/*

 * Copyright (c) 2006 Paolo Abeni (Italy)

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * 1. Redistributions of source code must retain the above copyright

 * notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 * notice, this list of conditions and the following disclaimer in the

 * documentation and/or other materials provided with the distribution.

 * 3. The name of the author may not be used to endorse or promote

 * products derived from this software without specific prior written

 * permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 *

 * USB sniffing API implementation for Linux platform

 * By Paolo Abeni <paolo.abeni@email.it>

 * Modifications: Kris Katterjohn <katterjohn@gmail.com>

 *

 */

#include <config.h>

#include "pcap/usb.h"

#include "pcap-int.h"

#include "pcap-usb-linux.h"

#include "pcap-usb-linux-common.h"

#include "extract.h"

#include <errno.h>

#include <stdlib.h>

#include <unistd.h>

#include <fcntl.h>

#include <limits.h>

#include <string.h>

#include <dirent.h>

#include <byteswap.h>

#include <netinet/in.h>

#include <sys/ioctl.h>

#include <sys/mman.h>

#include <sys/utsname.h>

#ifdef HAVE_LINUX_USBDEVICE_FS_H

/*

 * We might need <linux/compiler.h> to define __user for

 * <linux/usbdevice_fs.h>.

 */

#ifdef HAVE_LINUX_COMPILER_H

#include <linux/compiler.h>

#endif /* HAVE_LINUX_COMPILER_H */

#include <linux/usbdevice_fs.h>

#endif /* HAVE_LINUX_USBDEVICE_FS_H */

#include "diag-control.h"

#define USB_IFACE "usbmon"

#define USBMON_DEV_PREFIX "usbmon"

#define USBMON_DEV_PREFIX_LEN (sizeof USBMON_DEV_PREFIX - 1)

#define USB_LINE_LEN 4096

#if __BYTE_ORDER == __LITTLE_ENDIAN

#define htols(s) s

#define htoll(l) l

#define htol64(ll) ll

#else

#define htols(s) bswap_16(s)

#define htoll(l) bswap_32(l)

#define htol64(ll) bswap_64(ll)

#endif

struct mon_bin_stats {

  uint32_t queued;

  uint32_t dropped;

};

struct mon_bin_get {

  pcap_usb_header *hdr;

  void *data;

  size_t data_len;   /* Length of data (can be zero) */

};

struct mon_bin_mfetch {

  int32_t *offvec;   /* Vector of events fetched */

  int32_t nfetch;    /* Number of events to fetch (out: fetched) */

  int32_t nflush;    /* Number of events to flush */

};

#define MON_IOC_MAGIC 0x92

#define MON_IOCQ_URB_LEN _IO(MON_IOC_MAGIC, 1)

#define MON_IOCX_URB  _IOWR(MON_IOC_MAGIC, 2, struct mon_bin_hdr)

#define MON_IOCG_STATS _IOR(MON_IOC_MAGIC, 3, struct mon_bin_stats)

#define MON_IOCT_RING_SIZE _IO(MON_IOC_MAGIC, 4)

#define MON_IOCQ_RING_SIZE _IO(MON_IOC_MAGIC, 5)

#define MON_IOCX_GET   _IOW(MON_IOC_MAGIC, 6, struct mon_bin_get)

#define MON_IOCX_MFETCH _IOWR(MON_IOC_MAGIC, 7, struct mon_bin_mfetch)

#define MON_IOCH_MFLUSH _IO(MON_IOC_MAGIC, 8)

#define MON_BIN_SETUP 0x1 /* setup hdr is present*/

#define MON_BIN_SETUP_ZERO  0x2 /* setup buffer is not available */

#define MON_BIN_DATA_ZERO 0x4 /* data buffer is not available */

#define MON_BIN_ERROR 0x8

/*

 * Private data for capturing on Linux USB.

 */

struct pcap_usb_linux {

  u_char *mmapbuf;  /* memory-mapped region pointer */

  size_t mmapbuflen;  /* size of region */

  unsigned bus_index;

  u_int packets_read;

};

/* forward declaration */

static int usb_activate(pcap_t *);

static int usb_stats_linux_bin(pcap_t *, struct pcap_stat *);

static int usb_read_linux_bin(pcap_t *, int , pcap_handler , u_char *);

static int usb_read_linux_mmap(pcap_t *, int , pcap_handler , u_char *);

static int usb_inject_linux(pcap_t *, const void *, int);

static int usb_setdirection_linux(pcap_t *, pcap_direction_t);

static void usb_cleanup_linux_mmap(pcap_t *);

/* facility to add an USB device to the device list*/

static int

usb_dev_add(pcap_if_list_t *devlistp, int n, char *err_str)

{

  char dev_name[10];

  char dev_descr[30];

  snprintf(dev_name, sizeof(dev_name), USB_IFACE"%d", n);

  /*

   * XXX - is there any notion of "up" and "running"?

   */

  if (n == 0) {

    /*

     * As this refers to all buses, there's no notion of

     * "connected" vs. "disconnected", as that's a property

     * that would apply to a particular USB interface.

     */

    if (pcapint_add_dev(devlistp, dev_name,

        PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE,

        "Raw USB traffic, all USB buses", err_str) == NULL)

      return -1;

  } else {

    /*

     * XXX - is there a way to determine whether anything's

     * plugged into this bus interface or not, and set

     * PCAP_IF_CONNECTION_STATUS_CONNECTED or

     * PCAP_IF_CONNECTION_STATUS_DISCONNECTED?

     */

    snprintf(dev_descr, sizeof(dev_descr), "Raw USB traffic, bus number %d", n);

    if (pcapint_add_dev(devlistp, dev_name, 0, dev_descr, err_str) == NULL)

      return -1;

  }

  return 0;

}

int

usb_findalldevs(pcap_if_list_t *devlistp, char *err_str)

{

  struct dirent* data;

  int ret = 0;

  DIR* dir;

  int n;

  char* name;

  /*

   * We require 2.6.27 or later kernels, so we have binary-mode support.

   * The devices are of the form /dev/usbmon{N}.

   * Open /dev and scan it.

   */

  dir = opendir("/dev");

  if (dir != NULL) {

    while ((ret == 0) && ((data = readdir(dir)) != 0)) {

      name = data->d_name;

      /*

       * Is this a usbmon device?

       */

      if (strncmp(name, USBMON_DEV_PREFIX,

          USBMON_DEV_PREFIX_LEN) != 0)

        continue; /* no */

      /*

       * What's the device number?

       */

      if (sscanf(&name[USBMON_DEV_PREFIX_LEN], "%d", &n) == 0)

        continue; /* failed */

      ret = usb_dev_add(devlistp, n, err_str);

    }

    closedir(dir);

  }

  return 0;

}

/*

 * Matches what's in mon_bin.c in the Linux kernel.

 */

#define MIN_RING_SIZE (8*1024)

#define MAX_RING_SIZE (1200*1024)

static int

usb_set_ring_size(pcap_t* handle, int header_size)

{

  /*

   * A packet from binary usbmon has:

   *

   *  1) a fixed-length header, of size header_size;

   *  2) descriptors, for isochronous transfers;

   *  3) the payload.

   *

   * The kernel buffer has a size, defaulting to 300KB, with a

   * minimum of 8KB and a maximum of 1200KB.  The size is set with

   * the MON_IOCT_RING_SIZE ioctl; the size passed in is rounded up

   * to a page size.

   *

   * No more than {buffer size}/5 bytes worth of payload is saved.

   * Therefore, if we subtract the fixed-length size from the

   * snapshot length, we have the biggest payload we want (we

   * don't worry about the descriptors - if we have descriptors,

   * we'll just discard the last bit of the payload to get it

   * to fit).  We multiply that result by 5 and set the buffer

   * size to that value.

   */

  int ring_size;

  if (handle->snapshot < header_size)

    handle->snapshot = header_size;

  /* The maximum snapshot size is small enough that this won't overflow */

  ring_size = (handle->snapshot - header_size) * 5;

  /*

   * Will this get an error?

   * (There's no way to query the minimum or maximum, so we just

   * copy the value from the kernel source.  We don't round it

   * up to a multiple of the page size.)

   */

  if (ring_size > MAX_RING_SIZE) {

    /*

     * Yes.  Lower the ring size to the maximum, and set the

     * snapshot length to the value that would give us a

     * maximum-size ring.

     */

    ring_size = MAX_RING_SIZE;

    handle->snapshot = header_size + (MAX_RING_SIZE/5);

  } else if (ring_size < MIN_RING_SIZE) {

    /*

     * Yes.  Raise the ring size to the minimum, but leave

     * the snapshot length unchanged, so we show the

     * callback no more data than specified by the

     * snapshot length.

     */

    ring_size = MIN_RING_SIZE;

  }

  if (ioctl(handle->fd, MON_IOCT_RING_SIZE, ring_size) == -1) {

    pcapint_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,

        errno, "Can't set ring size from fd %d", handle->fd);

    return -1;

  }

  return ring_size;

}

static

int usb_mmap(pcap_t* handle)

{

  struct pcap_usb_linux *handlep = handle->priv;

  int len;

  /*

   * Attempt to set the ring size as appropriate for the snapshot

   * length, reducing the snapshot length if that'd make the ring

   * bigger than the kernel supports.

   */

  len = usb_set_ring_size(handle, (int)sizeof(pcap_usb_header_mmapped));

  if (len == -1) {

    /* Failed.  Fall back on non-memory-mapped access. */

    return 0;

  }

  handlep->mmapbuflen = len;

  handlep->mmapbuf = mmap(0, handlep->mmapbuflen, PROT_READ,

      MAP_SHARED, handle->fd, 0);

  if (handlep->mmapbuf == MAP_FAILED) {

    /*

     * Failed.  We don't treat that as a fatal error, we

     * just try to fall back on non-memory-mapped access.

     */

    return 0;

  }

  return 1;

}

#ifdef HAVE_LINUX_USBDEVICE_FS_H

#define CTRL_TIMEOUT    (5*1000)        /* milliseconds */

#define USB_DIR_IN    0x80

#define USB_TYPE_STANDARD 0x00

#define USB_RECIP_DEVICE  0x00

#define USB_REQ_GET_DESCRIPTOR  6

#define USB_DT_DEVICE   1

#define USB_DT_CONFIG   2

#define USB_DEVICE_DESCRIPTOR_SIZE  18

#define USB_CONFIG_DESCRIPTOR_SIZE  9

/* probe the descriptors of the devices attached to the bus */

/* the descriptors will end up in the captured packet stream */

/* and be decoded by external apps like wireshark */

/* without these identifying probes packet data can't be fully decoded */

static void

probe_devices(int bus)

{

  struct usbdevfs_ctrltransfer ctrl;

  struct dirent* data;

  int ret = 0;

  char busdevpath[sizeof("/dev/bus/usb/000/") + NAME_MAX];

  DIR* dir;

  uint8_t descriptor[USB_DEVICE_DESCRIPTOR_SIZE];

  uint8_t configdesc[USB_CONFIG_DESCRIPTOR_SIZE];

  /* scan usb bus directories for device nodes */

  snprintf(busdevpath, sizeof(busdevpath), "/dev/bus/usb/%03d", bus);

  dir = opendir(busdevpath);

  if (!dir)

    return;

  while ((ret >= 0) && ((data = readdir(dir)) != 0)) {

    int fd;

    char* name = data->d_name;

    if (name[0] == '.')

      continue;

    snprintf(busdevpath, sizeof(busdevpath), "/dev/bus/usb/%03d/%s", bus, data->d_name);

    fd = open(busdevpath, O_RDWR);

    if (fd == -1)

      continue;

    /*

     * Sigh.  Different kernels have different member names

     * for this structure.

     */

#ifdef HAVE_STRUCT_USBDEVFS_CTRLTRANSFER_BREQUESTTYPE

    ctrl.bRequestType = USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_DEVICE;

    ctrl.bRequest = USB_REQ_GET_DESCRIPTOR;

    ctrl.wValue = USB_DT_DEVICE << 8;

    ctrl.wIndex = 0;

    ctrl.wLength = sizeof(descriptor);

#else

    ctrl.requesttype = USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_DEVICE;

    ctrl.request = USB_REQ_GET_DESCRIPTOR;

    ctrl.value = USB_DT_DEVICE << 8;

    ctrl.index = 0;

    ctrl.length = sizeof(descriptor);

#endif

    ctrl.data = descriptor;

    ctrl.timeout = CTRL_TIMEOUT;

    ret = ioctl(fd, USBDEVFS_CONTROL, &ctrl);

    /* Request CONFIGURATION descriptor alone to know wTotalLength */

#ifdef HAVE_STRUCT_USBDEVFS_CTRLTRANSFER_BREQUESTTYPE

    ctrl.wValue = USB_DT_CONFIG << 8;

    ctrl.wLength = sizeof(configdesc);

#else

    ctrl.value = USB_DT_CONFIG << 8;

    ctrl.length = sizeof(configdesc);

#endif

    ctrl.data = configdesc;

    ret = ioctl(fd, USBDEVFS_CONTROL, &ctrl);

    if (ret >= 0) {

      uint16_t wtotallength;

      wtotallength = EXTRACT_LE_U_2(&configdesc[2]);

#ifdef HAVE_STRUCT_USBDEVFS_CTRLTRANSFER_BREQUESTTYPE

      ctrl.wLength = wtotallength;

#else

      ctrl.length = wtotallength;

#endif

      ctrl.data = malloc(wtotallength);

      if (ctrl.data) {

        ret = ioctl(fd, USBDEVFS_CONTROL, &ctrl);

        free(ctrl.data);

      }

    }

    close(fd);

  }

  closedir(dir);

}

#endif /* HAVE_LINUX_USBDEVICE_FS_H */

pcap_t *

usb_create(const char *device, char *ebuf, int *is_ours)

{

  const char *cp;

  unsigned bus_index;

  pcap_t *p;

  /* Does this look like a USB monitoring device? */

  cp = device;

  /* Does it begin with USB_IFACE? */

  if (strncmp(cp, USB_IFACE, sizeof USB_IFACE - 1) != 0) {

    /* Nope, doesn't begin with USB_IFACE */

    *is_ours = 0;

    return NULL;

  }

  /* Yes - is USB_IFACE followed by a number? */

  cp += sizeof USB_IFACE - 1;

  if (pcapint_get_decuint(cp, NULL, &bus_index) != 0) {

    /* Not followed by a valid number */

    *is_ours = 0;

    return NULL;

  }

  /* OK, it's probably ours. */

  *is_ours = 1;

  p = PCAP_CREATE_COMMON(ebuf, struct pcap_usb_linux);

  if (p == NULL)

    return (NULL);

  struct pcap_usb_linux *handlep = p->priv;

  p->activate_op = usb_activate;

  handlep->bus_index = bus_index;

  return (p);

}

static int

usb_activate(pcap_t* handle)

{

  struct pcap_usb_linux *handlep = handle->priv;

  char    full_path[USB_LINE_LEN];

  /*

   * Turn a negative snapshot value (invalid), a snapshot value of

   * 0 (unspecified), or a value bigger than the normal maximum

   * value, into the maximum allowed value.

   *

   * If some application really *needs* a bigger snapshot

   * length, we should just increase MAXIMUM_SNAPLEN.

   */

  if (handle->snapshot <= 0 || handle->snapshot > MAXIMUM_SNAPLEN)

    handle->snapshot = MAXIMUM_SNAPLEN;

  /* Initialize some components of the pcap structure. */

  handle->bufsize = handle->snapshot;

  handle->offset = 0;

  handle->linktype = DLT_USB_LINUX;

  handle->inject_op = usb_inject_linux;

  handle->setfilter_op = pcapint_install_bpf_program; /* no kernel filtering */

  handle->setdirection_op = usb_setdirection_linux;

  handle->set_datalink_op = NULL; /* can't change data link type */

  handle->getnonblock_op = pcapint_getnonblock_fd;

  handle->setnonblock_op = pcapint_setnonblock_fd;

  /*

   * We require 2.6.27 or later kernels, so we have binary-mode support.

   * Try to open the binary interface.

   */

  snprintf(full_path, USB_LINE_LEN, "/dev/"USBMON_DEV_PREFIX"%d",

      handlep->bus_index);

  handle->fd = open(full_path, O_RDONLY, 0);

  if (handle->fd < 0)

  {

    /*

     * The attempt failed; why?

     */

    switch (errno) {

    case ENOENT:

      /*

       * The device doesn't exist.

       * That could either mean that there's

       * no support for monitoring USB buses

       * (which probably means "the usbmon

       * module isn't loaded") or that there

       * is but that *particular* device

       * doesn't exist (no "scan all buses"

       * device if the bus index is 0, no

       * such bus if the bus index isn't 0).

       *

       * For now, don't provide an error message;

       * if we can determine what the particular

       * problem is, we should report that.

       */

      handle->errbuf[0] = '\0';

      return PCAP_ERROR_NO_SUCH_DEVICE;

    case EACCES:

      /*

       * We didn't have permission to open it.

       */

DIAG_OFF_FORMAT_TRUNCATION

      snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,

          "Attempt to open %s failed with EACCES - root privileges may be required",

          full_path);

DIAG_ON_FORMAT_TRUNCATION

      return PCAP_ERROR_PERM_DENIED;

    default:

      /*

       * Something went wrong.

       */

      pcapint_fmt_errmsg_for_errno(handle->errbuf,

          PCAP_ERRBUF_SIZE, errno,

          "Can't open USB bus file %s", full_path);

      return PCAP_ERROR;

    }

  }

  if (handle->opt.rfmon)

  {

    /*

     * Monitor mode doesn't apply to USB devices.

     */

    close(handle->fd);

    return PCAP_ERROR_RFMON_NOTSUP;

  }

  /* try to use fast mmap access */

  if (usb_mmap(handle))

  {

    /* We succeeded. */

    handle->linktype = DLT_USB_LINUX_MMAPPED;

    handle->stats_op = usb_stats_linux_bin;

    handle->read_op = usb_read_linux_mmap;

    handle->cleanup_op = usb_cleanup_linux_mmap;

#ifdef HAVE_LINUX_USBDEVICE_FS_H

    probe_devices(handlep->bus_index);

#endif

    /*

     * "handle->fd" is a real file, so

     * "select()" and "poll()" work on it.

     */

    handle->selectable_fd = handle->fd;

    return 0;

  }

  /*

   * We failed; try plain binary interface access.

   *

   * Attempt to set the ring size as appropriate for

   * the snapshot length, reducing the snapshot length

   * if that'd make the ring bigger than the kernel

   * supports.

   */

  if (usb_set_ring_size(handle, (int)sizeof(pcap_usb_header)) == -1) {

    /* Failed. */

    close(handle->fd);

    return PCAP_ERROR;

  }

  handle->stats_op = usb_stats_linux_bin;

  handle->read_op = usb_read_linux_bin;

#ifdef HAVE_LINUX_USBDEVICE_FS_H

  probe_devices(handlep->bus_index);

#endif

  /*

   * "handle->fd" is a real file, so "select()" and "poll()"

   * work on it.

   */

  handle->selectable_fd = handle->fd;

  /* for plain binary access and text access we need to allocate the read

   * buffer */

  handle->buffer = malloc(handle->bufsize);

  if (!handle->buffer) {

    pcapint_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,

        errno, "malloc");

    close(handle->fd);

    return PCAP_ERROR;

  }

  return 0;

}

static int

usb_inject_linux(pcap_t *handle, const void *buf _U_, int size _U_)

{

  snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,

      "Packet injection is not supported on USB devices");

  return (-1);

}

static int

usb_setdirection_linux(pcap_t *p, pcap_direction_t d)

{

  /*

   * It's guaranteed, at this point, that d is a valid

   * direction value.

   */

  p->direction = d;

  return 0;

}

static int

usb_stats_linux_bin(pcap_t *handle, struct pcap_stat *stats)

{

  struct pcap_usb_linux *handlep = handle->priv;

  int ret;

  struct mon_bin_stats st;

  ret = ioctl(handle->fd, MON_IOCG_STATS, &st);

  if (ret < 0)

  {

    pcapint_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,

        errno, "Can't read stats from fd %d", handle->fd);

    return -1;

  }

  stats->ps_recv = handlep->packets_read + st.queued;

  stats->ps_drop = st.dropped;

  stats->ps_ifdrop = 0;

  return 0;

}

/*

 * see <linux-kernel-source>/Documentation/usb/usbmon.txt and

 * <linux-kernel-source>/drivers/usb/mon/mon_bin.c binary ABI

 */

static int

usb_read_linux_bin(pcap_t *handle, int max_packets _U_, pcap_handler callback, u_char *user)

{

  struct pcap_usb_linux *handlep = handle->priv;

  struct mon_bin_get info;

  int ret;

  struct pcap_pkthdr pkth;

  u_int clen = handle->snapshot - sizeof(pcap_usb_header);

  /* the usb header is going to be part of 'packet' data*/

  info.hdr = (pcap_usb_header*) handle->buffer;

  info.data = handle->buffer + sizeof(pcap_usb_header);

  info.data_len = clen;

  /* ignore interrupt system call errors */

  do {

    ret = ioctl(handle->fd, MON_IOCX_GET, &info);

    if (handle->break_loop)

    {

      handle->break_loop = 0;

      return -2;

    }

  } while ((ret == -1) && (errno == EINTR));

  if (ret < 0)

  {

    if (errno == EAGAIN)

      return 0; /* no data there */

    pcapint_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,

        errno, "Can't read from fd %d", handle->fd);

    return -1;

  }

  /*

   * info.hdr->data_len is the number of bytes of isochronous

   * descriptors (if any) plus the number of bytes of data

   * provided.  There are no isochronous descriptors here,

   * because we're using the old 48-byte header.

   *

   * If info.hdr->data_flag is non-zero, there's no URB data;

   * info.hdr->urb_len is the size of the buffer into which

   * data is to be placed; it does not represent the amount

   * of data transferred.  If info.hdr->data_flag is zero,

   * there is URB data, and info.hdr->urb_len is the number

   * of bytes transmitted or received; it doesn't include

   * isochronous descriptors.

   *

   * The kernel may give us more data than the snaplen; if it did,

   * reduce the data length so that the total number of bytes we

   * tell our client we have is not greater than the snaplen.

   */

  if (info.hdr->data_len < clen)

    clen = info.hdr->data_len;

  info.hdr->data_len = clen;

  pkth.caplen = sizeof(pcap_usb_header) + clen;

  if (info.hdr->data_flag) {

    /*

     * No data; just base the original length on

     * info.hdr->data_len (so that it's >= the captured

     * length).

     */

    pkth.len = sizeof(pcap_usb_header) + info.hdr->data_len;

  } else {

    /*

     * We got data; base the original length on

     * info.hdr->urb_len, so that it includes data

     * discarded by the USB monitor device due to

     * its buffer being too small.

     */

    pkth.len = sizeof(pcap_usb_header) + info.hdr->urb_len;

  }

  pkth.ts.tv_sec = (time_t)pcap_4_byte_aligned_int64_val(info.hdr->ts_sec);

  pkth.ts.tv_usec = info.hdr->ts_usec;

  if (handle->fcode.bf_insns == NULL ||

      pcapint_filter(handle->fcode.bf_insns, handle->buffer,

        pkth.len, pkth.caplen)) {

    handlep->packets_read++;

    callback(user, &pkth, handle->buffer);

    return 1;

  }

  return 0; /* didn't pass filter */

}

/*

 * see <linux-kernel-source>/Documentation/usb/usbmon.txt and

 * <linux-kernel-source>/drivers/usb/mon/mon_bin.c binary ABI

 */

#define VEC_SIZE 32

static int

usb_read_linux_mmap(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)

{

  struct pcap_usb_linux *handlep = handle->priv;

  struct mon_bin_mfetch fetch;

  int32_t vec[VEC_SIZE];

  struct pcap_pkthdr pkth;

  u_char *bp;

  pcap_usb_header_mmapped* hdr;

  int nflush = 0;

  int packets = 0;

  u_int clen, max_clen;

  max_clen = handle->snapshot - sizeof(pcap_usb_header_mmapped);

  for (;;) {

    int i, ret;

    int limit;

    if (PACKET_COUNT_IS_UNLIMITED(max_packets)) {

      /*

       * There's no limit on the number of packets

       * to process, so try to fetch VEC_SIZE packets.

       */

      limit = VEC_SIZE;

    } else {

      /*

       * Try to fetch as many packets as we have left

       * to process, or VEC_SIZE packets, whichever

       * is less.

       *

       * At this point, max_packets > 0 (otherwise,

       * PACKET_COUNT_IS_UNLIMITED(max_packets)

       * would be true) and max_packets > packets

       * (packet starts out as 0, and the test

       * at the bottom of the loop exits if

       * max_packets <= packets), so limit is

       * guaranteed to be > 0.

       */

      limit = max_packets - packets;

      if (limit > VEC_SIZE)

        limit = VEC_SIZE;

    }

    /*

     * Try to fetch as many events as possible, up to

     * the limit, and flush the events we've processed

     * earlier (nflush) - MON_IOCX_MFETCH does both

     * (presumably to reduce the number of system

     * calls in loops like this).

     */

    fetch.offvec = vec;

    fetch.nfetch = limit;

    fetch.nflush = nflush;

    /* ignore interrupt system call errors */

    do {

      ret = ioctl(handle->fd, MON_IOCX_MFETCH, &fetch);

      if (handle->break_loop)

      {

        handle->break_loop = 0;

        return -2;

      }

    } while ((ret == -1) && (errno == EINTR));

    if (ret < 0)

    {

      if (errno == EAGAIN)

        return 0; /* no data there */

      pcapint_fmt_errmsg_for_errno(handle->errbuf,

          PCAP_ERRBUF_SIZE, errno, "Can't mfetch fd %d",

          handle->fd);

      return -1;

    }

    /* keep track of processed events, we will flush them later */

    nflush = fetch.nfetch;

    for (i=0; i<fetch.nfetch; ++i) {

      /*

       * XXX - we can't check break_loop here, as

       * we read the indices of packets into a

       * local variable, so if we're later called

       * to fetch more packets, those packets will

       * not be seen - and won't be flushed, either.

       *

       * Instead, we would have to keep the array

       * of indices in our private data, along

       * with the count of packets to flush - or

       * would have to flush the already-processed

       * packets if we break out of the loop here.

       */

      /* Get a pointer to this packet's buffer */

      bp = &handlep->mmapbuf[vec[i]];

      /* That begins with a metadata header */

      hdr = (pcap_usb_header_mmapped*) bp;

      /* discard filler */

      if (hdr->event_type == '@')

        continue;

      /*

       * hdr->data_len is the number of bytes of

       * isochronous descriptors (if any) plus the

       * number of bytes of data provided.

       *

       * If hdr->data_flag is non-zero, there's no

       * URB data; hdr->urb_len is the size of the

       * buffer into which data is to be placed; it does

       * not represent the amount of data transferred.

       * If hdr->data_flag is zero, there is URB data,

       * and hdr->urb_len is the number of bytes

       * transmitted or received; it doesn't include

       * isochronous descriptors.

       *

       * The kernel may give us more data than the

       * snaplen; if it did, reduce the data length

       * so that the total number of bytes we

       * tell our client we have is not greater than

       * the snaplen.

       */

      clen = max_clen;

      if (hdr->data_len < clen)

        clen = hdr->data_len;

      pkth.caplen = sizeof(pcap_usb_header_mmapped) + clen;

      if (hdr->data_flag) {

        /*

         * No data; just base the original length

         * on hdr->data_len (so that it's >= the

         * captured length).  Clamp the result

         * at UINT_MAX, so it fits in an unsigned

         * int.

         */

        pkth.len = u_int_sum(sizeof(pcap_usb_header_mmapped),

            hdr->data_len);

      } else {

        /*

         * We got data.

         */

        if (is_isochronous_transfer_completion(hdr)) {

          /*

           * For isochronous transfer completion

           * events, hdr->urb_len doesn't take

           * into account the way the data is

           * put into the buffer, as it doesn't

           * count any padding between the

           * chunks of isochronous data, so

           * we have to calculate the amount

           * of data from the isochronous

           * descriptors.

           */

          pkth.len = incoming_isochronous_transfer_completed_len(&pkth, bp);

        } else {

          /*

           * For everything else, the original

           * data length is just the length of

           * the memory-mapped Linux USB header

           * plus hdr->urb_len; we use

           * hdr->urb_len so that it includes

           * data discarded by the USB monitor

           * device due to its buffer being

           * too small.  Clamp the result at

           * UINT_MAX, so it fits in an

           * unsigned int.

           */

          pkth.len = u_int_sum(sizeof(pcap_usb_header_mmapped),

              hdr->urb_len);

        }

      }

      pkth.ts.tv_sec = (time_t)pcap_4_byte_aligned_int64_val(hdr->ts_sec);

      pkth.ts.tv_usec = hdr->ts_usec;

      if (handle->fcode.bf_insns == NULL ||

          pcapint_filter(handle->fcode.bf_insns, (u_char*) hdr,

            pkth.len, pkth.caplen)) {

        handlep->packets_read++;

        callback(user, &pkth, (u_char*) hdr);

        packets++;

      }

    }

    /*

     * If max_packets specifies "unlimited", we stop after

     * the first chunk.

     */

    if (PACKET_COUNT_IS_UNLIMITED(max_packets) ||

        (packets >= max_packets))

      break;

  }

  /* flush pending events*/

  if (ioctl(handle->fd, MON_IOCH_MFLUSH, nflush) == -1) {

    pcapint_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,

        errno, "Can't mflush fd %d", handle->fd);

    return -1;

  }

  return packets;

}

static void

usb_cleanup_linux_mmap(pcap_t* handle)

{

  struct pcap_usb_linux *handlep = handle->priv;

  /* if we have a memory-mapped buffer, unmap it */

  if (handlep->mmapbuf != NULL) {

    munmap(handlep->mmapbuf, handlep->mmapbuflen);

    handlep->mmapbuf = NULL;

  }

  pcapint_cleanup_live_common(handle);

}