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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: Ifcf710ef6024286a1cc3473d6ea3f858552b9926
This commit is contained in:
Pau Espin 2023-03-10 16:21:26 +01:00
parent 41089524a3
commit f031be9141
1 changed files with 15 additions and 3 deletions
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18
src/sccp_scoc.c
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@ -507,10 +507,22 @@ static struct sccp_connection *conn_create(struct osmo_sccp_user *user)
{
uint32_t conn_id;
/* 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, as we currently use the connection ID also as local reference,
* let's simply use 24 bit ids to fit all link types (excluding 0x00ffffff).
*/
do {
/* modulo 2^24 as we currently use the connection ID also as local
* reference, and that is limited to 24 bits */
user->inst->next_id = (user->inst->next_id + 1) % (1 << 24);
/* Optimized modulo operation (% 0x00FFFFFE) using bitwise AND plus CMP: */
user->inst->next_id = (user->inst->next_id + 1) & 0x00FFFFFF;
if (OSMO_UNLIKELY(user->inst->next_id == 0x00FFFFFF))
user->inst->next_id = 0;
conn_id = user->inst->next_id;
} while (conn_find_by_id(user->inst, conn_id));