2 * An implementation of the host initiated guest snapshot for Hyper-V.
5 * Copyright (C) 2013, Microsoft, Inc.
6 * Author : K. Y. Srinivasan <kys@microsoft.com>
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.
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
21 #include <sys/types.h>
22 #include <sys/socket.h>
24 #include <sys/ioctl.h>
33 #include <arpa/inet.h>
35 #include <linux/connector.h>
36 #include <linux/hyperv.h>
37 #include <linux/netlink.h>
41 static struct sockaddr_nl addr;
44 #define SOL_NETLINK 270
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)
51 int ret, fd = open(dir, O_RDONLY);
56 ret = ioctl(fd, cmd, 0);
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.
68 if ((cmd == FIFREEZE && errno == EBUSY) ||
69 (cmd == FITHAW && errno == EINVAL)) {
79 static int vss_operate(int operation)
81 char match[] = "/dev/";
85 int error = 0, root_seen = 0, save_errno = 0;
98 mounts = setmntent("/proc/mounts", "r");
102 while ((ent = getmntent(mounts))) {
103 if (strncmp(ent->mnt_fsname, match, strlen(match)))
105 if (hasmntopt(ent, MNTOPT_RO) != NULL)
107 if (strcmp(ent->mnt_type, "vfat") == 0)
109 if (strcmp(ent->mnt_dir, "/") == 0) {
113 error |= vss_do_freeze(ent->mnt_dir, cmd);
114 if (error && operation == VSS_OP_FREEZE)
119 error |= vss_do_freeze("/", cmd);
120 if (error && operation == VSS_OP_FREEZE)
127 vss_operate(VSS_OP_THAW);
128 /* Call syslog after we thaw all filesystems */
130 syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",
131 ent->mnt_dir, save_errno, strerror(save_errno));
133 syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,
134 strerror(save_errno));
140 static int netlink_send(int fd, struct cn_msg *msg)
142 struct nlmsghdr nlh = { .nlmsg_type = NLMSG_DONE };
144 struct msghdr message;
147 size = sizeof(struct cn_msg) + msg->len;
149 nlh.nlmsg_pid = getpid();
150 nlh.nlmsg_len = NLMSG_LENGTH(size);
152 iov[0].iov_base = &nlh;
153 iov[0].iov_len = sizeof(nlh);
155 iov[1].iov_base = msg;
156 iov[1].iov_len = size;
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;
164 return sendmsg(fd, &message, 0);
167 void print_usage(char *argv[])
169 fprintf(stderr, "Usage: %s [options]\n"
171 " -n, --no-daemon stay in foreground, don't daemonize\n"
172 " -h, --help print this help\n", argv[0]);
175 int main(int argc, char *argv[])
177 int fd, len, nl_group;
179 struct cn_msg *message;
181 struct nlmsghdr *incoming_msg;
182 struct cn_msg *incoming_cn_msg;
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;
189 static struct option long_options[] = {
190 {"help", no_argument, 0, 'h' },
191 {"no-daemon", no_argument, 0, 'n' },
195 while ((opt = getopt_long(argc, argv, "hn", long_options,
196 &long_index)) != -1) {
208 if (daemonize && daemon(1, 0))
211 openlog("Hyper-V VSS", 0, LOG_USER);
212 syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());
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");
221 fd = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR);
223 syslog(LOG_ERR, "netlink socket creation failed; error:%d %s",
224 errno, strerror(errno));
227 addr.nl_family = AF_NETLINK;
233 error = bind(fd, (struct sockaddr *)&addr, sizeof(addr));
235 syslog(LOG_ERR, "bind failed; error:%d %s", errno, strerror(errno));
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));
246 * Register ourselves with the kernel.
248 message = (struct cn_msg *)vss_recv_buffer;
249 message->id.idx = CN_VSS_IDX;
250 message->id.val = CN_VSS_VAL;
252 vss_msg = (struct hv_vss_msg *)message->data;
253 vss_msg->vss_hdr.operation = VSS_OP_REGISTER;
255 message->len = sizeof(struct hv_vss_msg);
257 len = netlink_send(fd, message);
259 syslog(LOG_ERR, "netlink_send failed; error:%d %s", errno, strerror(errno));
267 struct sockaddr *addr_p = (struct sockaddr *) &addr;
268 socklen_t addr_l = sizeof(addr);
272 if (poll(&pfd, 1, -1) < 0) {
273 syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno));
274 if (errno == EINVAL) {
282 len = recvfrom(fd, vss_recv_buffer, vss_recv_buffer_len, 0,
286 syslog(LOG_ERR, "recvfrom failed; pid:%u error:%d %s",
287 addr.nl_pid, errno, strerror(errno));
294 "Received packet from untrusted pid:%u",
299 incoming_msg = (struct nlmsghdr *)vss_recv_buffer;
301 if (incoming_msg->nlmsg_type != NLMSG_DONE)
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;
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");
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");
325 syslog(LOG_ERR, "Illegal op:%d\n", op);
327 vss_msg->error = error;
328 len = netlink_send(fd, incoming_cn_msg);
330 syslog(LOG_ERR, "net_link send failed; error:%d %s",
331 errno, strerror(errno));