tools/hv/hv_vss_daemon.c

   1 /*
   2  * An implementation of the host initiated guest snapshot for Hyper-V.
   3  *
   4  *
   5  * Copyright (C) 2013, Microsoft, Inc.
   6  * Author : K. Y. Srinivasan <kys@microsoft.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License version 2 as published
  10  * by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  15  * NON INFRINGEMENT.  See the GNU General Public License for more
  16  * details.
  17  *
  18  */
  19
  20
  21 #include <sys/types.h>
  22 #include <sys/socket.h>
  23 #include <sys/poll.h>
  24 #include <sys/ioctl.h>
  25 #include <fcntl.h>
  26 #include <stdio.h>
  27 #include <mntent.h>
  28 #include <stdlib.h>
  29 #include <unistd.h>
  30 #include <string.h>
  31 #include <ctype.h>
  32 #include <errno.h>
  33 #include <arpa/inet.h>
  34 #include <linux/fs.h>
  35 #include <linux/connector.h>
  36 #include <linux/hyperv.h>
  37 #include <linux/netlink.h>
  38 #include <syslog.h>
  39 #include <getopt.h>
  40
  41 static struct sockaddr_nl addr;
  42
  43 #ifndef SOL_NETLINK
  44 #define SOL_NETLINK 270
  45 #endif
  46
  47
  48 /* Don't use syslog() in the function since that can cause write to disk */
  49 static int vss_do_freeze(char *dir, unsigned int cmd)
  50 {
  51         int ret, fd = open(dir, O_RDONLY);
  52
  53         if (fd < 0)
  54                 return 1;
  55
  56         ret = ioctl(fd, cmd, 0);
  57
  58         /*
  59          * If a partition is mounted more than once, only the first
  60          * FREEZE/THAW can succeed and the later ones will get
  61          * EBUSY/EINVAL respectively: there could be 2 cases:
  62          * 1) a user may mount the same partition to differnt directories
  63          *  by mistake or on purpose;
  64          * 2) The subvolume of btrfs appears to have the same partition
  65          * mounted more than once.
  66          */
  67         if (ret) {
  68                 if ((cmd == FIFREEZE && errno == EBUSY) ||
  69                     (cmd == FITHAW && errno == EINVAL)) {
  70                         close(fd);
  71                         return 0;
  72                 }
  73         }
  74
  75         close(fd);
  76         return !!ret;
  77 }
  78
  79 static int vss_operate(int operation)
  80 {
  81         char match[] = "/dev/";
  82         FILE *mounts;
  83         struct mntent *ent;
  84         unsigned int cmd;
  85         int error = 0, root_seen = 0, save_errno = 0;
  86
  87         switch (operation) {
  88         case VSS_OP_FREEZE:
  89                 cmd = FIFREEZE;
  90                 break;
  91         case VSS_OP_THAW:
  92                 cmd = FITHAW;
  93                 break;
  94         default:
  95                 return -1;
  96         }
  97
  98         mounts = setmntent("/proc/mounts", "r");
  99         if (mounts == NULL)
 100                 return -1;
 101
 102         while ((ent = getmntent(mounts))) {
 103                 if (strncmp(ent->mnt_fsname, match, strlen(match)))
 104                         continue;
 105                 if (hasmntopt(ent, MNTOPT_RO) != NULL)
 106                         continue;
 107                 if (strcmp(ent->mnt_type, "vfat") == 0)
 108                         continue;
 109                 if (strcmp(ent->mnt_dir, "/") == 0) {
 110                         root_seen = 1;
 111                         continue;
 112                 }
 113                 error |= vss_do_freeze(ent->mnt_dir, cmd);
 114                 if (error && operation == VSS_OP_FREEZE)
 115                         goto err;
 116         }
 117
 118         if (root_seen) {
 119                 error |= vss_do_freeze("/", cmd);
 120                 if (error && operation == VSS_OP_FREEZE)
 121                         goto err;
 122         }
 123
 124         goto out;
 125 err:
 126         save_errno = errno;
 127         vss_operate(VSS_OP_THAW);
 128         /* Call syslog after we thaw all filesystems */
 129         if (ent)
 130                 syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",
 131                        ent->mnt_dir, save_errno, strerror(save_errno));
 132         else
 133                 syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,
 134                        strerror(save_errno));
 135 out:
 136         endmntent(mounts);
 137         return error;
 138 }
 139
 140 static int netlink_send(int fd, struct cn_msg *msg)
 141 {
 142         struct nlmsghdr nlh = { .nlmsg_type = NLMSG_DONE };
 143         unsigned int size;
 144         struct msghdr message;
 145         struct iovec iov[2];
 146
 147         size = sizeof(struct cn_msg) + msg->len;
 148
 149         nlh.nlmsg_pid = getpid();
 150         nlh.nlmsg_len = NLMSG_LENGTH(size);
 151
 152         iov[0].iov_base = &nlh;
 153         iov[0].iov_len = sizeof(nlh);
 154
 155         iov[1].iov_base = msg;
 156         iov[1].iov_len = size;
 157
 158         memset(&message, 0, sizeof(message));
 159         message.msg_name = &addr;
 160         message.msg_namelen = sizeof(addr);
 161         message.msg_iov = iov;
 162         message.msg_iovlen = 2;
 163
 164         return sendmsg(fd, &message, 0);
 165 }
 166
 167 void print_usage(char *argv[])
 168 {
 169         fprintf(stderr, "Usage: %s [options]\n"
 170                 "Options are:\n"
 171                 "  -n, --no-daemon        stay in foreground, don't daemonize\n"
 172                 "  -h, --help             print this help\n", argv[0]);
 173 }
 174
 175 int main(int argc, char *argv[])
 176 {
 177         int fd, len, nl_group;
 178         int error;
 179         struct cn_msg *message;
 180         struct pollfd pfd;
 181         struct nlmsghdr *incoming_msg;
 182         struct cn_msg   *incoming_cn_msg;
 183         int     op;
 184         struct hv_vss_msg *vss_msg;
 185         char *vss_recv_buffer;
 186         size_t vss_recv_buffer_len;
 187         int daemonize = 1, long_index = 0, opt;
 188
 189         static struct option long_options[] = {
 190                 {"help",        no_argument,       0,  'h' },
 191                 {"no-daemon",   no_argument,       0,  'n' },
 192                 {0,             0,                 0,  0   }
 193         };
 194
 195         while ((opt = getopt_long(argc, argv, "hn", long_options,
 196                                   &long_index)) != -1) {
 197                 switch (opt) {
 198                 case 'n':
 199                         daemonize = 0;
 200                         break;
 201                 case 'h':
 202                 default:
 203                         print_usage(argv);
 204                         exit(EXIT_FAILURE);
 205                 }
 206         }
 207
 208         if (daemonize && daemon(1, 0))
 209                 return 1;
 210
 211         openlog("Hyper-V VSS", 0, LOG_USER);
 212         syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());
 213
 214         vss_recv_buffer_len = NLMSG_LENGTH(0) + sizeof(struct cn_msg) + sizeof(struct hv_vss_msg);
 215         vss_recv_buffer = calloc(1, vss_recv_buffer_len);
 216         if (!vss_recv_buffer) {
 217                 syslog(LOG_ERR, "Failed to allocate netlink buffers");
 218                 exit(EXIT_FAILURE);
 219         }
 220
 221         fd = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR);
 222         if (fd < 0) {
 223                 syslog(LOG_ERR, "netlink socket creation failed; error:%d %s",
 224                                 errno, strerror(errno));
 225                 exit(EXIT_FAILURE);
 226         }
 227         addr.nl_family = AF_NETLINK;
 228         addr.nl_pad = 0;
 229         addr.nl_pid = 0;
 230         addr.nl_groups = 0;
 231
 232
 233         error = bind(fd, (struct sockaddr *)&addr, sizeof(addr));
 234         if (error < 0) {
 235                 syslog(LOG_ERR, "bind failed; error:%d %s", errno, strerror(errno));
 236                 close(fd);
 237                 exit(EXIT_FAILURE);
 238         }
 239         nl_group = CN_VSS_IDX;
 240         if (setsockopt(fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &nl_group, sizeof(nl_group)) < 0) {
 241                 syslog(LOG_ERR, "setsockopt failed; error:%d %s", errno, strerror(errno));
 242                 close(fd);
 243                 exit(EXIT_FAILURE);
 244         }
 245         /*
 246          * Register ourselves with the kernel.
 247          */
 248         message = (struct cn_msg *)vss_recv_buffer;
 249         message->id.idx = CN_VSS_IDX;
 250         message->id.val = CN_VSS_VAL;
 251         message->ack = 0;
 252         vss_msg = (struct hv_vss_msg *)message->data;
 253         vss_msg->vss_hdr.operation = VSS_OP_REGISTER;
 254
 255         message->len = sizeof(struct hv_vss_msg);
 256
 257         len = netlink_send(fd, message);
 258         if (len < 0) {
 259                 syslog(LOG_ERR, "netlink_send failed; error:%d %s", errno, strerror(errno));
 260                 close(fd);
 261                 exit(EXIT_FAILURE);
 262         }
 263
 264         pfd.fd = fd;
 265
 266         while (1) {
 267                 struct sockaddr *addr_p = (struct sockaddr *) &addr;
 268                 socklen_t addr_l = sizeof(addr);
 269                 pfd.events = POLLIN;
 270                 pfd.revents = 0;
 271
 272                 if (poll(&pfd, 1, -1) < 0) {
 273                         syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno));
 274                         if (errno == EINVAL) {
 275                                 close(fd);
 276                                 exit(EXIT_FAILURE);
 277                         }
 278                         else
 279                                 continue;
 280                 }
 281
 282                 len = recvfrom(fd, vss_recv_buffer, vss_recv_buffer_len, 0,
 283                                 addr_p, &addr_l);
 284
 285                 if (len < 0) {
 286                         syslog(LOG_ERR, "recvfrom failed; pid:%u error:%d %s",
 287                                         addr.nl_pid, errno, strerror(errno));
 288                         close(fd);
 289                         return -1;
 290                 }
 291
 292                 if (addr.nl_pid) {
 293                         syslog(LOG_WARNING,
 294                                 "Received packet from untrusted pid:%u",
 295                                 addr.nl_pid);
 296                         continue;
 297                 }
 298
 299                 incoming_msg = (struct nlmsghdr *)vss_recv_buffer;
 300
 301                 if (incoming_msg->nlmsg_type != NLMSG_DONE)
 302                         continue;
 303
 304                 incoming_cn_msg = (struct cn_msg *)NLMSG_DATA(incoming_msg);
 305                 vss_msg = (struct hv_vss_msg *)incoming_cn_msg->data;
 306                 op = vss_msg->vss_hdr.operation;
 307                 error =  HV_S_OK;
 308
 309                 switch (op) {
 310                 case VSS_OP_FREEZE:
 311                 case VSS_OP_THAW:
 312                         error = vss_operate(op);
 313                         syslog(LOG_INFO, "VSS: op=%s: %s\n",
 314                                 op == VSS_OP_FREEZE ? "FREEZE" : "THAW",
 315                                 error ? "failed" : "succeeded");
 316
 317                         if (error) {
 318                                 error = HV_E_FAIL;
 319                                 syslog(LOG_ERR, "op=%d failed!", op);
 320                                 syslog(LOG_ERR, "report it with these files:");
 321                                 syslog(LOG_ERR, "/etc/fstab and /proc/mounts");
 322                         }
 323                         break;
 324                 default:
 325                         syslog(LOG_ERR, "Illegal op:%d\n", op);
 326                 }
 327                 vss_msg->error = error;
 328                 len = netlink_send(fd, incoming_cn_msg);
 329                 if (len < 0) {
 330                         syslog(LOG_ERR, "net_link send failed; error:%d %s",
 331                                         errno, strerror(errno));
 332                         exit(EXIT_FAILURE);
 333                 }
 334         }
 335
 336 }