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/host-utils.h"
10 #include "qemu/sockets.h"
11 
12 #include <sys/socket.h>
13 #include <sys/un.h>
14 
15 #include "ivshmem-server.h"
16 
17 /* log a message on stdout if verbose=1 */
18 #define IVSHMEM_SERVER_DEBUG(server, fmt, ...) do { \
19         if ((server)->verbose) {         \
20             printf(fmt, ## __VA_ARGS__); \
21         }                                \
22     } while (0)
23 
24 /** maximum size of a huge page, used by ivshmem_server_ftruncate() */
25 #define IVSHMEM_SERVER_MAX_HUGEPAGE_SIZE (1024 * 1024 * 1024)
26 
27 /** default listen backlog (number of sockets not accepted) */
28 #define IVSHMEM_SERVER_LISTEN_BACKLOG 10
29 
30 /* send message to a client unix socket */
31 static int
32 ivshmem_server_send_one_msg(int sock_fd, int64_t peer_id, int fd)
33 {
34     int ret;
35     struct msghdr msg;
36     struct iovec iov[1];
37     union {
38         struct cmsghdr cmsg;
39         char control[CMSG_SPACE(sizeof(int))];
40     } msg_control;
41     struct cmsghdr *cmsg;
42 
43     peer_id = GINT64_TO_LE(peer_id);
44     iov[0].iov_base = &peer_id;
45     iov[0].iov_len = sizeof(peer_id);
46 
47     memset(&msg, 0, sizeof(msg));
48     msg.msg_iov = iov;
49     msg.msg_iovlen = 1;
50 
51     /* if fd is specified, add it in a cmsg */
52     if (fd >= 0) {
53         memset(&msg_control, 0, sizeof(msg_control));
54         msg.msg_control = &msg_control;
55         msg.msg_controllen = sizeof(msg_control);
56         cmsg = CMSG_FIRSTHDR(&msg);
57         cmsg->cmsg_level = SOL_SOCKET;
58         cmsg->cmsg_type = SCM_RIGHTS;
59         cmsg->cmsg_len = CMSG_LEN(sizeof(int));
60         memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
61     }
62 
63     ret = sendmsg(sock_fd, &msg, 0);
64     if (ret <= 0) {
65         return -1;
66     }
67 
68     return 0;
69 }
70 
71 /* free a peer when the server advertises a disconnection or when the
72  * server is freed */
73 static void
74 ivshmem_server_free_peer(IvshmemServer *server, IvshmemServerPeer *peer)
75 {
76     unsigned vector;
77     IvshmemServerPeer *other_peer;
78 
79     IVSHMEM_SERVER_DEBUG(server, "free peer %" PRId64 "\n", peer->id);
80     close(peer->sock_fd);
81     QTAILQ_REMOVE(&server->peer_list, peer, next);
82 
83     /* advertise the deletion to other peers */
84     QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
85         ivshmem_server_send_one_msg(other_peer->sock_fd, peer->id, -1);
86     }
87 
88     for (vector = 0; vector < peer->vectors_count; vector++) {
89         event_notifier_cleanup(&peer->vectors[vector]);
90     }
91 
92     g_free(peer);
93 }
94 
95 /* send the peer id and the shm_fd just after a new client connection */
96 static int
97 ivshmem_server_send_initial_info(IvshmemServer *server, IvshmemServerPeer *peer)
98 {
99     int ret;
100 
101     /* send our protocol version first */
102     ret = ivshmem_server_send_one_msg(peer->sock_fd, IVSHMEM_PROTOCOL_VERSION,
103                                       -1);
104     if (ret < 0) {
105         IVSHMEM_SERVER_DEBUG(server, "cannot send version: %s\n",
106                              strerror(errno));
107         return -1;
108     }
109 
110     /* send the peer id to the client */
111     ret = ivshmem_server_send_one_msg(peer->sock_fd, peer->id, -1);
112     if (ret < 0) {
113         IVSHMEM_SERVER_DEBUG(server, "cannot send peer id: %s\n",
114                              strerror(errno));
115         return -1;
116     }
117 
118     /* send the shm_fd */
119     ret = ivshmem_server_send_one_msg(peer->sock_fd, -1, server->shm_fd);
120     if (ret < 0) {
121         IVSHMEM_SERVER_DEBUG(server, "cannot send shm fd: %s\n",
122                              strerror(errno));
123         return -1;
124     }
125 
126     return 0;
127 }
128 
129 /* handle message on listening unix socket (new client connection) */
130 static int
131 ivshmem_server_handle_new_conn(IvshmemServer *server)
132 {
133     IvshmemServerPeer *peer, *other_peer;
134     struct sockaddr_un unaddr;
135     socklen_t unaddr_len;
136     int newfd;
137     unsigned i;
138 
139     /* accept the incoming connection */
140     unaddr_len = sizeof(unaddr);
141     newfd = qemu_accept(server->sock_fd,
142                         (struct sockaddr *)&unaddr, &unaddr_len);
143 
144     if (newfd < 0) {
145         IVSHMEM_SERVER_DEBUG(server, "cannot accept() %s\n", strerror(errno));
146         return -1;
147     }
148 
149     qemu_set_nonblock(newfd);
150     IVSHMEM_SERVER_DEBUG(server, "accept()=%d\n", newfd);
151 
152     /* allocate new structure for this peer */
153     peer = g_malloc0(sizeof(*peer));
154     peer->sock_fd = newfd;
155 
156     /* get an unused peer id */
157     /* XXX: this could use id allocation such as Linux IDA, or simply
158      * a free-list */
159     for (i = 0; i < G_MAXUINT16; i++) {
160         if (ivshmem_server_search_peer(server, server->cur_id) == NULL) {
161             break;
162         }
163         server->cur_id++;
164     }
165     if (i == G_MAXUINT16) {
166         IVSHMEM_SERVER_DEBUG(server, "cannot allocate new client id\n");
167         close(newfd);
168         g_free(peer);
169         return -1;
170     }
171     peer->id = server->cur_id++;
172 
173     /* create eventfd, one per vector */
174     peer->vectors_count = server->n_vectors;
175     for (i = 0; i < peer->vectors_count; i++) {
176         if (event_notifier_init(&peer->vectors[i], FALSE) < 0) {
177             IVSHMEM_SERVER_DEBUG(server, "cannot create eventfd\n");
178             goto fail;
179         }
180     }
181 
182     /* send peer id and shm fd */
183     if (ivshmem_server_send_initial_info(server, peer) < 0) {
184         IVSHMEM_SERVER_DEBUG(server, "cannot send initial info\n");
185         goto fail;
186     }
187 
188     /* advertise the new peer to others */
189     QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
190         for (i = 0; i < peer->vectors_count; i++) {
191             ivshmem_server_send_one_msg(other_peer->sock_fd, peer->id,
192                                         peer->vectors[i].wfd);
193         }
194     }
195 
196     /* advertise the other peers to the new one */
197     QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
198         for (i = 0; i < peer->vectors_count; i++) {
199             ivshmem_server_send_one_msg(peer->sock_fd, other_peer->id,
200                                         other_peer->vectors[i].wfd);
201         }
202     }
203 
204     /* advertise the new peer to itself */
205     for (i = 0; i < peer->vectors_count; i++) {
206         ivshmem_server_send_one_msg(peer->sock_fd, peer->id,
207                                     event_notifier_get_fd(&peer->vectors[i]));
208     }
209 
210     QTAILQ_INSERT_TAIL(&server->peer_list, peer, next);
211     IVSHMEM_SERVER_DEBUG(server, "new peer id = %" PRId64 "\n",
212                          peer->id);
213     return 0;
214 
215 fail:
216     while (i--) {
217         event_notifier_cleanup(&peer->vectors[i]);
218     }
219     close(newfd);
220     g_free(peer);
221     return -1;
222 }
223 
224 /* Try to ftruncate a file to next power of 2 of shmsize.
225  * If it fails; all power of 2 above shmsize are tested until
226  * we reach the maximum huge page size. This is useful
227  * if the shm file is in a hugetlbfs that cannot be truncated to the
228  * shm_size value. */
229 static int
230 ivshmem_server_ftruncate(int fd, unsigned shmsize)
231 {
232     int ret;
233     struct stat mapstat;
234 
235     /* align shmsize to next power of 2 */
236     shmsize = pow2ceil(shmsize);
237 
238     if (fstat(fd, &mapstat) != -1 && mapstat.st_size == shmsize) {
239         return 0;
240     }
241 
242     while (shmsize <= IVSHMEM_SERVER_MAX_HUGEPAGE_SIZE) {
243         ret = ftruncate(fd, shmsize);
244         if (ret == 0) {
245             return ret;
246         }
247         shmsize *= 2;
248     }
249 
250     return -1;
251 }
252 
253 /* Init a new ivshmem server */
254 int
255 ivshmem_server_init(IvshmemServer *server, const char *unix_sock_path,
256                     const char *shm_path, bool use_shm_open,
257                     size_t shm_size, unsigned n_vectors,
258                     bool verbose)
259 {
260     int ret;
261 
262     memset(server, 0, sizeof(*server));
263     server->verbose = verbose;
264 
265     ret = snprintf(server->unix_sock_path, sizeof(server->unix_sock_path),
266                    "%s", unix_sock_path);
267     if (ret < 0 || ret >= sizeof(server->unix_sock_path)) {
268         IVSHMEM_SERVER_DEBUG(server, "could not copy unix socket path\n");
269         return -1;
270     }
271     ret = snprintf(server->shm_path, sizeof(server->shm_path),
272                    "%s", shm_path);
273     if (ret < 0 || ret >= sizeof(server->shm_path)) {
274         IVSHMEM_SERVER_DEBUG(server, "could not copy shm path\n");
275         return -1;
276     }
277 
278     server->use_shm_open = use_shm_open;
279     server->shm_size = shm_size;
280     server->n_vectors = n_vectors;
281 
282     QTAILQ_INIT(&server->peer_list);
283 
284     return 0;
285 }
286 
287 /* open shm, create and bind to the unix socket */
288 int
289 ivshmem_server_start(IvshmemServer *server)
290 {
291     struct sockaddr_un s_un;
292     int shm_fd, sock_fd, ret;
293 
294     /* open shm file */
295     if (server->use_shm_open) {
296         IVSHMEM_SERVER_DEBUG(server, "Using POSIX shared memory: %s\n",
297                              server->shm_path);
298         shm_fd = shm_open(server->shm_path, O_CREAT | O_RDWR, S_IRWXU);
299     } else {
300         gchar *filename = g_strdup_printf("%s/ivshmem.XXXXXX", server->shm_path);
301         IVSHMEM_SERVER_DEBUG(server, "Using file-backed shared memory: %s\n",
302                              server->shm_path);
303         shm_fd = mkstemp(filename);
304         unlink(filename);
305         g_free(filename);
306     }
307 
308     if (shm_fd < 0) {
309         fprintf(stderr, "cannot open shm file %s: %s\n", server->shm_path,
310                 strerror(errno));
311         return -1;
312     }
313     if (ivshmem_server_ftruncate(shm_fd, server->shm_size) < 0) {
314         fprintf(stderr, "ftruncate(%s) failed: %s\n", server->shm_path,
315                 strerror(errno));
316         goto err_close_shm;
317     }
318 
319     IVSHMEM_SERVER_DEBUG(server, "create & bind socket %s\n",
320                          server->unix_sock_path);
321 
322     /* create the unix listening socket */
323     sock_fd = socket(AF_UNIX, SOCK_STREAM, 0);
324     if (sock_fd < 0) {
325         IVSHMEM_SERVER_DEBUG(server, "cannot create socket: %s\n",
326                              strerror(errno));
327         goto err_close_shm;
328     }
329 
330     s_un.sun_family = AF_UNIX;
331     ret = snprintf(s_un.sun_path, sizeof(s_un.sun_path), "%s",
332                    server->unix_sock_path);
333     if (ret < 0 || ret >= sizeof(s_un.sun_path)) {
334         IVSHMEM_SERVER_DEBUG(server, "could not copy unix socket path\n");
335         goto err_close_sock;
336     }
337     if (bind(sock_fd, (struct sockaddr *)&s_un, sizeof(s_un)) < 0) {
338         IVSHMEM_SERVER_DEBUG(server, "cannot connect to %s: %s\n", s_un.sun_path,
339                              strerror(errno));
340         goto err_close_sock;
341     }
342 
343     if (listen(sock_fd, IVSHMEM_SERVER_LISTEN_BACKLOG) < 0) {
344         IVSHMEM_SERVER_DEBUG(server, "listen() failed: %s\n", strerror(errno));
345         goto err_close_sock;
346     }
347 
348     server->sock_fd = sock_fd;
349     server->shm_fd = shm_fd;
350 
351     return 0;
352 
353 err_close_sock:
354     close(sock_fd);
355 err_close_shm:
356     if (server->use_shm_open) {
357         shm_unlink(server->shm_path);
358     }
359     close(shm_fd);
360     return -1;
361 }
362 
363 /* close connections to clients, the unix socket and the shm fd */
364 void
365 ivshmem_server_close(IvshmemServer *server)
366 {
367     IvshmemServerPeer *peer, *npeer;
368 
369     IVSHMEM_SERVER_DEBUG(server, "close server\n");
370 
371     QTAILQ_FOREACH_SAFE(peer, &server->peer_list, next, npeer) {
372         ivshmem_server_free_peer(server, peer);
373     }
374 
375     unlink(server->unix_sock_path);
376     if (server->use_shm_open) {
377         shm_unlink(server->shm_path);
378     }
379     close(server->sock_fd);
380     close(server->shm_fd);
381     server->sock_fd = -1;
382     server->shm_fd = -1;
383 }
384 
385 /* get the fd_set according to the unix socket and the peer list */
386 void
387 ivshmem_server_get_fds(const IvshmemServer *server, fd_set *fds, int *maxfd)
388 {
389     IvshmemServerPeer *peer;
390 
391     if (server->sock_fd == -1) {
392         return;
393     }
394 
395     FD_SET(server->sock_fd, fds);
396     if (server->sock_fd >= *maxfd) {
397         *maxfd = server->sock_fd + 1;
398     }
399 
400     QTAILQ_FOREACH(peer, &server->peer_list, next) {
401         FD_SET(peer->sock_fd, fds);
402         if (peer->sock_fd >= *maxfd) {
403             *maxfd = peer->sock_fd + 1;
404         }
405     }
406 }
407 
408 /* process incoming messages on the sockets in fd_set */
409 int
410 ivshmem_server_handle_fds(IvshmemServer *server, fd_set *fds, int maxfd)
411 {
412     IvshmemServerPeer *peer, *peer_next;
413 
414     if (server->sock_fd < maxfd && FD_ISSET(server->sock_fd, fds) &&
415         ivshmem_server_handle_new_conn(server) < 0 && errno != EINTR) {
416         IVSHMEM_SERVER_DEBUG(server, "ivshmem_server_handle_new_conn() "
417                              "failed\n");
418         return -1;
419     }
420 
421     QTAILQ_FOREACH_SAFE(peer, &server->peer_list, next, peer_next) {
422         /* any message from a peer socket result in a close() */
423         IVSHMEM_SERVER_DEBUG(server, "peer->sock_fd=%d\n", peer->sock_fd);
424         if (peer->sock_fd < maxfd && FD_ISSET(peer->sock_fd, fds)) {
425             ivshmem_server_free_peer(server, peer);
426         }
427     }
428 
429     return 0;
430 }
431 
432 /* lookup peer from its id */
433 IvshmemServerPeer *
434 ivshmem_server_search_peer(IvshmemServer *server, int64_t peer_id)
435 {
436     IvshmemServerPeer *peer;
437 
438     QTAILQ_FOREACH(peer, &server->peer_list, next) {
439         if (peer->id == peer_id) {
440             return peer;
441         }
442     }
443     return NULL;
444 }
445 
446 /* dump our info, the list of peers their vectors on stdout */
447 void
448 ivshmem_server_dump(const IvshmemServer *server)
449 {
450     const IvshmemServerPeer *peer;
451     unsigned vector;
452 
453     /* dump peers */
454     QTAILQ_FOREACH(peer, &server->peer_list, next) {
455         printf("peer_id = %" PRId64 "\n", peer->id);
456 
457         for (vector = 0; vector < peer->vectors_count; vector++) {
458             printf("  vector %d is enabled (fd=%d)\n", vector,
459                    event_notifier_get_fd(&peer->vectors[vector]));
460         }
461     }
462 }
463