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
41static 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 */
49static 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
79static 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;
128err:
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));
142out:
143	return error;
144}
145
146static 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
173void 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
181int 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