Merge branch 'on-waves/multiple-links'

17 files changed, 414 insertions, 387 deletions

diff --git a/include/bsc_data.h b/include/bsc_data.h
index d13a566..fa04c3a 100644
--- a/include/bsc_data.h
+++ b/include/bsc_data.h
@@ -1,7 +1,7 @@
 /* Everything related to the BSC connection */
 /*
- * (C) 2010 by Holger Hans Peter Freyther <zecke@selfish.org>
- * (C) 2010 by On-Waves
+ * (C) 2010-2011 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2010-2011 by On-Waves
  * All Rights Reserved
  *
  * This program is free software: you can redistribute it and/or modify
@@ -42,6 +42,8 @@ struct snmp_mtp_session;
  * A link to the underlying MTP2 library or such
  */
 struct link_data {
+	struct llist_head entry;
+
 	union {
 		struct {
 			struct thread_notifier *notifier;
@@ -52,16 +54,18 @@ struct link_data {
 			struct write_queue write_queue;
 			struct sockaddr_in remote;
 			struct snmp_mtp_session *session;
+			int link_index;
 			int reset_timeout;
 		} udp;
 	};
 
 	int pcap_fd;
 	struct bsc_data *bsc;
-	struct mtp_link *the_link;
+	struct mtp_link_set *the_link;
+
+	int available;
 
 	struct timer_list link_activate;
-	int forced_down;
 
 	int (*start)(struct link_data *);
 	int (*write)(struct link_data *, struct msgb *msg);
@@ -95,7 +99,9 @@ struct bsc_data {
 
 	int setup;
 
-	struct link_data link;
+	int pcap_fd;
+	int udp_reset_timeout;
+	struct mtp_link_set *link_set;
 
 	const char *token;
 
@@ -125,8 +131,11 @@ struct bsc_data {
 
 /* bsc related functions */
 void release_bsc_resources(struct bsc_data *bsc);
-void bsc_link_down(struct link_data *data);
-void bsc_link_up(struct link_data *data);
+void mtp_link_down(struct link_data *data);
+void mtp_link_up(struct link_data *data);
+
+void mtp_linkset_down(struct mtp_link_set *);
+void mtp_linkset_up(struct mtp_link_set *);
 
 /* msc related functions */
 int msc_init(struct bsc_data *bsc, int mgcp);
@@ -134,18 +143,18 @@ void msc_send_rlc(struct bsc_data *bsc, struct sccp_source_reference *src, struc
 void msc_send_reset(struct bsc_data *bsc);
 void msc_send_msg(struct bsc_data *bsc, int rc, struct sccp_parse_result *, struct msgb *msg);
 void msc_send_direct(struct bsc_data *bsc, struct msgb *msg);
-void msc_clear_queue(struct bsc_data *data);
 void msc_close_connection(struct bsc_data *data);
 
 /* connection tracking and action */
-void update_con_state(struct mtp_link *link, int rc, struct sccp_parse_result *result, struct msgb *msg, int from_msc, int sls);
+void update_con_state(struct mtp_link_set *link, int rc, struct sccp_parse_result *result, struct msgb *msg, int from_msc, int sls);
 unsigned int sls_for_src_ref(struct sccp_source_reference *ref);
 
-/* c7 init */
-int link_c7_init(struct link_data *data);
-
 /* udp init */
 int link_udp_init(struct link_data *data, int src_port, const char *dest_ip, int port);
+int link_init(struct bsc_data *bsc);
+int link_shutdown_all(struct mtp_link_set *);
+int link_reset_all(struct mtp_link_set *);
+int link_clear_all(struct mtp_link_set *);
 
 /* MGCP */
 void mgcp_forward(struct bsc_data *bsc, const uint8_t *data, unsigned int length);
diff --git a/include/bsc_sccp.h b/include/bsc_sccp.h
index c75bab6..8811a2b 100644
--- a/include/bsc_sccp.h
+++ b/include/bsc_sccp.h
@@ -54,7 +54,7 @@ struct active_sccp_con {
 	unsigned int rls_tries;
 
 	/* MTP link this was coming in */
-	struct mtp_link *link;
+	struct mtp_link_set *link;
 
 	/* sls id */
 	int sls;
diff --git a/include/isup_types.h b/include/isup_types.h
index be7964d..5347cb4 100644
--- a/include/isup_types.h
+++ b/include/isup_types.h
@@ -25,7 +25,7 @@
 #include <endian.h>
 
 struct msgb;
-struct mtp_link;
+struct mtp_link_set;
 
 /* This is from Table 4/Q.763 */
 #define ISUP_MSG_GRS	0x17
@@ -47,7 +47,7 @@ struct isup_msg_grs {
 	uint8_t  pointer_int;
 };
 
-int mtp_link_forward_isup(struct mtp_link *link, struct msgb *msg, int sls);
+int mtp_link_set_forward_isup(struct mtp_link_set *link, struct msgb *msg, int sls);
 
 int isup_parse_grs(const uint8_t *data, uint8_t length);
 
diff --git a/include/mtp_data.h b/include/mtp_data.h
index e98d073..349bf7a 100644
--- a/include/mtp_data.h
+++ b/include/mtp_data.h
@@ -1,6 +1,6 @@
 /*
- * (C) 2010 by Holger Hans Peter Freyther <zecke@selfish.org>
- * (C) 2010 by On-Waves
+ * (C) 2010-2011 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2010-2011 by On-Waves
  * All Rights Reserved
  *
  * This program is free software: you can redistribute it and/or modify
@@ -24,6 +24,9 @@
 #include <osmocore/timer.h>
 #include <osmocore/utils.h>
 
+struct bsc_data;
+struct link_data;
+
 /* MTP Level3 timers */
 
 /* Timers for SS7 */
@@ -34,7 +37,7 @@
 /**
  * The state of the mtp_link in terms of layer3 and upwards
  */
-struct mtp_link {
+struct mtp_link_set {
 	/* routing info.. */
 	int dpc, opc, sccp_opc;
 	int ni;
@@ -46,42 +49,47 @@ struct mtp_link {
 	int running;
 	int sccp_up;
 
+	int last_sls;
+
 	/* misc data */
 	uint8_t test_ptrn[14];
 
 	int sltm_pending;
-	struct llist_head pending_msgs;
 	int sltm_once;
 	int was_up;
 
-
-	/* the associated link */
-	int link;
-
 	int slta_misses;
 	struct timer_list t1_timer;
 	struct timer_list t2_timer;
 
 	struct timer_list delay_timer;
+
+	struct llist_head links;
+	struct link_data *slc[16];
+
+	/* custom data */
+	struct bsc_data *bsc;
 };
 
 
-struct mtp_link *mtp_link_alloc(void);
-void mtp_link_stop(struct mtp_link *link);
-void mtp_link_reset(struct mtp_link *link);
-int mtp_link_data(struct mtp_link *link, struct msgb *msg);
-int mtp_link_submit_sccp_data(struct mtp_link *link, int sls, const uint8_t *data, unsigned int length);
-int mtp_link_submit_isup_data(struct mtp_link *link, int sls, const uint8_t *data, unsigned int length);
+struct mtp_link_set *mtp_link_set_alloc(void);
+void mtp_link_set_stop(struct mtp_link_set *link);
+void mtp_link_set_reset(struct mtp_link_set *link);
+int mtp_link_set_data(struct mtp_link_set *link, struct msgb *msg);
+int mtp_link_set_submit_sccp_data(struct mtp_link_set *link, int sls, const uint8_t *data, unsigned int length);
+int mtp_link_set_submit_isup_data(struct mtp_link_set *link, int sls, const uint8_t *data, unsigned int length);
+
+void mtp_link_set_init_slc(struct mtp_link_set *set);
+void mtp_link_set_add_link(struct mtp_link_set *set, struct link_data *link);
 
 
 /* one time init function */
-void mtp_link_init(void);
+void mtp_link_set_init(void);
 
 /* to be implemented for MSU sending */
-void mtp_link_submit(struct mtp_link *link, struct msgb *msg);
-void mtp_link_forward_sccp(struct mtp_link *link, struct msgb *msg, int sls);
-void mtp_link_restart(struct mtp_link *link);
-void mtp_link_slta_recv(struct mtp_link *link);
-void mtp_link_sccp_down(struct mtp_link *link);
+void mtp_link_set_submit(struct link_data *link, struct msgb *msg);
+void mtp_link_set_forward_sccp(struct mtp_link_set *link, struct msgb *msg, int sls);
+void mtp_link_restart(struct link_data *link);
+void mtp_link_set_sccp_down(struct mtp_link_set *link);
 
 #endif
diff --git a/include/snmp_mtp.h b/include/snmp_mtp.h
index fea3c66..a42b08e 100644
--- a/include/snmp_mtp.h
+++ b/include/snmp_mtp.h
@@ -32,7 +32,7 @@ void snmp_mtp_start_c7_datalink(struct snmp_mtp_session *, int link_id);
 void snmp_mtp_stop_c7_datalink(struct snmp_mtp_session *, int link_id);
 
 struct snmp_mtp_session *snmp_mtp_session_create(char *host);
-void snmp_mtp_deactivate(struct snmp_mtp_session *);
-void snmp_mtp_activate(struct snmp_mtp_session *);
+void snmp_mtp_deactivate(struct snmp_mtp_session *, int link_id);
+void snmp_mtp_activate(struct snmp_mtp_session *, int link_id);
 
 #endif
diff --git a/src/Makefile.am b/src/Makefile.am
index 4ca99f7..83acf8d 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -10,13 +10,13 @@ mgcp_mgw_LDADD = $(LAFORGE_LIBS) $(NEXUSWARE_C7_LIBS) $(NEXUSWARE_UNIPORTE_LIBS)
 		 $(LIBOSMOVTY_LIBS) $(LIBOSMOCORE_LIBS) -lpthread
 
 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 \
+		     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 vty_interface.c isup.c
 cellmgr_ng_LDADD = $(LIBOSMOCORE_LIBS) $(LIBOSMOSCCP_LIBS) $(LIBOSMOVTY_LIBS) $(NEXUSWARE_C7_LIBS) \
 		   -lpthread -lnetsnmp -lcrypto
 
 udt_relay_SOURCES = main_udt.c mtp_layer3.c thread.c input/ipaccess.c pcap.c \
 		     msc_conn.c link_udp.c snmp_mtp.c debug.c vty_interface.c \
-		     bss_patch.c isup.c
+		     bss_patch.c isup.c links.c
 udt_relay_LDADD = $(LIBOSMOCORE_LIBS) $(LIBOSMOSCCP_LIBS) $(LIBOSMOVTY_LIBS) $(NEXUSWARE_C7_LIBS) \
 		   -lpthread -lnetsnmp -lcrypto
diff --git a/src/bsc_sccp.c b/src/bsc_sccp.c
index 69e2262..ea13c43 100644
--- a/src/bsc_sccp.c
+++ b/src/bsc_sccp.c
@@ -86,7 +86,7 @@ unsigned int sls_for_src_ref(struct sccp_source_reference *ref)
 
 	con = find_con_by_src_ref(ref);
 	if (!con)
-		return 13;
+		return -1;
 	return con->sls;
 }
 
diff --git a/src/isup.c b/src/isup.c
index 8af1464..340af16 100644
--- a/src/isup.c
+++ b/src/isup.c
@@ -90,7 +90,7 @@ int isup_parse_grs(const uint8_t *data, uint8_t in_length)
 
 
 /* Handle incoming ISUP data */
-static int handle_circuit_reset_grs(struct mtp_link *link, int sls, int cic,
+static int handle_circuit_reset_grs(struct mtp_link_set *link, int sls, int cic,
 				    const uint8_t *data, int size)
 {
 	struct msgb *resp;
@@ -104,12 +104,12 @@ static int handle_circuit_reset_grs(struct mtp_link *link, int sls, int cic,
 	if (!resp)
 		return -1;
 
-	mtp_link_submit_isup_data(link, sls, resp->l2h, msgb_l2len(resp));
+	mtp_link_set_submit_isup_data(link, sls, resp->l2h, msgb_l2len(resp));
 	msgb_free(resp);
 	return 0;
 }
 
-int mtp_link_forward_isup(struct mtp_link *link, struct msgb *msg, int sls)
+int mtp_link_set_forward_isup(struct mtp_link_set *link, struct msgb *msg, int sls)
 {
 	int rc = -1;
 	int payload_size;
diff --git a/src/link_udp.c b/src/link_udp.c
index b5da7f9..e05bd17 100644
--- a/src/link_udp.c
+++ b/src/link_udp.c
@@ -91,12 +91,12 @@ static int udp_read_cb(struct bsc_fd *fd)
 
 	if (hdr->data_type == UDP_DATA_RETR_COMPL || hdr->data_type == UDP_DATA_RETR_IMPOS) {
 		LOGP(DINP, LOGL_ERROR, "Link retrieval done. Restarting the link.\n");
-		bsc_link_down(link);
-		bsc_link_up(link);
+		mtp_link_down(link);
+		mtp_link_up(link);
 		goto exit;
 	} else if (hdr->data_type > UDP_DATA_MSU_PRIO_3) {
 		LOGP(DINP, LOGL_ERROR, "Link failure. retrieved message.\n");
-		bsc_link_down(link);
+		mtp_link_down(link);
 		goto exit;
 	}
 
@@ -113,7 +113,7 @@ static int udp_read_cb(struct bsc_fd *fd)
 	LOGP(DINP, LOGL_DEBUG, "MSU data on: %p data %s.\n", link, hexdump(msg->data, msg->len));
 	if (link->pcap_fd >= 0)
 		mtp_pcap_write_msu(link->pcap_fd, msg->l2h, msgb_l2len(msg));
-	mtp_link_data(link->the_link, msg);
+	mtp_link_set_data(link->the_link, msg);
 
 exit:
 	msgb_free(msg);
@@ -130,17 +130,16 @@ static void do_start(void *_data)
 {
 	struct link_data *link = (struct link_data *) _data;
 
-	link->forced_down = 0;
-	snmp_mtp_activate(link->udp.session);
-	bsc_link_up(link);
+	snmp_mtp_activate(link->udp.session, link->udp.link_index);
+	mtp_link_up(link);
 }
 
 static int udp_link_reset(struct link_data *link)
 {
 	LOGP(DINP, LOGL_NOTICE, "Will restart SLTM transmission in %d seconds.\n",
 	     link->udp.reset_timeout);
-	snmp_mtp_deactivate(link->udp.session);
-	bsc_link_down(link);
+	snmp_mtp_deactivate(link->udp.session, link->udp.link_index);
+	mtp_link_down(link);
 
 	/* restart the link in 90 seconds... to force a timeout on the BSC */
 	link->link_activate.cb = do_start;
@@ -156,7 +155,7 @@ static int udp_link_write(struct link_data *link, struct msgb *msg)
 	hdr = (struct udp_data_hdr *) msgb_push(msg, sizeof(*hdr));
 	hdr->format_type = UDP_FORMAT_SIMPLE_UDP;
 	hdr->data_type = UDP_DATA_MSU_PRIO_0;
-	hdr->data_link_index = htons(1);
+	hdr->data_link_index = htons(link->udp.link_index);
 	hdr->user_context = 0;
 	hdr->data_length = htonl(msgb_l2len(msg));
 
diff --git a/src/links.c b/src/links.c
new file mode 100644
index 0000000..023a7f4
--- /dev/null
+++ b/src/links.c
@@ -0,0 +1,177 @@
+/* link management code */
+/*
+ * (C) 2010-2011 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2010-2011 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 General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <bsc_data.h>
+#include <cellmgr_debug.h>
+#include <mtp_data.h>
+#include <snmp_mtp.h>
+
+#include <osmocore/talloc.h>
+
+extern struct bsc_data bsc;
+
+int is_one_up(struct mtp_link_set *set)
+{
+	struct link_data *entry;
+
+	llist_for_each_entry(entry, &set->links, entry)
+		if (entry->available)
+			return 1;
+	return 0;
+}
+
+void mtp_link_down(struct link_data *link)
+{
+	int one_up;
+	int was_up;
+
+	was_up = link->available;
+	link->available = 0;
+	one_up = is_one_up(link->the_link);
+
+	/* our linkset is now unsuable */
+	if (was_up && !one_up)
+		mtp_linkset_down(link->the_link);
+	link->clear_queue(link);
+	mtp_link_set_init_slc(link->the_link);
+}
+
+void mtp_link_up(struct link_data *link)
+{
+	int one_up;
+
+	one_up = is_one_up(link->the_link);
+	link->available = 1;
+
+	mtp_link_set_init_slc(link->the_link);
+	if (!one_up)
+		mtp_linkset_up(link->the_link);
+}
+
+void mtp_link_set_sccp_down(struct mtp_link_set *link)
+{
+}
+
+void mtp_link_set_submit(struct link_data *link, struct msgb *msg)
+{
+	link->write(link, msg);
+}
+
+void mtp_link_restart(struct link_data *link)
+{
+	LOGP(DINP, LOGL_ERROR, "Need to restart the SS7 link.\n");
+	link->reset(link);
+}
+
+static void start_rest(void *start)
+{
+	struct link_data *data;
+	bsc.setup = 1;
+
+	if (msc_init(&bsc, 1) != 0) {
+		fprintf(stderr, "Failed to init MSC part.\n");
+		exit(3);
+	}
+
+	llist_for_each_entry(data, &bsc.link_set->links, entry)
+		data->start(data);
+}
+
+int link_init(struct bsc_data *bsc)
+{
+	struct link_data *lnk;
+
+	bsc->link_set = mtp_link_set_alloc();
+	bsc->link_set->dpc = bsc->dpc;
+	bsc->link_set->opc = bsc->opc;
+	bsc->link_set->sccp_opc = bsc->sccp_opc > -1 ? bsc->sccp_opc : bsc->opc;
+	bsc->link_set->sltm_once = bsc->once;
+	bsc->link_set->ni = bsc->ni_ni;
+	bsc->link_set->spare = bsc->ni_spare;
+	bsc->link_set->bsc = bsc;
+
+	lnk = talloc_zero(bsc->link_set, struct link_data);
+	lnk->bsc = bsc;
+	lnk->udp.link_index = 1;
+	lnk->pcap_fd = bsc->pcap_fd;
+	lnk->udp.reset_timeout = bsc->udp_reset_timeout;
+	lnk->the_link = bsc->link_set;
+	mtp_link_set_add_link(bsc->link_set, lnk);
+
+	if (!bsc->src_port) {
+		LOGP(DINP, LOGL_ERROR, "You need to set a UDP address.\n");
+		return -1;
+	}
+
+	LOGP(DINP, LOGL_NOTICE, "Using UDP MTP mode.\n");
+
+	/* setup SNMP first, it is blocking */
+	lnk->udp.session = snmp_mtp_session_create(bsc->udp_ip);
+	if (!lnk->udp.session)
+		return -1;
+
+	/* now connect to the transport */
+	if (link_udp_init(lnk, bsc->src_port, bsc->udp_ip, bsc->udp_port) != 0)
+		return -1;
+
+	/*
+	 * We will ask the MTP link to be taken down for two
+	 * timeouts of the BSC to make sure we are missing the
+	 * SLTM and it begins a reset. Then we will take it up
+	 * again and do the usual business.
+	 */
+	snmp_mtp_deactivate(lnk->udp.session,
+			    lnk->udp.link_index);
+	bsc->start_timer.cb = start_rest;
+	bsc->start_timer.data = &bsc;
+	bsc_schedule_timer(&bsc->start_timer, lnk->udp.reset_timeout, 0);
+	LOGP(DMSC, LOGL_NOTICE, "Making sure SLTM will timeout.\n");
+
+	return 0;
+}
+
+int link_shutdown_all(struct mtp_link_set *set)
+{
+	struct link_data *lnk;
+
+	llist_for_each_entry(lnk, &set->links, entry)
+		lnk->shutdown(lnk);
+	return 0;
+}
+
+int link_reset_all(struct mtp_link_set *set)
+{
+	struct link_data *lnk;
+
+	llist_for_each_entry(lnk, &set->links, entry)
+		lnk->reset(lnk);
+	return 0;
+}
+
+int link_clear_all(struct mtp_link_set *set)
+{
+	struct link_data *lnk;
+
+	llist_for_each_entry(lnk, &set->links, entry)
+		lnk->clear_queue(lnk);
+	return 0;
+}
diff --git a/src/main.c b/src/main.c
index a977df4..3163527 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,7 +1,7 @@
 /* Bloated main routine, refactor */
 /*
- * (C) 2010 by Holger Hans Peter Freyther <zecke@selfish.org>
- * (C) 2010 by On-Waves
+ * (C) 2010-2011 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2010-2011 by On-Waves
  * All Rights Reserved
  *
  * This program is free software: you can redistribute it and/or modify
@@ -26,7 +26,6 @@
 #include <bss_patch.h>
 #include <bssap_sccp.h>
 #include <bsc_data.h>
-#include <snmp_mtp.h>
 #include <cellmgr_debug.h>
 #include <bsc_sccp.h>
 
@@ -65,18 +64,11 @@ static char *config = "cellmgr_ng.cfg";
 struct bsc_data bsc;
 extern void cell_vty_init(void);
 
-static void send_reset_ack(struct mtp_link *link, int sls);
+static void send_reset_ack(struct mtp_link_set *link, int sls);
 static void bsc_resources_released(struct bsc_data *bsc);
-static void handle_local_sccp(struct mtp_link *link, struct msgb *inp, struct sccp_parse_result *res, int sls);
+static void handle_local_sccp(struct mtp_link_set *link, struct msgb *inp, struct sccp_parse_result *res, int sls);
 static void clear_connections(struct bsc_data *bsc);
-static void send_local_rlsd(struct mtp_link *link, struct sccp_parse_result *res);
-
-int link_c7_init(struct link_data *data) __attribute__((__weak__));
-
-int link_c7_init(struct link_data *data)
-{
-	return -1;
-}
+static void send_local_rlsd(struct mtp_link_set *link, struct sccp_parse_result *res);
 
 /* send a RSIP to the MGCP GW */
 static void mgcp_reset(struct bsc_data *bsc)
@@ -91,23 +83,7 @@ static void mgcp_reset(struct bsc_data *bsc)
 /*
  * methods called from the MTP Level3 part
  */
-void mtp_link_submit(struct mtp_link *link, struct msgb *msg)
-{
-	bsc.link.write(&bsc.link, msg);
-}
-
-void mtp_link_restart(struct mtp_link *link)
-{
-	LOGP(DINP, LOGL_ERROR, "Need to restart the SS7 link.\n");
-	bsc.link.reset(&bsc.link);
-}
-
-void mtp_link_sccp_down(struct mtp_link *link)
-{
-	msc_clear_queue(&bsc);
-}
-
-void mtp_link_forward_sccp(struct mtp_link *link, struct msgb *_msg, int sls)
+void mtp_link_set_forward_sccp(struct mtp_link_set *link, struct msgb *_msg, int sls)
 {
 	int rc;
 	struct sccp_parse_result result;
@@ -115,7 +91,6 @@ void mtp_link_forward_sccp(struct mtp_link *link, struct msgb *_msg, int sls)
 	rc = bss_patch_filter_msg(_msg, &result);
 	if (rc == BSS_FILTER_RESET) {
 		LOGP(DMSC, LOGL_NOTICE, "Filtering BSS Reset from the BSC\n");
-		msc_clear_queue(&bsc);
 		mgcp_reset(&bsc);
 		send_reset_ack(link, sls);
 		return;
@@ -155,7 +130,7 @@ void mtp_link_forward_sccp(struct mtp_link *link, struct msgb *_msg, int sls)
 /*
  * handle local message in close down mode
  */
-static void handle_local_sccp(struct mtp_link *link, struct msgb *inpt, struct sccp_parse_result *result, int sls)
+static void handle_local_sccp(struct mtp_link_set *link, struct msgb *inpt, struct sccp_parse_result *result, int sls)
 {
 	/* Handle msg with a reject */
 	if (inpt->l2h[0] == SCCP_MSG_TYPE_CR) {
@@ -166,7 +141,7 @@ static void handle_local_sccp(struct mtp_link *link, struct msgb *inpt, struct s
 		cr = (struct sccp_connection_request *) inpt->l2h;
 		msg = create_sccp_refuse(&cr->source_local_reference);
 		if (msg) {
-			mtp_link_submit_sccp_data(link, sls, msg->l2h, msgb_l2len(msg));
+			mtp_link_set_submit_sccp_data(link, sls, msg->l2h, msgb_l2len(msg));
 			msgb_free(msg);
 		}
 		return;
@@ -186,7 +161,7 @@ static void handle_local_sccp(struct mtp_link *link, struct msgb *inpt, struct s
 					LOGP(DINP, LOGL_DEBUG, "Sending a release request now.\n");
 					msg = create_sccp_rlsd(&con->dst_ref, &con->src_ref);
 					if (msg) {
-						mtp_link_submit_sccp_data(link, con->sls, msg->l2h, msgb_l2len(msg));
+						mtp_link_set_submit_sccp_data(link, con->sls, msg->l2h, msgb_l2len(msg));
 						msgb_free(msg);
 					}
 					return;
@@ -219,7 +194,7 @@ static void clear_connections(struct bsc_data *bsc)
 		free_con(con);
 	}
 
-	bsc->link.clear_queue(&bsc->link);
+	link_clear_all(bsc->link_set);
 }
 
 void bsc_resources_released(struct bsc_data *bsc)
@@ -235,9 +210,9 @@ static void bsc_reset_timeout(void *_data)
 	/* no reset */
 	if (bsc->reset_count > 0) {
 		LOGP(DINP, LOGL_ERROR, "The BSC did not answer the GSM08.08 reset. Restart MTP\n");
-		mtp_link_stop(bsc->link.the_link);
+		mtp_link_set_stop(bsc->link_set);
 		clear_connections(bsc);
-		bsc->link.reset(&bsc->link);
+		link_reset_all(bsc->link_set);
 		bsc_resources_released(bsc);
 		return;
 	}
@@ -249,7 +224,7 @@ static void bsc_reset_timeout(void *_data)
 	}
 
 	++bsc->reset_count;
-	mtp_link_submit_sccp_data(bsc->link.the_link, 13, msg->l2h, msgb_l2len(msg));
+	mtp_link_set_submit_sccp_data(bsc->link_set, -1, msg->l2h, msgb_l2len(msg));
 	msgb_free(msg);
 	bsc_schedule_timer(&bsc->reset_timeout, 20, 0);
 }
@@ -294,7 +269,7 @@ void release_bsc_resources(struct bsc_data *bsc)
 			continue;
 
 		/* wait for the clear commands */
-		mtp_link_submit_sccp_data(bsc->link.the_link, con->sls, msg->l2h, msgb_l2len(msg));
+		mtp_link_set_submit_sccp_data(bsc->link_set, con->sls, msg->l2h, msgb_l2len(msg));
 		msgb_free(msg);
 	}
 
@@ -307,42 +282,30 @@ void release_bsc_resources(struct bsc_data *bsc)
 		bsc->reset_count = 0;
 		bsc_schedule_timer(&bsc->reset_timeout, 10, 0);
 	}
-
-	/* clear pending messages from the MSC */
-	msc_clear_queue(bsc);
 }
 
-void bsc_link_down(struct link_data *data)
+void mtp_linkset_down(struct mtp_link_set *set)
 {
-	int was_up;
-	struct mtp_link *link = data->the_link;
-
-	link->available = 0;
-	was_up = link->sccp_up;
-	mtp_link_stop(link);
-	clear_connections(data->bsc);
-	mgcp_reset(data->bsc);
-
-	data->clear_queue(data);
-
-	/* clear pending messages from the MSC */
-	msc_clear_queue(data->bsc);
+	set->available = 0;
+	mtp_link_set_stop(set);
+	clear_connections(set->bsc);
+	mgcp_reset(set->bsc);
 
 	/* If we have an A link send a reset to the MSC */
-	msc_send_reset(data->bsc);
+	msc_send_reset(set->bsc);
 }
 
-void bsc_link_up(struct link_data *data)
+void mtp_linkset_up(struct mtp_link_set *set)
 {
-	data->the_link->available = 1;
+	set->available = 1;
 
 	/* we have not gone through link down */
-	if (data->bsc->msc_link_down) {
-		clear_connections(data->bsc);
-		bsc_resources_released(data->bsc);
+	if (set->bsc->msc_link_down) {
+		clear_connections(set->bsc);
+		bsc_resources_released(set->bsc);
 	}
 
-	mtp_link_reset(data->the_link);
+	mtp_link_set_reset(set);
 }
 
 /**
@@ -356,7 +319,7 @@ static void send_rlc_to_bsc(unsigned int sls, struct sccp_source_reference *src,
 	if (!msg)
 		return;
 
-	mtp_link_submit_sccp_data(bsc.link.the_link, sls, msg->l2h, msgb_l2len(msg));
+	mtp_link_set_submit_sccp_data(bsc.link_set, sls, msg->l2h, msgb_l2len(msg));
 	msgb_free(msg);
 }
 
@@ -382,7 +345,7 @@ static void handle_rlsd(struct sccp_connection_released *rlsd, int from_msc)
 				 &rlsd->source_local_reference);
 		}
 	} else {
-		unsigned int sls = 13;
+		unsigned int sls = -1;
 		con = find_con_by_src_dest_ref(&rlsd->source_local_reference,
 					       &rlsd->destination_local_reference);
 		if (con) {
@@ -417,7 +380,7 @@ static void handle_rlsd(struct sccp_connection_released *rlsd, int from_msc)
  *      1.) We are destroying the connection, we might send a RLC to
  *          the MSC if we are waiting for one.
  */
-void update_con_state(struct mtp_link *link, int rc, struct sccp_parse_result *res, struct msgb *msg, int from_msc, int sls)
+void update_con_state(struct mtp_link_set *link, int rc, struct sccp_parse_result *res, struct msgb *msg, int from_msc, int sls)
 {
 	struct active_sccp_con *con;
 	struct sccp_connection_request *cr;
@@ -537,11 +500,11 @@ static void send_local_rlsd_for_con(void *data)
 	++con->rls_tries;
 	LOGP(DINP, LOGL_DEBUG, "Sending RLSD for 0x%x the %d time.\n",
 	     sccp_src_ref_to_int(&con->src_ref), con->rls_tries);
-	mtp_link_submit_sccp_data(bsc.link.the_link, con->sls, rlsd->l2h, msgb_l2len(rlsd));
+	mtp_link_set_submit_sccp_data(bsc.link_set, con->sls, rlsd->l2h, msgb_l2len(rlsd));
 	msgb_free(rlsd);
 }
 
-static void send_local_rlsd(struct mtp_link *link, struct sccp_parse_result *res)
+static void send_local_rlsd(struct mtp_link_set *link, struct sccp_parse_result *res)
 {
 	struct active_sccp_con *con;
 
@@ -554,7 +517,7 @@ static void send_local_rlsd(struct mtp_link *link, struct sccp_parse_result *res
 	send_local_rlsd_for_con(con);
 }
 
-static void send_reset_ack(struct mtp_link *link, int sls)
+static void send_reset_ack(struct mtp_link_set *link, int sls)
 {
 	static const uint8_t reset_ack[] = {
 		0x09, 0x00, 0x03, 0x05, 0x7, 0x02, 0x42, 0xfe,
@@ -562,7 +525,7 @@ static void send_reset_ack(struct mtp_link *link, int sls)
 		0x00, 0x01, 0x31
 	};
 
-	mtp_link_submit_sccp_data(link, sls, reset_ack, sizeof(reset_ack));
+	mtp_link_set_submit_sccp_data(link, sls, reset_ack, sizeof(reset_ack));
 }
 
 static void print_usage()
@@ -584,7 +547,7 @@ static void sigint()
 	printf("Terminating.\n");
 	handled = 1;
 	if (bsc.setup)
-		bsc.link.shutdown(&bsc.link);
+		link_shutdown_all(bsc.link_set);
 	exit(0);
 
 out:
@@ -630,14 +593,14 @@ static void handle_options(int argc, char **argv)
 			print_help();
 			exit(0);
 		case 'p':
-			if (bsc.link.pcap_fd >= 0)
-				close(bsc.link.pcap_fd);
-			bsc.link.pcap_fd = open(optarg, O_WRONLY | O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR | S_IRGRP| S_IROTH);
-			if (bsc.link.pcap_fd < 0) {
+			if (bsc.pcap_fd >= 0)
+				close(bsc.pcap_fd);
+			bsc.pcap_fd = open(optarg, O_WRONLY | O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR | S_IRGRP| S_IROTH);
+			if (bsc.pcap_fd < 0) {
 				fprintf(stderr, "Failed to open PCAP file.\n");
 				exit(0);
 			}
-			mtp_pcap_write_header(bsc.link.pcap_fd);
+			mtp_pcap_write_header(bsc.pcap_fd);
 			break;
 		case 'c':
 			config = optarg;
@@ -653,19 +616,6 @@ static void handle_options(int argc, char **argv)
 	}
 }
 
-static void start_rest(void *start)
-{
-	bsc.setup = 1;
-
-	if (msc_init(&bsc, 1) != 0) {
-		fprintf(stderr, "Failed to init MSC part.\n");
-		exit(3);
-	}
-
-	bsc.link.start(&bsc.link);
-}
-
-
 int main(int argc, char **argv)
 {
 	int rc;
@@ -680,7 +630,7 @@ int main(int argc, char **argv)
 	bsc.ni_ni = MTP_NI_NATION_NET;
 	bsc.ni_spare = 0;
 
-	mtp_link_init();
+	mtp_link_set_init();
 	thread_init();
 
 	log_init(&log_info);
@@ -700,8 +650,8 @@ int main(int argc, char **argv)
 
 	bsc.setup = 0;
 	bsc.msc_address = "127.0.0.1";
-	bsc.link.pcap_fd = -1;
-	bsc.link.udp.reset_timeout = 180;
+	bsc.pcap_fd = -1;
+	bsc.udp_reset_timeout = 180;
 	bsc.ping_time = 20;
 	bsc.pong_time = 5;
 	bsc.msc_time = 20;
@@ -723,51 +673,8 @@ int main(int argc, char **argv)
 	if (rc < 0)
 		return rc;
 
-	bsc.link.the_link = mtp_link_alloc();
-	bsc.link.the_link->dpc = bsc.dpc;
-	bsc.link.the_link->opc = bsc.opc;
-	bsc.link.the_link->sccp_opc = bsc.sccp_opc > -1 ? bsc.sccp_opc : bsc.opc;
-	bsc.link.the_link->link = 0;
-	bsc.link.the_link->sltm_once = bsc.once;
-	bsc.link.the_link->ni = bsc.ni_ni;
-	bsc.link.the_link->spare = bsc.ni_spare;
-	bsc.link.bsc = &bsc;
-
-	if (bsc.udp_ip) {
-		LOGP(DINP, LOGL_NOTICE, "Using UDP MTP mode.\n");
-
-		/* setup SNMP first, it is blocking */
-		bsc.link.udp.session = snmp_mtp_session_create(bsc.udp_ip);
-		if (!bsc.link.udp.session)
-			return -1;
-
-		/* now connect to the transport */
-		if (link_udp_init(&bsc.link, bsc.src_port, bsc.udp_ip, bsc.udp_port) != 0)
-			return -1;
-
-		/* 
-		 * We will ask the MTP link to be taken down for two
-		 * timeouts of the BSC to make sure we are missing the
-		 * SLTM and it begins a reset. Then we will take it up
-		 * again and do the usual business.
-		 */
-		snmp_mtp_deactivate(bsc.link.udp.session);
-		bsc.start_timer.cb = start_rest;
-		bsc.start_timer.data = &bsc;
-		bsc_schedule_timer(&bsc.start_timer, bsc.link.udp.reset_timeout, 0);
-		LOGP(DMSC, LOGL_NOTICE, "Making sure SLTM will timeout.\n");
-	} else {
-		LOGP(DINP, LOGL_NOTICE, "Using NexusWare C7 input.\n");
-		if (link_c7_init(&bsc.link) != 0)
-			return -1;
-
-		/* give time to things to start*/
-		bsc.start_timer.cb = start_rest;
-		bsc.start_timer.data = &bsc;
-		bsc_schedule_timer(&bsc.start_timer, 30, 0);
-		LOGP(DMSC, LOGL_NOTICE, "Waiting to continue to startup.\n");
-	}
-
+	if (link_init(&bsc) != 0)
+		return -1;
 
         while (1) {
 		bsc_select_main(0);
diff --git a/src/main_udt.c b/src/main_udt.c
index f44be21..f13d4dd 100644
--- a/src/main_udt.c
+++ b/src/main_udt.c
@@ -1,7 +1,7 @@
 /* Relay UDT/all SCCP messages */
 /*
- * (C) 2010 by Holger Hans Peter Freyther <zecke@selfish.org>
- * (C) 2010 by On-Waves
+ * (C) 2010-2011 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2010-2011 by On-Waves
  * All Rights Reserved
  *
  * This program is free software: you can redistribute it and/or modify
@@ -62,59 +62,27 @@ static char *config = "udt_relay.cfg";
 struct bsc_data bsc;
 extern void cell_vty_init(void);
 
-int link_c7_init(struct link_data *data) __attribute__((__weak__));
-
-int link_c7_init(struct link_data *data)
-{
-	return -1;
-}
-
 /*
  * methods called from the MTP Level3 part
  */
-void mtp_link_submit(struct mtp_link *link, struct msgb *msg)
-{
-	bsc.link.write(&bsc.link, msg);
-}
-
-void mtp_link_restart(struct mtp_link *link)
-{
-	LOGP(DINP, LOGL_ERROR, "Need to restart the SS7 link.\n");
-	bsc.link.reset(&bsc.link);
-}
-
-void mtp_link_sccp_down(struct mtp_link *link)
-{
-	msc_clear_queue(&bsc);
-}
-
-void mtp_link_forward_sccp(struct mtp_link *link, struct msgb *_msg, int sls)
+void mtp_link_set_forward_sccp(struct mtp_link_set *link, struct msgb *_msg, int sls)
 {
 	msc_send_direct(&bsc, _msg);
 }
 
-void bsc_link_down(struct link_data *data)
+void mtp_linkset_down(struct mtp_link_set *set)
 {
-	int was_up;
-	struct mtp_link *link = data->the_link;
-
-	link->available = 0;
-	was_up = link->sccp_up;
-	mtp_link_stop(link);
-
-	data->clear_queue(data);
-
-	/* clear pending messages from the MSC */
-	msc_clear_queue(data->bsc);
+	set->available = 0;
+	mtp_link_set_stop(set);
 
 	/* If we have an A link send a reset to the MSC */
-	msc_send_reset(data->bsc);
+	msc_send_reset(set->bsc);
 }
 
-void bsc_link_up(struct link_data *data)
+void mtp_linkset_up(struct mtp_link_set *set)
 {
-	data->the_link->available = 1;
-	mtp_link_reset(data->the_link);
+	set->available = 1;
+	mtp_link_set_reset(set);
 }
 
 static void print_usage()
@@ -136,7 +104,7 @@ static void sigint()
 	printf("Terminating.\n");
 	handled = 1;
 	if (bsc.setup)
-		bsc.link.shutdown(&bsc.link);
+		link_shutdown_all(bsc.link_set);
 	exit(0);
 
 out:
@@ -182,14 +150,14 @@ static void handle_options(int argc, char **argv)
 			print_help();
 			exit(0);
 		case 'p':
-			if (bsc.link.pcap_fd >= 0)
-				close(bsc.link.pcap_fd);
-			bsc.link.pcap_fd = open(optarg, O_WRONLY | O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR | S_IRGRP| S_IROTH);
-			if (bsc.link.pcap_fd < 0) {
+			if (bsc.pcap_fd >= 0)
+				close(bsc.pcap_fd);
+			bsc.pcap_fd = open(optarg, O_WRONLY | O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR | S_IRGRP| S_IROTH);
+			if (bsc.pcap_fd < 0) {
 				fprintf(stderr, "Failed to open PCAP file.\n");
 				exit(0);
 			}
-			mtp_pcap_write_header(bsc.link.pcap_fd);
+			mtp_pcap_write_header(bsc.pcap_fd);
 			break;
 		case 'c':
 			config = optarg;
@@ -205,19 +173,6 @@ static void handle_options(int argc, char **argv)
 	}
 }
 
-static void start_rest(void *start)
-{
-	bsc.setup = 1;
-
-	if (msc_init(&bsc, 0) != 0) {
-		fprintf(stderr, "Failed to init MSC part.\n");
-		exit(3);
-	}
-
-	bsc.link.start(&bsc.link);
-}
-
-
 int main(int argc, char **argv)
 {
 	int rc;
@@ -232,7 +187,7 @@ int main(int argc, char **argv)
 	bsc.ni_ni = MTP_NI_NATION_NET;
 	bsc.ni_spare = 0;
 
-	mtp_link_init();
+	mtp_link_set_init();
 	thread_init();
 
 	log_init(&log_info);
@@ -252,8 +207,8 @@ int main(int argc, char **argv)
 
 	bsc.setup = 0;
 	bsc.msc_address = "127.0.0.1";
-	bsc.link.pcap_fd = -1;
-	bsc.link.udp.reset_timeout = 180;
+	bsc.pcap_fd = -1;
+	bsc.udp_reset_timeout = 180;
 	bsc.ping_time = 20;
 	bsc.pong_time = 5;
 	bsc.msc_time = 20;
@@ -276,51 +231,8 @@ int main(int argc, char **argv)
 	if (rc < 0)
 		return rc;
 
-	bsc.link.the_link = mtp_link_alloc();
-	bsc.link.the_link->dpc = bsc.dpc;
-	bsc.link.the_link->opc = bsc.opc;
-	bsc.link.the_link->sccp_opc = bsc.sccp_opc > -1 ? bsc.sccp_opc : bsc.opc;
-	bsc.link.the_link->link = 0;
-	bsc.link.the_link->sltm_once = bsc.once;
-	bsc.link.the_link->ni = bsc.ni_ni;
-	bsc.link.the_link->spare = bsc.ni_spare;
-	bsc.link.bsc = &bsc;
-
-	if (bsc.udp_ip) {
-		LOGP(DINP, LOGL_NOTICE, "Using UDP MTP mode.\n");
-
-		/* setup SNMP first, it is blocking */
-		bsc.link.udp.session = snmp_mtp_session_create(bsc.udp_ip);
-		if (!bsc.link.udp.session)
-			return -1;
-
-		/* now connect to the transport */
-		if (link_udp_init(&bsc.link, bsc.src_port, bsc.udp_ip, bsc.udp_port) != 0)
-			return -1;
-
-		/* 
-		 * We will ask the MTP link to be taken down for two
-		 * timeouts of the BSC to make sure we are missing the
-		 * SLTM and it begins a reset. Then we will take it up
-		 * again and do the usual business.
-		 */
-		snmp_mtp_deactivate(bsc.link.udp.session);
-		bsc.start_timer.cb = start_rest;
-		bsc.start_timer.data = &bsc;
-		bsc_schedule_timer(&bsc.start_timer, bsc.link.udp.reset_timeout, 0);
-		LOGP(DMSC, LOGL_NOTICE, "Making sure SLTM will timeout.\n");
-	} else {
-		LOGP(DINP, LOGL_NOTICE, "Using NexusWare C7 input.\n");
-		if (link_c7_init(&bsc.link) != 0)
-			return -1;
-
-		/* give time to things to start*/
-		bsc.start_timer.cb = start_rest;
-		bsc.start_timer.data = &bsc;
-		bsc_schedule_timer(&bsc.start_timer, 30, 0);
-		LOGP(DMSC, LOGL_NOTICE, "Waiting to continue to startup.\n");
-	}
-
+	if (link_init(&bsc) != 0)
+		return -1;
 
         while (1) {
 		bsc_select_main(0);
@@ -331,8 +243,6 @@ int main(int argc, char **argv)
 
 void release_bsc_resources(struct bsc_data *bsc)
 {
-	/* clear pending messages from the MSC */
-	msc_clear_queue(bsc);
 }
 
 struct msgb *create_sccp_rlc(struct sccp_source_reference *src_ref,
@@ -348,7 +258,7 @@ struct msgb *create_reset()
 	return NULL;
 }
 
-void update_con_state(struct mtp_link *link, int rc, struct sccp_parse_result *res, struct msgb *msg, int from_msc, int sls)
+void update_con_state(struct mtp_link_set *link, int rc, struct sccp_parse_result *res, struct msgb *msg, int from_msc, int sls)
 {
 	LOGP(DMSC, LOGL_ERROR, "Should not be called.\n");
 	return;
diff --git a/src/msc_conn.c b/src/msc_conn.c
index 77c4039..bc05744 100644
--- a/src/msc_conn.c
+++ b/src/msc_conn.c
@@ -46,48 +46,13 @@ static void msc_send_id_response(struct bsc_data *bsc);
 static void msc_send(struct bsc_data *bsc, struct msgb *msg, int proto);
 static void msc_schedule_reconnect(struct bsc_data *bsc);
 
-void mtp_link_slta_recv(struct mtp_link *link)
+int send_or_queue_bsc_msg(struct mtp_link_set *link, int sls, struct msgb *msg)
 {
-	struct msgb *msg;
-	unsigned int sls;
-
-	while (!llist_empty(&link->pending_msgs)) {
-		msg = msgb_dequeue(&link->pending_msgs);
-		sls = (unsigned int) msg->l3h;
-
-		if (mtp_link_submit_sccp_data(link, sls, msg->l2h, msgb_l2len(msg)) != 0)
-			LOGP(DMSC, LOGL_ERROR, "Could not forward SCCP message.\n");
-
-		msgb_free(msg);
-	}
-}
-
-int send_or_queue_bsc_msg(struct mtp_link *link, int sls, struct msgb *msg)
-{
-	if (link->sltm_pending) {
-		LOGP(DMSC, LOGL_NOTICE, "Queueing msg for pending SLTM.\n");
-		msg->l3h = (uint8_t *) sls;
-		msgb_enqueue(&link->pending_msgs, msg);
-		return 1;
-	}
-
-	if (mtp_link_submit_sccp_data(link, sls, msg->l2h, msgb_l2len(msg)) != 0)
+	if (mtp_link_set_submit_sccp_data(link, sls, msg->l2h, msgb_l2len(msg)) != 0)
 		LOGP(DMSC, LOGL_ERROR, "Could not forward SCCP message.\n");
 	return 0;
 }
 
-
-void msc_clear_queue(struct bsc_data *data)
-{
-	struct msgb *msg;
-
-	LOGP(DMSC, LOGL_NOTICE, "Clearing the MSC to BSC queue.\n");
-	while (!llist_empty(&data->link.the_link->pending_msgs)) {
-		msg = msgb_dequeue(&data->link.the_link->pending_msgs);
-		msgb_free(msg);
-	}
-}
-
 void msc_close_connection(struct bsc_data *bsc)
 {
 	struct bsc_fd *bfd = &bsc->msc_connection.bfd;
@@ -157,7 +122,7 @@ static int ipaccess_a_fd_cb(struct bsc_fd *bfd)
 {
 	int error;
 	struct ipaccess_head *hh;
-	struct mtp_link *link;
+	struct mtp_link_set *link;
 	struct bsc_data *bsc;
 	struct msgb *msg;
 
@@ -181,7 +146,7 @@ static int ipaccess_a_fd_cb(struct bsc_fd *bfd)
 	hh = (struct ipaccess_head *) msg->data;
 	ipaccess_rcvmsg_base(msg, bfd);
 
-	link = bsc->link.the_link;
+	link = bsc->link_set;
 
 	/* initialize the networking. This includes sending a GSM08.08 message */
 	if (hh->proto == IPAC_PROTO_IPACCESS) {
@@ -203,7 +168,7 @@ static int ipaccess_a_fd_cb(struct bsc_fd *bfd)
 
 		/* we can not forward it right now */
 		if (bsc->forward_only && link->sccp_up) {
-			if (send_or_queue_bsc_msg(link, 13, msg) != 1)
+			if (send_or_queue_bsc_msg(link, -1, msg) != 1)
 				msgb_free(msg);
 			return 0;
 		}
diff --git a/src/mtp_layer3.c b/src/mtp_layer3.c
index 93a588c..531e121 100644
--- a/src/mtp_layer3.c
+++ b/src/mtp_layer3.c
@@ -20,6 +20,7 @@
  */
 #include <mtp_data.h>
 #include <mtp_level3.h>
+#include <bsc_data.h>
 #include <cellmgr_debug.h>
 #include <isup_types.h>
 
@@ -33,9 +34,9 @@
 
 static void *tall_mtp_ctx = NULL;
 
-static int mtp_int_submit(struct mtp_link *link, int pc, int sls, int type, const uint8_t *data, unsigned int length);
+static int mtp_int_submit(struct mtp_link_set *link, int pc, int sls, int type, const uint8_t *data, unsigned int length);
 
-static struct msgb *mtp_msg_alloc(struct mtp_link *link)
+static struct msgb *mtp_msg_alloc(struct mtp_link_set *link)
 {
 	struct mtp_level_3_hdr *hdr;
 	struct msgb *msg = msgb_alloc_headroom(4096, 128, "mtp-msg");
@@ -52,7 +53,7 @@ static struct msgb *mtp_msg_alloc(struct mtp_link *link)
 	return msg;
 }
 
-static struct msgb *mtp_create_sltm(struct mtp_link *link)
+static struct msgb *mtp_create_sltm(struct mtp_link_set *link)
 {
 	const uint8_t test_ptrn[14] = { 'G', 'S', 'M', 'M', 'M', 'S', };
 	struct mtp_level_3_hdr *hdr;
@@ -79,7 +80,7 @@ static struct msgb *mtp_create_sltm(struct mtp_link *link)
 	return msg;
 }
 
-static struct msgb *mtp_create_slta(struct mtp_link *link, struct mtp_level_3_mng *in_mng, int l3_len)
+static struct msgb *mtp_create_slta(struct mtp_link_set *link, struct mtp_level_3_mng *in_mng, int l3_len)
 {
 	struct mtp_level_3_hdr *hdr;
 	struct mtp_level_3_mng *mng;
@@ -100,7 +101,7 @@ static struct msgb *mtp_create_slta(struct mtp_link *link, struct mtp_level_3_mn
 	return out;
 }
 
-static struct msgb *mtp_tfp_alloc(struct mtp_link *link, int apoc)
+static struct msgb *mtp_tfp_alloc(struct mtp_link_set *link, int apoc)
 {
 	struct mtp_level_3_hdr *hdr;
 	struct mtp_level_3_prohib *prb;
@@ -118,7 +119,7 @@ static struct msgb *mtp_tfp_alloc(struct mtp_link *link, int apoc)
 	return out;
 }
 
-static struct msgb *mtp_tra_alloc(struct mtp_link *link)
+static struct msgb *mtp_tra_alloc(struct mtp_link_set *link)
 {
 	struct mtp_level_3_hdr *hdr;
 	struct mtp_level_3_cmn *cmn;
@@ -135,7 +136,7 @@ static struct msgb *mtp_tra_alloc(struct mtp_link *link)
 	return out;
 }
 
-static struct msgb *mtp_sccp_alloc_scmg(struct mtp_link *link,
+static struct msgb *mtp_sccp_alloc_scmg(struct mtp_link_set *link,
 					int type, int assn, int sls)
 {
 	struct sccp_data_unitdata *udt;
@@ -186,12 +187,12 @@ static struct msgb *mtp_sccp_alloc_scmg(struct mtp_link *link,
 	return out;
 }
 
-void mtp_link_init(void)
+void mtp_link_set_init(void)
 {
 	tall_mtp_ctx = talloc_named_const(NULL, 1, "mtp-link");
 }
 
-static void mtp_send_sltm(struct mtp_link *link)
+static void mtp_send_sltm(struct mtp_link_set *link)
 {
 	struct msgb *msg;
 
@@ -202,12 +203,12 @@ static void mtp_send_sltm(struct mtp_link *link)
 		return;
 	}
 
-	mtp_link_submit(link, msg);
+	mtp_link_set_submit(link->slc[0], msg);
 }
 
 static void mtp_sltm_t1_timeout(void *_link)
 {
-	struct mtp_link *link = (struct mtp_link *) _link;
+	struct mtp_link_set *link = (struct mtp_link_set *) _link;
 
 	if (link->slta_misses == 0) {
 		LOGP(DINP, LOGL_ERROR, "No SLTM response. Retrying. Link: %p\n", link);
@@ -219,14 +220,14 @@ static void mtp_sltm_t1_timeout(void *_link)
 		link->sccp_up = 0;
 		link->running = 0;
 		bsc_del_timer(&link->t2_timer);
-		mtp_link_sccp_down(link);
-		mtp_link_restart(link);
+		mtp_link_set_sccp_down(link);
+		mtp_link_restart(link->slc[0]);
 	}
 }
 
 static void mtp_sltm_t2_timeout(void *_link)
 {
-	struct mtp_link *link = (struct mtp_link *) _link;
+	struct mtp_link_set *link = (struct mtp_link_set *) _link;
 
 	if (!link->running) {
 		LOGP(DINP, LOGL_INFO, "Not restarting SLTM timer on link: %p\n", link);
@@ -249,11 +250,11 @@ static void mtp_delayed_start(void *link)
 	mtp_sltm_t2_timeout(link);
 }
 
-struct mtp_link *mtp_link_alloc(void)
+struct mtp_link_set *mtp_link_set_alloc(void)
 {
-	struct mtp_link *link;
+	struct mtp_link_set *link;
 
-	link = talloc_zero(tall_mtp_ctx, struct mtp_link);
+	link = talloc_zero(tall_mtp_ctx, struct mtp_link_set);
 	if (!link)
 		return NULL;
 
@@ -264,11 +265,12 @@ struct mtp_link *mtp_link_alloc(void)
 	link->t2_timer.cb = mtp_sltm_t2_timeout;
 	link->delay_timer.data = link;
 	link->delay_timer.cb = mtp_delayed_start;
-	INIT_LLIST_HEAD(&link->pending_msgs);
+	INIT_LLIST_HEAD(&link->links);
+
 	return link;
 }
 
-void mtp_link_stop(struct mtp_link *link)
+void mtp_link_set_stop(struct mtp_link_set *link)
 {
 	bsc_del_timer(&link->t1_timer);
 	bsc_del_timer(&link->t2_timer);
@@ -277,17 +279,17 @@ void mtp_link_stop(struct mtp_link *link)
 	link->running = 0;
 	link->sltm_pending = 0;
 
-	mtp_link_sccp_down(link);
+	mtp_link_set_sccp_down(link);
 }
 
-void mtp_link_reset(struct mtp_link *link)
+void mtp_link_set_reset(struct mtp_link_set *link)
 {
-	mtp_link_stop(link);
+	mtp_link_set_stop(link);
 	link->running = 1;
 	bsc_schedule_timer(&link->delay_timer, START_DELAY);
 }
 
-static int mtp_link_sign_msg(struct mtp_link *link, struct mtp_level_3_hdr *hdr, int l3_len)
+static int mtp_link_sign_msg(struct mtp_link_set *link, struct mtp_level_3_hdr *hdr, int l3_len)
 {
 	struct msgb *msg;
 	struct mtp_level_3_cmn *cmn;
@@ -309,18 +311,18 @@ static int mtp_link_sign_msg(struct mtp_link *link, struct mtp_level_3_hdr *hdr,
 		case MTP_RESTR_MSG_ALLWED:
 			LOGP(DINP, LOGL_INFO, "Received Restart Allowed. SST could be next: %p\n", link);
 			link->sccp_up = 0;
-			mtp_link_sccp_down(link);
+			mtp_link_set_sccp_down(link);
 
 			msg = mtp_tfp_alloc(link, 0);
 			if (!msg)
 				return -1;
-			mtp_link_submit(link, msg);
+			mtp_link_set_submit(link->slc[0], msg);
 
 			msg = mtp_tra_alloc(link);
 			if (!msg)
 				return -1;
 
-			mtp_link_submit(link, msg);
+			mtp_link_set_submit(link->slc[0], msg);
 			link->sccp_up = 1;
 			link->was_up = 1;
 			LOGP(DINP, LOGL_INFO, "SCCP traffic allowed. %p\n", link);
@@ -349,7 +351,7 @@ static int mtp_link_sign_msg(struct mtp_link *link, struct mtp_level_3_hdr *hdr,
 	return -1;
 }
 
-static int mtp_link_regular_msg(struct mtp_link *link, struct mtp_level_3_hdr *hdr, int l3_len)
+static int mtp_link_regular_msg(struct mtp_link_set *link, struct mtp_level_3_hdr *hdr, int l3_len)
 {
 	struct msgb *out;
 	struct mtp_level_3_mng *mng;
@@ -372,7 +374,7 @@ static int mtp_link_regular_msg(struct mtp_link *link, struct mtp_level_3_hdr *h
 			out = mtp_create_slta(link, mng, l3_len);
 			if (!out)
 				return -1;
-			mtp_link_submit(link, out);
+			mtp_link_set_submit(link->slc[0], out);
 			return 0;
 			break;
 		case MTP_TST_MSG_SLTA:
@@ -394,7 +396,6 @@ static int mtp_link_regular_msg(struct mtp_link *link, struct mtp_level_3_hdr *h
 			/* we had a matching slta */
 			bsc_del_timer(&link->t1_timer);
 			link->sltm_pending = 0;
-			mtp_link_slta_recv(link);
 			return 0;
 			break;
 		}
@@ -404,7 +405,7 @@ static int mtp_link_regular_msg(struct mtp_link *link, struct mtp_level_3_hdr *h
 	return -1;
 }
 
-static int mtp_link_sccp_data(struct mtp_link *link, struct mtp_level_3_hdr *hdr, struct msgb *msg, int l3_len)
+static int mtp_link_sccp_data(struct mtp_link_set *link, struct mtp_level_3_hdr *hdr, struct msgb *msg, int l3_len)
 {
 	struct msgb *out;
 	struct sccp_con_ctrl_prt_mgt *prt;
@@ -457,15 +458,15 @@ static int mtp_link_sccp_data(struct mtp_link *link, struct mtp_level_3_hdr *hdr
 		if (!out)
 			return -1;
 
-		mtp_link_submit(link, out);
+		mtp_link_set_submit(link->slc[MTP_LINK_SLS(hdr->addr)], out);
 		return 0;
 	}
 
-	mtp_link_forward_sccp(link, msg, MTP_LINK_SLS(hdr->addr));
+	mtp_link_set_forward_sccp(link, msg, MTP_LINK_SLS(hdr->addr));
 	return 0;
 }
 
-int mtp_link_data(struct mtp_link *link, struct msgb *msg)
+int mtp_link_set_data(struct mtp_link_set *link, struct msgb *msg)
 {
 	int rc = -1;
 	struct mtp_level_3_hdr *hdr;
@@ -494,7 +495,7 @@ int mtp_link_data(struct mtp_link *link, struct msgb *msg)
 		break;
 	case MTP_SI_MNT_ISUP:
 		msg->l3h = &hdr->data[0];
-		rc = mtp_link_forward_isup(link, msg, MTP_LINK_SLS(hdr->addr));
+		rc = mtp_link_set_forward_isup(link, msg, MTP_LINK_SLS(hdr->addr));
 		break;
 	default:
 		fprintf(stderr, "Unhandled: %u\n", hdr->ser_ind);
@@ -504,7 +505,7 @@ int mtp_link_data(struct mtp_link *link, struct msgb *msg)
 	return rc;
 }
 
-int mtp_link_submit_sccp_data(struct mtp_link *link, int sls, const uint8_t *data, unsigned int length)
+int mtp_link_set_submit_sccp_data(struct mtp_link_set *link, int sls, const uint8_t *data, unsigned int length)
 {
 
 	if (!link->sccp_up) {
@@ -512,16 +513,21 @@ int mtp_link_submit_sccp_data(struct mtp_link *link, int sls, const uint8_t *dat
 		return -1;
 	}
 
+	if (sls == -1) {
+		sls = link->last_sls;
+		link->last_sls = (link->last_sls + 1) % 16;
+	}
+
 	return mtp_int_submit(link, link->sccp_opc, sls, MTP_SI_MNT_SCCP, data, length);
 }
 
-int mtp_link_submit_isup_data(struct mtp_link *link, int sls,
+int mtp_link_set_submit_isup_data(struct mtp_link_set *link, int sls,
 			      const uint8_t *data, unsigned int length)
 {
 	return mtp_int_submit(link, link->opc, sls, MTP_SI_MNT_ISUP, data, length);
 }
 
-static int mtp_int_submit(struct mtp_link *link, int pc, int sls, int type,
+static int mtp_int_submit(struct mtp_link_set *link, int pc, int sls, int type,
 			  const uint8_t *data, unsigned int length)
 {
 	uint8_t *put_ptr;
@@ -541,6 +547,52 @@ static int mtp_int_submit(struct mtp_link *link, int pc, int sls, int type,
 	put_ptr = msgb_put(msg, length);
 	memcpy(put_ptr, data, length);
 
-	mtp_link_submit(link, msg);
+	mtp_link_set_submit(link->slc[sls % 16], msg);
 	return 0;
 }
+
+static struct link_data *find_next_link(struct mtp_link_set *set,
+					struct link_data *data)
+{
+	int found = 0;
+	struct link_data *next;
+
+	if (llist_empty(&set->links))
+		return NULL;
+
+	if (data == NULL)
+		found = 1;
+
+	/* try to find the next one */
+	llist_for_each_entry(next, &set->links, entry) {
+		if (found && next->available)
+			return next;
+		if (next == data)
+			found = 1;
+	}
+
+	/* try to find any one */
+	llist_for_each_entry(next, &set->links, entry)
+		if (next->available)
+			return next;
+
+	return NULL;
+}
+
+void mtp_link_set_init_slc(struct mtp_link_set *set)
+{
+	struct link_data *link = NULL;
+	int i;
+
+
+	for (i = 0; i < ARRAY_SIZE(set->slc); ++i) {
+		link = find_next_link(set, link);
+		set->slc[i] = link;
+	}
+}
+
+void mtp_link_set_add_link(struct mtp_link_set *set, struct link_data *lnk)
+{
+	llist_add_tail(&lnk->entry, &set->links);
+	mtp_link_set_init_slc(set);
+}
diff --git a/src/snmp_mtp.c b/src/snmp_mtp.c
index 6d85f31..ba3a219 100644
--- a/src/snmp_mtp.c
+++ b/src/snmp_mtp.c
@@ -100,12 +100,12 @@ struct snmp_mtp_session *snmp_mtp_session_create(char *host)
 	return session;
 }
 
-void snmp_mtp_deactivate(struct snmp_mtp_session *session)
+void snmp_mtp_deactivate(struct snmp_mtp_session *session, int index)
 {
-	snmp_mtp_stop_c7_datalink(session, 1);
+	snmp_mtp_stop_c7_datalink(session, index);
 }
 
-void snmp_mtp_activate(struct snmp_mtp_session *session)
+void snmp_mtp_activate(struct snmp_mtp_session *session, int index)
 {
-	snmp_mtp_start_c7_datalink(session, 1);
+	snmp_mtp_start_c7_datalink(session, index);
 }
diff --git a/src/vty_interface.c b/src/vty_interface.c
index 6ddf549..0cf5929 100644
--- a/src/vty_interface.c
+++ b/src/vty_interface.c
@@ -72,7 +72,7 @@ static int config_write_cell(struct vty *vty)
 		vty_out(vty, " udp dest ip %s%s", bsc.udp_ip, VTY_NEWLINE);
 	vty_out(vty, " udp dest port %d%s", bsc.udp_port, VTY_NEWLINE);
 	vty_out(vty, " udp src port %d%s", bsc.src_port, VTY_NEWLINE);
-	vty_out(vty, " udp reset %d%s", bsc.link.udp.reset_timeout, VTY_NEWLINE);
+	vty_out(vty, " udp reset %d%s", bsc.udp_reset_timeout, VTY_NEWLINE);
 	vty_out(vty, " msc ip %s%s", bsc.msc_address, VTY_NEWLINE);
 	vty_out(vty, " msc ip-dscp %d%s", bsc.msc_ip_dscp, VTY_NEWLINE);
 	vty_out(vty, " msc token %s%s", bsc.token, VTY_NEWLINE);
@@ -166,7 +166,7 @@ DEFUN(cfg_udp_reset, cfg_udp_reset_cmd,
       "udp reset TIMEOUT",
       "Set the timeout to take the link down")
 {
-	bsc.link.udp.reset_timeout = atoi(argv[0]);
+	bsc.udp_reset_timeout = atoi(argv[0]);
 	return CMD_SUCCESS;
 }
 
diff --git a/tests/isup/isup_parse_test.c b/tests/isup/isup_parse_test.c
index 5b19ed0..5c3341c 100644
--- a/tests/isup/isup_parse_test.c
+++ b/tests/isup/isup_parse_test.c
@@ -62,4 +62,4 @@ int main(int argc, char **argv)
 }
 
 /* stubs */
-int mtp_link_submit_isup_data() {return -1;}
+int mtp_link_set_submit_isup_data() {return -1;}