/* -*- 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);

}