Major update; Code now supports SAI, LU and ISD transactions

We also introduce a 'gsup_router' which enables us to route
a transaction to a given VLR.  It works based on the SERIAL attribute
communicated at time of the IPA multiplex setup as part of the CCM
sub-protocol.
diff --git a/src/gsup_router.c b/src/gsup_router.c
new file mode 100644
index 0000000..e9aed78
--- /dev/null
+++ b/src/gsup_router.c
@@ -0,0 +1,85 @@
+/* (C) 2016 by Harald Welte <laforge@gnumonks.org>
+ *
+ * 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 <errno.h>
+
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/talloc.h>
+
+#include "gsup_server.h"
+
+struct gsup_route {
+	struct llist_head list;
+
+	uint8_t *addr;
+	struct osmo_gsup_conn *conn;
+};
+
+/* find a route for the given address */
+struct osmo_gsup_conn *gsup_route_find(struct osmo_gsup_server *gs,
+					const uint8_t *addr, size_t addrlen)
+{
+	struct gsup_route *gr;
+
+	llist_for_each_entry(gr, &gs->routes, list) {
+		if (talloc_total_size(gr->addr) == addrlen &&
+		    !memcmp(gr->addr, addr, addrlen))
+			return gr->conn;
+	}
+	return NULL;
+}
+
+/* add a new route for the given address to the given conn */
+int gsup_route_add(struct osmo_gsup_conn *conn, const uint8_t *addr, size_t addrlen)
+{
+	struct gsup_route *gr;
+
+	/* Check if we already have a route for this address */
+	if (gsup_route_find(conn->server, addr, addrlen))
+		return -EEXIST;
+
+	/* allocate new route and populate it */
+	gr = talloc_zero(conn->server, struct gsup_route);
+	if (!gr)
+		return -ENOMEM;
+
+	gr->addr = talloc_memdup(gr, addr, addrlen);
+	gr->conn = conn;
+	llist_add_tail(&gr->list, &conn->server->routes);
+
+	return 0;
+}
+
+/* delete all routes for the given connection */
+int gsup_route_del_conn(struct osmo_gsup_conn *conn)
+{
+	struct gsup_route *gr, *gr2;
+	unsigned int num_deleted = 0;
+
+	llist_for_each_entry_safe(gr, gr2, &conn->server->routes, list) {
+		if (gr->conn == conn) {
+			llist_del(&gr->list);
+			talloc_free(gr);
+			num_deleted++;
+		}
+	}
+
+	return num_deleted;
+}