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/* -*- Mode: C; c-basic-offset:8 ; indent-tabs-mode:t -*- */
/*
* Linux usbfs backend for libusb
* Copyright (C) 2007-2009 Daniel Drake <dsd@gentoo.org>
* Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
* Copyright (c) 2013 Nathan Hjelm <hjelmn@mac.com>
* Copyright (c) 2016 Chris Dickens <christopher.a.dickens@gmail.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "libusbi.h"
#include "linux_usbfs.h"
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <pthread.h>
#include <string.h>
#include <unistd.h>
#ifdef HAVE_ASM_TYPES_H
#include <asm/types.h>
#endif
#include <sys/socket.h>
#include <linux/netlink.h>
#define NL_GROUP_KERNEL 1
#ifndef SOCK_CLOEXEC
#define SOCK_CLOEXEC 0
#endif
#ifndef SOCK_NONBLOCK
#define SOCK_NONBLOCK 0
#endif
static int linux_netlink_socket = -1;
static usbi_event_t netlink_control_event = USBI_INVALID_EVENT;
static pthread_t libusb_linux_event_thread;
static void *linux_netlink_event_thread_main(void *arg);
static int set_fd_cloexec_nb(int fd, int socktype)
{
int flags;
#if defined(FD_CLOEXEC)
/* Make sure the netlink socket file descriptor is marked as CLOEXEC */
if (!(socktype & SOCK_CLOEXEC)) {
flags = fcntl(fd, F_GETFD);
if (flags == -1) {
usbi_err(NULL, "failed to get netlink fd flags, errno=%d", errno);
return -1;
}
if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1) {
usbi_err(NULL, "failed to set netlink fd flags, errno=%d", errno);
return -1;
}
}
#endif
/* Make sure the netlink socket is non-blocking */
if (!(socktype & SOCK_NONBLOCK)) {
flags = fcntl(fd, F_GETFL);
if (flags == -1) {
usbi_err(NULL, "failed to get netlink fd status flags, errno=%d", errno);
return -1;
}
if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1) {
usbi_err(NULL, "failed to set netlink fd status flags, errno=%d", errno);
return -1;
}
}
return 0;
}
int linux_netlink_start_event_monitor(void)
{
struct sockaddr_nl sa_nl = { .nl_family = AF_NETLINK, .nl_groups = NL_GROUP_KERNEL };
int socktype = SOCK_RAW | SOCK_NONBLOCK | SOCK_CLOEXEC;
int opt = 1;
int ret;
linux_netlink_socket = socket(PF_NETLINK, socktype, NETLINK_KOBJECT_UEVENT);
if (linux_netlink_socket == -1 && errno == EINVAL) {
usbi_dbg(NULL, "failed to create netlink socket of type %d, attempting SOCK_RAW", socktype);
socktype = SOCK_RAW;
linux_netlink_socket = socket(PF_NETLINK, socktype, NETLINK_KOBJECT_UEVENT);
}
if (linux_netlink_socket == -1) {
usbi_err(NULL, "failed to create netlink socket, errno=%d", errno);
goto err;
}
ret = set_fd_cloexec_nb(linux_netlink_socket, socktype);
if (ret == -1)
goto err_close_socket;
ret = bind(linux_netlink_socket, (struct sockaddr *)&sa_nl, sizeof(sa_nl));
if (ret == -1) {
usbi_err(NULL, "failed to bind netlink socket, errno=%d", errno);
goto err_close_socket;
}
ret = setsockopt(linux_netlink_socket, SOL_SOCKET, SO_PASSCRED, &opt, sizeof(opt));
if (ret == -1) {
usbi_err(NULL, "failed to set netlink socket SO_PASSCRED option, errno=%d", errno);
goto err_close_socket;
}
ret = usbi_create_event(&netlink_control_event);
if (ret) {
usbi_err(NULL, "failed to create netlink control event");
goto err_close_socket;
}
ret = pthread_create(&libusb_linux_event_thread, NULL, linux_netlink_event_thread_main, NULL);
if (ret != 0) {
usbi_err(NULL, "failed to create netlink event thread (%d)", ret);
goto err_destroy_event;
}
return LIBUSB_SUCCESS;
err_destroy_event:
usbi_destroy_event(&netlink_control_event);
netlink_control_event = (usbi_event_t)USBI_INVALID_EVENT;
err_close_socket:
close(linux_netlink_socket);
linux_netlink_socket = -1;
err:
return LIBUSB_ERROR_OTHER;
}
int linux_netlink_stop_event_monitor(void)
{
int ret;
assert(linux_netlink_socket != -1);
/* Signal the control event and wait for the thread to exit */
usbi_signal_event(&netlink_control_event);
ret = pthread_join(libusb_linux_event_thread, NULL);
if (ret)
usbi_warn(NULL, "failed to join netlink event thread (%d)", ret);
usbi_destroy_event(&netlink_control_event);
netlink_control_event = (usbi_event_t)USBI_INVALID_EVENT;
close(linux_netlink_socket);
linux_netlink_socket = -1;
return LIBUSB_SUCCESS;
}
static const char *netlink_message_parse(const char *buffer, size_t len, const char *key)
{
const char *end = buffer + len;
size_t keylen = strlen(key);
while (buffer < end && *buffer) {
if (strncmp(buffer, key, keylen) == 0 && buffer[keylen] == '=')
return buffer + keylen + 1;
buffer += strlen(buffer) + 1;
}
return NULL;
}
/* parse parts of netlink message common to both libudev and the kernel */
static int linux_netlink_parse(const char *buffer, size_t len, int *detached,
const char **sys_name, uint8_t *busnum, uint8_t *devaddr)
{
const char *tmp, *slash;
errno = 0;
*sys_name = NULL;
*detached = 0;
*busnum = 0;
*devaddr = 0;
tmp = netlink_message_parse(buffer, len, "ACTION");
if (!tmp) {
return -1;
} else if (strcmp(tmp, "remove") == 0) {
*detached = 1;
} else if (strcmp(tmp, "add") != 0) {
usbi_dbg(NULL, "unknown device action %s", tmp);
return -1;
}
/* check that this is a usb message */
tmp = netlink_message_parse(buffer, len, "SUBSYSTEM");
if (!tmp || strcmp(tmp, "usb") != 0) {
/* not usb. ignore */
return -1;
}
/* check that this is an actual usb device */
tmp = netlink_message_parse(buffer, len, "DEVTYPE");
if (!tmp || strcmp(tmp, "usb_device") != 0) {
/* not usb. ignore */
return -1;
}
tmp = netlink_message_parse(buffer, len, "BUSNUM");
if (tmp) {
*busnum = (uint8_t)(strtoul(tmp, NULL, 10) & 0xff);
if (errno) {
errno = 0;
return -1;
}
tmp = netlink_message_parse(buffer, len, "DEVNUM");
if (NULL == tmp)
return -1;
*devaddr = (uint8_t)(strtoul(tmp, NULL, 10) & 0xff);
if (errno) {
errno = 0;
return -1;
}
} else {
/* no bus number. try "DEVICE" */
tmp = netlink_message_parse(buffer, len, "DEVICE");
if (!tmp) {
/* not usb. ignore */
return -1;
}
/* Parse a device path such as /dev/bus/usb/003/004 */
slash = strrchr(tmp, '/');
if (!slash)
return -1;
*busnum = (uint8_t)(strtoul(slash - 3, NULL, 10) & 0xff);
if (errno) {
errno = 0;
return -1;
}
*devaddr = (uint8_t)(strtoul(slash + 1, NULL, 10) & 0xff);
if (errno) {
errno = 0;
return -1;
}
return 0;
}
tmp = netlink_message_parse(buffer, len, "DEVPATH");
if (!tmp)
return -1;
slash = strrchr(tmp, '/');
if (slash)
*sys_name = slash + 1;
/* found a usb device */
return 0;
}
static int linux_netlink_read_message(void)
{
char cred_buffer[CMSG_SPACE(sizeof(struct ucred))];
char msg_buffer[2048];
const char *sys_name = NULL;
uint8_t busnum, devaddr;
int detached, r;
ssize_t len;
struct cmsghdr *cmsg;
struct ucred *cred;
struct sockaddr_nl sa_nl;
struct iovec iov = { .iov_base = msg_buffer, .iov_len = sizeof(msg_buffer) };
struct msghdr msg = {
.msg_iov = &iov, .msg_iovlen = 1,
.msg_control = cred_buffer, .msg_controllen = sizeof(cred_buffer),
.msg_name = &sa_nl, .msg_namelen = sizeof(sa_nl)
};
/* read netlink message */
len = recvmsg(linux_netlink_socket, &msg, 0);
if (len == -1) {
if (errno != EAGAIN && errno != EINTR)
usbi_err(NULL, "error receiving message from netlink, errno=%d", errno);
return -1;
}
if (len < 32 || (msg.msg_flags & MSG_TRUNC)) {
usbi_err(NULL, "invalid netlink message length");
return -1;
}
if (sa_nl.nl_groups != NL_GROUP_KERNEL || sa_nl.nl_pid != 0) {
usbi_dbg(NULL, "ignoring netlink message from unknown group/PID (%u/%u)",
(unsigned int)sa_nl.nl_groups, (unsigned int)sa_nl.nl_pid);
return -1;
}
cmsg = CMSG_FIRSTHDR(&msg);
if (!cmsg || cmsg->cmsg_type != SCM_CREDENTIALS) {
usbi_dbg(NULL, "ignoring netlink message with no sender credentials");
return -1;
}
cred = (struct ucred *)CMSG_DATA(cmsg);
if (cred->uid != 0) {
usbi_dbg(NULL, "ignoring netlink message with non-zero sender UID %u", (unsigned int)cred->uid);
return -1;
}
r = linux_netlink_parse(msg_buffer, (size_t)len, &detached, &sys_name, &busnum, &devaddr);
if (r)
return r;
usbi_dbg(NULL, "netlink hotplug found device busnum: %hhu, devaddr: %hhu, sys_name: %s, removed: %s",
busnum, devaddr, sys_name, detached ? "yes" : "no");
/* signal device is available (or not) to all contexts */
if (detached)
linux_device_disconnected(busnum, devaddr);
else
linux_hotplug_enumerate(busnum, devaddr, sys_name);
return 0;
}
static void *linux_netlink_event_thread_main(void *arg)
{
struct pollfd fds[] = {
{ .fd = USBI_EVENT_OS_HANDLE(&netlink_control_event),
.events = USBI_EVENT_POLL_EVENTS },
{ .fd = linux_netlink_socket,
.events = POLLIN },
};
int r;
UNUSED(arg);
#if defined(HAVE_PTHREAD_SETNAME_NP)
r = pthread_setname_np(pthread_self(), "libusb_event");
if (r)
usbi_warn(NULL, "failed to set hotplug event thread name, error=%d", r);
#endif
usbi_dbg(NULL, "netlink event thread entering");
while (1) {
r = poll(fds, 2, -1);
if (r == -1) {
/* check for temporary failure */
if (errno == EINTR)
continue;
usbi_err(NULL, "poll() failed, errno=%d", errno);
break;
}
if (fds[0].revents) {
/* activity on control event, exit */
break;
}
if (fds[1].revents) {
usbi_mutex_static_lock(&linux_hotplug_lock);
linux_netlink_read_message();
usbi_mutex_static_unlock(&linux_hotplug_lock);
}
}
usbi_dbg(NULL, "netlink event thread exiting");
return NULL;
}
void linux_netlink_hotplug_poll(void)
{
int r;
usbi_mutex_static_lock(&linux_hotplug_lock);
do {
r = linux_netlink_read_message();
} while (r == 0);
usbi_mutex_static_unlock(&linux_hotplug_lock);
}