Report better error from server when socket create fails, GitHub issue

1201.

client.c

@@ -452,6 +452,7 @@ client_write(int fd, const char *data, size_t size)
 {
 	ssize_t	used;
 
+	log_debug("%s: %.*s", __func__, (int)size, data);
 	while (size != 0) {
 		used = write(fd, data, size);
 		if (used == -1) {

server-client.c

@@ -161,7 +161,7 @@ server_client_is_default_key_table(struct client *c, struct key_table *table)
 }
 
 /* Create a new client. */
-void
+struct client *
 server_client_create(int fd)
 {
 	struct client	*c;
@@ -214,6 +214,7 @@ server_client_create(int fd)
 
 	TAILQ_INSERT_TAIL(&clients, c, entry);
 	log_debug("new client %p", c);
+	return (c);
 }
 
 /* Open client terminal if needed. */
@@ -1550,6 +1551,9 @@ server_client_dispatch_command(struct client *c, struct imsg *imsg)
 	int			  argc;
 	char			**argv, *cause;
 
+	if (c->flags & CLIENT_EXIT)
+		return;
+
 	if (imsg->hdr.len - IMSG_HEADER_SIZE < sizeof data)
 		fatalx("bad MSG_COMMAND size");
 	memcpy(&data, imsg->data, sizeof data);

server.c

@@ -50,7 +50,6 @@ static struct event	 server_ev_accept;
 
 struct cmd_find_state	 marked_pane;
 
-static int	server_create_socket(void);
 static int	server_loop(void);
 static void	server_send_exit(void);
 static void	server_accept(int, short, void *);
@@ -99,39 +98,62 @@ server_check_marked(void)
 
 /* Create server socket. */
 static int
-server_create_socket(void)
+server_create_socket(char **cause)
 {
 	struct sockaddr_un	sa;
 	size_t			size;
 	mode_t			mask;
-	int			fd;
+	int			fd, saved_errno;
 
 	memset(&sa, 0, sizeof sa);
 	sa.sun_family = AF_UNIX;
 	size = strlcpy(sa.sun_path, socket_path, sizeof sa.sun_path);
 	if (size >= sizeof sa.sun_path) {
 		errno = ENAMETOOLONG;
-		return (-1);
+		goto fail;
 	}
 	unlink(sa.sun_path);
 
 	if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
-		return (-1);
+		goto fail;
 
 	mask = umask(S_IXUSR|S_IXGRP|S_IRWXO);
-	if (bind(fd, (struct sockaddr *) &sa, sizeof(sa)) == -1) {
+	if (bind(fd, (struct sockaddr *)&sa, sizeof sa) == -1) {
+		saved_errno = errno;
 		close(fd);
-		return (-1);
+		errno = saved_errno;
+		goto fail;
 	}
 	umask(mask);
 
 	if (listen(fd, 128) == -1) {
+		saved_errno = errno;
 		close(fd);
-		return (-1);
+		errno = saved_errno;
+		goto fail;
 	}
 	setblocking(fd, 0);
 
 	return (fd);
+
+fail:
+	if (cause != NULL) {
+		xasprintf(cause, "error creating %s (%s)", socket_path,
+		    strerror(errno));
+	}
+	return (-1);
+}
+
+/* Server error callback. */
+static enum cmd_retval
+server_start_error(struct cmdq_item *item, void *data)
+{
+	char	*error = data;
+
+	cmdq_error(item, "%s", error);
+	free(error);
+
+	return (CMD_RETURN_NORMAL);
 }
 
 /* Fork new server. */
@@ -142,6 +164,8 @@ server_start(struct tmuxproc *client, struct event_base *base, int lockfd,
 	int		 pair[2];
 	struct job	*job;
 	sigset_t	 set, oldset;
+	struct client	*c;
+	char		*cause = NULL;
 
 	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, pair) != 0)
 		fatal("socketpair failed");
@@ -183,11 +207,10 @@ server_start(struct tmuxproc *client, struct event_base *base, int lockfd,
 
 	gettimeofday(&start_time, NULL);
 
-	server_fd = server_create_socket();
+	server_fd = server_create_socket(&cause);
-	if (server_fd == -1)
+	if (server_fd != -1)
-		fatal("couldn't create socket");
 		server_update_socket();
-	server_client_create(pair[1]);
+	c = server_client_create(pair[1]);
 
 	if (lockfd >= 0) {
 		unlink(lockfile);
@@ -195,6 +218,11 @@ server_start(struct tmuxproc *client, struct event_base *base, int lockfd,
 		close(lockfd);
 	}
 
+	if (cause != NULL) {
+		cmdq_append(c, cmdq_get_callback(server_start_error, cause));
+		c->flags |= CLIENT_EXIT;
+	}
+
 	start_cfg();
 
 	server_add_accept(0);
@@ -375,7 +403,7 @@ server_signal(int sig)
 		break;
 	case SIGUSR1:
 		event_del(&server_ev_accept);
-		fd = server_create_socket();
+		fd = server_create_socket(NULL);
 		if (fd != -1) {
 			close(server_fd);
 			server_fd = fd;

tmux.h

@@ -1885,7 +1885,7 @@ void	 server_client_set_key_table(struct client *, const char *);
 const char *server_client_get_key_table(struct client *);
 int	 server_client_check_nested(struct client *);
 void	 server_client_handle_key(struct client *, key_code);
-void	 server_client_create(int);
+struct client *server_client_create(int);
 int	 server_client_open(struct client *, char **);
 void	 server_client_unref(struct client *);
 void	 server_client_lost(struct client *);