cellmgr: Patch the MGCP messages and replace the domain name

Replace the domain name with a new name domain that can be configured
via the VTY interface.

3 files changed, 115 insertions, 2 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 4d68f30..5684a8a 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -14,7 +14,7 @@ cellmgr_ng_SOURCES = main.c mtp_layer3.c thread.c input/ipaccess.c pcap.c \
 		     bss_patch.c bssap_sccp.c bsc_sccp.c bsc_ussd.c links.c \
 		     msc_conn.c link_udp.c snmp_mtp.c debug.c isup.c \
 		     mtp_link.c counter.c sccp_state.c bsc.c ss7_application.c \
-		     vty_interface_legacy.c vty_interface_cmds.c
+		     vty_interface_legacy.c vty_interface_cmds.c mgcp_patch.c
 cellmgr_ng_LDADD = $(LIBOSMOCORE_LIBS) $(LIBOSMOGSM_LIBS) $(LIBOSMOVTY_LIBS) \
 		   $(LIBOSMOSCCP_LIBS) $(NEXUSWARE_C7_LIBS) \
 		   -lpthread -lnetsnmp -lcrypto
@@ -23,7 +23,7 @@ osmo_stp_SOURCES = main_stp.c mtp_layer3.c thread.c pcap.c link_udp.c snmp_mtp.c
 		   debug.c links.c isup.c sctp_m2ua.c msc_conn.c sccp_state.c \
 		   bss_patch.c bssap_sccp.c bsc_sccp.c bsc_ussd.c input/ipaccess.c \
 		   mtp_link.c counter.c bsc.c ss7_application.c \
-		   vty_interface.c vty_interface_cmds.c
+		   vty_interface.c vty_interface_cmds.c mgcp_patch.c
 osmo_stp_LDADD = $(LIBOSMOCORE_LIBS) $(LIBOSMOGSM_LIBS) $(LIBOSMOVTY_LIBS) \
 		 $(LIBOSMOSCCP_LIBS) $(NEXUSWARE_C7_LIBS) \
 		   -lpthread -lnetsnmp -lcrypto -lm2ua -lsctp
diff --git a/src/mgcp_patch.c b/src/mgcp_patch.c
new file mode 100644
index 0000000..f4a8579
--- /dev/null
+++ b/src/mgcp_patch.c
@@ -0,0 +1,111 @@
+/* MGCP message patching */
+/*
+ * (C) 2011 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2011 by On-Waves
+ * All Rights Reserved
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <mgcp_patch.h>
+#include <cellmgr_debug.h>
+#include <ss7_application.h>
+#include <string.h>
+
+#include <osmocom/gsm/tlv.h>
+
+
+struct msgb *mgcp_patch(struct ss7_application *app, struct msgb *msg)
+{
+	char *token, *remaining;
+	struct msgb *out;
+	int len, out_len, state, i;
+
+	if (!app->mgcp_domain_name)
+		return msg;
+
+	if (msgb_tailroom(msg) <= strlen(app->mgcp_domain_name)) {
+		LOGP(DMGCP, LOGL_ERROR, "Not enough space to add a zero line.\n");
+		return msg;
+	}
+
+	msg->l2h[msgb_l2len(msg)] = '\0';
+
+	/**
+	 * We now need to rewrite the message, but actually only the first
+	 * line and the rest can be copied.
+	 */
+	out = msgb_alloc_headroom(4096, 128, "MGCP Patch Copy");
+	if (!out) {
+		LOGP(DMGCP, LOGL_ERROR, "Failed to create the MSGB copy.\n");
+		return NULL;
+	}
+
+
+	remaining = (char *) msg->l2h;
+	token = strsep(&remaining, "\n");
+	if (!token) {
+		LOGP(DMGCP, LOGL_ERROR, "Failed to split the MGCP.\n");
+		msgb_free(out);
+		return msg;
+	}
+
+	len = strlen(token);
+	out->l2h = msgb_put(out, 0);
+
+	/*
+	 * State machine for copying and modifying the MGCP line, first find
+	 * half of the endpoint, put ours, copy the rest of the line
+	 */
+	state = 0;
+	for (i = 0; i < len; ++i) {
+		switch (state) {
+		case 2:
+			if (token[i] == '@')
+				state += 1;
+			msgb_v_put(out, token[i]);
+			break;
+		case 3:
+			/* copy the new name */
+			out->l3h = msgb_put(out, strlen(app->mgcp_domain_name));
+			memcpy(out->l3h, app->mgcp_domain_name, msgb_l3len(out));
+
+			/* skip everything to the next whitespace */
+			for (; i < len; ++i) {
+				if (token[i] == ' ') {
+					break;
+				}
+			}
+
+			for (; i < len; ++i)
+				msgb_v_put(out, token[i]);
+			msgb_v_put(out, '\n');
+			break;
+		default:
+			if (token[i] == ' ')
+				state += 1;
+			msgb_v_put(out, token[i]);
+			break;
+		}
+	}
+
+	/* append the rest */
+	out_len = msgb_l2len(msg) - len - 1;
+	out->l3h = msgb_put(out, out_len);
+	memcpy(out->l3h, &msg->l2h[len + 1], out_len);
+
+	msgb_free(msg);
+	return out;
+}
+
diff --git a/src/msc_conn.c b/src/msc_conn.c
index 551a781..0e61dd3 100644
--- a/src/msc_conn.c
+++ b/src/msc_conn.c
@@ -27,6 +27,7 @@
 #include <mtp_data.h>
 #include <cellmgr_debug.h>
 #include <ss7_application.h>
+#include <mgcp_patch.h>
 
 #include <osmocom/core/talloc.h>
 #include <osmocom/gsm/tlv.h>
@@ -158,6 +159,7 @@ static int ipaccess_a_fd_cb(struct osmo_fd *bfd)
 	} else if (hh->proto == IPAC_PROTO_SCCP) {
 		msc_dispatch_sccp(fw, msg);
 	} else if (hh->proto == NAT_MUX) {
+		msg = mgcp_patch(fw->app, msg);
 		mgcp_forward(fw, msg->l2h, msgb_l2len(msg));
 	} else {
 		LOGP(DMSC, LOGL_ERROR, "Unknown IPA proto 0x%x\n", hh->proto);