sccp_scoc: separate conn_id from local_refosmith/conn-id-scoping

Properly generate a local_ref for each connection, that is unique for
each SCU user. Previously, the conn_id was used as local_ref.

Related: OS#3871
Change-Id: Ifd55c6b7ed2558ff072042079cf45f5068a971de

2 files changed, 64 insertions, 16 deletions

diff --git a/src/sccp_internal.h b/src/sccp_internal.h
index ad8a6fd..10ec285 100644
--- a/src/sccp_internal.h
+++ b/src/sccp_internal.h
@@ -78,6 +78,9 @@ struct osmo_sccp_user {
 
 	/* Application Server FSM Instance */
 	struct osmo_fsm_inst *as_fi;
+
+	/* next local reference to allocate */
+	uint32_t next_local_ref;
 };
 
 extern int DSCCP;
diff --git a/src/sccp_scoc.c b/src/sccp_scoc.c
index 91a1ab7..2f5be28 100644
--- a/src/sccp_scoc.c
+++ b/src/sccp_scoc.c
@@ -47,6 +47,7 @@
  */
 
 #include <string.h>
+#include <errno.h>
 
 #include <osmocom/core/utils.h>
 #include <osmocom/core/linuxlist.h>
@@ -93,6 +94,11 @@ struct sccp_connection {
 	 * it whever sending data to the peer. Only relevant over the
 	 * wire, not to be used across the SCCP user SAP */
 	uint32_t remote_ref;
+	/* SCCP Local Connection Reference. Generated by the local SCCP stack
+	 * (conn_get_unused_local_ref()) to uniquely identify a SCCP connection.
+	 * The local_ref is unique for each (SCCP connection, SCU user) tuple. Only
+	 * relevant over the wire, not to be used accross the SCCP user SAP. */
+	uint32_t local_ref;
 
 	uint32_t importance;
 	uint32_t sccp_class;
@@ -456,15 +462,49 @@ static struct sccp_connection *conn_find_by_id(struct osmo_sccp_instance *inst,
 	return NULL;
 }
 
+static struct sccp_connection *conn_find_by_local_ref(struct osmo_sccp_user *user, uint32_t local_ref)
+{
+	struct sccp_connection *conn;
+
+	llist_for_each_entry(conn, &user->inst->connections, list) {
+		if (conn->user == user && conn->local_ref == local_ref)
+			return conn;
+	}
+	return NULL;
+}
+
+static int conn_unused_local_ref(struct osmo_sccp_user *user, uint32_t *local_ref)
+{
+	uint32_t current;
+	uint32_t start = user->next_local_ref;
+
+	do {
+		current = user->next_local_ref++;
+		if (current == start) {
+			LOGP(DLSCCP, LOGL_ERROR, "No unused local reference available for user %s\n", user->name);
+			return -ENOSPC;
+		}
+	} while (conn_find_by_local_ref(user, current));
+
+	*local_ref = current;
+	return 0;
+}
+
 #define INIT_TIMER(x, fn, priv)		do { (x)->cb = fn; (x)->data = priv; } while (0)
 
 /* allocate + init a SCCP Connection with given ID */
 static struct sccp_connection *conn_create_id(struct osmo_sccp_user *user, uint32_t conn_id)
 {
-	struct sccp_connection *conn = talloc_zero(user->inst, struct sccp_connection);
+	uint32_t local_ref;
+	struct sccp_connection *conn;
 	char name[16];
 
+	if (conn_unused_local_ref(user, &local_ref) < 0)
+		return NULL;
+
+	conn = talloc_zero(user->inst, struct sccp_connection);
 	conn->conn_id = conn_id;
+	conn->local_ref = local_ref;
 	conn->inst = user->inst;
 	conn->user = user;
 
@@ -538,7 +578,7 @@ static struct xua_msg *xua_gen_relre(struct sccp_connection *conn,
 	xua->hdr = XUA_HDR(SUA_MSGC_CO, SUA_CO_RELRE);
 	xua_msg_add_u32(xua, SUA_IEI_ROUTE_CTX, conn->inst->route_ctx);
 	xua_msg_add_u32(xua, SUA_IEI_DEST_REF, conn->remote_ref);
-	xua_msg_add_u32(xua, SUA_IEI_SRC_REF, conn->conn_id);
+	xua_msg_add_u32(xua, SUA_IEI_SRC_REF, conn->local_ref);
 	xua_msg_add_u32(xua, SUA_IEI_CAUSE, SUA_CAUSE_T_RELEASE | cause);
 	/* optional: importance */
 	if (prim && msgb_l2(prim->oph.msg))
@@ -581,7 +621,7 @@ static struct xua_msg *xua_gen_msg_co(struct sccp_connection *conn, uint32_t eve
 		xua->hdr = XUA_HDR(SUA_MSGC_CO, SUA_CO_CORE);
 		xua_msg_add_u32(xua, SUA_IEI_ROUTE_CTX, conn->inst->route_ctx);
 		xua_msg_add_u32(xua, SUA_IEI_PROTO_CLASS, conn->sccp_class);
-		xua_msg_add_u32(xua, SUA_IEI_SRC_REF, conn->conn_id);
+		xua_msg_add_u32(xua, SUA_IEI_SRC_REF, conn->local_ref);
 		xua_msg_add_sccp_addr(xua, SUA_IEI_DEST_ADDR, &conn->called_addr);
 		xua_msg_add_u32(xua, SUA_IEI_SEQ_CTRL, 0); /* TODO */
 		/* optional: sequence number (class 3 only) */
@@ -597,7 +637,7 @@ static struct xua_msg *xua_gen_msg_co(struct sccp_connection *conn, uint32_t eve
 		xua_msg_add_u32(xua, SUA_IEI_ROUTE_CTX, conn->inst->route_ctx);
 		xua_msg_add_u32(xua, SUA_IEI_PROTO_CLASS, conn->sccp_class);
 		xua_msg_add_u32(xua, SUA_IEI_DEST_REF, conn->remote_ref);
-		xua_msg_add_u32(xua, SUA_IEI_SRC_REF, conn->conn_id);
+		xua_msg_add_u32(xua, SUA_IEI_SRC_REF, conn->local_ref);
 		xua_msg_add_u32(xua, SUA_IEI_SEQ_CTRL, 0); /* TODO */
 		/* optional: sequence number (class 3 only) */
 		if (conn->called_addr.presence)
@@ -618,7 +658,7 @@ static struct xua_msg *xua_gen_msg_co(struct sccp_connection *conn, uint32_t eve
 		xua->hdr = XUA_HDR(SUA_MSGC_CO, SUA_CO_RELRE);
 		xua_msg_add_u32(xua, SUA_IEI_ROUTE_CTX, conn->inst->route_ctx);
 		xua_msg_add_u32(xua, SUA_IEI_DEST_REF, conn->remote_ref);
-		xua_msg_add_u32(xua, SUA_IEI_SRC_REF, conn->conn_id);
+		xua_msg_add_u32(xua, SUA_IEI_SRC_REF, conn->local_ref);
 		xua_msg_add_u32(xua, SUA_IEI_CAUSE, SUA_CAUSE_T_RELEASE | prim->u.disconnect.cause);
 		/* optional: importance */
 		if (prim && msgb_l2(prim->oph.msg) && msgb_l2len(prim->oph.msg))
@@ -629,7 +669,7 @@ static struct xua_msg *xua_gen_msg_co(struct sccp_connection *conn, uint32_t eve
 		xua->hdr = XUA_HDR(SUA_MSGC_CO, SUA_CO_RELCO);
 		xua_msg_add_u32(xua, SUA_IEI_ROUTE_CTX, conn->inst->route_ctx);
 		xua_msg_add_u32(xua, SUA_IEI_DEST_REF, conn->remote_ref);
-		xua_msg_add_u32(xua, SUA_IEI_SRC_REF, conn->conn_id);
+		xua_msg_add_u32(xua, SUA_IEI_SRC_REF, conn->local_ref);
 		/* optional: importance */
 		break;
 	case SUA_CO_CODT: /* Connection Oriented Data Transfer == SCCP DT1 */
@@ -647,7 +687,7 @@ static struct xua_msg *xua_gen_msg_co(struct sccp_connection *conn, uint32_t eve
 		xua->hdr = XUA_HDR(SUA_MSGC_CO, SUA_CO_COIT);
 		xua_msg_add_u32(xua, SUA_IEI_ROUTE_CTX, conn->inst->route_ctx);
 		xua_msg_add_u32(xua, SUA_IEI_PROTO_CLASS, conn->sccp_class);
-		xua_msg_add_u32(xua, SUA_IEI_SRC_REF, conn->conn_id);
+		xua_msg_add_u32(xua, SUA_IEI_SRC_REF, conn->local_ref);
 		xua_msg_add_u32(xua, SUA_IEI_DEST_REF, conn->remote_ref);
 		/* optional: sequence number; credit (both class 3 only) */
 		break;
@@ -1354,6 +1394,16 @@ static struct osmo_sccp_user *sccp_find_user(struct osmo_sccp_instance *inst,
 	return sccp_user_find(inst, called_addr.ssn, called_addr.pc);
 }
 
+static struct sccp_connection *sccp_find_connection(struct osmo_sccp_instance *inst, struct xua_msg *xua)
+{
+	uint32_t local_ref = xua_msg_get_u32(xua, SUA_IEI_DEST_REF);
+	struct osmo_sccp_user *user = sccp_find_user(inst, xua);
+
+	if (user)
+		return conn_find_by_local_ref(user, local_ref);
+	return NULL;
+}
+
 /*! \brief SCOC: Receive SCRC Routing Failure
  *  \param[in] inst SCCP Instance on which we operate
  *  \param[in] xua SUA message that was failed to route
@@ -1361,12 +1411,9 @@ static struct osmo_sccp_user *sccp_find_user(struct osmo_sccp_instance *inst,
 void sccp_scoc_rx_scrc_rout_fail(struct osmo_sccp_instance *inst,
 				struct xua_msg *xua, uint32_t return_cause)
 {
-	uint32_t conn_id;
-	struct sccp_connection *conn;
+	struct sccp_connection *conn = sccp_find_connection(inst, xua);
 
 	/* try to dispatch to connection FSM (if any) */
-	conn_id = xua_msg_get_u32(xua, SUA_IEI_DEST_REF);
-	conn = conn_find_by_id(inst, conn_id);
 	if (conn) {
 		osmo_fsm_inst_dispatch(conn->fi,
 					SCOC_E_RCOC_ROUT_FAIL_IND, xua);
@@ -1626,13 +1673,11 @@ void sccp_scoc_rx_from_scrc(struct osmo_sccp_instance *inst,
 		conn = conn_create(scu);
 		conn->incoming = true;
 	} else {
-		uint32_t conn_id;
 		/* Resolve existing connection */
-		conn_id = xua_msg_get_u32(xua, SUA_IEI_DEST_REF);
-		conn = conn_find_by_id(inst, conn_id);
+		conn = sccp_find_connection(inst, xua);
 		if (!conn) {
 			LOGP(DLSCCP, LOGL_NOTICE, "Cannot find connection for "
-			     "local reference %u\n", conn_id);
+			     "local reference %u\n", xua_msg_get_u32(xua, SUA_IEI_DEST_REF));
 			sccp_scoc_rx_unass_local_ref(inst, xua);
 			return;
 		}
@@ -1641,7 +1686,7 @@ void sccp_scoc_rx_from_scrc(struct osmo_sccp_instance *inst,
 	OSMO_ASSERT(conn->fi);
 
 	DEBUGP(DLSCCP, "Received %s for local reference %u\n",
-		xua_hdr_dump(xua, &xua_dialect_sua), conn->conn_id);
+		xua_hdr_dump(xua, &xua_dialect_sua), conn->local_ref);
 
 	if (xua->hdr.msg_type != SUA_CO_CORE &&
 	    xua->hdr.msg_type != SUA_CO_COAK &&