diff --git a/src/libosmo-mgcp/mgcp_osmux.c b/src/libosmo-mgcp/mgcp_osmux.c
new file mode 100644
index 0000000..743d3f9
--- /dev/null
+++ b/src/libosmo-mgcp/mgcp_osmux.c
@@ -0,0 +1,583 @@
+/*
+ * (C) 2012-2013 by Pablo Neira Ayuso <pablo@gnumonks.org>
+ * (C) 2012-2013 by On Waves ehf <http://www.on-waves.com>
+ * All rights not specifically granted under this license are 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.
+ */
+
+#include <stdio.h> /* for printf */
+#include <string.h> /* for memcpy */
+#include <stdlib.h> /* for abs */
+#include <inttypes.h> /* for PRIu64 */
+#include <netinet/in.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/talloc.h>
+
+#include <osmocom/netif/osmux.h>
+#include <osmocom/netif/rtp.h>
+
+#include <osmocom/legacy_mgcp/mgcp.h>
+#include <osmocom/legacy_mgcp/mgcp_internal.h>
+#include <osmocom/legacy_mgcp/osmux.h>
+
+static struct osmo_fd osmux_fd;
+
+static LLIST_HEAD(osmux_handle_list);
+
+struct osmux_handle {
+	struct llist_head head;
+	struct osmux_in_handle *in;
+	struct in_addr rem_addr;
+	int rem_port;
+	int refcnt;
+};
+
+static void *osmux;
+
+static void osmux_deliver(struct msgb *batch_msg, void *data)
+{
+	struct osmux_handle *handle = data;
+	struct sockaddr_in out = {
+		.sin_family = AF_INET,
+		.sin_port = handle->rem_port,
+	};
+
+	memcpy(&out.sin_addr, &handle->rem_addr, sizeof(handle->rem_addr));
+	sendto(osmux_fd.fd, batch_msg->data, batch_msg->len, 0,
+		(struct sockaddr *)&out, sizeof(out));
+	msgb_free(batch_msg);
+}
+
+static struct osmux_handle *
+osmux_handle_find_get(struct in_addr *addr, int rem_port)
+{
+	struct osmux_handle *h;
+
+	/* Lookup for existing OSMUX handle for this destination address. */
+	llist_for_each_entry(h, &osmux_handle_list, head) {
+		if (memcmp(&h->rem_addr, addr, sizeof(struct in_addr)) == 0 &&
+		    h->rem_port == rem_port) {
+			LOGP(DLMGCP, LOGL_DEBUG, "using existing OSMUX handle "
+						"for addr=%s:%d\n",
+				inet_ntoa(*addr), ntohs(rem_port));
+			h->refcnt++;
+			return h;
+		}
+	}
+
+	return NULL;
+}
+
+static void osmux_handle_put(struct osmux_in_handle *in)
+{
+	struct osmux_handle *h;
+
+	/* Lookup for existing OSMUX handle for this destination address. */
+	llist_for_each_entry(h, &osmux_handle_list, head) {
+		if (h->in == in) {
+			if (--h->refcnt == 0) {
+				LOGP(DLMGCP, LOGL_INFO,
+				     "Releasing unused osmux handle for %s:%d\n",
+				     inet_ntoa(h->rem_addr),
+				     ntohs(h->rem_port));
+				LOGP(DLMGCP, LOGL_INFO, "Stats: "
+				     "input RTP msgs: %u bytes: %"PRIu64" "
+				     "output osmux msgs: %u bytes: %"PRIu64"\n",
+				     in->stats.input_rtp_msgs,
+				     in->stats.input_rtp_bytes,
+				     in->stats.output_osmux_msgs,
+				     in->stats.output_osmux_bytes);
+				llist_del(&h->head);
+				osmux_xfrm_input_fini(h->in);
+				talloc_free(h);
+			}
+			return;
+		}
+	}
+	LOGP(DLMGCP, LOGL_ERROR, "cannot find Osmux input handle %p\n", in);
+}
+
+static struct osmux_handle *
+osmux_handle_alloc(struct mgcp_config *cfg, struct in_addr *addr, int rem_port)
+{
+	struct osmux_handle *h;
+
+	h = talloc_zero(osmux, struct osmux_handle);
+	if (!h)
+		return NULL;
+	h->rem_addr = *addr;
+	h->rem_port = rem_port;
+	h->refcnt++;
+
+	h->in = talloc_zero(h, struct osmux_in_handle);
+	if (!h->in) {
+		talloc_free(h);
+		return NULL;
+	}
+
+	h->in->osmux_seq = 0; /* sequence number to start OSmux message from */
+	h->in->batch_factor = cfg->osmux_batch;
+	/* If batch size is zero, the library defaults to 1470 bytes. */
+	h->in->batch_size = cfg->osmux_batch_size;
+	h->in->deliver = osmux_deliver;
+	osmux_xfrm_input_init(h->in);
+	h->in->data = h;
+
+	llist_add(&h->head, &osmux_handle_list);
+
+	LOGP(DLMGCP, LOGL_DEBUG, "created new OSMUX handle for addr=%s:%d\n",
+		inet_ntoa(*addr), ntohs(rem_port));
+
+	return h;
+}
+
+static struct osmux_in_handle *
+osmux_handle_lookup(struct mgcp_config *cfg, struct in_addr *addr, int rem_port)
+{
+	struct osmux_handle *h;
+
+	h = osmux_handle_find_get(addr, rem_port);
+	if (h != NULL)
+		return h->in;
+
+	h = osmux_handle_alloc(cfg, addr, rem_port);
+	if (h == NULL)
+		return NULL;
+
+	return h->in;
+}
+
+int osmux_xfrm_to_osmux(int type, char *buf, int rc, struct mgcp_endpoint *endp)
+{
+	int ret;
+	struct msgb *msg;
+
+	msg = msgb_alloc(4096, "RTP");
+	if (!msg)
+		return 0;
+
+	memcpy(msg->data, buf, rc);
+	msgb_put(msg, rc);
+
+	while ((ret = osmux_xfrm_input(endp->osmux.in, msg, endp->osmux.cid)) > 0) {
+		/* batch full, build and deliver it */
+		osmux_xfrm_input_deliver(endp->osmux.in);
+	}
+	return 0;
+}
+
+static struct mgcp_endpoint *
+endpoint_lookup(struct mgcp_config *cfg, int cid,
+		struct in_addr *from_addr, int type)
+{
+	struct mgcp_endpoint *tmp = NULL;
+	int i;
+
+	/* Lookup for the endpoint that corresponds to this port */
+	for (i=0; i<cfg->trunk.number_endpoints; i++) {
+		struct in_addr *this;
+
+		tmp = &cfg->trunk.endpoints[i];
+
+		if (!tmp->allocated)
+			continue;
+
+		switch(type) {
+		case MGCP_DEST_NET:
+			this = &tmp->net_end.addr;
+			break;
+		case MGCP_DEST_BTS:
+			this = &tmp->bts_end.addr;
+			break;
+		default:
+			/* Should not ever happen */
+			LOGP(DLMGCP, LOGL_ERROR, "Bad type %d. Fix your code.\n", type);
+			return NULL;
+		}
+
+		if (tmp->osmux.cid == cid && this->s_addr == from_addr->s_addr)
+			return tmp;
+	}
+
+	LOGP(DLMGCP, LOGL_ERROR, "Cannot find endpoint with cid=%d\n", cid);
+
+	return NULL;
+}
+
+static void scheduled_tx_net_cb(struct msgb *msg, void *data)
+{
+	struct mgcp_endpoint *endp = data;
+	struct sockaddr_in addr = {
+		.sin_addr = endp->net_end.addr,
+		.sin_port = endp->net_end.rtp_port,
+	};
+
+	endp->bts_end.octets += msg->len;
+	endp->bts_end.packets++;
+
+	mgcp_send(endp, MGCP_DEST_NET, 1, &addr, (char *)msg->data, msg->len);
+	msgb_free(msg);
+}
+
+static void scheduled_tx_bts_cb(struct msgb *msg, void *data)
+{
+	struct mgcp_endpoint *endp = data;
+	struct sockaddr_in addr = {
+		.sin_addr = endp->bts_end.addr,
+		.sin_port = endp->bts_end.rtp_port,
+	};
+
+	endp->net_end.octets += msg->len;
+	endp->net_end.packets++;
+
+	mgcp_send(endp, MGCP_DEST_BTS, 1, &addr, (char *)msg->data, msg->len);
+	msgb_free(msg);
+}
+
+static struct msgb *osmux_recv(struct osmo_fd *ofd, struct sockaddr_in *addr)
+{
+	struct msgb *msg;
+	socklen_t slen = sizeof(*addr);
+	int ret;
+
+	msg = msgb_alloc(4096, "OSMUX");
+	if (!msg) {
+		LOGP(DLMGCP, LOGL_ERROR, "cannot allocate message\n");
+		return NULL;
+	}
+	ret = recvfrom(ofd->fd, msg->data, msg->data_len, 0,
+			(struct sockaddr *)addr, &slen);
+	if (ret <= 0) {
+		msgb_free(msg);
+		LOGP(DLMGCP, LOGL_ERROR, "cannot receive message\n");
+		return NULL;
+	}
+	msgb_put(msg, ret);
+
+	return msg;
+}
+
+#define osmux_chunk_length(msg, rem) (rem - msg->len);
+
+int osmux_read_from_bsc_nat_cb(struct osmo_fd *ofd, unsigned int what)
+{
+	struct msgb *msg;
+	struct osmux_hdr *osmuxh;
+	struct llist_head list;
+	struct sockaddr_in addr;
+	struct mgcp_config *cfg = ofd->data;
+	uint32_t rem;
+
+	msg = osmux_recv(ofd, &addr);
+	if (!msg)
+		return -1;
+
+	/* not any further processing dummy messages */
+	if (msg->data[0] == MGCP_DUMMY_LOAD)
+		goto out;
+
+	rem = msg->len;
+	while((osmuxh = osmux_xfrm_output_pull(msg)) != NULL) {
+		struct mgcp_endpoint *endp;
+
+		/* Yes, we use MGCP_DEST_NET to locate the origin */
+		endp = endpoint_lookup(cfg, osmuxh->circuit_id,
+				       &addr.sin_addr, MGCP_DEST_NET);
+		if (!endp) {
+			LOGP(DLMGCP, LOGL_ERROR,
+			     "Cannot find an endpoint for circuit_id=%d\n",
+			     osmuxh->circuit_id);
+			goto out;
+		}
+		endp->osmux.stats.octets += osmux_chunk_length(msg, rem);
+		endp->osmux.stats.chunks++;
+		rem = msg->len;
+
+		osmux_xfrm_output(osmuxh, &endp->osmux.out, &list);
+		osmux_tx_sched(&list, scheduled_tx_bts_cb, endp);
+	}
+out:
+	msgb_free(msg);
+	return 0;
+}
+
+/* This is called from the bsc-nat */
+static int osmux_handle_dummy(struct mgcp_config *cfg, struct sockaddr_in *addr,
+			      struct msgb *msg)
+{
+	struct mgcp_endpoint *endp;
+	uint8_t osmux_cid;
+
+	if (msg->len < 1 + sizeof(osmux_cid)) {
+		LOGP(DLMGCP, LOGL_ERROR,
+		     "Discarding truncated Osmux dummy load\n");
+		goto out;
+	}
+
+	LOGP(DLMGCP, LOGL_DEBUG, "Received Osmux dummy load from %s\n",
+	     inet_ntoa(addr->sin_addr));
+
+	if (!cfg->osmux) {
+		LOGP(DLMGCP, LOGL_ERROR,
+		     "bsc wants to use Osmux but bsc-nat did not request it\n");
+		goto out;
+	}
+
+	/* extract the osmux CID from the dummy message */
+	memcpy(&osmux_cid, &msg->data[1], sizeof(osmux_cid));
+
+	endp = endpoint_lookup(cfg, osmux_cid, &addr->sin_addr, MGCP_DEST_BTS);
+	if (!endp) {
+		LOGP(DLMGCP, LOGL_ERROR,
+		     "Cannot find endpoint for Osmux CID %d\n", osmux_cid);
+		goto out;
+	}
+
+	if (endp->osmux.state == OSMUX_STATE_ENABLED)
+		goto out;
+
+	if (osmux_enable_endpoint(endp, &addr->sin_addr, addr->sin_port) < 0 ) {
+		LOGP(DLMGCP, LOGL_ERROR,
+		     "Could not enable osmux in endpoint %d\n",
+		     ENDPOINT_NUMBER(endp));
+		goto out;
+	}
+
+	LOGP(DLMGCP, LOGL_INFO, "Enabling osmux in endpoint %d for %s:%u\n",
+	     ENDPOINT_NUMBER(endp), inet_ntoa(addr->sin_addr),
+	     ntohs(addr->sin_port));
+out:
+	msgb_free(msg);
+	return 0;
+}
+
+int osmux_read_from_bsc_cb(struct osmo_fd *ofd, unsigned int what)
+{
+	struct msgb *msg;
+	struct osmux_hdr *osmuxh;
+	struct llist_head list;
+	struct sockaddr_in addr;
+	struct mgcp_config *cfg = ofd->data;
+	uint32_t rem;
+
+	msg = osmux_recv(ofd, &addr);
+	if (!msg)
+		return -1;
+
+	/* not any further processing dummy messages */
+	if (msg->data[0] == MGCP_DUMMY_LOAD)
+		return osmux_handle_dummy(cfg, &addr, msg);
+
+	rem = msg->len;
+	while((osmuxh = osmux_xfrm_output_pull(msg)) != NULL) {
+		struct mgcp_endpoint *endp;
+
+		/* Yes, we use MGCP_DEST_BTS to locate the origin */
+		endp = endpoint_lookup(cfg, osmuxh->circuit_id,
+				       &addr.sin_addr, MGCP_DEST_BTS);
+		if (!endp) {
+			LOGP(DLMGCP, LOGL_ERROR,
+			     "Cannot find an endpoint for circuit_id=%d\n",
+			     osmuxh->circuit_id);
+			goto out;
+		}
+		endp->osmux.stats.octets += osmux_chunk_length(msg, rem);
+		endp->osmux.stats.chunks++;
+		rem = msg->len;
+
+		osmux_xfrm_output(osmuxh, &endp->osmux.out, &list);
+		osmux_tx_sched(&list, scheduled_tx_net_cb, endp);
+	}
+out:
+	msgb_free(msg);
+	return 0;
+}
+
+int osmux_init(int role, struct mgcp_config *cfg)
+{
+	int ret;
+
+	switch(role) {
+	case OSMUX_ROLE_BSC:
+		osmux_fd.cb = osmux_read_from_bsc_nat_cb;
+		break;
+	case OSMUX_ROLE_BSC_NAT:
+		osmux_fd.cb = osmux_read_from_bsc_cb;
+		break;
+	default:
+		LOGP(DLMGCP, LOGL_ERROR, "wrong role for OSMUX\n");
+		return -1;
+	}
+	osmux_fd.data = cfg;
+
+	ret = mgcp_create_bind(cfg->osmux_addr, &osmux_fd, cfg->osmux_port);
+	if (ret < 0) {
+		LOGP(DLMGCP, LOGL_ERROR, "cannot bind OSMUX socket\n");
+		return ret;
+	}
+	mgcp_set_ip_tos(osmux_fd.fd, cfg->endp_dscp);
+	osmux_fd.when |= BSC_FD_READ;
+
+	ret = osmo_fd_register(&osmux_fd);
+	if (ret < 0) {
+		LOGP(DLMGCP, LOGL_ERROR, "cannot register OSMUX socket\n");
+		return ret;
+	}
+	cfg->osmux_init = 1;
+
+	return 0;
+}
+
+int osmux_enable_endpoint(struct mgcp_endpoint *endp, struct in_addr *addr, uint16_t port)
+{
+	/* If osmux is enabled, initialize the output handler. This handler is
+	 * used to reconstruct the RTP flow from osmux. The RTP SSRC is
+	 * allocated based on the circuit ID (endp->osmux.cid), which is unique
+	 * in the local scope to the BSC/BSC-NAT. We use it to divide the RTP
+	 * SSRC space (2^32) by the 256 possible circuit IDs, then randomly
+	 * select one value from that window. Thus, we have no chance to have
+	 * overlapping RTP SSRC traveling to the BTSes behind the BSC,
+	 * similarly, for flows traveling to the MSC.
+	 */
+	static const uint32_t rtp_ssrc_winlen = UINT32_MAX / 256;
+
+	if (endp->osmux.state == OSMUX_STATE_DISABLED) {
+		LOGP(DLMGCP, LOGL_ERROR, "Endpoint %u didn't request Osmux\n",
+		     ENDPOINT_NUMBER(endp));
+		return -1;
+	}
+
+	osmux_xfrm_output_init(&endp->osmux.out,
+			       (endp->osmux.cid * rtp_ssrc_winlen) +
+			       (random() % rtp_ssrc_winlen));
+
+	endp->osmux.in = osmux_handle_lookup(endp->cfg, addr, port);
+	if (!endp->osmux.in) {
+		LOGP(DLMGCP, LOGL_ERROR, "Cannot allocate input osmux handle\n");
+		return -1;
+	}
+	if (!osmux_xfrm_input_open_circuit(endp->osmux.in, endp->osmux.cid,
+					   endp->cfg->osmux_dummy)) {
+		LOGP(DLMGCP, LOGL_ERROR, "Cannot open osmux circuit %u\n",
+		     endp->osmux.cid);
+		return -1;
+	}
+
+	switch (endp->cfg->role) {
+		case MGCP_BSC_NAT:
+			endp->type = MGCP_OSMUX_BSC_NAT;
+			break;
+		case MGCP_BSC:
+			endp->type = MGCP_OSMUX_BSC;
+			break;
+	}
+	endp->osmux.state = OSMUX_STATE_ENABLED;
+
+	return 0;
+}
+
+void osmux_disable_endpoint(struct mgcp_endpoint *endp)
+{
+	LOGP(DLMGCP, LOGL_INFO, "Releasing endpoint %u using Osmux CID %u\n",
+	     ENDPOINT_NUMBER(endp), endp->osmux.cid);
+	osmux_xfrm_input_close_circuit(endp->osmux.in, endp->osmux.cid);
+	endp->osmux.state = OSMUX_STATE_DISABLED;
+	endp->osmux.cid = -1;
+	osmux_handle_put(endp->osmux.in);
+}
+
+void osmux_release_cid(struct mgcp_endpoint *endp)
+{
+	if (endp->osmux.allocated_cid >= 0)
+		osmux_put_cid(endp->osmux.allocated_cid);
+	endp->osmux.allocated_cid = -1;
+}
+
+void osmux_allocate_cid(struct mgcp_endpoint *endp)
+{
+	osmux_release_cid(endp);
+	endp->osmux.allocated_cid = osmux_get_cid();
+}
+
+/* We don't need to send the dummy load for osmux so often as another endpoint
+ * may have already punched the hole in the firewall. This approach is simple
+ * though.
+ */
+int osmux_send_dummy(struct mgcp_endpoint *endp)
+{
+	char buf[1 + sizeof(uint8_t)];
+	struct in_addr addr_unset = {};
+
+	buf[0] = MGCP_DUMMY_LOAD;
+	memcpy(&buf[1], &endp->osmux.cid, sizeof(endp->osmux.cid));
+
+	/* Wait until we have the connection information from MDCX */
+	if (memcmp(&endp->net_end.addr, &addr_unset, sizeof(addr_unset)) == 0)
+		return 0;
+
+	if (endp->osmux.state == OSMUX_STATE_ACTIVATING) {
+		if (osmux_enable_endpoint(endp, &endp->net_end.addr,
+					  htons(endp->cfg->osmux_port)) < 0) {
+			LOGP(DLMGCP, LOGL_ERROR,
+			     "Could not activate osmux in endpoint %d\n",
+			     ENDPOINT_NUMBER(endp));
+		}
+		LOGP(DLMGCP, LOGL_ERROR,
+		     "Osmux CID %u for %s:%u is now enabled\n",
+		     endp->osmux.cid, inet_ntoa(endp->net_end.addr),
+		     endp->cfg->osmux_port);
+	}
+	LOGP(DLMGCP, LOGL_DEBUG,
+	     "sending OSMUX dummy load to %s CID %u\n",
+	     inet_ntoa(endp->net_end.addr), endp->osmux.cid);
+
+	return mgcp_udp_send(osmux_fd.fd, &endp->net_end.addr,
+			     htons(endp->cfg->osmux_port), buf, sizeof(buf));
+}
+
+/* bsc-nat allocates/releases the Osmux circuit ID */
+static uint8_t osmux_cid_bitmap[(OSMUX_CID_MAX + 1) / 8];
+
+int osmux_used_cid(void)
+{
+	int i, j, used = 0;
+
+	for (i = 0; i < sizeof(osmux_cid_bitmap); i++) {
+		for (j = 0; j < 8; j++) {
+			if (osmux_cid_bitmap[i] & (1 << j))
+				used += 1;
+		}
+	}
+
+	return used;
+}
+
+int osmux_get_cid(void)
+{
+	int i, j;
+
+	for (i = 0; i < sizeof(osmux_cid_bitmap); i++) {
+		for (j = 0; j < 8; j++) {
+			if (osmux_cid_bitmap[i] & (1 << j))
+				continue;
+
+			osmux_cid_bitmap[i] |= (1 << j);
+			LOGP(DLMGCP, LOGL_DEBUG,
+			     "Allocating Osmux CID %u from pool\n", (i * 8) + j);
+			return (i * 8) + j;
+		}
+	}
+
+	LOGP(DLMGCP, LOGL_ERROR, "All Osmux circuits are in use!\n");
+	return -1;
+}
+
+void osmux_put_cid(uint8_t osmux_cid)
+{
+	LOGP(DLMGCP, LOGL_DEBUG, "Osmux CID %u is back to the pool\n", osmux_cid);
+	osmux_cid_bitmap[osmux_cid / 8] &= ~(1 << (osmux_cid % 8));
+}