocator avoid-interference
@@ -194,18 +196,34 @@ OsmoBSC(config-net-bts)# show running-config
 ... !channel allocator avoid-interference
 
 OsmoBSC(config-net-bts)# show running-config
-... !channel allocator allow-tch-for-signalling
-OsmoBSC(config-net-bts)# channel allocator allow-tch-for-signalling 0
+... !channel allocator tch-signalling-policy
+OsmoBSC(config-net-bts)# channel allocator tch-signalling-policy never
 OsmoBSC(config-net-bts)# show running-config
 ...
  bts 0
 ...
-  channel allocator allow-tch-for-signalling 0
+  channel allocator tch-signalling-policy never
 ...
 
-OsmoBSC(config-net-bts)# channel allocator allow-tch-for-signalling 1
+OsmoBSC(config-net-bts)# channel allocator tch-signalling-policy emergency
 OsmoBSC(config-net-bts)# show running-config
-... !channel allocator allow-tch-for-signalling
+...
+ bts 0
+...
+  channel allocator tch-signalling-policy emergency
+...
+
+OsmoBSC(config-net-bts)# channel allocator tch-signalling-policy voice
+OsmoBSC(config-net-bts)# show running-config
+...
+ bts 0
+...
+  channel allocator tch-signalling-policy voice
+...
+
+OsmoBSC(config-net-bts)# channel allocator tch-signalling-policy always
+OsmoBSC(config-net-bts)# show running-config
+... !channel allocator tch-signalling-policy
 
 OsmoBSC(config-net-bts)# immediate-assignment?
   immediate-assignment  Configure time of Immediate Assignment after ChanRqd RACH (Abis optimization)