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plugins/libplugin.c: Allow freeing notification struct command *.

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We always allocate a new `struct command` when we get a full JSON
object from stdin:

b2df01dc73/plugins/libplugin.c (L1229-L1233)

If it happens to be a notification, we pass the `struct command` to
the handler, and not free it ourselves:

b2df01dc73/plugins/libplugin.c (L1270-L1275)

There are only nine points in `plugins/libplugin.c` where we `tal_free`
anything, and only one of them frees a `struct command`:

b2df01dc73/plugins/libplugin.c (L224-L234)

The above function `command_complete` is not appropriate for
notification handlers; the above function sends out a response
to our stdout, which a notification handler should not do.

However, as-is, it does mean that notification handling leaks
`struct command` objects, which can be problematic if we ever
have future built-in plugins which are significantly more
dependent on notifications.

This commit changes notification handlers to return
`struct command_result *`, because possibly in the future
notification handlers may want to perform `send_outreq`, so we
might as well use our standard convention for callbacks, and
to encourage future developers to check how to properly
terminate notification handlers (and free up the
`struct command`).

We also now provide a `notification_handled` function which a
notification handler must eventually call, as well as a
`notification_handler_pending` which is just a snowclone of
`command_still_pending`.
This commit is contained in:
ZmnSCPxj jxPCSnmZ
2021-10-01 07:59:40 +08:00
committed by Rusty Russell
parent e393791d4b
commit d4690358d9
5 changed files with 46 additions and 20 deletions
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15
tests/plugins/test_libplugin.c
View File

@@ -48,24 +48,25 @@ json_peer_connected(struct command *cmd,
return command_finished(cmd, response);
}
static void json_connected(struct command *cmd,
const char *buf,
const jsmntok_t *params)
static struct command_result *json_connected(struct command *cmd,
const char *buf,
const jsmntok_t *params)
{
const jsmntok_t *idtok = json_get_member(buf, params, "id");
assert(idtok);
plugin_log(cmd->plugin, LOG_INFORM, "%s connected",
json_strdup(tmpctx, buf, idtok));
return notification_handled(cmd);
}
static void json_shutdown(struct command *cmd,
const char *buf,
const jsmntok_t *params)
static struct command_result *json_shutdown(struct command *cmd,
const char *buf,
const jsmntok_t *params)
{
plugin_log(cmd->plugin, LOG_DBG, "shutdown called");
if (dont_shutdown)
return;
return notification_handled(cmd);
plugin_exit(cmd->plugin, 0);
}