Clarify type and values of sccp.conn_id

Currently, the conn_id is allocated in a range 0..0xffffff by
bsc_sccp_inst_next_conn_id(), and -1 means it is unset.

This means allocation expects "int" to be at least 32 bits integer,
in order to fit 24 bits for 0..0xffffff plus the -1.
Hence, let's define the variable as uint32_t, as already done in
libosmo-sccp. Use last value 0xFFFFFFFF ((uint32_t)-1) and avoid playing
with the value being unsigned sometimes and signed only for "unset"
value.

The value is actually already handled as unsigned (printed with %u) in
most places.

Change-Id: If019bcbc1e28929fe8d981fef9103835fc6ead2e

5 files changed, 30 insertions, 21 deletions

diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h
index 533be93ca..268aa0cc8 100644
--- a/include/osmocom/bsc/gsm_data.h
+++ b/include/osmocom/bsc/gsm_data.h
@@ -51,6 +51,9 @@
  * with delta = time between expiration of T3124 and receiving HANDOVER FAILURE by the serving BSC. */
 #define GSM_NY1_DEFAULT ((unsigned long)((GSM_T3124_MAX + GSM_NY1_REQ_DELTA)/GSM_T3105_DEFAULT + 1))
 
+#define SCCP_CONN_ID_UNSET	0xFFFFFFFF
+#define SCCP_CONN_ID_MAX	0x00FFFFFF
+
 struct mgcp_client_conf;
 struct mgcp_client;
 struct gsm0808_cell_id;
@@ -328,8 +331,10 @@ struct gsm_subscriber_connection {
 		/* SCCP connection related */
 		struct bsc_msc_data *msc;
 
-		/* Sigtran connection ID */
-		int conn_id;
+		/* Sigtran connection ID:
+		*  if set: Range (0..SCCP_CONN_ID_MAX) (24 bit)
+		*  if unset: SCCP_CONN_ID_UNSET (-1) if unset */
+		uint32_t conn_id;
 		enum subscr_sccp_state state;
 	} sccp;
 
@@ -379,7 +384,10 @@ struct gsm_subscriber_connection {
 
 		/* Lb interface to the SMLC: BSSMAP-LE/SCCP connection associated with this subscriber */
 		struct {
-			int conn_id;
+			/* Sigtran connection ID:
+			*  if set: Range (0..SCCP_CONN_ID_MAX) (24 bit)
+			*  if unset: SCCP_CONN_ID_UNSET (-1) if unset */
+			uint32_t conn_id;
 			enum subscr_sccp_state state;
 		} lb;
 	} lcs;
@@ -1022,7 +1030,7 @@ enum gsm_phys_chan_config gsm_pchan_by_lchan_type(enum gsm_chan_t type);
 enum gsm48_rr_cause bsc_gsm48_rr_cause_from_gsm0808_cause(enum gsm0808_cause c);
 enum gsm48_rr_cause bsc_gsm48_rr_cause_from_rsl_cause(uint8_t c);
 
-int bsc_sccp_inst_next_conn_id(struct osmo_sccp_instance *sccp);
+uint32_t bsc_sccp_inst_next_conn_id(struct osmo_sccp_instance *sccp);
 
 /* Interference Measurement Parameters */
 struct gsm_interf_meas_params {
diff --git a/src/osmo-bsc/bsc_sccp.c b/src/osmo-bsc/bsc_sccp.c
index 0cd1dc9f3..30d4c4c94 100644
--- a/src/osmo-bsc/bsc_sccp.c
+++ b/src/osmo-bsc/bsc_sccp.c
@@ -26,7 +26,7 @@
 #include <osmocom/bsc/lb.h>
 
 /* We need an unused SCCP conn_id across all SCCP users. */
-int bsc_sccp_inst_next_conn_id(struct osmo_sccp_instance *sccp)
+uint32_t bsc_sccp_inst_next_conn_id(struct osmo_sccp_instance *sccp)
 {
 	static uint32_t next_id = 1;
 	int i;
@@ -34,11 +34,13 @@ int bsc_sccp_inst_next_conn_id(struct osmo_sccp_instance *sccp)
 	/* This looks really suboptimal, but in most cases the static next_id should indicate exactly the next unused
 	 * conn_id, and we only iterate all conns once to make super sure that it is not already in use. */
 
-	for (i = 0; i < 0xFFFFFF; i++) {
+	for (i = 0; i < SCCP_CONN_ID_MAX; i++) {
 		struct gsm_subscriber_connection *conn;
 		uint32_t conn_id = next_id;
 		bool conn_id_already_used = false;
-		next_id = (next_id + 1) & 0xffffff;
+
+		/* Optimized modulo operation using bitwise AND: */
+		next_id = (next_id + 1) & SCCP_CONN_ID_MAX;
 
 		llist_for_each_entry(conn, &bsc_gsmnet->subscr_conns, entry) {
 			if (conn->sccp.msc && conn->sccp.msc->a.sccp == sccp) {
@@ -60,5 +62,5 @@ int bsc_sccp_inst_next_conn_id(struct osmo_sccp_instance *sccp)
 		if (!conn_id_already_used)
 			return conn_id;
 	}
-	return -1;
+	return SCCP_CONN_ID_UNSET;
 }
diff --git a/src/osmo-bsc/bsc_subscr_conn_fsm.c b/src/osmo-bsc/bsc_subscr_conn_fsm.c
index ebfbe82a2..e37f0300e 100644
--- a/src/osmo-bsc/bsc_subscr_conn_fsm.c
+++ b/src/osmo-bsc/bsc_subscr_conn_fsm.c
@@ -1226,8 +1226,7 @@ struct gsm_subscriber_connection *bsc_subscr_con_allocate(struct gsm_network *ne
 	conn->network = net;
 	INIT_LLIST_HEAD(&conn->dtap_queue);
 	INIT_LLIST_HEAD(&conn->hodec2.penalty_timers);
-	conn->sccp.conn_id = -1;
-
+	conn->sccp.conn_id = SCCP_CONN_ID_UNSET;
 	/* Default clear cause (on RR translates to GSM48_RR_CAUSE_ABNORMAL_UNSPEC) */
 	conn->clear_cause = GSM0808_CAUSE_EQUIPMENT_FAILURE;
 
diff --git a/src/osmo-bsc/lb.c b/src/osmo-bsc/lb.c
index 6f3cfac7c..c34d88ea3 100644
--- a/src/osmo-bsc/lb.c
+++ b/src/osmo-bsc/lb.c
@@ -32,7 +32,7 @@
 #include <osmocom/bsc/lcs_loc_req.h>
 #include <osmocom/bsc/bssmap_reset.h>
 
-static struct gsm_subscriber_connection *get_bsc_conn_by_lb_conn_id(int conn_id)
+static struct gsm_subscriber_connection *get_bsc_conn_by_lb_conn_id(uint32_t conn_id)
 {
 	struct gsm_subscriber_connection *conn;
 
@@ -229,7 +229,7 @@ static int sccp_sap_up(struct osmo_prim_hdr *oph, void *_scu)
 static int lb_open_conn(struct gsm_subscriber_connection *conn, struct msgb *msg)
 {
 	struct osmo_ss7_instance *ss7;
-	int conn_id;
+	uint32_t conn_id;
 	int rc;
 
 	OSMO_ASSERT(conn);
@@ -242,14 +242,14 @@ static int lb_open_conn(struct gsm_subscriber_connection *conn, struct msgb *msg
 	}
 
 	conn_id = bsc_sccp_inst_next_conn_id(bsc_gsmnet->smlc->sccp);
-	if (conn_id < 0) {
+	if (conn_id == SCCP_CONN_ID_UNSET) {
 		LOGPFSMSL(conn->fi, DLCS, LOGL_ERROR, "Unable to allocate SCCP Connection ID for BSSMAP-LE to SMLC\n");
 		return -ENOSPC;
 	}
 	conn->lcs.lb.conn_id = conn_id;
 	ss7 = osmo_ss7_instance_find(bsc_gsmnet->smlc->cs7_instance);
 	OSMO_ASSERT(ss7);
-	LOGPFSMSL(conn->fi, DLCS, LOGL_INFO, "Opening new SCCP connection (id=%i) to SMLC: %s\n", conn_id,
+	LOGPFSMSL(conn->fi, DLCS, LOGL_INFO, "Opening new SCCP connection (id=%u) to SMLC: %s\n", conn_id,
 		  osmo_sccp_addr_name(ss7, &bsc_gsmnet->smlc->smlc_addr));
 
 	rc = osmo_sccp_tx_conn_req_msg(bsc_gsmnet->smlc->sccp_user, conn_id, &bsc_gsmnet->smlc->bsc_addr,
diff --git a/src/osmo-bsc/osmo_bsc_sigtran.c b/src/osmo-bsc/osmo_bsc_sigtran.c
index 88ee01c2e..748b3f0b0 100644
--- a/src/osmo-bsc/osmo_bsc_sigtran.c
+++ b/src/osmo-bsc/osmo_bsc_sigtran.c
@@ -46,9 +46,9 @@ static struct llist_head *msc_list;
 #define DEFAULT_ASP_REMOTE_IP "localhost"
 
 /* Helper function to Check if the given connection id is already assigned */
-static struct gsm_subscriber_connection *get_bsc_conn_by_conn_id(int conn_id)
+static struct gsm_subscriber_connection *get_bsc_conn_by_conn_id(uint32_t conn_id)
 {
-	conn_id &= 0xFFFFFF;
+	conn_id &= SCCP_CONN_ID_MAX;
 	struct gsm_subscriber_connection *conn;
 
 	llist_for_each_entry(conn, &bsc_gsmnet->subscr_conns, entry) {
@@ -317,13 +317,13 @@ __attribute__((weak)) int osmo_bsc_sigtran_open_conn(struct gsm_subscriber_conne
 {
 	struct osmo_ss7_instance *ss7;
 	struct bsc_msc_data *msc;
-	int conn_id;
+	uint32_t conn_id;
 	int rc;
 
 	OSMO_ASSERT(conn);
 	OSMO_ASSERT(msg);
 	OSMO_ASSERT(conn->sccp.msc);
-	OSMO_ASSERT(conn->sccp.conn_id == -1);
+	OSMO_ASSERT(conn->sccp.conn_id == SCCP_CONN_ID_UNSET);
 
 	msc = conn->sccp.msc;
 
@@ -333,14 +333,14 @@ __attribute__((weak)) int osmo_bsc_sigtran_open_conn(struct gsm_subscriber_conne
 	}
 
 	conn->sccp.conn_id = conn_id = bsc_sccp_inst_next_conn_id(conn->sccp.msc->a.sccp);
-	if (conn->sccp.conn_id < 0) {
+	if (conn->sccp.conn_id == SCCP_CONN_ID_UNSET) {
 		LOGP(DMSC, LOGL_ERROR, "Unable to allocate SCCP Connection ID\n");
 		return -1;
 	}
-	LOGP(DMSC, LOGL_DEBUG, "Allocated new connection id: %d\n", conn->sccp.conn_id);
+	LOGP(DMSC, LOGL_DEBUG, "Allocated new connection id: %u\n", conn->sccp.conn_id);
 	ss7 = osmo_ss7_instance_find(msc->a.cs7_instance);
 	OSMO_ASSERT(ss7);
-	LOGP(DMSC, LOGL_INFO, "Opening new SCCP connection (id=%i) to MSC %d: %s\n", conn_id,
+	LOGP(DMSC, LOGL_INFO, "Opening new SCCP connection (id=%u) to MSC %d: %s\n", conn_id,
 	     msc->nr, osmo_sccp_addr_name(ss7, &msc->a.msc_addr));
 
 	rc = osmo_sccp_tx_conn_req_msg(msc->a.sccp_user, conn_id, &msc->a.bsc_addr,