Store session backup to persistent storage

docs/arch/design.md

@@ -233,6 +233,19 @@ All backup session indexes are successive in the enumeration and starts with `BK
 
 For each kind of backup session data, there are insert functions that call `build_xml_node_data` and load functions that calls `load_xml_node_data`.
 
+### NOTE:
+This backup session feature has been limited to soft reboot and system upgrade, thus in case of power cycle or hard reboot, icwmp can not store the
+data in `/etc/icwmpd/icwmpd_backkup_session.xml`. Due to this limitation there is a chance that icwmp may send wrong event or not send an expected
+event in the first inform message after power up. For e.g: icwmp after power cycle may send `0 BOOTSTRAP` event even though it connects the same ACS.
+
+So, to avoid this problem a compile time flag `PERSIST_BACKUP_SESSION_EVENTS` has been added, by enabling this flag icwmp will store the backup session
+information in flash (persistent storage) drive at every successful session end and after boot up icwmp loads the session information from flash drive
+if there exist any.
+
+#### Precaution:
+This feature will increase the flash write operation, so user need to reconsider about enabling this flag. If flash has less write limit then it is
+better to disable this feature because after exceeding the write limit, flash could be corrupted.
+
 ## UCI and config mangement
 
 - [UCI](./docs/api/uci/cwmp.md)

src/backupSession.c

@@ -58,7 +58,6 @@ void bkp_session_save()
 	fp = fopen(CWMP_BKP_FILE, "w");
 	mxmlSaveFile(bkp_tree, fp, MXML_NO_CALLBACK);
 	fclose(fp);
-	sync();
 }
 
 void bkp_session_create_file()

src/backupSession.h

@@ -23,6 +23,11 @@
 
 #define CWMP_BACKUP_SESSION "<cwmp></cwmp>"
 #define CWMP_BKP_FILE "/var/run/icwmpd/icwmpd_backup_session.xml"
+
+#ifdef PERSIST_BACKUP_SESSION_EVENTS
+#define CWMP_BKP_FILE_PERSISTENT "/etc/icwmpd/icwmpd_backup_session.xml"
+#endif
+
 typedef enum backup_loading
 {
 	ALL,

src/common.c

@@ -469,7 +469,7 @@ int copy(const char *from, const char *to)
 	if (fd_from < 0)
 		return -1;
 
-	fd_to = open(to, O_WRONLY | O_CREAT | O_EXCL, 0666);
+	fd_to = open(to, O_WRONLY | O_CREAT | O_EXCL | O_SYNC, 0666);
 	if (fd_to < 0)
 		goto out_error;
 

src/session.c

@@ -411,6 +411,16 @@ void start_cwmp_session(void)
 
 		cwmp_ctx.retry_count_session = 0;
 		set_cwmp_session_status(SESSION_SUCCESS, 0);
+
+#ifdef PERSIST_BACKUP_SESSION_EVENTS
+		// session ended successfully so store next session events in persistent
+		// storage to avoid loss of events over power cycle
+		if (file_exists(CWMP_BKP_FILE)) {
+			CWMP_LOG(DEBUG, "Copied events backup file to persistent storage");
+			copy(CWMP_BKP_FILE, CWMP_BKP_FILE_PERSISTENT);
+		}
+#endif
+
 		if (cwmp_ctx.throttle_session_triggered == true) {
 			cwmp_ctx.throttle_session_triggered = false;
 			if (!cwmp_ctx.throttle_session) {