// SPDX-License-Identifier: GPL-2.0-only
/*
 * An implementation of host to guest copy functionality for Linux.
 *
 * Copyright (C) 2014, Microsoft, Inc.
 *
 * Author : K. Y. Srinivasan <kys@microsoft.com>
 */


#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;
                }
        }
}