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 (at) gentoo.org> 5 * Copyright (c) 2001 Johannes Erdfelt <johannes (at) erdfelt.com> 6 * Copyright (c) 2013 Nathan Hjelm <hjelmn (at) mac.com> 7 * Copyright (c) 2016 Chris Dickens <christopher.a.dickens (at) 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 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 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 } 155 156 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 } 182 183 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 */ 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 } 290 291 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 } 355 356 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 } 390 391 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
