add iscsi_force_reconnect()

If a connection attempt is hung, then iscsi_reconnect() won't do anything. This
makes sense if we'd just re-try to connect to the same target, but if (for
example) login redirect might point us to a different, healthy, target, it
should be possible to restart the full connection process on request.

Signed-off-by: John Levon <john.levon@nutanix.com>

include/iscsi.h

@@ -492,6 +492,33 @@ EXTERN int iscsi_reconnect(struct iscsi_context *iscsi);
  */
 EXTERN int iscsi_reconnect_sync(struct iscsi_context *iscsi);
 
+/*
+ * Disconnect a connection to a target and try to reconnect (async version).
+ * This call returns immediately and the reconnect is processed in the
+ * background. Commands send to this connection will be queued and not
+ * processed until we have successfully reconnected.
+ *
+ * This will re-start connection (to the configured original portal) even if a
+ * pending reconnection is already underway, which may be useful if the current
+ * connection is not progressing.  It does not over-ride any existing re-try
+ * backoff or max retries state.
+ *
+ * Returns:
+ *  0 reconnect was successful
+ * <0 error
+ */
+EXTERN int iscsi_force_reconnect(struct iscsi_context *iscsi);
+
+/*
+ * Disconnect a connection to a target and try to force reconnection (sync
+ * version). This call will block until the connection is reestablished.
+ *
+ * Returns:
+ *  0 reconnect was successful
+ * <0 error
+ */
+EXTERN int iscsi_force_reconnect_sync(struct iscsi_context *iscsi);
+
 /*
  * Asynchronous call to perform an ISCSI login.
  *

lib/connect.c

@@ -378,7 +378,7 @@ void iscsi_reconnect_cb(struct iscsi_context *iscsi, int status,
 	iscsi->pending_reconnect = 0;
 }
 
-int iscsi_reconnect(struct iscsi_context *iscsi)
+static int reconnect(struct iscsi_context *iscsi, int force)
 {
 	struct iscsi_context *tmp_iscsi;
 
@@ -397,7 +397,7 @@ int iscsi_reconnect(struct iscsi_context *iscsi)
 		return 0;
 	}
 
-	if (iscsi->old_iscsi && !iscsi->pending_reconnect) {
+	if (iscsi->old_iscsi && !iscsi->pending_reconnect && !force) {
 		return 0;
 	}
 
@@ -477,3 +477,13 @@ int iscsi_reconnect(struct iscsi_context *iscsi)
 	return iscsi_full_connect_async(iscsi, iscsi->portal,
 	                                iscsi->lun, iscsi_reconnect_cb, NULL);
 }
+
+int iscsi_reconnect(struct iscsi_context *iscsi)
+{
+	return reconnect(iscsi, 0);
+}
+
+int iscsi_force_reconnect(struct iscsi_context *iscsi)
+{
+	return reconnect(iscsi, 1);
+}

lib/libiscsi.def

@@ -2,6 +2,7 @@ LIBRARY libiscsi
 EXPORTS
 iscsi_connect_async
 iscsi_connect_sync
+iscsi_force_reconnect_sync
 iscsi_reconnect_sync
 iscsi_create_context
 iscsi_destroy_context
@@ -10,6 +11,7 @@ iscsi_disconnect
 iscsi_discovery_async
 iscsi_discovery_sync
 iscsi_free_discovery_data
+iscsi_force_reconnect
 iscsi_full_connect_async
 iscsi_full_connect_sync
 iscsi_get_error
@@ -283,4 +285,4 @@ scsi_task_set_iov_in
 scsi_task_set_iov_out
 scsi_version_to_str
 scsi_version_descriptor_to_str
-win32_poll
+win32_poll

lib/libiscsi.syms.in

@@ -13,6 +13,8 @@ iscsi_discovery_sync
 iscsi_extended_copy_sync
 iscsi_extended_copy_task
 iscsi_free_discovery_data
+iscsi_force_reconnect
+iscsi_force_reconnect_sync
 iscsi_full_connect_async
 iscsi_full_connect_sync
 iscsi_get_error

lib/sync.c

@@ -226,6 +226,22 @@ int iscsi_reconnect_sync(struct iscsi_context *iscsi)
 	return (state.status == SCSI_STATUS_GOOD) ? 0 : -1;
 }
 
+int iscsi_force_reconnect_sync(struct iscsi_context *iscsi)
+{
+	struct iscsi_sync_state state;
+
+	memset(&state, 0, sizeof(state));
+
+	if (iscsi_force_reconnect(iscsi) != 0) {
+		iscsi_set_error(iscsi, "Failed to reconnect. %s", iscsi_get_error(iscsi));
+		return -1;
+	}
+
+	reconnect_event_loop(iscsi, &state);
+
+	return (state.status == SCSI_STATUS_GOOD) ? 0 : -1;
+}
+
 static void
 iscsi_task_mgmt_sync_cb(struct iscsi_context *iscsi, int status,
 	      void *command_data, void *private_data)