tty: Add restoration of controlling terminal v4

The idea behind is pretty simple -- once we find
that there is a controlling terminal present we
do call ioctl on appropriate /dev/pts/N.

This is done in a bit unusuall manner. When we
find that there is a controling terminal present
we do create an additional FdinfoEntry for it
with object id taken from existing master peer.

The file engine stack this new FdinfoEntry on
fd_info_head head list. Thus we will have at
least two entries on this list. One for real
Fdinfo associated with master peer and one for
our new generated Fdfinfo entry, it depends on
pid which one become a file master.

Finally we do use post_open_fd hook in our
tty code which allows us to open controlling
terminal and yield proper ioctl on it.

v2:
 - restore control terminals via service fd,
   still need to speedup service fd retrieval.

v3:
 - use prepare_ctl_tty() helper to generate
   control terminal fdinfo entry

v4:
 - use post_open_fd
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -134,6 +134,12 @@ static int prepare_shared(void)
 		ret = prepare_fd_pid(pi->pid.virt, pi->rst);
 		if (ret < 0)
 			break;
+
+		if (pi->ctl_tty_id) {
+			ret = prepare_ctl_tty(pi->pid.virt, pi->rst, pi->ctl_tty_id);
+			if (ret < 0)
+				break;
+		}
 	}
 
 	mark_pipe_master();

files.c

@@ -196,6 +196,25 @@ static int collect_fd(int pid, FdinfoEntry *e, struct rst_info *rst_info)
 	return 0;
 }
 
+int prepare_ctl_tty(int pid, struct rst_info *rst_info, u32 ctl_tty_id)
+{
+	FdinfoEntry *e = xmalloc(sizeof(*e));
+	if (!e)
+		return -1;
+	fdinfo_entry__init(e);
+
+	e->id		= ctl_tty_id;
+	e->fd		= get_service_fd(CTL_TTY_OFF);
+	e->type		= FD_TYPES__TTY;
+
+	if (collect_fd(pid, e, rst_info)) {
+		xfree(e);
+		return -1;
+	}
+
+	return 0;
+}
+
 int prepare_fd_pid(int pid, struct rst_info *rst_info)
 {
 	int fdinfo_fd, ret = 0;
@@ -358,6 +377,9 @@ static int post_open_fd(int pid, FdinfoEntry *fe, struct file_desc *d)
 	if (!d->ops->post_open)
 		return 0;
 
+	if (fe->fd == get_service_fd(CTL_TTY_OFF))
+		return d->ops->post_open(d, fe->fd);
+
 	fle = file_master(d);
 	if ((fle->pid != pid) || (fe->fd != fle->fe->fd))
 		return 0;

include/crtools.h

@@ -106,6 +106,7 @@ enum {
 	IMG_FD_OFF,
 	SELF_EXE_FD_OFF,
 	PROC_FD_OFF,
+	CTL_TTY_OFF,
 };
 
 int get_service_fd(int type);

include/files.h

@@ -87,6 +87,7 @@ extern void show_saved_files(void);
 
 extern int prepare_fds(struct pstree_item *me);
 extern int prepare_fd_pid(int pid, struct rst_info *rst_info);
+extern int prepare_ctl_tty(int pid, struct rst_info *rst_info, u32 ctl_tty_id);
 extern int prepare_shared_fdinfo(void);
 extern int get_filemap_fd(int pid, VmaEntry *vma_entry);
 extern int prepare_fs(int pid);

include/pstree.h

@@ -11,6 +11,7 @@ struct pstree_item {
 	pid_t			pgid;
 	pid_t			sid;
 	pid_t			born_sid;
+	u32			ctl_tty_id;
 	int			state;		/* TASK_XXX constants */
 	int			nr_threads;	/* number of threads */
 	struct pid		*threads;	/* array of threads */

tty.c

@@ -320,6 +320,55 @@ static int tty_get_pgrp(int fd)
 	return prgp;
 }
 
+static int tty_set_sid(int fd)
+{
+	if (ioctl(fd, TIOCSCTTY, 1)) {
+		pr_perror("Can't set sid on terminal fd %d\n", fd);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int tty_set_prgp(int fd, int group)
+{
+	if (ioctl(fd, TIOCSPGRP, &group)) {
+		pr_perror("Failed to set group %d on %d\n", group, fd);
+		return -1;
+	}
+	return 0;
+}
+
+static int tty_restore_ctl_terminal(struct file_desc *d, int fd)
+{
+	struct tty_info *info = container_of(d, struct tty_info, d);
+	int slave, ret = -1;
+	char pts_name[64];
+
+	if (fd != get_service_fd(CTL_TTY_OFF))
+		return 0;
+
+	snprintf(pts_name, sizeof(pts_name), PTS_FMT, info->tie->pty->index);
+	slave = open(pts_name, O_RDONLY);
+	if (slave < 0) {
+		pr_perror("Can't open %s", pts_name);
+		return -1;
+	}
+
+	pr_info("Restore session %d by %d tty (index %d)\n",
+		 info->tie->sid, (int)getpid(),
+		 info->tie->pty->index);
+
+	ret = tty_set_sid(slave);
+	if (!ret)
+		ret = tty_set_prgp(slave, info->tie->pgrp);
+
+	close(slave);
+	close(fd);
+
+	return ret;
+}
+
 static char *tty_type(struct tty_info *info)
 {
 	static char *tty_types[] = {
@@ -526,20 +575,44 @@ static int tty_transport(FdinfoEntry *fe, struct file_desc *d)
 static struct file_desc_ops tty_desc_ops = {
 	.type		= FD_TYPES__TTY,
 	.open		= tty_open,
+	.post_open	= tty_restore_ctl_terminal,
 	.want_transport = tty_transport,
 };
 
+static int tty_find_restoring_task(struct tty_info *info)
+{
+	struct pstree_item *item;
+
+	if (info->tie->sid == 0)
+		return 0;
+
+	pr_info("Set a control terminal to %d\n", info->tie->sid);
+
+	for_each_pstree_item(item) {
+		if (item->sid == info->tie->sid) {
+			item->ctl_tty_id = info->tfe->id;
+			return 0;
+		}
+	}
+
+	pr_err("No task found with sid %d\n", info->tie->sid);
+	return -1;
+}
+
 static int tty_setup_slavery(void)
 {
 	struct tty_info *info, *peer, *m;
 
 	list_for_each_entry(info, &all_ttys, list) {
+		tty_find_restoring_task(info);
 
 		peer = info;
 		list_for_each_entry_safe_continue(peer, m, &all_ttys, list) {
 			if (peer->tie->pty->index != info->tie->pty->index)
 				continue;
 
+			tty_find_restoring_task(peer);
+
 			list_add(&peer->sibling, &info->sibling);
 			list_del(&peer->list);
 		}