res_pjsip: PJSIP Transport state monitor refactor.

The fix for the issue is broken up into three parts.

This is part one which refactors the transport state monitor code to allow
more modules to be able to monitor transports.

* Pull the management of PJPROJECT's transport state callback code from
res_pjsip_transport_management.c into res_pjsip.  Now other modules can
dynamically add and remove themselves from transport monitoring without
worrying about breaking PJPROJECT's callback chain.

* Add the ability for other modules to get a callback whenever a specific
transport is shutdown.

ASTERISK-27147

Change-Id: I7d9a31371eb1487c9b7050cf82a9af5180a57912

1 files changed, 87 insertions, 0 deletions

diff --git a/include/asterisk/res_pjsip.h b/include/asterisk/res_pjsip.h
index 890ce59fb..31db36766 100644
--- a/include/asterisk/res_pjsip.h
+++ b/include/asterisk/res_pjsip.h
@@ -2926,4 +2926,91 @@ int ast_sip_dtmf_to_str(const enum ast_sip_dtmf_mode dtmf,
  */
 int ast_sip_str_to_dtmf(const char *dtmf_mode);
 
+/*!
+ * \brief Transport shutdown monitor callback.
+ * \since 13.18.0
+ *
+ * \param data User data to know what to do when transport shuts down.
+ *
+ * \note The callback does not need to care that data is an ao2 object.
+ *
+ * \return Nothing
+ */
+typedef void (*ast_transport_monitor_shutdown_cb)(void *data);
+
+enum ast_transport_monitor_reg {
+	/*! \brief Successfully registered the transport monitor */
+	AST_TRANSPORT_MONITOR_REG_SUCCESS,
+	/*! \brief Replaced the already existing transport monitor with new one. */
+	AST_TRANSPORT_MONITOR_REG_REPLACED,
+	/*!
+	 * \brief Transport not found to monitor.
+	 * \note Transport is either already shutdown or is not reliable.
+	 */
+	AST_TRANSPORT_MONITOR_REG_NOT_FOUND,
+	/*! \brief Error while registering transport monitor. */
+	AST_TRANSPORT_MONITOR_REG_FAILED,
+};
+
+/*!
+ * \brief Register a reliable transport shutdown monitor callback.
+ * \since 13.18.0
+ *
+ * \param transport Transport to monitor for shutdown.
+ * \param cb Who to call when transport is shutdown.
+ * \param ao2_data Data to pass with the callback.
+ *
+ * \return enum ast_transport_monitor_reg
+ */
+enum ast_transport_monitor_reg ast_sip_transport_monitor_register(pjsip_transport *transport,
+	ast_transport_monitor_shutdown_cb cb, void *ao2_data);
+
+/*!
+ * \brief Unregister a reliable transport shutdown monitor callback.
+ * \since 13.18.0
+ *
+ * \param transport Transport to monitor for shutdown.
+ * \param cb Who to call when transport is shutdown.
+ *
+ * \return Nothing
+ */
+void ast_sip_transport_monitor_unregister(pjsip_transport *transport, ast_transport_monitor_shutdown_cb cb);
+
+/*!
+ * \brief Unregister monitor callback from all reliable transports.
+ * \since 13.18.0
+ *
+ * \param cb Who to call when a transport is shutdown.
+ *
+ * \return Nothing
+ */
+void ast_sip_transport_monitor_unregister_all(ast_transport_monitor_shutdown_cb cb);
+
+/*! Transport state notification registration element.  */
+struct ast_sip_tpmgr_state_callback {
+	/*! PJPROJECT transport state notification callback */
+	pjsip_tp_state_callback cb;
+	AST_LIST_ENTRY(ast_sip_tpmgr_state_callback) node;
+};
+
+/*!
+ * \brief Register a transport state notification callback element.
+ * \since 13.18.0
+ *
+ * \param element What we are registering.
+ *
+ * \return Nothing
+ */
+void ast_sip_transport_state_register(struct ast_sip_tpmgr_state_callback *element);
+
+/*!
+ * \brief Unregister a transport state notification callback element.
+ * \since 13.18.0
+ *
+ * \param element What we are unregistering.
+ *
+ * \return Nothing
+ */
+void ast_sip_transport_state_unregister(struct ast_sip_tpmgr_state_callback *element);
+
 #endif /* _RES_PJSIP_H */