Add vty command "radio-link-timeout infinite" for uplink rx testing

When we are performing Rx sensitivity testing on a BTS, we want to
deactivate the connection failure criterion / radio link timeout, i.e.
no matter how many SACCH frames in uplink are failed to decode, the BTS
should never close the channel.

OsmoBTS Change-Id I736f21f6528db5c16fa80cdb905af20673797be5 covers a way
how this behavior can be requested from the BTS via an OML attribute.
This patch adds support to the BSC to actually set that attribute.

Do not use this in production networks, as the BTS will keep open radio
channels indefinitely even if the phone is gone and no longer
transmitting anything.  This is a pure testing feature.

Change-Id: I6cb94e0f024934f7baeeb728ca9ed3042fbf16d2
diff --git a/openbsc/src/libbsc/bsc_vty.c b/openbsc/src/libbsc/bsc_vty.c
index 2fc39ab..9fc2895 100644
--- a/openbsc/src/libbsc/bsc_vty.c
+++ b/openbsc/src/libbsc/bsc_vty.c
@@ -604,9 +604,11 @@
 		vty_out(vty, "  periodic location update %u%s",
 			bts->si_common.chan_desc.t3212 * 6, VTY_NEWLINE);
 
-	vty_out(vty, "  radio-link-timeout %d%s",
-		get_radio_link_timeout(&bts->si_common.cell_options),
-		VTY_NEWLINE);
+	if (gsm_bts_get_radio_link_timeout(bts) < 0)
+		vty_out(vty, "  radio-link-timeout infinite%s", VTY_NEWLINE);
+	else
+		vty_out(vty, "  radio-link-timeout %d%s",
+			gsm_bts_get_radio_link_timeout(bts), VTY_NEWLINE);
 	vty_out(vty, "  channel allocator %s%s",
 		bts->chan_alloc_reverse ? "descending" : "ascending",
 		VTY_NEWLINE);
@@ -2299,7 +2301,25 @@
 {
 	struct gsm_bts *bts = vty->index;
 
-	set_radio_link_timeout(&bts->si_common.cell_options, atoi(argv[0]));
+	gsm_bts_set_radio_link_timeout(bts, atoi(argv[0]));
+
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_bts_radio_link_timeout_inf, cfg_bts_radio_link_timeout_inf_cmd,
+	"radio-link-timeout infinite",
+	"Radio link timeout criterion (BTS side)\n"
+	"Infinite Radio link timeout value (use only for BTS RF testing)\n")
+{
+	struct gsm_bts *bts = vty->index;
+
+	if (bts->type != GSM_BTS_TYPE_OSMOBTS) {
+		vty_out(vty, "%% infinite radio link timeout not supported by this BTS%s", VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
+	vty_out(vty, "%% INFINITE RADIO LINK TIMEOUT, USE ONLY FOR BTS RF TESTING%s", VTY_NEWLINE);
+	gsm_bts_set_radio_link_timeout(bts, -1);
 
 	return CMD_SUCCESS;
 }
@@ -4180,6 +4200,7 @@
 	install_element(BTS_NODE, &cfg_bts_penalty_time_cmd);
 	install_element(BTS_NODE, &cfg_bts_penalty_time_rsvd_cmd);
 	install_element(BTS_NODE, &cfg_bts_radio_link_timeout_cmd);
+	install_element(BTS_NODE, &cfg_bts_radio_link_timeout_inf_cmd);
 	install_element(BTS_NODE, &cfg_bts_gprs_mode_cmd);
 	install_element(BTS_NODE, &cfg_bts_gprs_11bit_rach_support_for_egprs_cmd);
 	install_element(BTS_NODE, &cfg_bts_gprs_ns_timer_cmd);
diff --git a/openbsc/src/libbsc/bts_ipaccess_nanobts_omlattr.c b/openbsc/src/libbsc/bts_ipaccess_nanobts_omlattr.c
index 0291129..473e1ca 100644
--- a/openbsc/src/libbsc/bts_ipaccess_nanobts_omlattr.c
+++ b/openbsc/src/libbsc/bts_ipaccess_nanobts_omlattr.c
@@ -38,6 +38,7 @@
 {
 	struct msgb *msgb;
 	uint8_t buf[256];
+	int rlt;
 	msgb = msgb_alloc(1024, "nanobts_attr_bts");
 
 	memcpy(buf, "\x55\x5b\x61\x67\x6d\x73", 6);
@@ -46,9 +47,16 @@
 	/* interference avg. period in numbers of SACCH multifr */
 	msgb_tv_put(msgb, NM_ATT_INTAVE_PARAM, 0x06);
 
-	/* conn fail based on SACCH error rate */
-	buf[0] = 0x01;
-	buf[1] = get_radio_link_timeout(&bts->si_common.cell_options);
+	rlt = gsm_bts_get_radio_link_timeout(bts);
+	if (rlt == -1) {
+		/* Osmocom extension: Use infinite radio link timeout */
+		buf[0] = 0xFF;
+		buf[1] = 0x00;
+	} else {
+		/* conn fail based on SACCH error rate */
+		buf[0] = 0x01;
+		buf[1] = rlt;
+	}
 	msgb_tl16v_put(msgb, NM_ATT_CONN_FAIL_CRIT, 2, buf);
 
 	memcpy(buf, "\x1e\x24\x24\xa8\x34\x21\xa8", 7);
diff --git a/openbsc/src/libcommon/gsm_data.c b/openbsc/src/libcommon/gsm_data.c
index 8830ce1..db7de08 100644
--- a/openbsc/src/libcommon/gsm_data.c
+++ b/openbsc/src/libcommon/gsm_data.c
@@ -323,8 +323,7 @@
 	bts->si_common.chan_desc.bs_pa_mfrms = RSL_BS_PA_MFRMS_5; /* paging frames */
 	bts->si_common.chan_desc.bs_ag_blks_res = 1; /* reserved AGCH blocks */
 	bts->si_common.chan_desc.t3212 = 5; /* Use 30 min periodic update interval as sane default */
-	set_radio_link_timeout(&bts->si_common.cell_options, 32);
-				/* Use RADIO LINK TIMEOUT of 32 seconds */
+	gsm_bts_set_radio_link_timeout(bts, 32); /* Use RADIO LINK TIMEOUT of 32 */
 
 	llist_add_tail(&bts->list, &net->bts_list);
 
@@ -435,3 +434,40 @@
 	}
 	return 1;
 }
+
+/* get the radio link timeout (based on SACCH decode errors, according
+ * to algorithm specified in TS 05.08 section 5.2.  A value of -1
+ * indicates we should use an infinitely long timeout, which only works
+ * with OsmoBTS as the BTS implementation */
+int gsm_bts_get_radio_link_timeout(const struct gsm_bts *bts)
+{
+	const struct gsm48_cell_options *cell_options = &bts->si_common.cell_options;
+
+	if (bts->infinite_radio_link_timeout)
+		return -1;
+	else {
+		/* Encoding as per Table 10.5.21 of TS 04.08 */
+		return (cell_options->radio_link_timeout + 1) << 2;
+	}
+}
+
+/* set the radio link timeout (based on SACCH decode errors, according
+ * to algorithm specified in TS 05.08 Section 5.2.  A value of -1
+ * indicates we should use an infinitely long timeout, which only works
+ * with OsmoBTS as the BTS implementation */
+void gsm_bts_set_radio_link_timeout(struct gsm_bts *bts, int value)
+{
+	struct gsm48_cell_options *cell_options = &bts->si_common.cell_options;
+
+	if (value < 0)
+		bts->infinite_radio_link_timeout = true;
+	else {
+		bts->infinite_radio_link_timeout = false;
+		/* Encoding as per Table 10.5.21 of TS 04.08 */
+		if (value < 4)
+			value = 4;
+		if (value > 64)
+			value = 64;
+		cell_options->radio_link_timeout = (value >> 2) - 1;
+	}
+}