1 /*
2  * Copyright 6WIND S.A., 2014
3  *
4  * This work is licensed under the terms of the GNU GPL, version 2 or
5  * (at your option) any later version.  See the COPYING file in the
6  * top-level directory.
7  */
8 #include "qemu/osdep.h"
9 #include "qemu-common.h"
10 #include "qemu/host-utils.h"
11 #include "qemu/sockets.h"
12 
13 #include <sys/socket.h>
14 #include <sys/un.h>
15 
16 #include "ivshmem-server.h"
17 
18 /* log a message on stdout if verbose=1 */
19 #define IVSHMEM_SERVER_DEBUG(server, fmt, ...) do { \
20         if ((server)->verbose) {         \
21             printf(fmt, ## __VA_ARGS__); \
22         }                                \
23     } while (0)
24 
25 /** maximum size of a huge page, used by ivshmem_server_ftruncate() */
26 #define IVSHMEM_SERVER_MAX_HUGEPAGE_SIZE (1024 * 1024 * 1024)
27 
28 /** default listen backlog (number of sockets not accepted) */
29 #define IVSHMEM_SERVER_LISTEN_BACKLOG 10
30 
31 /* send message to a client unix socket */
32 static int
33 ivshmem_server_send_one_msg(int sock_fd, int64_t peer_id, int fd)
34 {
35     int ret;
36     struct msghdr msg;
37     struct iovec iov[1];
38     union {
39         struct cmsghdr cmsg;
40         char control[CMSG_SPACE(sizeof(int))];
41     } msg_control;
42     struct cmsghdr *cmsg;
43 
44     peer_id = GINT64_TO_LE(peer_id);
45     iov[0].iov_base = &peer_id;
46     iov[0].iov_len = sizeof(peer_id);
47 
48     memset(&msg, 0, sizeof(msg));
49     msg.msg_iov = iov;
50     msg.msg_iovlen = 1;
51 
52     /* if fd is specified, add it in a cmsg */
53     if (fd >= 0) {
54         memset(&msg_control, 0, sizeof(msg_control));
55         msg.msg_control = &msg_control;
56         msg.msg_controllen = sizeof(msg_control);
57         cmsg = CMSG_FIRSTHDR(&msg);
58         cmsg->cmsg_level = SOL_SOCKET;
59         cmsg->cmsg_type = SCM_RIGHTS;
60         cmsg->cmsg_len = CMSG_LEN(sizeof(int));
61         memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
62     }
63 
64     ret = sendmsg(sock_fd, &msg, 0);
65     if (ret <= 0) {
66         return -1;
67     }
68 
69     return 0;
70 }
71 
72 /* free a peer when the server advertises a disconnection or when the
73  * server is freed */
74 static void
75 ivshmem_server_free_peer(IvshmemServer *server, IvshmemServerPeer *peer)
76 {
77     unsigned vector;
78     IvshmemServerPeer *other_peer;
79 
80     IVSHMEM_SERVER_DEBUG(server, "free peer %" PRId64 "\n", peer->id);
81     close(peer->sock_fd);
82     QTAILQ_REMOVE(&server->peer_list, peer, next);
83 
84     /* advertise the deletion to other peers */
85     QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
86         ivshmem_server_send_one_msg(other_peer->sock_fd, peer->id, -1);
87     }
88 
89     for (vector = 0; vector < peer->vectors_count; vector++) {
90         event_notifier_cleanup(&peer->vectors[vector]);
91     }
92 
93     g_free(peer);
94 }
95 
96 /* send the peer id and the shm_fd just after a new client connection */
97 static int
98 ivshmem_server_send_initial_info(IvshmemServer *server, IvshmemServerPeer *peer)
99 {
100     int ret;
101 
102     /* send our protocol version first */
103     ret = ivshmem_server_send_one_msg(peer->sock_fd, IVSHMEM_PROTOCOL_VERSION,
104                                       -1);
105     if (ret < 0) {
106         IVSHMEM_SERVER_DEBUG(server, "cannot send version: %s\n",
107                              strerror(errno));
108         return -1;
109     }
110 
111     /* send the peer id to the client */
112     ret = ivshmem_server_send_one_msg(peer->sock_fd, peer->id, -1);
113     if (ret < 0) {
114         IVSHMEM_SERVER_DEBUG(server, "cannot send peer id: %s\n",
115                              strerror(errno));
116         return -1;
117     }
118 
119     /* send the shm_fd */
120     ret = ivshmem_server_send_one_msg(peer->sock_fd, -1, server->shm_fd);
121     if (ret < 0) {
122         IVSHMEM_SERVER_DEBUG(server, "cannot send shm fd: %s\n",
123                              strerror(errno));
124         return -1;
125     }
126 
127     return 0;
128 }
129 
130 /* handle message on listening unix socket (new client connection) */
131 static int
132 ivshmem_server_handle_new_conn(IvshmemServer *server)
133 {
134     IvshmemServerPeer *peer, *other_peer;
135     struct sockaddr_un unaddr;
136     socklen_t unaddr_len;
137     int newfd;
138     unsigned i;
139 
140     /* accept the incoming connection */
141     unaddr_len = sizeof(unaddr);
142     newfd = qemu_accept(server->sock_fd,
143                         (struct sockaddr *)&unaddr, &unaddr_len);
144 
145     if (newfd < 0) {
146         IVSHMEM_SERVER_DEBUG(server, "cannot accept() %s\n", strerror(errno));
147         return -1;
148     }
149 
150     qemu_set_nonblock(newfd);
151     IVSHMEM_SERVER_DEBUG(server, "accept()=%d\n", newfd);
152 
153     /* allocate new structure for this peer */
154     peer = g_malloc0(sizeof(*peer));
155     peer->sock_fd = newfd;
156 
157     /* get an unused peer id */
158     /* XXX: this could use id allocation such as Linux IDA, or simply
159      * a free-list */
160     for (i = 0; i < G_MAXUINT16; i++) {
161         if (ivshmem_server_search_peer(server, server->cur_id) == NULL) {
162             break;
163         }
164         server->cur_id++;
165     }
166     if (i == G_MAXUINT16) {
167         IVSHMEM_SERVER_DEBUG(server, "cannot allocate new client id\n");
168         close(newfd);
169         g_free(peer);
170         return -1;
171     }
172     peer->id = server->cur_id++;
173 
174     /* create eventfd, one per vector */
175     peer->vectors_count = server->n_vectors;
176     for (i = 0; i < peer->vectors_count; i++) {
177         if (event_notifier_init(&peer->vectors[i], FALSE) < 0) {
178             IVSHMEM_SERVER_DEBUG(server, "cannot create eventfd\n");
179             goto fail;
180         }
181     }
182 
183     /* send peer id and shm fd */
184     if (ivshmem_server_send_initial_info(server, peer) < 0) {
185         IVSHMEM_SERVER_DEBUG(server, "cannot send initial info\n");
186         goto fail;
187     }
188 
189     /* advertise the new peer to others */
190     QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
191         for (i = 0; i < peer->vectors_count; i++) {
192             ivshmem_server_send_one_msg(other_peer->sock_fd, peer->id,
193                                         peer->vectors[i].wfd);
194         }
195     }
196 
197     /* advertise the other peers to the new one */
198     QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
199         for (i = 0; i < peer->vectors_count; i++) {
200             ivshmem_server_send_one_msg(peer->sock_fd, other_peer->id,
201                                         other_peer->vectors[i].wfd);
202         }
203     }
204 
205     /* advertise the new peer to itself */
206     for (i = 0; i < peer->vectors_count; i++) {
207         ivshmem_server_send_one_msg(peer->sock_fd, peer->id,
208                                     event_notifier_get_fd(&peer->vectors[i]));
209     }
210 
211     QTAILQ_INSERT_TAIL(&server->peer_list, peer, next);
212     IVSHMEM_SERVER_DEBUG(server, "new peer id = %" PRId64 "\n",
213                          peer->id);
214     return 0;
215 
216 fail:
217     while (i--) {
218         event_notifier_cleanup(&peer->vectors[i]);
219     }
220     close(newfd);
221     g_free(peer);
222     return -1;
223 }
224 
225 /* Try to ftruncate a file to next power of 2 of shmsize.
226  * If it fails; all power of 2 above shmsize are tested until
227  * we reach the maximum huge page size. This is useful
228  * if the shm file is in a hugetlbfs that cannot be truncated to the
229  * shm_size value. */
230 static int
231 ivshmem_server_ftruncate(int fd, unsigned shmsize)
232 {
233     int ret;
234     struct stat mapstat;
235 
236     /* align shmsize to next power of 2 */
237     shmsize = pow2ceil(shmsize);
238 
239     if (fstat(fd, &mapstat) != -1 && mapstat.st_size == shmsize) {
240         return 0;
241     }
242 
243     while (shmsize <= IVSHMEM_SERVER_MAX_HUGEPAGE_SIZE) {
244         ret = ftruncate(fd, shmsize);
245         if (ret == 0) {
246             return ret;
247         }
248         shmsize *= 2;
249     }
250 
251     return -1;
252 }
253 
254 /* Init a new ivshmem server */
255 int
256 ivshmem_server_init(IvshmemServer *server, const char *unix_sock_path,
257                     const char *shm_path, bool use_shm_open,
258                     size_t shm_size, unsigned n_vectors,
259                     bool verbose)
260 {
261     int ret;
262 
263     memset(server, 0, sizeof(*server));
264     server->verbose = verbose;
265 
266     ret = snprintf(server->unix_sock_path, sizeof(server->unix_sock_path),
267                    "%s", unix_sock_path);
268     if (ret < 0 || ret >= sizeof(server->unix_sock_path)) {
269         IVSHMEM_SERVER_DEBUG(server, "could not copy unix socket path\n");
270         return -1;
271     }
272     ret = snprintf(server->shm_path, sizeof(server->shm_path),
273                    "%s", shm_path);
274     if (ret < 0 || ret >= sizeof(server->shm_path)) {
275         IVSHMEM_SERVER_DEBUG(server, "could not copy shm path\n");
276         return -1;
277     }
278 
279     server->use_shm_open = use_shm_open;
280     server->shm_size = shm_size;
281     server->n_vectors = n_vectors;
282 
283     QTAILQ_INIT(&server->peer_list);
284 
285     return 0;
286 }
287 
288 /* open shm, create and bind to the unix socket */
289 int
290 ivshmem_server_start(IvshmemServer *server)
291 {
292     struct sockaddr_un sun;
293     int shm_fd, sock_fd, ret;
294 
295     /* open shm file */
296     if (server->use_shm_open) {
297         IVSHMEM_SERVER_DEBUG(server, "Using POSIX shared memory: %s\n",
298                              server->shm_path);
299         shm_fd = shm_open(server->shm_path, O_CREAT | O_RDWR, S_IRWXU);
300     } else {
301         gchar *filename = g_strdup_printf("%s/ivshmem.XXXXXX", server->shm_path);
302         IVSHMEM_SERVER_DEBUG(server, "Using file-backed shared memory: %s\n",
303                              server->shm_path);
304         shm_fd = mkstemp(filename);
305         unlink(filename);
306         g_free(filename);
307     }
308 
309     if (shm_fd < 0) {
310         fprintf(stderr, "cannot open shm file %s: %s\n", server->shm_path,
311                 strerror(errno));
312         return -1;
313     }
314     if (ivshmem_server_ftruncate(shm_fd, server->shm_size) < 0) {
315         fprintf(stderr, "ftruncate(%s) failed: %s\n", server->shm_path,
316                 strerror(errno));
317         goto err_close_shm;
318     }
319 
320     IVSHMEM_SERVER_DEBUG(server, "create & bind socket %s\n",
321                          server->unix_sock_path);
322 
323     /* create the unix listening socket */
324     sock_fd = socket(AF_UNIX, SOCK_STREAM, 0);
325     if (sock_fd < 0) {
326         IVSHMEM_SERVER_DEBUG(server, "cannot create socket: %s\n",
327                              strerror(errno));
328         goto err_close_shm;
329     }
330 
331     sun.sun_family = AF_UNIX;
332     ret = snprintf(sun.sun_path, sizeof(sun.sun_path), "%s",
333                    server->unix_sock_path);
334     if (ret < 0 || ret >= sizeof(sun.sun_path)) {
335         IVSHMEM_SERVER_DEBUG(server, "could not copy unix socket path\n");
336         goto err_close_sock;
337     }
338     if (bind(sock_fd, (struct sockaddr *)&sun, sizeof(sun)) < 0) {
339         IVSHMEM_SERVER_DEBUG(server, "cannot connect to %s: %s\n", sun.sun_path,
340                              strerror(errno));
341         goto err_close_sock;
342     }
343 
344     if (listen(sock_fd, IVSHMEM_SERVER_LISTEN_BACKLOG) < 0) {
345         IVSHMEM_SERVER_DEBUG(server, "listen() failed: %s\n", strerror(errno));
346         goto err_close_sock;
347     }
348 
349     server->sock_fd = sock_fd;
350     server->shm_fd = shm_fd;
351 
352     return 0;
353 
354 err_close_sock:
355     close(sock_fd);
356 err_close_shm:
357     close(shm_fd);
358     return -1;
359 }
360 
361 /* close connections to clients, the unix socket and the shm fd */
362 void
363 ivshmem_server_close(IvshmemServer *server)
364 {
365     IvshmemServerPeer *peer, *npeer;
366 
367     IVSHMEM_SERVER_DEBUG(server, "close server\n");
368 
369     QTAILQ_FOREACH_SAFE(peer, &server->peer_list, next, npeer) {
370         ivshmem_server_free_peer(server, peer);
371     }
372 
373     unlink(server->unix_sock_path);
374     close(server->sock_fd);
375     close(server->shm_fd);
376     server->sock_fd = -1;
377     server->shm_fd = -1;
378 }
379 
380 /* get the fd_set according to the unix socket and the peer list */
381 void
382 ivshmem_server_get_fds(const IvshmemServer *server, fd_set *fds, int *maxfd)
383 {
384     IvshmemServerPeer *peer;
385 
386     if (server->sock_fd == -1) {
387         return;
388     }
389 
390     FD_SET(server->sock_fd, fds);
391     if (server->sock_fd >= *maxfd) {
392         *maxfd = server->sock_fd + 1;
393     }
394 
395     QTAILQ_FOREACH(peer, &server->peer_list, next) {
396         FD_SET(peer->sock_fd, fds);
397         if (peer->sock_fd >= *maxfd) {
398             *maxfd = peer->sock_fd + 1;
399         }
400     }
401 }
402 
403 /* process incoming messages on the sockets in fd_set */
404 int
405 ivshmem_server_handle_fds(IvshmemServer *server, fd_set *fds, int maxfd)
406 {
407     IvshmemServerPeer *peer, *peer_next;
408 
409     if (server->sock_fd < maxfd && FD_ISSET(server->sock_fd, fds) &&
410         ivshmem_server_handle_new_conn(server) < 0 && errno != EINTR) {
411         IVSHMEM_SERVER_DEBUG(server, "ivshmem_server_handle_new_conn() "
412                              "failed\n");
413         return -1;
414     }
415 
416     QTAILQ_FOREACH_SAFE(peer, &server->peer_list, next, peer_next) {
417         /* any message from a peer socket result in a close() */
418         IVSHMEM_SERVER_DEBUG(server, "peer->sock_fd=%d\n", peer->sock_fd);
419         if (peer->sock_fd < maxfd && FD_ISSET(peer->sock_fd, fds)) {
420             ivshmem_server_free_peer(server, peer);
421         }
422     }
423 
424     return 0;
425 }
426 
427 /* lookup peer from its id */
428 IvshmemServerPeer *
429 ivshmem_server_search_peer(IvshmemServer *server, int64_t peer_id)
430 {
431     IvshmemServerPeer *peer;
432 
433     QTAILQ_FOREACH(peer, &server->peer_list, next) {
434         if (peer->id == peer_id) {
435             return peer;
436         }
437     }
438     return NULL;
439 }
440 
441 /* dump our info, the list of peers their vectors on stdout */
442 void
443 ivshmem_server_dump(const IvshmemServer *server)
444 {
445     const IvshmemServerPeer *peer;
446     unsigned vector;
447 
448     /* dump peers */
449     QTAILQ_FOREACH(peer, &server->peer_list, next) {
450         printf("peer_id = %" PRId64 "\n", peer->id);
451 
452         for (vector = 0; vector < peer->vectors_count; vector++) {
453             printf("  vector %d is enabled (fd=%d)\n", vector,
454                    event_notifier_get_fd(&peer->vectors[vector]));
455         }
456     }
457 }
458