MGCP: add 'X-Osmo-IGN: C' for SCCPlite by default

Use libosmo-mgcp-client's new X-Osmo-IGN header to indicate that CallIDs are
allowed to mismatch.

Add VTY commands 'msc' / 'mgw x-osmo-ign call-id' and 'no mgw x-osmo-ign' to
switch this behavior explicitly.

For SCCPlite MSCs, unless a specific config was issued, always send
'X-Osmo-IGN: C' by default, to ignore CallID mismatches.

Depends: Id7ae275ffde8ea9389270cfe3db087ee8db00b51 (osmo-mgw)
Change-Id: I257ad574d8060fef19afce9798bd8a5a7f8c99fe

3 files changed, 53 insertions, 1 deletions

diff --git a/src/osmo-bsc/lchan_rtp_fsm.c b/src/osmo-bsc/lchan_rtp_fsm.c
index 091af5e67..93883afdb 100644
--- a/src/osmo-bsc/lchan_rtp_fsm.c
+++ b/src/osmo-bsc/lchan_rtp_fsm.c
@@ -29,6 +29,7 @@
 #include <osmocom/bsc/mgw_endpoint_fsm.h>
 #include <osmocom/bsc/bsc_subscr_conn_fsm.h>
 #include <osmocom/bsc/abis_rsl.h>
+#include <osmocom/bsc/bsc_msc_data.h>
 
 static struct osmo_fsm lchan_rtp_fsm;
 
@@ -154,8 +155,11 @@ static void lchan_rtp_fsm_wait_mgw_endpoint_available_onenter(struct osmo_fsm_in
 
 	lchan->mgw_endpoint_ci_bts = mgw_endpoint_ci_add(mgwep, "to-BTS");
 
-	if (lchan->conn)
+	if (lchan->conn) {
 		crcx_info.call_id = lchan->conn->sccp.conn_id;
+		if (lchan->conn->sccp.msc)
+			crcx_info.x_osmo_ign = lchan->conn->sccp.msc->x_osmo_ign;
+	}
 	crcx_info.ptime = 20;
 	mgcp_pick_codec(&crcx_info, lchan, true);
 
diff --git a/src/osmo-bsc/osmo_bsc_sigtran.c b/src/osmo-bsc/osmo_bsc_sigtran.c
index 7e5f5f68e..96f06874a 100644
--- a/src/osmo-bsc/osmo_bsc_sigtran.c
+++ b/src/osmo-bsc/osmo_bsc_sigtran.c
@@ -35,6 +35,7 @@
 #include <osmocom/bsc/gsm_04_80.h>
 #include <osmocom/bsc/bsc_subscr_conn_fsm.h>
 #include <osmocom/bsc/gsm_data.h>
+#include <osmocom/mgcp/mgcp_common.h>
 
 /* A pointer to a list with all involved MSCs
  * (a copy of the pointer location submitted with osmo_bsc_sigtran_init() */
@@ -496,6 +497,15 @@ int osmo_bsc_sigtran_init(struct llist_head *mscs)
 		if (!msc->a.sccp)
 			return -EINVAL;
 
+		/* In SCCPlite, the MSC side of the MGW endpoint is configured by the MSC. Since we have
+		 * no way to figure out which CallID ('C:') the MSC will issue in its CRCX command, set
+		 * an X-Osmo-IGN flag telling osmo-mgw to ignore CallID mismatches for this endpoint.
+		 * If an explicit VTY command has already indicated whether or not to send X-Osmo-IGN, do
+		 * not overwrite that setting. */
+		if (msc->a.asp_proto == OSMO_SS7_ASP_PROT_IPA
+		    && !msc->x_osmo_ign_configured)
+			msc->x_osmo_ign |= MGCP_X_OSMO_IGN_CALLID;
+
 		/* If unset, use default local SCCP address */
 		if (!msc->a.bsc_addr.presence)
 			osmo_sccp_local_addr_by_instance(&msc->a.bsc_addr, msc->a.sccp,
diff --git a/src/osmo-bsc/osmo_bsc_vty.c b/src/osmo-bsc/osmo_bsc_vty.c
index efa12e09b..f90ad6f9d 100644
--- a/src/osmo-bsc/osmo_bsc_vty.c
+++ b/src/osmo-bsc/osmo_bsc_vty.c
@@ -191,6 +191,13 @@ static void write_msc(struct vty *vty, struct bsc_msc_data *msc)
 
 	/* write MGW configuration */
 	mgcp_client_config_write(vty, " ");
+
+	if (msc->x_osmo_ign_configured) {
+		if (!msc->x_osmo_ign)
+			vty_out(vty, " no mgw x-osmo-ign%s", VTY_NEWLINE);
+		else
+			vty_out(vty, " mgw x-osmo-ign call-id%s", VTY_NEWLINE);
+	}
 }
 
 static int config_write_msc(struct vty *vty)
@@ -672,6 +679,35 @@ DEFUN(cfg_net_msc_lcls_mismtch,
 	return CMD_SUCCESS;
 }
 
+DEFUN(cfg_msc_mgw_x_osmo_ign,
+      cfg_msc_mgw_x_osmo_ign_cmd,
+      "mgw x-osmo-ign call-id",
+      MGCP_CLIENT_MGW_STR
+      "Set a (non-standard) X-Osmo-IGN header in all CRCX messages for RTP streams"
+      " associated with this MSC, useful for A/SCCPlite MSCs, since osmo-bsc cannot know"
+      " the MSC's chosen CallID. This is enabled by default for A/SCCPlite connections,"
+      " disabled by default for all others.\n"
+      "Send 'X-Osmo-IGN: C' to ignore CallID mismatches. See OsmoMGW.\n")
+{
+	struct bsc_msc_data *msc = bsc_msc_data(vty);
+	msc->x_osmo_ign |= MGCP_X_OSMO_IGN_CALLID;
+	msc->x_osmo_ign_configured = true;
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_msc_no_mgw_x_osmo_ign,
+      cfg_msc_no_mgw_x_osmo_ign_cmd,
+      "no mgw x-osmo-ign",
+      NO_STR
+      MGCP_CLIENT_MGW_STR
+      "Do not send X-Osmo-IGN MGCP header to this MSC\n")
+{
+	struct bsc_msc_data *msc = bsc_msc_data(vty);
+	msc->x_osmo_ign = 0;
+	msc->x_osmo_ign_configured = true;
+	return CMD_SUCCESS;
+}
+
 DEFUN(cfg_net_bsc_mid_call_text,
       cfg_net_bsc_mid_call_text_cmd,
       "mid-call-text .TEXT",
@@ -983,6 +1019,8 @@ int bsc_vty_init_extra(void)
 	install_element(CFG_LOG_NODE, &logging_fltr_imsi_cmd);
 
 	mgcp_client_vty_init(net, MSC_NODE, net->mgw.conf);
+	install_element(MSC_NODE, &cfg_msc_mgw_x_osmo_ign_cmd);
+	install_element(MSC_NODE, &cfg_msc_no_mgw_x_osmo_ign_cmd);
 
 	return 0;
 }