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TOMOYO Linux Cross Reference
Linux/tools/hv/hv_vss_daemon.c

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  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         char errdir[1024] = {0};
 85         unsigned int cmd;
 86         int error = 0, root_seen = 0, save_errno = 0;
 87 
 88         switch (operation) {
 89         case VSS_OP_FREEZE:
 90                 cmd = FIFREEZE;
 91                 break;
 92         case VSS_OP_THAW:
 93                 cmd = FITHAW;
 94                 break;
 95         default:
 96                 return -1;
 97         }
 98 
 99         mounts = setmntent("/proc/mounts", "r");
100         if (mounts == NULL)
101                 return -1;
102 
103         while ((ent = getmntent(mounts))) {
104                 if (strncmp(ent->mnt_fsname, match, strlen(match)))
105                         continue;
106                 if (hasmntopt(ent, MNTOPT_RO) != NULL)
107                         continue;
108                 if (strcmp(ent->mnt_type, "vfat") == 0)
109                         continue;
110                 if (strcmp(ent->mnt_dir, "/") == 0) {
111                         root_seen = 1;
112                         continue;
113                 }
114                 error |= vss_do_freeze(ent->mnt_dir, cmd);
115                 if (error && operation == VSS_OP_FREEZE)
116                         goto err;
117         }
118 
119         endmntent(mounts);
120 
121         if (root_seen) {
122                 error |= vss_do_freeze("/", cmd);
123                 if (error && operation == VSS_OP_FREEZE)
124                         goto err;
125         }
126 
127         goto out;
128 err:
129         save_errno = errno;
130         if (ent) {
131                 strncpy(errdir, ent->mnt_dir, sizeof(errdir)-1);
132                 endmntent(mounts);
133         }
134         vss_operate(VSS_OP_THAW);
135         /* Call syslog after we thaw all filesystems */
136         if (ent)
137                 syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",
138                        errdir, save_errno, strerror(save_errno));
139         else
140                 syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,
141                        strerror(save_errno));
142 out:
143         return error;
144 }
145 
146 static int netlink_send(int fd, struct cn_msg *msg)
147 {
148         struct nlmsghdr nlh = { .nlmsg_type = NLMSG_DONE };
149         unsigned int size;
150         struct msghdr message;
151         struct iovec iov[2];
152 
153         size = sizeof(struct cn_msg) + msg->len;
154 
155         nlh.nlmsg_pid = getpid();
156         nlh.nlmsg_len = NLMSG_LENGTH(size);
157 
158         iov[0].iov_base = &nlh;
159         iov[0].iov_len = sizeof(nlh);
160 
161         iov[1].iov_base = msg;
162         iov[1].iov_len = size;
163 
164         memset(&message, 0, sizeof(message));
165         message.msg_name = &addr;
166         message.msg_namelen = sizeof(addr);
167         message.msg_iov = iov;
168         message.msg_iovlen = 2;
169 
170         return sendmsg(fd, &message, 0);
171 }
172 
173 void print_usage(char *argv[])
174 {
175         fprintf(stderr, "Usage: %s [options]\n"
176                 "Options are:\n"
177                 "  -n, --no-daemon        stay in foreground, don't daemonize\n"
178                 "  -h, --help             print this help\n", argv[0]);
179 }
180 
181 int main(int argc, char *argv[])
182 {
183         int fd, len, nl_group;
184         int error;
185         struct cn_msg *message;
186         struct pollfd pfd;
187         struct nlmsghdr *incoming_msg;
188         struct cn_msg   *incoming_cn_msg;
189         int     op;
190         struct hv_vss_msg *vss_msg;
191         char *vss_recv_buffer;
192         size_t vss_recv_buffer_len;
193         int daemonize = 1, long_index = 0, opt;
194 
195         static struct option long_options[] = {
196                 {"help",        no_argument,       0,  'h' },
197                 {"no-daemon",   no_argument,       0,  'n' },
198                 {0,             0,                 0,  0   }
199         };
200 
201         while ((opt = getopt_long(argc, argv, "hn", long_options,
202                                   &long_index)) != -1) {
203                 switch (opt) {
204                 case 'n':
205                         daemonize = 0;
206                         break;
207                 case 'h':
208                 default:
209                         print_usage(argv);
210                         exit(EXIT_FAILURE);
211                 }
212         }
213 
214         if (daemonize && daemon(1, 0))
215                 return 1;
216 
217         openlog("Hyper-V VSS", 0, LOG_USER);
218         syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());
219 
220         vss_recv_buffer_len = NLMSG_LENGTH(0) + sizeof(struct cn_msg) + sizeof(struct hv_vss_msg);
221         vss_recv_buffer = calloc(1, vss_recv_buffer_len);
222         if (!vss_recv_buffer) {
223                 syslog(LOG_ERR, "Failed to allocate netlink buffers");
224                 exit(EXIT_FAILURE);
225         }
226 
227         fd = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR);
228         if (fd < 0) {
229                 syslog(LOG_ERR, "netlink socket creation failed; error:%d %s",
230                                 errno, strerror(errno));
231                 exit(EXIT_FAILURE);
232         }
233         addr.nl_family = AF_NETLINK;
234         addr.nl_pad = 0;
235         addr.nl_pid = 0;
236         addr.nl_groups = 0;
237 
238 
239         error = bind(fd, (struct sockaddr *)&addr, sizeof(addr));
240         if (error < 0) {
241                 syslog(LOG_ERR, "bind failed; error:%d %s", errno, strerror(errno));
242                 close(fd);
243                 exit(EXIT_FAILURE);
244         }
245         nl_group = CN_VSS_IDX;
246         if (setsockopt(fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &nl_group, sizeof(nl_group)) < 0) {
247                 syslog(LOG_ERR, "setsockopt failed; error:%d %s", errno, strerror(errno));
248                 close(fd);
249                 exit(EXIT_FAILURE);
250         }
251         /*
252          * Register ourselves with the kernel.
253          */
254         message = (struct cn_msg *)vss_recv_buffer;
255         message->id.idx = CN_VSS_IDX;
256         message->id.val = CN_VSS_VAL;
257         message->ack = 0;
258         vss_msg = (struct hv_vss_msg *)message->data;
259         vss_msg->vss_hdr.operation = VSS_OP_REGISTER;
260 
261         message->len = sizeof(struct hv_vss_msg);
262 
263         len = netlink_send(fd, message);
264         if (len < 0) {
265                 syslog(LOG_ERR, "netlink_send failed; error:%d %s", errno, strerror(errno));
266                 close(fd);
267                 exit(EXIT_FAILURE);
268         }
269 
270         pfd.fd = fd;
271 
272         while (1) {
273                 struct sockaddr *addr_p = (struct sockaddr *) &addr;
274                 socklen_t addr_l = sizeof(addr);
275                 pfd.events = POLLIN;
276                 pfd.revents = 0;
277 
278                 if (poll(&pfd, 1, -1) < 0) {
279                         syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno));
280                         if (errno == EINVAL) {
281                                 close(fd);
282                                 exit(EXIT_FAILURE);
283                         }
284                         else
285                                 continue;
286                 }
287 
288                 len = recvfrom(fd, vss_recv_buffer, vss_recv_buffer_len, 0,
289                                 addr_p, &addr_l);
290 
291                 if (len < 0) {
292                         syslog(LOG_ERR, "recvfrom failed; pid:%u error:%d %s",
293                                         addr.nl_pid, errno, strerror(errno));
294                         close(fd);
295                         return -1;
296                 }
297 
298                 if (addr.nl_pid) {
299                         syslog(LOG_WARNING,
300                                 "Received packet from untrusted pid:%u",
301                                 addr.nl_pid);
302                         continue;
303                 }
304 
305                 incoming_msg = (struct nlmsghdr *)vss_recv_buffer;
306 
307                 if (incoming_msg->nlmsg_type != NLMSG_DONE)
308                         continue;
309 
310                 incoming_cn_msg = (struct cn_msg *)NLMSG_DATA(incoming_msg);
311                 vss_msg = (struct hv_vss_msg *)incoming_cn_msg->data;
312                 op = vss_msg->vss_hdr.operation;
313                 error =  HV_S_OK;
314 
315                 switch (op) {
316                 case VSS_OP_FREEZE:
317                 case VSS_OP_THAW:
318                         error = vss_operate(op);
319                         syslog(LOG_INFO, "VSS: op=%s: %s\n",
320                                 op == VSS_OP_FREEZE ? "FREEZE" : "THAW",
321                                 error ? "failed" : "succeeded");
322 
323                         if (error) {
324                                 error = HV_E_FAIL;
325                                 syslog(LOG_ERR, "op=%d failed!", op);
326                                 syslog(LOG_ERR, "report it with these files:");
327                                 syslog(LOG_ERR, "/etc/fstab and /proc/mounts");
328                         }
329                         break;
330                 default:
331                         syslog(LOG_ERR, "Illegal op:%d\n", op);
332                 }
333                 vss_msg->error = error;
334                 len = netlink_send(fd, incoming_cn_msg);
335                 if (len < 0) {
336                         syslog(LOG_ERR, "net_link send failed; error:%d %s",
337                                         errno, strerror(errno));
338                         exit(EXIT_FAILURE);
339                 }
340         }
341 
342 }
343 

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