ctrl: fix deferred commands (and hence fix osmo-bts-sysmo 'clock-info' cmd)

The CTRL interface has a ctrl_cmd_def_* API that allows deferring a CTRL
command reply until later. However, the command handling currently fails to
acknowledge this and deallocates the struct ctrl_cmd anyway.

Fix: in struct ctrl_cmd, add a defer pointer to be populated by
ctrl_cmd_def_make(). A cmd thus marked as deferred is not deallocated at the
end of command handling. This fix needs no change in calling code.

(Another idea was to return a different code than CTRL_CMD_HANDLED when the
command is to be deferred, but that would require adjusting each user of
ctrl_cmd_def_make(). The implicit marking is safer and easier.)

Show that handling deferred commands is fixed by adjusting the expectations of
ctrl_test.c's test_deferred_cmd() and removing the now obsolete exit_early
label.

One symptom of the breakage is that osmo-bts-sysmo crashes when asked to report
a trx's clock-info, which is aggravated by the fact that the sysmobts-mgr does
ask osmo-bts-sysmo for a clock-info.

The crash appears since Id583b413f8b8bd16e5cf92a8a9e8663903646381 -- it looked
like just fixing an obvious memory leak, which it did as shown by the unit
test, but deferred ctrl commands actually relied on that leak. Both fixed now.

Related: OS#3120
Change-Id: I24232be7dcf7be79f4def91ddc8b8f8005b56318

1 files changed, 3 insertions, 0 deletions

diff --git a/include/osmocom/ctrl/control_cmd.h b/include/osmocom/ctrl/control_cmd.h
index 865b006b..a5df753d 100644
--- a/include/osmocom/ctrl/control_cmd.h
+++ b/include/osmocom/ctrl/control_cmd.h
@@ -56,6 +56,8 @@ struct ctrl_connection {
 	struct llist_head def_cmds;
 };
 
+struct ctrl_cmd_def;
+
 struct ctrl_cmd {
 	struct ctrl_connection *ccon;
 	enum ctrl_type type;
@@ -64,6 +66,7 @@ struct ctrl_cmd {
 	char *variable;
 	char *value;
 	char *reply;
+	struct ctrl_cmd_def *defer;
 };
 
 #define ctrl_cmd_reply_printf(cmd, fmt, args ...) \