From 3ff6ac2e782cdfe1d32240556478a2b5a3b8c057 Mon Sep 17 00:00:00 2001
From: David Härdeman <david@hardeman.nu>
Date: Wed, 10 Jun 2020 00:27:53 +0200
Subject: Make server stop/start exec asynchronous

---
 server.c | 106 +++++++++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 76 insertions(+), 30 deletions(-)

(limited to 'server.c')

diff --git a/server.c b/server.c
index c3bb433..7ec0804 100644
--- a/server.c
+++ b/server.c
@@ -1,3 +1,4 @@
+#define _GNU_SOURCE
 #include <stdlib.h>
 #include <string.h>
 #include <arpa/inet.h>
@@ -5,7 +6,10 @@
 #include <inttypes.h>
 #include <sys/types.h>
 #include <sys/wait.h>
-#include <unistd.h>
+#include <sched.h>
+#include <poll.h>
+#include <errno.h>
+#include <sched.h>
 
 #include "main.h"
 #include "uring.h"
@@ -87,6 +91,8 @@ server_delete(struct cfg *cfg, struct server *scfg)
 		uring_cancel(cfg, &local->task);
 	}
 
+	uring_poll_cancel(cfg, &scfg->exec_task);
+	uring_task_put(cfg, &scfg->exec_task);
 	uring_task_put(cfg, &scfg->task);
 }
 
@@ -229,42 +235,81 @@ out:
 	return false;
 }
 
+static void
+server_exec_free(struct uring_task *task)
+{
+	//struct server *scfg = container_of(task, struct server, exec_task);
+
+	fprintf(stderr, "%s called\n", __func__);
+}
+
+#ifndef P_PIDFD
+#define P_PIDFD 3
+#endif
+
+static void
+server_exec_done(struct cfg *cfg, struct uring_task *task, int res)
+{
+	struct server *scfg = container_of(task, struct server, exec_task);
+	int r;
+	siginfo_t info;
+
+	if (task->dead)
+		goto out;
+
+	if (!(res & POLLIN)) {
+		fprintf(stderr, "%s: unexpected result: %i\n", __func__, res);
+		goto out;
+	}
+
+	r = waitid(P_PIDFD, scfg->exec_task.fd, &info, WEXITED);
+        if (r < 0) {
+                perror("waitid");
+		goto out;
+        }
+
+	fprintf(stderr, "Command executed, return value: %i\n", info.si_status);
+out:
+	uring_task_close_fd(cfg, &scfg->exec_task);
+}
+
+static int
+server_exec_child(void *ptr)
+{
+	const char *cmd = ptr;
+
+	execl(cmd, cmd, NULL);
+	return errno;
+}
+
+#ifndef CLONE_PIDFD
+#define CLONE_PIDFD 0x00001000
+#endif
+
 static bool
-exec_cmd(struct cfg *cfg, struct server *scfg, const char *cmd)
+server_exec(struct cfg *cfg, struct server *scfg, const char *cmd)
 {
-	pid_t pid, wpid;
-	int wstatus;
+	char stack[4096]; /* Beautiful/horrible hack :) */
+	int pidfd;
+	int r;
 
 	if (!cfg || !scfg || !cmd)
 		return false;
 
-	pid = fork();
-	if (pid < 0) {
-		perror("fork");
+	if (scfg->exec_task.fd >= 0)
 		return false;
 
-	} else if (pid > 0) {
-		do {
-			wpid = waitpid(pid, &wstatus, 0);
-			if (wpid < 0) {
-				perror("waitpid");
-				return false;
-			}
-		} while (!WIFEXITED(wstatus));
-
-		fprintf(stderr, "Child %s exited: %i\n", cmd,
-			WEXITSTATUS(wstatus));
-
-		if (WEXITSTATUS(wstatus) == 0)
-			return true;
-		else
-			return false;
-
-	} else {
-		execl(cmd, cmd, NULL);
-		perror("execl");
-		exit(EXIT_FAILURE);
+        r = clone(server_exec_child, stack + sizeof(stack),
+                  CLONE_VM | CLONE_VFORK | CLONE_PIDFD | SIGCHLD,
+                  (void *)cmd, &pidfd);
+	if (r < 0) {
+		perror("clone");
+		return false;
 	}
+
+	uring_task_set_fd(&scfg->exec_task, pidfd);
+	uring_poll(cfg, &scfg->exec_task, POLLIN, server_exec_done);
+	return true;
 }
 
 bool
@@ -276,7 +321,7 @@ server_start(struct cfg *cfg, struct server *scfg)
 	switch (scfg->start_method) {
 
 	case SERVER_START_METHOD_EXEC:
-		return exec_cmd(cfg, scfg, scfg->start_exec);
+		return server_exec(cfg, scfg, scfg->start_exec);
 
 	case SERVER_START_METHOD_UNDEFINED:
 	default:
@@ -295,7 +340,7 @@ server_stop(struct cfg *cfg, struct server *scfg)
 	switch (scfg->stop_method) {
 
 	case SERVER_STOP_METHOD_EXEC:
-		return exec_cmd(cfg, scfg, scfg->stop_exec);
+		return server_exec(cfg, scfg, scfg->stop_exec);
 
 	case SERVER_STOP_METHOD_RCON:
 		rcon_init(cfg, scfg);
@@ -558,6 +603,7 @@ server_new(struct cfg *cfg, const char *name)
 	scfg->stop_method = SERVER_STOP_METHOD_UNDEFINED;
 	scfg->start_method = SERVER_START_METHOD_UNDEFINED;
 	uring_task_init(&scfg->task, "scfg", uring_parent(cfg), server_free);
+	uring_task_init(&scfg->exec_task, "exec", &scfg->task, server_exec_free);
 	list_init(&scfg->remotes);
 	list_init(&scfg->locals);
 	list_init(&scfg->proxys);
-- 
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