libctrl: Add support for 'deferred control commands'

Sometimes a control interface command cannot be processed
and responded immediately, but we need to process it asynchronously.

In order to support this, we introduce the 'ctrl_cmd_def', which
represents such a deferred command.  It is created by the service
implementing the command using ctrl_cmd_def_make(), and a response is
later sent using ctrl_cmd_def_send().

ctrl_cmd_def_is_zombie() must be called to handle the case where
the control connection has disconnected/died between receiving the
command and sending the response.

1 files changed, 15 insertions, 0 deletions

diff --git a/include/osmocom/ctrl/control_cmd.h b/include/osmocom/ctrl/control_cmd.h
index 9e949631..8f2eaa25 100644
--- a/include/osmocom/ctrl/control_cmd.h
+++ b/include/osmocom/ctrl/control_cmd.h
@@ -45,6 +45,9 @@ struct ctrl_connection {
 
 	/* Pending commands for this connection */
 	struct llist_head cmds;
+
+	/* Pending deferred commands for this connection */
+	struct llist_head def_cmds;
 };
 
 struct ctrl_cmd {
@@ -75,6 +78,18 @@ struct ctrl_cmd_map {
 	enum ctrl_type type;
 };
 
+/* deferred control command, i.e. responded asynchronously */
+struct ctrl_cmd_def {
+	struct llist_head list;		/* ctrl_connection.def_cmds */
+	struct ctrl_cmd *cmd;
+	void *data;			/* opaque user data */
+};
+
+struct ctrl_cmd_def *
+ctrl_cmd_def_make(const void *ctx, struct ctrl_cmd *cmd, void *data, unsigned int secs);
+int ctrl_cmd_def_is_zombie(struct ctrl_cmd_def *cd);
+int ctrl_cmd_def_send(struct ctrl_cmd_def *cd);
+
 int ctrl_cmd_exec(vector vline, struct ctrl_cmd *command, vector node, void *data);
 int ctrl_cmd_install(enum ctrl_node_type node, struct ctrl_cmd_element *cmd);
 int ctrl_cmd_send(struct osmo_wqueue *queue, struct ctrl_cmd *cmd);