GSUP: implement TCAP-like session management
Unlike TCAP/MAP, GSUP is just a transport layer without the
dialogue/context. This prevents us from having session based
communication, required e.g. for USSD. But we can emulate
TCAP dialogue by adding additional IEs, which would allow
to relate each message to a particular session.
This change introduces the following IEs:
- OSMO_GSUP_SESSION_ID_IE,
- OSMO_GSUP_SESSION_STATE_IE,
which optionally can be used to indicate that the message is
related to a session with given ID, and to manage session
state, i.e. initiate, continue, and finish.
Change-Id: I1cee271fed0284a134ffed103c0d4bebbcfde2a8
Related: OS#1597
diff --git a/include/osmocom/gsm/gsup.h b/include/osmocom/gsm/gsup.h
index a7fa820..5f45699 100644
--- a/include/osmocom/gsm/gsup.h
+++ b/include/osmocom/gsm/gsup.h
@@ -82,6 +82,9 @@
OSMO_GSUP_AUTS_IE = 0x26,
OSMO_GSUP_RES_IE = 0x27,
OSMO_GSUP_CN_DOMAIN_IE = 0x28,
+
+ OSMO_GSUP_SESSION_ID_IE = 0x30,
+ OSMO_GSUP_SESSION_STATE_IE = 0x31,
};
/*! GSUP message type */
@@ -132,6 +135,18 @@
OSMO_GSUP_CN_DOMAIN_CS = 2,
};
+/*! TCAP-like session state */
+enum osmo_gsup_session_state {
+ /*! Undefined session state */
+ OSMO_GSUP_SESSION_STATE_NONE = 0x00,
+ /*! Initiation of a new session */
+ OSMO_GSUP_SESSION_STATE_BEGIN = 0x01,
+ /*! Communication of an existing session */
+ OSMO_GSUP_SESSION_STATE_CONTINUE = 0x02,
+ /*! Indication of the session end */
+ OSMO_GSUP_SESSION_STATE_END = 0x03,
+};
+
/*! parsed/decoded PDP context information */
struct osmo_gsup_pdp_info {
unsigned int context_id;
@@ -176,6 +191,12 @@
enum osmo_gsup_cn_domain cn_domain;
const uint8_t *pdp_charg_enc;
size_t pdp_charg_enc_len;
+
+ /*! Session state \ref osmo_gsup_session_state */
+ enum osmo_gsup_session_state session_state;
+ /*! Unique session identifier and origination flag.
+ * Encoded only when \ref session_state != 0x00 */
+ uint32_t session_id;
};
int osmo_gsup_decode(const uint8_t *data, size_t data_len,