criu/fifo.c

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>

#include "crtools.h"
#include "image.h"
#include "files.h"
#include "files-reg.h"
#include "pipes.h"

#include "fifo.h"

/*
 * FIFO checkpoint and restore is done in a bit unusual manner.
 * We use files-reg.c engine to save fifo path and flags,
 * thus regular files image will contain fifo descriptos which
 * are useless for reg-files engine itself but needed for our fifo
 * engine.
 *
 * In particual we dump fifo-entry automatically and appropriate
 * reg-file entry manually, thus on restore we need to ask reg-file
 * engine to restore fifo path and flags via direct call.
 */

struct fifo_info {
	struct list_head	list;
	struct file_desc	d;
	struct fifo_entry	*fe;
	bool			restore_data;
};

static LIST_HEAD(fifo_head);
static struct pipe_data_dump pd_fifo = { .img_type = CR_FD_FIFO_DATA, };

static int dump_one_fifo(int lfd, u32 id, const struct fd_parms *p)
{
	int img = fdset_fd(glob_fdset, CR_FD_FIFO);
	struct fifo_entry e;

	/*
	 * It's a trick here, we use regular files dumping
	 * code to save path to a fifo, then we reuse it
	 * on restore.
	 */
	if (dump_one_reg_file(lfd, id, p))
		return -1;

	pr_info("Dumping fifo %d with id %#x pipe_id %#x\n",
			lfd, id, pipe_id(p));

	e.id		= id;
	e.pipe_id	= pipe_id(p);

	if (write_img(img, &e) < 0)
		return -1;

	return dump_one_pipe_data(&pd_fifo, lfd, p);
}

static const struct fdtype_ops fifo_ops = {
	.type		= FDINFO_FIFO,
	.make_gen_id	= make_gen_id,
	.dump		= dump_one_fifo,
};

int dump_fifo(struct fd_parms *p, int lfd, const struct cr_fdset *set)
{
	return do_dump_gen_file(p, lfd, &fifo_ops, set);
}

static struct pipe_data_rst *pd_hash_fifo[PIPE_DATA_HASH_SIZE];

static int do_open_fifo(struct reg_file_info *rfi, void *arg)
{
	struct fifo_info *info = arg;
	int new_fifo, fake_fifo = -1;

	/*
	 * The fifos (except read-write fifos) do wait until
	 * another pipe-end get connected, so to be able to
	 * proceed the restoration procedure we open a fake
	 * fifo here.
	 */
	fake_fifo = open(rfi->path, O_RDWR);
	if (fake_fifo < 0) {
		pr_perror("Can't open fake fifo %#x [%s]", info->fe->id, rfi->path);
		return -1;
	}

	new_fifo = open(rfi->path, rfi->rfe.flags);
	if (new_fifo < 0) {
		pr_perror("Can't open fifo %#x [%s]", info->fe->id, rfi->path);
		goto out;
	}

	if (info->restore_data)
		if (restore_pipe_data(CR_FD_FIFO_DATA, fake_fifo,
					info->fe->pipe_id, pd_hash_fifo)) {
			close(new_fifo);
			new_fifo = -1;
		}

out:
	close(fake_fifo);
	return new_fifo;
}

static int open_fifo_fd(struct file_desc *d)
{
	struct fifo_info *info = container_of(d, struct fifo_info, d);

	return open_path_by_id(info->fe->id, do_open_fifo, info);
}

static struct file_desc_ops fifo_desc_ops = {
	.type		= FDINFO_FIFO,
	.open		= open_fifo_fd,
};

int collect_fifo(void)
{
	struct fifo_info *info = NULL, *f;
	int img, ret;

	img = open_image_ro(CR_FD_FIFO);
	if (img < 0)
		return -1;

	while (1) {
		ret = -1;
		info = xzalloc(sizeof(*info));
		if (!info)
			break;

		info->fe = xzalloc(sizeof(*info->fe));
		if (!info->fe)
			break;

		ret = read_img_eof(img, info->fe);
		if (ret <= 0)
			break;

		pr_info("Collected fifo entry ID %#x PIPE ID %#x\n",
			info->fe->id, info->fe->pipe_id);

		file_desc_add(&info->d, info->fe->id, &fifo_desc_ops);

		/* check who will restore the fifo data */
		list_for_each_entry(f, &fifo_head, list)
			if (f->fe->pipe_id == info->fe->pipe_id)
				break;

		if (&f->list == &fifo_head) {
			list_add(&info->list, &fifo_head);
			info->restore_data = true;
		}
	}

	xfree(info ? info->fe : NULL);
	xfree(info);
	close(img);

	return collect_pipe_data(CR_FD_FIFO_DATA, pd_hash_fifo);
}