1 /* -*- Mode: C; c-basic-offset:8 ; indent-tabs-mode:t -*- */
2 /*
3 * Linux usbfs backend for libusb
4 * Copyright (C) 2007-2009 Daniel Drake <dsd@gentoo.org>
5 * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
6 * Copyright (c) 2013 Nathan Hjelm <hjelmn@mac.com>
7 * Copyright (c) 2016 Chris Dickens <christopher.a.dickens@gmail.com>
8 *
9 * This library is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
13 *
14 * This library is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with this library; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24 #include "libusbi.h"
25 #include "linux_usbfs.h"
26
27 #include <errno.h>
28 #include <fcntl.h>
29 #include <poll.h>
30 #include <pthread.h>
31 #include <string.h>
32 #include <unistd.h>
33
34 #ifdef HAVE_ASM_TYPES_H
35 #include <asm/types.h>
36 #endif
37 #include <linux/netlink.h>
38 #include <sys/socket.h>
39
40 #define NL_GROUP_KERNEL 1
41
42 #ifndef SOCK_CLOEXEC
43 #define SOCK_CLOEXEC 0
44 #endif
45
46 #ifndef SOCK_NONBLOCK
47 #define SOCK_NONBLOCK 0
48 #endif
49
50 static int linux_netlink_socket = -1;
51 static usbi_event_t netlink_control_event = USBI_INVALID_EVENT;
52 static pthread_t libusb_linux_event_thread;
53
54 static void *linux_netlink_event_thread_main(void *arg);
55
set_fd_cloexec_nb(int fd,int socktype)56 static int set_fd_cloexec_nb(int fd, int socktype)
57 {
58 int flags;
59
60 #if defined(FD_CLOEXEC)
61 /* Make sure the netlink socket file descriptor is marked as CLOEXEC */
62 if (!(socktype & SOCK_CLOEXEC)) {
63 flags = fcntl(fd, F_GETFD);
64 if (flags == -1) {
65 usbi_err(NULL, "failed to get netlink fd flags, errno=%d", errno);
66 return -1;
67 }
68
69 if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1) {
70 usbi_err(NULL, "failed to set netlink fd flags, errno=%d", errno);
71 return -1;
72 }
73 }
74 #endif
75
76 /* Make sure the netlink socket is non-blocking */
77 if (!(socktype & SOCK_NONBLOCK)) {
78 flags = fcntl(fd, F_GETFL);
79 if (flags == -1) {
80 usbi_err(NULL, "failed to get netlink fd status flags, errno=%d", errno);
81 return -1;
82 }
83
84 if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1) {
85 usbi_err(NULL, "failed to set netlink fd status flags, errno=%d", errno);
86 return -1;
87 }
88 }
89
90 return 0;
91 }
92
linux_netlink_start_event_monitor(void)93 int linux_netlink_start_event_monitor(void)
94 {
95 struct sockaddr_nl sa_nl = { .nl_family = AF_NETLINK, .nl_groups = NL_GROUP_KERNEL };
96 int socktype = SOCK_RAW | SOCK_NONBLOCK | SOCK_CLOEXEC;
97 int opt = 1;
98 int ret;
99
100 linux_netlink_socket = socket(PF_NETLINK, socktype, NETLINK_KOBJECT_UEVENT);
101 if (linux_netlink_socket == -1 && errno == EINVAL) {
102 usbi_dbg("failed to create netlink socket of type %d, attempting SOCK_RAW", socktype);
103 socktype = SOCK_RAW;
104 linux_netlink_socket = socket(PF_NETLINK, socktype, NETLINK_KOBJECT_UEVENT);
105 }
106
107 if (linux_netlink_socket == -1) {
108 usbi_err(NULL, "failed to create netlink socket, errno=%d", errno);
109 goto err;
110 }
111
112 ret = set_fd_cloexec_nb(linux_netlink_socket, socktype);
113 if (ret == -1)
114 goto err_close_socket;
115
116 ret = bind(linux_netlink_socket, (struct sockaddr *)&sa_nl, sizeof(sa_nl));
117 if (ret == -1) {
118 usbi_err(NULL, "failed to bind netlink socket, errno=%d", errno);
119 goto err_close_socket;
120 }
121
122 ret = setsockopt(linux_netlink_socket, SOL_SOCKET, SO_PASSCRED, &opt, sizeof(opt));
123 if (ret == -1) {
124 usbi_err(NULL, "failed to set netlink socket SO_PASSCRED option, errno=%d", errno);
125 goto err_close_socket;
126 }
127
128 ret = usbi_create_event(&netlink_control_event);
129 if (ret) {
130 usbi_err(NULL, "failed to create netlink control event");
131 goto err_close_socket;
132 }
133
134 ret = pthread_create(&libusb_linux_event_thread, NULL, linux_netlink_event_thread_main, NULL);
135 if (ret != 0) {
136 usbi_err(NULL, "failed to create netlink event thread (%d)", ret);
137 goto err_destroy_event;
138 }
139
140 return LIBUSB_SUCCESS;
141
142 err_destroy_event:
143 usbi_destroy_event(&netlink_control_event);
144 netlink_control_event = (usbi_event_t)USBI_INVALID_EVENT;
145 err_close_socket:
146 close(linux_netlink_socket);
147 linux_netlink_socket = -1;
148 err:
149 return LIBUSB_ERROR_OTHER;
150 }
151
linux_netlink_stop_event_monitor(void)152 int linux_netlink_stop_event_monitor(void)
153 {
154 int ret;
155
156 assert(linux_netlink_socket != -1);
157
158 /* Signal the control event and wait for the thread to exit */
159 usbi_signal_event(&netlink_control_event);
160
161 ret = pthread_join(libusb_linux_event_thread, NULL);
162 if (ret)
163 usbi_warn(NULL, "failed to join netlink event thread (%d)", ret);
164
165 usbi_destroy_event(&netlink_control_event);
166 netlink_control_event = (usbi_event_t)USBI_INVALID_EVENT;
167
168 close(linux_netlink_socket);
169 linux_netlink_socket = -1;
170
171 return LIBUSB_SUCCESS;
172 }
173
netlink_message_parse(const char * buffer,size_t len,const char * key)174 static const char *netlink_message_parse(const char *buffer, size_t len, const char *key)
175 {
176 const char *end = buffer + len;
177 size_t keylen = strlen(key);
178
179 while (buffer < end && *buffer) {
180 if (strncmp(buffer, key, keylen) == 0 && buffer[keylen] == '=')
181 return buffer + keylen + 1;
182 buffer += strlen(buffer) + 1;
183 }
184
185 return NULL;
186 }
187
188 /* parse parts of netlink message common to both libudev and the kernel */
linux_netlink_parse(const char * buffer,size_t len,int * detached,const char ** sys_name,uint8_t * busnum,uint8_t * devaddr)189 static int linux_netlink_parse(const char *buffer, size_t len, int *detached,
190 const char **sys_name, uint8_t *busnum, uint8_t *devaddr)
191 {
192 const char *tmp, *slash;
193
194 errno = 0;
195
196 *sys_name = NULL;
197 *detached = 0;
198 *busnum = 0;
199 *devaddr = 0;
200
201 tmp = netlink_message_parse(buffer, len, "ACTION");
202 if (!tmp) {
203 return -1;
204 } else if (strcmp(tmp, "remove") == 0) {
205 *detached = 1;
206 } else if (strcmp(tmp, "add") != 0) {
207 usbi_dbg("unknown device action %s", tmp);
208 return -1;
209 }
210
211 /* check that this is a usb message */
212 tmp = netlink_message_parse(buffer, len, "SUBSYSTEM");
213 if (!tmp || strcmp(tmp, "usb") != 0) {
214 /* not usb. ignore */
215 return -1;
216 }
217
218 /* check that this is an actual usb device */
219 tmp = netlink_message_parse(buffer, len, "DEVTYPE");
220 if (!tmp || strcmp(tmp, "usb_device") != 0) {
221 /* not usb. ignore */
222 return -1;
223 }
224
225 tmp = netlink_message_parse(buffer, len, "BUSNUM");
226 if (tmp) {
227 *busnum = (uint8_t)(strtoul(tmp, NULL, 10) & 0xff);
228 if (errno) {
229 errno = 0;
230 return -1;
231 }
232
233 tmp = netlink_message_parse(buffer, len, "DEVNUM");
234 if (NULL == tmp)
235 return -1;
236
237 *devaddr = (uint8_t)(strtoul(tmp, NULL, 10) & 0xff);
238 if (errno) {
239 errno = 0;
240 return -1;
241 }
242 } else {
243 /* no bus number. try "DEVICE" */
244 tmp = netlink_message_parse(buffer, len, "DEVICE");
245 if (!tmp) {
246 /* not usb. ignore */
247 return -1;
248 }
249
250 /* Parse a device path such as /dev/bus/usb/003/004 */
251 slash = strrchr(tmp, '/');
252 if (!slash)
253 return -1;
254
255 *busnum = (uint8_t)(strtoul(slash - 3, NULL, 10) & 0xff);
256 if (errno) {
257 errno = 0;
258 return -1;
259 }
260
261 *devaddr = (uint8_t)(strtoul(slash + 1, NULL, 10) & 0xff);
262 if (errno) {
263 errno = 0;
264 return -1;
265 }
266
267 return 0;
268 }
269
270 tmp = netlink_message_parse(buffer, len, "DEVPATH");
271 if (!tmp)
272 return -1;
273
274 slash = strrchr(tmp, '/');
275 if (slash)
276 *sys_name = slash + 1;
277
278 /* found a usb device */
279 return 0;
280 }
281
linux_netlink_read_message(void)282 static int linux_netlink_read_message(void)
283 {
284 char cred_buffer[CMSG_SPACE(sizeof(struct ucred))];
285 char msg_buffer[2048];
286 const char *sys_name = NULL;
287 uint8_t busnum, devaddr;
288 int detached, r;
289 ssize_t len;
290 struct cmsghdr *cmsg;
291 struct ucred *cred;
292 struct sockaddr_nl sa_nl;
293 struct iovec iov = { .iov_base = msg_buffer, .iov_len = sizeof(msg_buffer) };
294 struct msghdr msg = {
295 .msg_iov = &iov, .msg_iovlen = 1,
296 .msg_control = cred_buffer, .msg_controllen = sizeof(cred_buffer),
297 .msg_name = &sa_nl, .msg_namelen = sizeof(sa_nl)
298 };
299
300 /* read netlink message */
301 len = recvmsg(linux_netlink_socket, &msg, 0);
302 if (len == -1) {
303 if (errno != EAGAIN && errno != EINTR)
304 usbi_err(NULL, "error receiving message from netlink, errno=%d", errno);
305 return -1;
306 }
307
308 if (len < 32 || (msg.msg_flags & MSG_TRUNC)) {
309 usbi_err(NULL, "invalid netlink message length");
310 return -1;
311 }
312
313 if (sa_nl.nl_groups != NL_GROUP_KERNEL || sa_nl.nl_pid != 0) {
314 usbi_dbg("ignoring netlink message from unknown group/PID (%u/%u)",
315 (unsigned int)sa_nl.nl_groups, (unsigned int)sa_nl.nl_pid);
316 return -1;
317 }
318
319 cmsg = CMSG_FIRSTHDR(&msg);
320 if (!cmsg || cmsg->cmsg_type != SCM_CREDENTIALS) {
321 usbi_dbg("ignoring netlink message with no sender credentials");
322 return -1;
323 }
324
325 cred = (struct ucred *)CMSG_DATA(cmsg);
326 if (cred->uid != 0) {
327 usbi_dbg("ignoring netlink message with non-zero sender UID %u", (unsigned int)cred->uid);
328 return -1;
329 }
330
331 r = linux_netlink_parse(msg_buffer, (size_t)len, &detached, &sys_name, &busnum, &devaddr);
332 if (r)
333 return r;
334
335 usbi_dbg("netlink hotplug found device busnum: %hhu, devaddr: %hhu, sys_name: %s, removed: %s",
336 busnum, devaddr, sys_name, detached ? "yes" : "no");
337
338 /* signal device is available (or not) to all contexts */
339 if (detached)
340 linux_device_disconnected(busnum, devaddr);
341 else
342 linux_hotplug_enumerate(busnum, devaddr, sys_name);
343
344 return 0;
345 }
346
linux_netlink_event_thread_main(void * arg)347 static void *linux_netlink_event_thread_main(void *arg)
348 {
349 struct pollfd fds[] = {
350 { .fd = USBI_EVENT_OS_HANDLE(&netlink_control_event),
351 .events = USBI_EVENT_POLL_EVENTS },
352 { .fd = linux_netlink_socket,
353 .events = POLLIN },
354 };
355 int r;
356
357 UNUSED(arg);
358
359 #if defined(HAVE_PTHREAD_SETNAME_NP)
360 r = pthread_setname_np(pthread_self(), "libusb_event");
361 if (r)
362 usbi_warn(NULL, "failed to set hotplug event thread name, error=%d", r);
363 #endif
364
365 usbi_dbg("netlink event thread entering");
366
367 while (1) {
368 r = poll(fds, 2, -1);
369 if (r == -1) {
370 /* check for temporary failure */
371 if (errno == EINTR)
372 continue;
373 usbi_err(NULL, "poll() failed, errno=%d", errno);
374 break;
375 }
376 if (fds[0].revents) {
377 /* activity on control event, exit */
378 break;
379 }
380 if (fds[1].revents) {
381 usbi_mutex_static_lock(&linux_hotplug_lock);
382 linux_netlink_read_message();
383 usbi_mutex_static_unlock(&linux_hotplug_lock);
384 }
385 }
386
387 usbi_dbg("netlink event thread exiting");
388
389 return NULL;
390 }
391
linux_netlink_hotplug_poll(void)392 void linux_netlink_hotplug_poll(void)
393 {
394 int r;
395
396 usbi_mutex_static_lock(&linux_hotplug_lock);
397 do {
398 r = linux_netlink_read_message();
399 } while (r == 0);
400 usbi_mutex_static_unlock(&linux_hotplug_lock);
401 }
402