files: Create per-process transport sock and bind it

This will be used instead of currently existing per-fd
transport sockets, which are used on receive_fd stage.

v2: Create the socket before CR_STATE_FORKING state.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/cr-restore.c

@@ -267,10 +267,6 @@ static int root_prepare_shared(void)
 	if (ret)
 		goto err;
 
-	ret = open_transport_socket();
-	if (ret)
-		goto err;
-
 	show_saved_files();
 err:
 	return ret;
@@ -607,8 +603,6 @@ static int restore_one_alive_task(int pid, CoreEntry *core)
 	if (prepare_vmas(current, ta))
 		return -1;
 
-	close_service_fd(TRANSPORT_FD_OFF);
-
 	return sigreturn_restore(pid, ta, args_len, core);
 }
 
@@ -1349,6 +1343,9 @@ static int restore_task_with_children(void *_arg)
 		fini_restore_mntns();
 	}
 
+	if (open_transport_socket())
+		return -1;
+
 	if (restore_finish_stage(task_entries, CR_STATE_FORKING) < 0)
 		goto err;
 

criu/files.c

@@ -1229,6 +1229,7 @@ int prepare_fds(struct pstree_item *me)
 			break;
 	}
 out_w:
+	close_service_fd(TRANSPORT_FD_OFF);
 	if (rsti(me)->fdt)
 		futex_inc_and_wake(&rsti(me)->fdt->fdt_lock);
 out:
@@ -1663,15 +1664,28 @@ int inherit_fd_fini()
 	return 0;
 }
 
-int open_transport_socket()
+int open_transport_socket(void)
 {
-	int sock;
+	struct fdt *fdt = rsti(current)->fdt;
+	pid_t pid = current->pid.virt;
+	struct sockaddr_un saddr;
+	int sock, slen;
+
+	if (!task_alive(current) || (fdt && fdt->pid != pid))
+		return 0;
 
 	sock = socket(PF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC, 0);
 	if (sock < 0) {
 		pr_perror("Can't create socket");
 		return -1;
 	}
+
+	transport_name_gen(&saddr, &slen, pid, -1);
+	if (bind(sock, (struct sockaddr *)&saddr, slen) < 0) {
+		pr_perror("Can't bind transport socket %s", saddr.sun_path + 1);
+		return -1;
+	}
+
 	if (install_service_fd(TRANSPORT_FD_OFF, sock) < 0) {
 		close(sock);
 		return -1;

criu/util.c

@@ -484,6 +484,9 @@ int clone_service_fd(int id)
 		int old = __get_service_fd(i, service_fd_id);
 		int new = __get_service_fd(i, id);
 
+		/* Do not dup parent's transport fd */
+		if (i == TRANSPORT_FD_OFF)
+			continue;
 		ret = dup2(old, new);
 		if (ret == -1) {
 			if (errno == EBADF)