From 50600dce9570a63d509d76219d825f84c572b885 Mon Sep 17 00:00:00 2001
From: ZmnSCPxj jxPCSnmZ <zmnscpxj@protonmail.com>
Date: Wed, 29 Jul 2020 16:56:42 +0800
Subject: [PATCH] lightningd/lightningd.c: Create API to exit lightningd with
 an exit code.

---
 lightningd/lightningd.c | 42 ++++++++++++++++++++++++++++++++---------
 lightningd/lightningd.h | 10 ++++++++++
 2 files changed, 43 insertions(+), 9 deletions(-)

diff --git a/lightningd/lightningd.c b/lightningd/lightningd.c
index fc8a80714..c7cbedd2b 100644
--- a/lightningd/lightningd.c
+++ b/lightningd/lightningd.c
@@ -281,6 +281,11 @@ static struct lightningd *new_lightningd(const tal_t *ctx)
 	 */
 	ld->rpc_filemode = 0600;
 
+	/*~ This is the exit code to use on exit.
+	 * Set to NULL meaning we are not interested in exiting yet.
+	 */
+	ld->exit_code = NULL;
+
 	return ld;
 }
 
@@ -752,6 +757,14 @@ static void hsm_ecdh_failed(enum status_failreason fail,
 	fatal("hsm failure: %s", fmt);
 }
 
+/*~ This signals to the mainloop that some part wants to cleanly exit now.  */
+void lightningd_exit(struct lightningd *ld, int exit_code)
+{
+	ld->exit_code = tal(ld, int);
+	*ld->exit_code = exit_code;
+	io_break(ld);
+}
+
 int main(int argc, char *argv[])
 {
 	struct lightningd *ld;
@@ -764,6 +777,8 @@ int main(int argc, char *argv[])
 	struct ext_key *bip32_base;
 	struct rlimit nofile = {1024, 1024};
 
+	int exit_code = 0;
+
 	/*~ Make sure that we limit ourselves to something reasonable. Modesty
 	 *  is a virtue. */
 	setrlimit(RLIMIT_NOFILE, &nofile);
@@ -1003,10 +1018,17 @@ int main(int argc, char *argv[])
 	assert(io_loop_ret == ld);
 	ld->state = LD_STATE_SHUTDOWN;
 
-	/* Keep this fd around, to write final response at the end. */
-	stop_fd = io_conn_fd(ld->stop_conn);
-	io_close_taken_fd(ld->stop_conn);
-	stop_response = tal_steal(NULL, ld->stop_response);
+	/* Were we exited via `lightningd_exit`?  */
+	if (ld->exit_code) {
+		exit_code = *ld->exit_code;
+		stop_fd = -1;
+		stop_response = NULL;
+	} else {
+		/* Keep this fd around, to write final response at the end. */
+		stop_fd = io_conn_fd(ld->stop_conn);
+		io_close_taken_fd(ld->stop_conn);
+		stop_response = tal_steal(NULL, ld->stop_response);
+	}
 
 	shutdown_subdaemons(ld);
 
@@ -1041,11 +1063,13 @@ int main(int argc, char *argv[])
 
 	daemon_shutdown();
 
-	/* Finally, send response to shutdown command */
-	write_all(stop_fd, stop_response, strlen(stop_response));
-	close(stop_fd);
-	tal_free(stop_response);
+	/* Finally, send response to shutdown command if appropriate.  */
+	if (stop_fd >= 0) {
+		write_all(stop_fd, stop_response, strlen(stop_response));
+		close(stop_fd);
+		tal_free(stop_response);
+	}
 
 	/*~ Farewell.  Next stop: hsmd/hsmd.c. */
-	return 0;
+	return exit_code;
 }
diff --git a/lightningd/lightningd.h b/lightningd/lightningd.h
index b5d7b3698..5ad15243e 100644
--- a/lightningd/lightningd.h
+++ b/lightningd/lightningd.h
@@ -271,6 +271,9 @@ struct lightningd {
 	/* Total number of coin moves we've seen, since
 	 * coin move tracking was cool */
 	s64 coin_moves_count;
+
+	/* If non-NULL, contains the exit code to use.  */
+	int *exit_code;
 };
 
 /* Turning this on allows a tal allocation to return NULL, rather than aborting.
@@ -289,4 +292,11 @@ void test_subdaemons(const struct lightningd *ld);
 /* Notify lightningd about new blocks. */
 void notify_new_block(struct lightningd *ld, u32 block_height);
 
+/* Signal a clean exit from lightningd.
+ * NOTE! This function **returns**.
+ * This just causes the main loop to exit, so you have to return
+ * all the way to the main loop for `lightningd` to exit.
+ */
+void lightningd_exit(struct lightningd *ld, int exit_code);
+
 #endif /* LIGHTNING_LIGHTNINGD_LIGHTNINGD_H */