4 Mar
2025
4 Mar
'25
9:14 p.m.
pespin has uploaded this change for review. (
https://gerrit.osmocom.org/c/libosmo-sigtran/+/39689?usp=email )
Change subject: sccp: Apply SLS on locally-originated transmitted Connection-Oriented
messages
......................................................................
sccp: Apply SLS on locally-originated transmitted Connection-Oriented messages
Change-Id: I1956acf631867b12b647d14c10057ded20d7fa2f
---
M src/sccp_scoc.c
1 file changed, 34 insertions(+), 3 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/libosmo-sigtran refs/changes/89/39689/1
diff --git a/src/sccp_scoc.c b/src/sccp_scoc.c
index c11dddf..8222bde 100644
--- a/src/sccp_scoc.c
+++ b/src/sccp_scoc.c
@@ -102,6 +102,11 @@
uint32_t sccp_class;
uint32_t release_cause; /* WAIT_CONN_CONF */
+ /* SLS to be used to transmit all Connection-oriented messages
+ * (ITU-T Q.714 1.1.2.3 Protocol class 2).
+ * SLS is 4 bits, as described in ITU Q.704 Figure 3 */
+ uint8_t tx_co_mtp_sls;
+
struct msgb *opt_data_cache;
/* incoming (true) or outgoing (false) */
@@ -450,6 +455,26 @@
#define INIT_TIMER(x, fn, priv) do { (x)->cb = fn; (x)->data = priv; } while (0)
+/* Generate an SLS to be used for Connection-oriented messages on this SCCP connection.
+ * SLS is 4 bits, as described in ITU Q.704 Figure 3.
+ * ITU-T Q.714 1.1.2.3 Protocol class 2:
+ * "Messages belonging to a given signalling connection shall contain the same
+ * value of the SLS field to ensure sequencing as described in 1.1.2.2"
+ */
+static uint8_t sccp_conn_gen_tx_co_mtp_sls(const struct sccp_connection *conn)
+{
+ /* Implementation: Derive the SLS from conn->conn_id. */
+ const uint32_t id = conn->conn_id;
+ uint8_t sls;
+
+ /* First shrink it to 1 byte: */
+ sls = ((id >> (3*8)) ^ (id >> (2*8)) ^ (id >> (1*8)) ^ (id)) &
0xff;
+ /* Now shrink it 8 -> 4 bits: */
+ sls = ((sls >> 4) ^ sls) & 0x0f;
+
+ return sls;
+}
+
/* allocate + init a SCCP Connection with given ID */
static struct sccp_connection *conn_create_id(struct osmo_sccp_user *user, uint32_t
conn_id)
{
@@ -472,6 +497,8 @@
INIT_TIMER(&conn->t_int, int_tmr_cb, conn);
INIT_TIMER(&conn->t_rep_rel, rep_rel_tmr_cb, conn);
+ conn->tx_co_mtp_sls = sccp_conn_gen_tx_co_mtp_sls(conn);
+
/* this might change at runtime, as it is not a constant :/ */
sccp_scoc_fsm.log_subsys = DLSCCP;
@@ -715,6 +742,13 @@
if (!xua)
return NULL;
+ /* amend this with point code information; Many CO msgs
+ * includes neither called nor calling party address! */
+ xua->mtp.dpc = conn->remote_pc;
+
+ /* Apply SLS calculated for the connection (ITU-T Q.714 1.1.2.3). */
+ xua->mtp.sls = conn->tx_co_mtp_sls;
+
switch (msg_type) {
case SUA_CO_CORE: /* Connect Request == SCCP CR */
xua->hdr = XUA_HDR(SUA_MSGC_CO, SUA_CO_CORE);
@@ -835,9 +869,6 @@
if (!xua)
return -ENOMEM;
- /* amend this with point code information; Many CO msgs
- * includes neither called nor calling party address! */
- xua->mtp.dpc = conn->remote_pc;
sccp_scrc_rx_scoc_conn_msg(conn->inst, xua);
xua_msg_free(xua);
return 0;
--
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Gerrit-MessageType: newchange
Gerrit-Project: libosmo-sigtran
Gerrit-Branch: master
Gerrit-Change-Id: I1956acf631867b12b647d14c10057ded20d7fa2f
Gerrit-Change-Number: 39689
Gerrit-PatchSet: 1
Gerrit-Owner: pespin <pespin(a)sysmocom.de>