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bscc_sccp: Avoid allocating conn_id 0x00FFFFFF 

The 0x00FFFFFF source local reference is reserved in M3UA/SCCP, hence
avoid allocating a conn_id with that value since later on when reused as
a source local reference it would fail to be encoded.

Change-Id: I5c62bbfa89140d754edccb4404503cb70d5fde89
This commit is contained in:
Pau Espin 2023-03-09 13:09:03 +01:00
parent c5b7d94e0f
commit 06d1cff11a
2 changed files with 18 additions and 3 deletions
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2
include/osmocom/bsc/gsm_data.h
View File

@ -52,7 +52,7 @@
#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
#define SCCP_CONN_ID_MAX 0x00FFFFFE
struct mgcp_client_conf;
struct mgcp_client;

19
src/osmo-bsc/bsc_sccp.c
View File

@ -21,6 +21,8 @@
*
*/
#include <osmocom/core/utils.h>
#include <osmocom/bsc/gsm_data.h>
#include <osmocom/bsc/bsc_msc_data.h>
#include <osmocom/bsc/lb.h>
@ -31,6 +33,17 @@ uint32_t bsc_sccp_inst_next_conn_id(struct osmo_sccp_instance *sccp)
static uint32_t next_id = 1;
int i;
/* SUA: RFC3868 sec 3.10.4:
* The source reference number is a 4 octet long integer.
* This is allocated by the source SUA instance.
* M3UA/SCCP: ITU-T Q.713 sec 3.3:
* The "source local reference" parameter field is a three-octet field containing a
* reference number which is generated and used by the local node to identify the
* connection section after the connection section is set up.
* The coding "all ones" is reserved for future use.
* Hence, let's simply use 24 bit ids to fit all link types (excluding 0x00ffffff).
*/
/* 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. */
@ -39,8 +52,10 @@ uint32_t bsc_sccp_inst_next_conn_id(struct osmo_sccp_instance *sccp)
uint32_t conn_id = next_id;
bool conn_id_already_used = false;
/* Optimized modulo operation using bitwise AND: */
next_id = (next_id + 1) & SCCP_CONN_ID_MAX;
/* Optimized modulo operation (% SCCP_CONN_ID_MAX) using bitwise AND plus CMP: */
next_id = (next_id + 1) & 0x00FFFFFF;
if (OSMO_UNLIKELY(next_id == 0x00FFFFFF))
next_id = 0;
llist_for_each_entry(conn, &bsc_gsmnet->subscr_conns, entry) {
if (conn->sccp.msc && conn->sccp.msc->a.sccp == sccp) {