/*
 * 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 <sys/socket.h>
#include <sys/poll.h>
#include <linux/types.h>
#include <linux/kdev_t.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <linux/hyperv.h>
#include <syslog.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <dirent.h>

static int target_fd;
static char target_fname[W_MAX_PATH];

static int hv_start_fcopy(struct hv_start_fcopy *smsg)
{
	int error = HV_E_FAIL;
	char *q, *p;

	/*
	 * If possile append a path seperator to the path.
	 */
	if (strlen((char *)smsg->path_name) < (W_MAX_PATH - 2))
		strcat((char *)smsg->path_name, "/");

	p = (char *)smsg->path_name;
	snprintf(target_fname, sizeof(target_fname), "%s/%s",
		(char *)smsg->path_name, 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_CLOEXEC, 0744);
	if (target_fd == -1) {
		syslog(LOG_INFO, "Open Failed: %s", strerror(errno));
		goto done;
	}

	error = 0;
done:
	return error;
}

static int hv_copy_data(struct hv_do_fcopy *cpmsg)
{
	ssize_t bytes_written;

	bytes_written = pwrite(target_fd, cpmsg->data, cpmsg->size,
				cpmsg->offset);

	if (bytes_written != cpmsg->size)
		return HV_E_FAIL;

	return 0;
}

static int hv_copy_finished(void)
{
	close(target_fd);
	return 0;
}
static int hv_copy_cancel(void)
{
	close(target_fd);
	unlink(target_fname);
	return 0;

}

int main(void)
{
	int fd, fcopy_fd, len;
	int error;
	int version = FCOPY_CURRENT_VERSION;
	char *buffer[4096 * 2];
	struct hv_fcopy_hdr *in_msg;

	if (daemon(1, 0)) {
		syslog(LOG_ERR, "daemon() failed; error: %s", strerror(errno));
		exit(EXIT_FAILURE);
	}

	openlog("HV_FCOPY", 0, LOG_USER);
	syslog(LOG_INFO, "HV_FCOPY starting; pid is:%d", getpid());

	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.
		 */
		len = pread(fcopy_fd, buffer, (4096 * 2), 0);
		if (len < 0) {
			syslog(LOG_ERR, "pread failed: %s", strerror(errno));
			exit(EXIT_FAILURE);
		}
		in_msg = (struct hv_fcopy_hdr *)buffer;

		switch (in_msg->operation) {
		case START_FILE_COPY:
			error = hv_start_fcopy((struct hv_start_fcopy *)in_msg);
			break;
		case WRITE_TO_FILE:
			error = hv_copy_data((struct hv_do_fcopy *)in_msg);
			break;
		case COMPLETE_FCOPY:
			error = hv_copy_finished();
			break;
		case CANCEL_FCOPY:
			error = hv_copy_cancel();
			break;

		default:
			syslog(LOG_ERR, "Unknown operation: %d",
				in_msg->operation);

		}

		if (pwrite(fcopy_fd, &error, sizeof(int), 0) != sizeof(int)) {
			syslog(LOG_ERR, "pwrite failed: %s", strerror(errno));
			exit(EXIT_FAILURE);
		}
	}
}