diff --git a/include/osmocom/mgcp_client/mgcp_common.h b/include/osmocom/mgcp_client/mgcp_common.h
new file mode 100644
index 0000000..0eb1388
--- /dev/null
+++ b/include/osmocom/mgcp_client/mgcp_common.h
@@ -0,0 +1,71 @@
+/* MGCP common implementations.
+ * These are used in libosmo-mgcp as well as libosmo-mgcp-client.
+ * To avoid interdependency, these are implemented in .h file only. */
+
+/*
+ * (C) 2017 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ * (C) 2009-2012 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2009-2012 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/>.
+ *
+ */
+
+/* Two copies of this file are kept in osmocom/mgcp/ and osmocom/mgcp_client/.
+ * Since both are by definition identical, use the old header exclusion ifdefs
+ * instead of '#pragma once' to avoid including both of these files.
+ * Though at the time of writing there are no such users, this allows including
+ * both libosmo-mgcp and libosmo-mgcp-client headers in the same file. */
+#ifndef OSMO_MGCP_COMMON_H
+#define OSMO_MGCP_COMMON_H
+
+#include <string.h>
+#include <errno.h>
+
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/logging.h>
+
+#define for_each_non_empty_line(line, save)			\
+	for (line = strtok_r(NULL, "\r\n", &save); line;	\
+	     line = strtok_r(NULL, "\r\n", &save))
+
+enum mgcp_connection_mode {
+	MGCP_CONN_NONE = 0,
+	MGCP_CONN_RECV_ONLY = 1,
+	MGCP_CONN_SEND_ONLY = 2,
+	MGCP_CONN_RECV_SEND = MGCP_CONN_RECV_ONLY | MGCP_CONN_SEND_ONLY,
+	MGCP_CONN_LOOPBACK  = 4 | MGCP_CONN_RECV_SEND,
+};
+
+/* Ensure that the msg->l2h is NUL terminated. */
+static inline int mgcp_msg_terminate_nul(struct msgb *msg)
+{
+	unsigned char *tail = msg->l2h + msgb_l2len(msg); /* char after l2 data */
+	if (tail[-1] == '\0')
+		/* nothing to do */;
+	else if (msgb_tailroom(msg) > 0)
+		tail[0] = '\0';
+	else if (tail[-1] == '\r' || tail[-1] == '\n')
+		tail[-1] = '\0';
+	else {
+		LOGP(DLMGCP, LOGL_ERROR, "Cannot NUL terminate MGCP message: "
+		     "Length: %d, Buffer size: %d\n",
+		     msgb_l2len(msg), msg->data_len);
+		return -ENOTSUP;
+	}
+	return 0;
+}
+
+#endif