/*

 * An implementation of host to guest copy functionality for Linux.

 *

 * Copyright (C) 2014, 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 <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <string.h>

#include <errno.h>

#include <linux/hyperv.h>

#include <linux/limits.h>

#include <syslog.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <getopt.h>

static int target_fd;

static char target_fname[PATH_MAX];

static unsigned long long filesize;

static int hv_start_fcopy(struct hv_start_fcopy *smsg)

{

	int error = HV_E_FAIL;

	char *q, *p;

	filesize = 0;

	p = (char *)smsg->path_name;

	snprintf(target_fname, sizeof(target_fname), "%s/%s",

		 (char *)smsg->path_name, (char *)smsg->file_name);

	syslog(LOG_INFO, "Target file name: %s", target_fname);

	/*

	 * Check to see if the path is already in place; if not,

	 * create if required.

	 */

	while ((q = strchr(p, '/')) != NULL) {

		if (q == p) {

			p++;

			continue;

		}

		*q = '\0';

		if (access((char *)smsg->path_name, F_OK)) {

			if (smsg->copy_flags & CREATE_PATH) {

				if (mkdir((char *)smsg->path_name, 0755)) {

					syslog(LOG_ERR, "Failed to create %s",

						(char *)smsg->path_name);

					goto done;

				}

			} else {

				syslog(LOG_ERR, "Invalid path: %s",

					(char *)smsg->path_name);

				goto done;

			}

		}

		p = q + 1;

		*q = '/';

	}

	if (!access(target_fname, F_OK)) {

		syslog(LOG_INFO, "File: %s exists", target_fname);

		if (!(smsg->copy_flags & OVER_WRITE)) {

			error = HV_ERROR_ALREADY_EXISTS;

			goto done;

		}

	}

	target_fd = open(target_fname,

			 O_RDWR | O_CREAT | O_TRUNC | O_CLOEXEC, 0744);

	if (target_fd == -1) {

		syslog(LOG_INFO, "Open Failed: %s", strerror(errno));

		goto done;

	}

	error = 0;

done:

	if (error)

		target_fname[0] = '\0';

	return error;

}

static int hv_copy_data(struct hv_do_fcopy *cpmsg)

{

	ssize_t bytes_written;

	int ret = 0;

	bytes_written = pwrite(target_fd, cpmsg->data, cpmsg->size,

				cpmsg->offset);

	filesize += cpmsg->size;

	if (bytes_written != cpmsg->size) {

		switch (errno) {

		case ENOSPC:

			ret = HV_ERROR_DISK_FULL;

			break;

		default:

			ret = HV_E_FAIL;

			break;

		}

		syslog(LOG_ERR, "pwrite failed to write %llu bytes: %ld (%s)",

		       filesize, (long)bytes_written, strerror(errno));

	}

	return ret;

}

/*

 * Reset target_fname to "" in the two below functions for hibernation: if

 * the fcopy operation is aborted by hibernation, the daemon should remove the

 * partially-copied file; to achieve this, the hv_utils driver always fakes a

 * CANCEL_FCOPY message upon suspend, and later when the VM resumes back,

 * the daemon calls hv_copy_cancel() to remove the file; if a file is copied

 * successfully before suspend, hv_copy_finished() must reset target_fname to

 * avoid that the file can be incorrectly removed upon resume, since the faked

 * CANCEL_FCOPY message is spurious in this case.

 */

static int hv_copy_finished(void)

{

	close(target_fd);

	target_fname[0] = '\0';

	return 0;

}

static int hv_copy_cancel(void)

{

	close(target_fd);

	if (strlen(target_fname) > 0) {

		unlink(target_fname);

		target_fname[0] = '\0';

	}

	return 0;

}

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 fcopy_fd = -1;

	int error;

	int daemonize = 1, long_index = 0, opt;

	int version = FCOPY_CURRENT_VERSION;

	union {

		struct hv_fcopy_hdr hdr;

		struct hv_start_fcopy start;

		struct hv_do_fcopy copy;

		__u32 kernel_modver;

	} buffer = { };

	int in_handshake;

	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':

		default:

			print_usage(argv);

			exit(EXIT_FAILURE);

		}

	}

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

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

		exit(EXIT_FAILURE);

	}

	openlog("HV_FCOPY", 0, LOG_USER);

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

reopen_fcopy_fd:

	if (fcopy_fd != -1)

		close(fcopy_fd);

	/* Remove any possible partially-copied file on error */

	hv_copy_cancel();

	in_handshake = 1;

	fcopy_fd = open("/dev/vmbus/hv_fcopy", O_RDWR);

	if (fcopy_fd < 0) {

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

			errno, strerror(errno));

		exit(EXIT_FAILURE);

	}

	/*

	 * Register with the kernel.

	 */

	if ((write(fcopy_fd, &version, sizeof(int))) != sizeof(int)) {

		syslog(LOG_ERR, "Registration failed: %s", strerror(errno));

		exit(EXIT_FAILURE);

	}

	while (1) {

		/*

		 * In this loop we process fcopy messages after the

		 * handshake is complete.

		 */

		ssize_t len;

		len = pread(fcopy_fd, &buffer, sizeof(buffer), 0);

		if (len < 0) {

			syslog(LOG_ERR, "pread failed: %s", strerror(errno));

			goto reopen_fcopy_fd;

		}

		if (in_handshake) {

			if (len != sizeof(buffer.kernel_modver)) {

				syslog(LOG_ERR, "invalid version negotiation");

				exit(EXIT_FAILURE);

			}

			in_handshake = 0;

			syslog(LOG_INFO, "kernel module version: %u",

			       buffer.kernel_modver);

			continue;

		}

		switch (buffer.hdr.operation) {

		case START_FILE_COPY:

			error = hv_start_fcopy(&buffer.start);

			break;

		case WRITE_TO_FILE:

			error = hv_copy_data(&buffer.copy);

			break;

		case COMPLETE_FCOPY:

			error = hv_copy_finished();

			break;

		case CANCEL_FCOPY:

			error = hv_copy_cancel();

			break;

		default:

			error = HV_E_FAIL;

			syslog(LOG_ERR, "Unknown operation: %d",

				buffer.hdr.operation);

		}

		/*

		 * pwrite() may return an error due to the faked CANCEL_FCOPY

		 * message upon hibernation. Ignore the error by resetting the

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

		 */

		if (pwrite(fcopy_fd, &error, sizeof(int), 0) != sizeof(int)) {

			syslog(LOG_ERR, "pwrite failed: %s", strerror(errno));

			goto reopen_fcopy_fd;

		}

	}

}