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
48static int linux_netlink_socket = -1;
49static int netlink_control_pipe[2] = { -1, -1 };
50static pthread_t libusb_linux_event_thread;
51
52static void *linux_netlink_event_thread_main(void *arg);
53
54static 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
89int 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
144err_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;
149err_close_socket:
150	close(linux_netlink_socket);
151	linux_netlink_socket = -1;
152err:
153	return LIBUSB_ERROR_OTHER;
154}
155
156int 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
183static 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 */
198static 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
291static 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
356static 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
391void 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