/*

 * An implementation of the host initiated guest snapshot for Hyper-V.

 *

 *

 * Copyright (C) 2013, Microsoft, Inc.

 * Author : K. Y. Srinivasan <kys@microsoft.com>

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 as published

 * by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or

 * NON INFRINGEMENT.  See the GNU General Public License for more

 * details.

 *

 */

#include <sys/types.h>

#include <sys/poll.h>

#include <sys/ioctl.h>

#include <sys/stat.h>

#include <sys/sysmacros.h>

#include <fcntl.h>

#include <stdio.h>

#include <mntent.h>

#include <stdlib.h>

#include <unistd.h>

#include <string.h>

#include <ctype.h>

#include <errno.h>

#include <linux/fs.h>

#include <linux/major.h>

#include <linux/hyperv.h>

#include <syslog.h>

#include <getopt.h>

#include <stdbool.h>

#include <dirent.h>

static bool fs_frozen;

/* Don't use syslog() in the function since that can cause write to disk */

static int vss_do_freeze(char *dir, unsigned int cmd)

{

	int ret, fd = open(dir, O_RDONLY);

	if (fd < 0)

		return 1;

	ret = ioctl(fd, cmd, 0);

	/*

	 * If a partition is mounted more than once, only the first

	 * FREEZE/THAW can succeed and the later ones will get

	 * EBUSY/EINVAL respectively: there could be 2 cases:

	 * 1) a user may mount the same partition to different directories

	 *  by mistake or on purpose;

	 * 2) The subvolume of btrfs appears to have the same partition

	 * mounted more than once.

	 */

	if (ret) {

		if ((cmd == FIFREEZE && errno == EBUSY) ||

		    (cmd == FITHAW && errno == EINVAL)) {

			close(fd);

			return 0;

		}

	}

	close(fd);

	return !!ret;

}

static bool is_dev_loop(const char *blkname)

{

	char *buffer;

	DIR *dir;

	struct dirent *entry;

	bool ret = false;

	buffer = malloc(PATH_MAX);

	if (!buffer) {

		syslog(LOG_ERR, "Can't allocate memory!");

		exit(1);

	}

	snprintf(buffer, PATH_MAX, "%s/loop", blkname);

	if (!access(buffer, R_OK | X_OK)) {

		ret = true;

		goto free_buffer;

	} else if (errno != ENOENT) {

		syslog(LOG_ERR, "Can't access: %s; error:%d %s!",

		       buffer, errno, strerror(errno));

	}

	snprintf(buffer, PATH_MAX, "%s/slaves", blkname);

	dir = opendir(buffer);

	if (!dir) {

		if (errno != ENOENT)

			syslog(LOG_ERR, "Can't opendir: %s; error:%d %s!",

			       buffer, errno, strerror(errno));

		goto free_buffer;

	}

	while ((entry = readdir(dir)) != NULL) {

		if (strcmp(entry->d_name, ".") == 0 ||

		    strcmp(entry->d_name, "..") == 0)

			continue;

		snprintf(buffer, PATH_MAX, "%s/slaves/%s", blkname,

			 entry->d_name);

		if (is_dev_loop(buffer)) {

			ret = true;

			break;

		}

	}

	closedir(dir);

free_buffer:

	free(buffer);

	return ret;

}

static int vss_operate(int operation)

{

	char match[] = "/dev/";

	FILE *mounts;

	struct mntent *ent;

	struct stat sb;

	char errdir[1024] = {0};

	char blkdir[23]; /* /sys/dev/block/XXX:XXX */

	unsigned int cmd;

	int error = 0, root_seen = 0, save_errno = 0;

	switch (operation) {

	case VSS_OP_FREEZE:

		cmd = FIFREEZE;

		break;

	case VSS_OP_THAW:

		cmd = FITHAW;

		break;

	default:

		return -1;

	}

	mounts = setmntent("/proc/mounts", "r");

	if (mounts == NULL)

		return -1;

	while ((ent = getmntent(mounts))) {

		if (strncmp(ent->mnt_fsname, match, strlen(match)))

			continue;

		if (stat(ent->mnt_fsname, &sb)) {

			syslog(LOG_ERR, "Can't stat: %s; error:%d %s!",

			       ent->mnt_fsname, errno, strerror(errno));

		} else {

			sprintf(blkdir, "/sys/dev/block/%d:%d",

				major(sb.st_rdev), minor(sb.st_rdev));

			if (is_dev_loop(blkdir))

				continue;

		}

		if (hasmntopt(ent, MNTOPT_RO) != NULL)

			continue;

		if (strcmp(ent->mnt_type, "vfat") == 0)

			continue;

		if (strcmp(ent->mnt_dir, "/") == 0) {

			root_seen = 1;

			continue;

		}

		error |= vss_do_freeze(ent->mnt_dir, cmd);

		if (operation == VSS_OP_FREEZE) {

			if (error)

				goto err;

			fs_frozen = true;

		}

	}

	endmntent(mounts);

	if (root_seen) {

		error |= vss_do_freeze("/", cmd);

		if (operation == VSS_OP_FREEZE) {

			if (error)

				goto err;

			fs_frozen = true;

		}

	}

	if (operation == VSS_OP_THAW && !error)

		fs_frozen = false;

	goto out;

err:

	save_errno = errno;

	if (ent) {

		strncpy(errdir, ent->mnt_dir, sizeof(errdir)-1);

		endmntent(mounts);

	}

	vss_operate(VSS_OP_THAW);

	fs_frozen = false;

	/* Call syslog after we thaw all filesystems */

	if (ent)

		syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",

		       errdir, save_errno, strerror(save_errno));

	else

		syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,

		       strerror(save_errno));

out:

	return error;

}

void print_usage(char *argv[])

{

	fprintf(stderr, "Usage: %s [options]\n"

		"Options are:\n"

		"  -n, --no-daemon        stay in foreground, don't daemonize\n"

		"  -h, --help             print this help\n", argv[0]);

}

int main(int argc, char *argv[])

{

	int vss_fd = -1, len;

	int error;

	struct pollfd pfd;

	int	op;

	struct hv_vss_msg vss_msg[1];

	int daemonize = 1, long_index = 0, opt;

	int in_handshake;

	__u32 kernel_modver;

	static struct option long_options[] = {

		{"help",	no_argument,	   0,  'h' },

		{"no-daemon",	no_argument,	   0,  'n' },

		{0,		0,		   0,  0   }

	};

	while ((opt = getopt_long(argc, argv, "hn", long_options,

				  &long_index)) != -1) {

		switch (opt) {

		case 'n':

			daemonize = 0;

			break;

		case 'h':

			print_usage(argv);

			exit(0);

		default:

			print_usage(argv);

			exit(EXIT_FAILURE);

		}

	}

	if (daemonize && daemon(1, 0))

		return 1;

	openlog("Hyper-V VSS", 0, LOG_USER);

	syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());

reopen_vss_fd:

	if (vss_fd != -1)

		close(vss_fd);

	if (fs_frozen) {

		if (vss_operate(VSS_OP_THAW) || fs_frozen) {

			syslog(LOG_ERR, "failed to thaw file system: err=%d",

			       errno);

			exit(EXIT_FAILURE);

		}

	}

	in_handshake = 1;

	vss_fd = open("/dev/vmbus/hv_vss", O_RDWR);

	if (vss_fd < 0) {

		syslog(LOG_ERR, "open /dev/vmbus/hv_vss failed; error: %d %s",

		       errno, strerror(errno));

		exit(EXIT_FAILURE);

	}

	/*

	 * Register ourselves with the kernel.

	 */

	vss_msg->vss_hdr.operation = VSS_OP_REGISTER1;

	len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));

	if (len < 0) {

		syslog(LOG_ERR, "registration to kernel failed; error: %d %s",

		       errno, strerror(errno));

		close(vss_fd);

		exit(EXIT_FAILURE);

	}

	pfd.fd = vss_fd;

	while (1) {

		pfd.events = POLLIN;

		pfd.revents = 0;

		if (poll(&pfd, 1, -1) < 0) {

			syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno));

			if (errno == EINVAL) {

				close(vss_fd);

				exit(EXIT_FAILURE);

			}

			else

				continue;

		}

		len = read(vss_fd, vss_msg, sizeof(struct hv_vss_msg));

		if (in_handshake) {

			if (len != sizeof(kernel_modver)) {

				syslog(LOG_ERR, "invalid version negotiation");

				exit(EXIT_FAILURE);

			}

			kernel_modver = *(__u32 *)vss_msg;

			in_handshake = 0;

			syslog(LOG_INFO, "VSS: kernel module version: %d",

			       kernel_modver);

			continue;

		}

		if (len != sizeof(struct hv_vss_msg)) {

			syslog(LOG_ERR, "read failed; error:%d %s",

			       errno, strerror(errno));

			goto reopen_vss_fd;

		}

		op = vss_msg->vss_hdr.operation;

		error =  HV_S_OK;

		switch (op) {

		case VSS_OP_FREEZE:

		case VSS_OP_THAW:

			error = vss_operate(op);

			syslog(LOG_INFO, "VSS: op=%s: %s\n",

				op == VSS_OP_FREEZE ? "FREEZE" : "THAW",

				error ? "failed" : "succeeded");

			if (error) {

				error = HV_E_FAIL;

				syslog(LOG_ERR, "op=%d failed!", op);

				syslog(LOG_ERR, "report it with these files:");

				syslog(LOG_ERR, "/etc/fstab and /proc/mounts");

			}

			break;

		case VSS_OP_HOT_BACKUP:

			syslog(LOG_INFO, "VSS: op=CHECK HOT BACKUP\n");

			break;

		default:

			syslog(LOG_ERR, "Illegal op:%d\n", op);

		}

		/*

		 * The write() may return an error due to the faked VSS_OP_THAW

		 * message upon hibernation. Ignore the error by resetting the

		 * dev file, i.e. closing and re-opening it.

		 */

		vss_msg->error = error;

		len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));

		if (len != sizeof(struct hv_vss_msg)) {

			syslog(LOG_ERR, "write failed; error: %d %s", errno,

			       strerror(errno));

			goto reopen_vss_fd;

		}

	}

	close(vss_fd);

	exit(0);

}