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 <config.h>
25
26 #include <assert.h>
27 #include <errno.h>
28 #include <fcntl.h>
29 #include <poll.h>
30 #include <stdio.h>
31 #include <stdlib.h>
32 #include <string.h>
33 #include <unistd.h>
34 #include <sys/types.h>
35
36 #ifdef HAVE_ASM_TYPES_H
37 #include <asm/types.h>
38 #endif
39
40 #include <sys/socket.h>
41 #include <linux/netlink.h>
42
43 #include "libusbi.h"
44 #include "linux_usbfs.h"
45
46 #define NL_GROUP_KERNEL 1
47
48 static int linux_netlink_socket = -1;
49 static int netlink_control_pipe[2] = { -1, -1 };
50 static pthread_t libusb_linux_event_thread;
51
52 static void *linux_netlink_event_thread_main(void *arg);
53
set_fd_cloexec_nb(int fd)54 static int set_fd_cloexec_nb(int fd)
55 {
56 int flags;
57
58 #if defined(FD_CLOEXEC)
59 flags = fcntl(fd, F_GETFD);
60 if (flags == -1) {
61 usbi_err(NULL, "failed to get netlink fd flags (%d)", errno);
62 return -1;
63 }
64
65 if (!(flags & FD_CLOEXEC)) {
66 if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1) {
67 usbi_err(NULL, "failed to set netlink fd flags (%d)", errno);
68 return -1;
69 }
70 }
71 #endif
72
73 flags = fcntl(fd, F_GETFL);
74 if (flags == -1) {
75 usbi_err(NULL, "failed to get netlink fd status flags (%d)", errno);
76 return -1;
77 }
78
79 if (!(flags & O_NONBLOCK)) {
80 if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1) {
81 usbi_err(NULL, "failed to set netlink fd status flags (%d)", errno);
82 return -1;
83 }
84 }
85
86 return 0;
87 }
88
linux_netlink_start_event_monitor(void)89 int linux_netlink_start_event_monitor(void)
90 {
91 struct sockaddr_nl sa_nl = { .nl_family = AF_NETLINK, .nl_groups = NL_GROUP_KERNEL };
92 int socktype = SOCK_RAW;
93 int opt = 1;
94 int ret;
95
96 #if defined(SOCK_CLOEXEC)
97 socktype |= SOCK_CLOEXEC;
98 #endif
99 #if defined(SOCK_NONBLOCK)
100 socktype |= SOCK_NONBLOCK;
101 #endif
102
103 linux_netlink_socket = socket(PF_NETLINK, socktype, NETLINK_KOBJECT_UEVENT);
104 if (linux_netlink_socket == -1 && errno == EINVAL) {
105 usbi_dbg("failed to create netlink socket of type %d, attempting SOCK_RAW", socktype);
106 linux_netlink_socket = socket(PF_NETLINK, SOCK_RAW, NETLINK_KOBJECT_UEVENT);
107 }
108
109 if (linux_netlink_socket == -1) {
110 usbi_err(NULL, "failed to create netlink socket (%d)", errno);
111 goto err;
112 }
113
114 ret = set_fd_cloexec_nb(linux_netlink_socket);
115 if (ret == -1)
116 goto err_close_socket;
117
118 ret = bind(linux_netlink_socket, (struct sockaddr *)&sa_nl, sizeof(sa_nl));
119 if (ret == -1) {
120 usbi_err(NULL, "failed to bind netlink socket (%d)", errno);
121 goto err_close_socket;
122 }
123
124 ret = setsockopt(linux_netlink_socket, SOL_SOCKET, SO_PASSCRED, &opt, sizeof(opt));
125 if (ret == -1) {
126 usbi_err(NULL, "failed to set netlink socket SO_PASSCRED option (%d)", errno);
127 goto err_close_socket;
128 }
129
130 ret = usbi_pipe(netlink_control_pipe);
131 if (ret) {
132 usbi_err(NULL, "failed to create netlink control pipe");
133 goto err_close_socket;
134 }
135
136 ret = pthread_create(&libusb_linux_event_thread, NULL, linux_netlink_event_thread_main, NULL);
137 if (ret != 0) {
138 usbi_err(NULL, "failed to create netlink event thread (%d)", ret);
139 goto err_close_pipe;
140 }
141
142 return LIBUSB_SUCCESS;
143
144 err_close_pipe:
145 close(netlink_control_pipe[0]);
146 close(netlink_control_pipe[1]);
147 netlink_control_pipe[0] = -1;
148 netlink_control_pipe[1] = -1;
149 err_close_socket:
150 close(linux_netlink_socket);
151 linux_netlink_socket = -1;
152 err:
153 return LIBUSB_ERROR_OTHER;
154 }
155
linux_netlink_stop_event_monitor(void)156 int linux_netlink_stop_event_monitor(void)
157 {
158 char dummy = 1;
159 ssize_t r;
160
161 assert(linux_netlink_socket != -1);
162
163 /* Write some dummy data to the control pipe and
164 * wait for the thread to exit */
165 r = usbi_write(netlink_control_pipe[1], &dummy, sizeof(dummy));
166 if (r <= 0)
167 usbi_warn(NULL, "netlink control pipe signal failed");
168
169 pthread_join(libusb_linux_event_thread, NULL);
170
171 close(linux_netlink_socket);
172 linux_netlink_socket = -1;
173
174 /* close and reset control pipe */
175 close(netlink_control_pipe[0]);
176 close(netlink_control_pipe[1]);
177 netlink_control_pipe[0] = -1;
178 netlink_control_pipe[1] = -1;
179
180 return LIBUSB_SUCCESS;
181 }
182
netlink_message_parse(const char * buffer,size_t len,const char * key)183 static const char *netlink_message_parse(const char *buffer, size_t len, const char *key)
184 {
185 const char *end = buffer + len;
186 size_t keylen = strlen(key);
187
188 while (buffer < end && *buffer) {
189 if (strncmp(buffer, key, keylen) == 0 && buffer[keylen] == '=')
190 return buffer + keylen + 1;
191 buffer += strlen(buffer) + 1;
192 }
193
194 return NULL;
195 }
196
197 /* 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)198 static int linux_netlink_parse(const char *buffer, size_t len, int *detached,
199 const char **sys_name, uint8_t *busnum, uint8_t *devaddr)
200 {
201 const char *tmp, *slash;
202
203 errno = 0;
204
205 *sys_name = NULL;
206 *detached = 0;
207 *busnum = 0;
208 *devaddr = 0;
209
210 tmp = netlink_message_parse(buffer, len, "ACTION");
211 if (!tmp) {
212 return -1;
213 } else if (strcmp(tmp, "remove") == 0) {
214 *detached = 1;
215 } else if (strcmp(tmp, "add") != 0) {
216 usbi_dbg("unknown device action %s", tmp);
217 return -1;
218 }
219
220 /* check that this is a usb message */
221 tmp = netlink_message_parse(buffer, len, "SUBSYSTEM");
222 if (!tmp || strcmp(tmp, "usb") != 0) {
223 /* not usb. ignore */
224 return -1;
225 }
226
227 /* check that this is an actual usb device */
228 tmp = netlink_message_parse(buffer, len, "DEVTYPE");
229 if (!tmp || strcmp(tmp, "usb_device") != 0) {
230 /* not usb. ignore */
231 return -1;
232 }
233
234 tmp = netlink_message_parse(buffer, len, "BUSNUM");
235 if (tmp) {
236 *busnum = (uint8_t)(strtoul(tmp, NULL, 10) & 0xff);
237 if (errno) {
238 errno = 0;
239 return -1;
240 }
241
242 tmp = netlink_message_parse(buffer, len, "DEVNUM");
243 if (NULL == tmp)
244 return -1;
245
246 *devaddr = (uint8_t)(strtoul(tmp, NULL, 10) & 0xff);
247 if (errno) {
248 errno = 0;
249 return -1;
250 }
251 } else {
252 /* no bus number. try "DEVICE" */
253 tmp = netlink_message_parse(buffer, len, "DEVICE");
254 if (!tmp) {
255 /* not usb. ignore */
256 return -1;
257 }
258
259 /* Parse a device path such as /dev/bus/usb/003/004 */
260 slash = strrchr(tmp, '/');
261 if (!slash)
262 return -1;
263
264 *busnum = (uint8_t)(strtoul(slash - 3, NULL, 10) & 0xff);
265 if (errno) {
266 errno = 0;
267 return -1;
268 }
269
270 *devaddr = (uint8_t)(strtoul(slash + 1, NULL, 10) & 0xff);
271 if (errno) {
272 errno = 0;
273 return -1;
274 }
275
276 return 0;
277 }
278
279 tmp = netlink_message_parse(buffer, len, "DEVPATH");
280 if (!tmp)
281 return -1;
282
283 slash = strrchr(tmp, '/');
284 if (slash)
285 *sys_name = slash + 1;
286
287 /* found a usb device */
288 return 0;
289 }
290
linux_netlink_read_message(void)291 static int linux_netlink_read_message(void)
292 {
293 char cred_buffer[CMSG_SPACE(sizeof(struct ucred))];
294 char msg_buffer[2048];
295 const char *sys_name = NULL;
296 uint8_t busnum, devaddr;
297 int detached, r;
298 ssize_t len;
299 struct cmsghdr *cmsg;
300 struct ucred *cred;
301 struct sockaddr_nl sa_nl;
302 struct iovec iov = { .iov_base = msg_buffer, .iov_len = sizeof(msg_buffer) };
303 struct msghdr msg = {
304 .msg_iov = &iov, .msg_iovlen = 1,
305 .msg_control = cred_buffer, .msg_controllen = sizeof(cred_buffer),
306 .msg_name = &sa_nl, .msg_namelen = sizeof(sa_nl)
307 };
308
309 /* read netlink message */
310 len = recvmsg(linux_netlink_socket, &msg, 0);
311 if (len == -1) {
312 if (errno != EAGAIN && errno != EINTR)
313 usbi_err(NULL, "error receiving message from netlink (%d)", errno);
314 return -1;
315 }
316
317 if (len < 32 || (msg.msg_flags & MSG_TRUNC)) {
318 usbi_err(NULL, "invalid netlink message length");
319 return -1;
320 }
321
322 if (sa_nl.nl_groups != NL_GROUP_KERNEL || sa_nl.nl_pid != 0) {
323 usbi_dbg("ignoring netlink message from unknown group/PID (%u/%u)",
324 (unsigned int)sa_nl.nl_groups, (unsigned int)sa_nl.nl_pid);
325 return -1;
326 }
327
328 cmsg = CMSG_FIRSTHDR(&msg);
329 if (!cmsg || cmsg->cmsg_type != SCM_CREDENTIALS) {
330 usbi_dbg("ignoring netlink message with no sender credentials");
331 return -1;
332 }
333
334 cred = (struct ucred *)CMSG_DATA(cmsg);
335 if (cred->uid != 0) {
336 usbi_dbg("ignoring netlink message with non-zero sender UID %u", (unsigned int)cred->uid);
337 return -1;
338 }
339
340 r = linux_netlink_parse(msg_buffer, (size_t)len, &detached, &sys_name, &busnum, &devaddr);
341 if (r)
342 return r;
343
344 usbi_dbg("netlink hotplug found device busnum: %hhu, devaddr: %hhu, sys_name: %s, removed: %s",
345 busnum, devaddr, sys_name, detached ? "yes" : "no");
346
347 /* signal device is available (or not) to all contexts */
348 if (detached)
349 linux_device_disconnected(busnum, devaddr);
350 else
351 linux_hotplug_enumerate(busnum, devaddr, sys_name);
352
353 return 0;
354 }
355
linux_netlink_event_thread_main(void * arg)356 static void *linux_netlink_event_thread_main(void *arg)
357 {
358 char dummy;
359 ssize_t r;
360 struct pollfd fds[] = {
361 { .fd = netlink_control_pipe[0],
362 .events = POLLIN },
363 { .fd = linux_netlink_socket,
364 .events = POLLIN },
365 };
366
367 UNUSED(arg);
368
369 usbi_dbg("netlink event thread entering");
370
371 while (poll(fds, 2, -1) >= 0) {
372 if (fds[0].revents & POLLIN) {
373 /* activity on control pipe, read the byte and exit */
374 r = usbi_read(netlink_control_pipe[0], &dummy, sizeof(dummy));
375 if (r <= 0)
376 usbi_warn(NULL, "netlink control pipe read failed");
377 break;
378 }
379 if (fds[1].revents & POLLIN) {
380 usbi_mutex_static_lock(&linux_hotplug_lock);
381 linux_netlink_read_message();
382 usbi_mutex_static_unlock(&linux_hotplug_lock);
383 }
384 }
385
386 usbi_dbg("netlink event thread exiting");
387
388 return NULL;
389 }
390
linux_netlink_hotplug_poll(void)391 void linux_netlink_hotplug_poll(void)
392 {
393 int r;
394
395 usbi_mutex_static_lock(&linux_hotplug_lock);
396 do {
397 r = linux_netlink_read_message();
398 } while (r == 0);
399 usbi_mutex_static_unlock(&linux_hotplug_lock);
400 }
401