xref: /freebsd/contrib/libpcap/pcap-usb-linux.c (revision eda14cbc264d6969b02f2b1994cef11148e914f1)

/*
 * 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>
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "pcap-int.h"
#include "pcap-usb-linux.h"
#include "pcap/usb.h"

#ifdef NEED_STRERROR_H
#include "strerror.h"
#endif

#include <ctype.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 */

#define USB_IFACE "usbmon"
#define USB_TEXT_DIR_OLD "/sys/kernel/debug/usbmon"
#define USB_TEXT_DIR "/sys/kernel/debug/usb/usbmon"
#define SYS_USB_BUS_DIR "/sys/bus/usb/devices"
#define PROC_USB_BUS_DIR "/proc/bus/usb"
#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 */
	int bus_index;
	u_int packets_read;
};

/* forward declaration */
static int usb_activate(pcap_t *);
static int usb_stats_linux(pcap_t *, struct pcap_stat *);
static int usb_stats_linux_bin(pcap_t *, struct pcap_stat *);
static int usb_read_linux(pcap_t *, int , pcap_handler , u_char *);
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 *, size_t);
static int usb_setdirection_linux(pcap_t *, pcap_direction_t);
static void usb_cleanup_linux_mmap(pcap_t *);

static int
have_binary_usbmon(void)
{
	struct utsname utsname;
	char *version_component, *endp;
	int major, minor, subminor;

	if (uname(&utsname) == 0) {
		/*
		 * 2.6.21 is the first release with the binary-mode
		 * USB monitoring.
		 */
		version_component = utsname.release;
		major = strtol(version_component, &endp, 10);
		if (endp != version_component && *endp == '.') {
			/*
			 * OK, that was a valid major version.
			 * Is it 3 or greater?  If so, we have binary
			 * mode support.
			 */
			if (major >= 3)
				return 1;

			/*
			 * Is it 1 or less?  If so, we don't have binary
			 * mode support.  (In fact, we don't have any
			 * USB monitoring....)
			 */
			if (major <= 1)
				return 0;
		}

		/*
		 * OK, this is a 2.x kernel.
		 * What's the minor version?
		 */
		version_component = endp + 1;
		minor = strtol(version_component, &endp, 10);
		if (endp != version_component &&
		    (*endp == '.' || *endp == '\0')) {
			/*
			 * OK, that was a valid minor version.
			 * Is is 2.6 or later?  (There shouldn't be a
			 * "later", as 2.6.x went to 3.x, but we'll
			 * check anyway.)
			 */
			if (minor < 6) {
				/*
				 * No, so no binary support (did 2.4 have
				 * any USB monitoring at all?)
				 */
				return 0;
			}

			/*
			 * OK, this is a 2.6.x kernel.
			 * What's the subminor version?
			 */
			version_component = endp + 1;
			subminor = strtol(version_component, &endp, 10);
			if (endp != version_component &&
			    (*endp == '.' || *endp == '\0')) {
				/*
				 * OK, that was a valid subminor version.
				 * Is it 21 or greater?
				 */
				if (subminor >= 21) {
					/*
					 * Yes - we have binary mode
					 * support.
					 */
					return 1;
				}
			}
		}
	}

	/*
	 * Either uname() failed, in which case we just say "no binary
	 * mode support", or we don't have binary mode support.
	 */
	return 0;
}

/* 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];
	pcap_snprintf(dev_name, 10, 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 (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?
		 */
		pcap_snprintf(dev_descr, 30, "Raw USB traffic, bus number %d", n);
		if (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)
{
	char usb_mon_dir[PATH_MAX];
	char *usb_mon_prefix;
	size_t usb_mon_prefix_len;
	struct dirent* data;
	int ret = 0;
	DIR* dir;
	int n;
	char* name;
	size_t len;

	if (have_binary_usbmon()) {
		/*
		 * We have binary-mode support.
		 * What do the device names look like?
		 * Split LINUX_USB_MON_DEV into a directory that we'll
		 * scan and a file name prefix that we'll check for.
		 */
		pcap_strlcpy(usb_mon_dir, LINUX_USB_MON_DEV, sizeof usb_mon_dir);
		usb_mon_prefix = strrchr(usb_mon_dir, '/');
		if (usb_mon_prefix == NULL) {
			/*
			 * This "shouldn't happen".  Just give up if it
			 * does.
			 */
			return 0;
		}
		*usb_mon_prefix++ = '\0';
		usb_mon_prefix_len = strlen(usb_mon_prefix);

		/*
		 * Open the directory and scan it.
		 */
		dir = opendir(usb_mon_dir);
		if (dir != NULL) {
			while ((ret == 0) && ((data = readdir(dir)) != 0)) {
				name = data->d_name;

				/*
				 * Is this a usbmon device?
				 */
				if (strncmp(name, usb_mon_prefix, usb_mon_prefix_len) != 0)
					continue;	/* no */

				/*
				 * What's the device number?
				 */
				if (sscanf(&name[usb_mon_prefix_len], "%d", &n) == 0)
					continue;	/* failed */

				ret = usb_dev_add(devlistp, n, err_str);
			}

			closedir(dir);
		}
		return 0;
	} else {
		/*
		 * We have only text mode support.
		 * We don't look for the text devices because we can't
		 * look for them without root privileges, and we don't
		 * want to require root privileges to enumerate devices
		 * (we want to let the user to try a device and get
		 * an error, rather than seeing no devices and asking
		 * "why am I not seeing devices" and forcing a long
		 * process of poking to figure out whether it's "no
		 * privileges" or "your kernel is too old" or "the
		 * usbmon module isn't loaded" or...).
		 *
		 * Instead, we look to see what buses we have.
		 * If the kernel is so old that it doesn't have
		 * binary-mode support, it's also so old that
		 * it doesn't have a "scan all buses" device.
		 *
		 * First, try scanning sysfs USB bus directory.
		 */
		dir = opendir(SYS_USB_BUS_DIR);
		if (dir != NULL) {
			while ((ret == 0) && ((data = readdir(dir)) != 0)) {
				name = data->d_name;

				if (strncmp(name, "usb", 3) != 0)
					continue;

				if (sscanf(&name[3], "%d", &n) == 0)
					continue;

				ret = usb_dev_add(devlistp, n, err_str);
			}

			closedir(dir);
			return 0;
		}

		/* That didn't work; try scanning procfs USB bus directory. */
		dir = opendir(PROC_USB_BUS_DIR);
		if (dir != NULL) {
			while ((ret == 0) && ((data = readdir(dir)) != 0)) {
				name = data->d_name;
				len = strlen(name);

				/* if this file name does not end with a number it's not of our interest */
				if ((len < 1) || !isdigit(name[--len]))
					continue;
				while (isdigit(name[--len]));
				if (sscanf(&name[len+1], "%d", &n) != 1)
					continue;

				ret = usb_dev_add(devlistp, n, err_str);
			}

			closedir(dir);
			return ret;
		}

		/* neither of them worked */
		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 wqy 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) {
		pcap_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

/* 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 buf[sizeof("/dev/bus/usb/000/") + NAME_MAX];
	DIR* dir;

	/* scan usb bus directories for device nodes */
	pcap_snprintf(buf, sizeof(buf), "/dev/bus/usb/%03d", bus);
	dir = opendir(buf);
	if (!dir)
		return;

	while ((ret >= 0) && ((data = readdir(dir)) != 0)) {
		int fd;
		char* name = data->d_name;

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

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

		fd = open(buf, 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(buf);
#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(buf);
#endif
		ctrl.data = buf;
		ctrl.timeout = CTRL_TIMEOUT;

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

		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;
	char *cpend;
	long devnum;
	pcap_t *p;

	/* Does this look like a USB monitoring device? */
	cp = strrchr(device, '/');
	if (cp == NULL)
		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;
	devnum = strtol(cp, &cpend, 10);
	if (cpend == cp || *cpend != '\0') {
		/* Not followed by a number. */
		*is_ours = 0;
		return NULL;
	}
	if (devnum < 0) {
		/* Followed by a non-valid number. */
		*is_ours = 0;
		return NULL;
	}

	/* OK, it's probably ours. */
	*is_ours = 1;

	p = pcap_create_common(ebuf, sizeof (struct pcap_usb_linux));
	if (p == NULL)
		return (NULL);

	p->activate_op = usb_activate;
	return (p);
}

static int
usb_activate(pcap_t* handle)
{
	struct pcap_usb_linux *handlep = handle->priv;
	char 		full_path[USB_LINE_LEN];
	int		ret;

	/*
	 * 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 = 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 = pcap_getnonblock_fd;
	handle->setnonblock_op = pcap_setnonblock_fd;

	/*get usb bus index from device name */
	if (sscanf(handle->opt.device, USB_IFACE"%d", &handlep->bus_index) != 1)
	{
		pcap_snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
			"Can't get USB bus index from %s", handle->opt.device);
		return PCAP_ERROR;
	}

	if (have_binary_usbmon())
	{
		/*
		 * We have binary-mode support.
		 * Try to open the binary interface.
		 */
		pcap_snprintf(full_path, USB_LINE_LEN, LINUX_USB_MON_DEV"%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).
				 */
				return PCAP_ERROR_NO_SUCH_DEVICE;

			case EACCES:
				/*
				 * We didn't have permission to open it.
				 */
				return PCAP_ERROR_PERM_DENIED;

			default:
				/*
				 * Something went wrong.
				 */
				pcap_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
	}
	else {
		/*
		 * We don't have binary mode support.
		 * Try opening the text-mode device.
		 */
		pcap_snprintf(full_path, USB_LINE_LEN, USB_TEXT_DIR"/%dt", handlep->bus_index);
		handle->fd = open(full_path, O_RDONLY, 0);
		if (handle->fd < 0)
		{
			if (errno == ENOENT)
			{
				/*
				 * Not found at the new location; try
				 * the old location.
				 */
				pcap_snprintf(full_path, USB_LINE_LEN, USB_TEXT_DIR_OLD"/%dt", handlep->bus_index);
				handle->fd = open(full_path, O_RDONLY, 0);
			}
			if (handle->fd < 0) {
				if (errno == ENOENT)
				{
					/*
					 * The problem is that the file
					 * doesn't exist.  Report that as
					 * "no such device".  (That could
					 * mean "no such USB bus" or
					 * "monitoring not supported".)
					 */
					ret = PCAP_ERROR_NO_SUCH_DEVICE;
				}
				else if (errno == EACCES)
				{
					/*
					 * The problem is that we don't
					 * have sufficient permission to
					 * open the file.  Report that.
					 */
					ret = PCAP_ERROR_PERM_DENIED;
				}
				else
				{
					/*
					 * Some other error.
					 */
					ret = PCAP_ERROR;
				}
				pcap_fmt_errmsg_for_errno(handle->errbuf,
				    PCAP_ERRBUF_SIZE, errno,
				    "Can't open USB bus file %s",
				    full_path);
				return ret;
			}
		}

		if (handle->opt.rfmon)
		{
			/*
			 * Monitor mode doesn't apply to USB devices.
			 */
			close(handle->fd);
			return PCAP_ERROR_RFMON_NOTSUP;
		}

		handle->stats_op = usb_stats_linux;
		handle->read_op = usb_read_linux;
	}

	/*
	 * "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) {
		pcap_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,
		    errno, "malloc");
		close(handle->fd);
		return PCAP_ERROR;
	}
	return 0;
}

static inline int
ascii_to_int(char c)
{
	return c < 'A' ? c- '0': ((c<'a') ? c - 'A' + 10: c-'a'+10);
}

/*
 * see <linux-kernel-source>/Documentation/usb/usbmon.txt and
 * <linux-kernel-source>/drivers/usb/mon/mon_text.c for urb string
 * format description
 */
static int
usb_read_linux(pcap_t *handle, int max_packets _U_, pcap_handler callback, u_char *user)
{
	/* see:
	* /usr/src/linux/Documentation/usb/usbmon.txt
	* for message format
	*/
	struct pcap_usb_linux *handlep = handle->priv;
	unsigned timestamp;
	int tag, cnt, ep_num, dev_addr, dummy, ret, urb_len, data_len;
	char etype, pipeid1, pipeid2, status[16], urb_tag, line[USB_LINE_LEN];
	char *string = line;
	u_char * rawdata = handle->buffer;
	struct pcap_pkthdr pkth;
	pcap_usb_header* uhdr = (pcap_usb_header*)handle->buffer;
	u_char urb_transfer=0;
	int incoming=0;

	/* ignore interrupt system call errors */
	do {
		ret = read(handle->fd, line, USB_LINE_LEN - 1);
		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 */

		pcap_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,
		    errno, "Can't read from fd %d", handle->fd);
		return -1;
	}

	/* read urb header; %n argument may increment return value, but it's
	* not mandatory, so does not count on it*/
	string[ret] = 0;
	ret = sscanf(string, "%x %d %c %c%c:%d:%d %s%n", &tag, &timestamp, &etype,
		&pipeid1, &pipeid2, &dev_addr, &ep_num, status,
		&cnt);
	if (ret < 8)
	{
		pcap_snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		    "Can't parse USB bus message '%s', too few tokens (expected 8 got %d)",
		    string, ret);
		return -1;
	}
	uhdr->id = tag;
	uhdr->device_address = dev_addr;
	uhdr->bus_id = handlep->bus_index;
	uhdr->status = 0;
	string += cnt;

	/* don't use usbmon provided timestamp, since it have low precision*/
	if (gettimeofday(&pkth.ts, NULL) < 0)
	{
		pcap_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,
		    errno, "Can't get timestamp for message '%s'", string);
		return -1;
	}
	uhdr->ts_sec = pkth.ts.tv_sec;
	uhdr->ts_usec = pkth.ts.tv_usec;

	/* parse endpoint information */
	if (pipeid1 == 'C')
		urb_transfer = URB_CONTROL;
	else if (pipeid1 == 'Z')
		urb_transfer = URB_ISOCHRONOUS;
	else if (pipeid1 == 'I')
		urb_transfer = URB_INTERRUPT;
	else if (pipeid1 == 'B')
		urb_transfer = URB_BULK;
	if (pipeid2 == 'i') {
		ep_num |= URB_TRANSFER_IN;
		incoming = 1;
	}
	if (etype == 'C')
		incoming = !incoming;

	/* direction check*/
	if (incoming)
	{
		if (handle->direction == PCAP_D_OUT)
			return 0;
	}
	else
		if (handle->direction == PCAP_D_IN)
			return 0;
	uhdr->event_type = etype;
	uhdr->transfer_type = urb_transfer;
	uhdr->endpoint_number = ep_num;
	pkth.caplen = sizeof(pcap_usb_header);
	rawdata += sizeof(pcap_usb_header);

	/* check if this is a setup packet */
	ret = sscanf(status, "%d", &dummy);
	if (ret != 1)
	{
		/* this a setup packet, setup data can be filled with underscore if
		* usbmon has not been able to read them, so we must parse this fields as
		* strings */
		pcap_usb_setup* shdr;
		char str1[3], str2[3], str3[5], str4[5], str5[5];
		ret = sscanf(string, "%s %s %s %s %s%n", str1, str2, str3, str4,
		str5, &cnt);
		if (ret < 5)
		{
			pcap_snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
				"Can't parse USB bus message '%s', too few tokens (expected 5 got %d)",
				string, ret);
			return -1;
		}
		string += cnt;

		/* try to convert to corresponding integer */
		shdr = &uhdr->setup;
		shdr->bmRequestType = strtoul(str1, 0, 16);
		shdr->bRequest = strtoul(str2, 0, 16);
		shdr->wValue = htols(strtoul(str3, 0, 16));
		shdr->wIndex = htols(strtoul(str4, 0, 16));
		shdr->wLength = htols(strtoul(str5, 0, 16));

		uhdr->setup_flag = 0;
	}
	else
		uhdr->setup_flag = 1;

	/* read urb data */
	ret = sscanf(string, " %d%n", &urb_len, &cnt);
	if (ret < 1)
	{
		pcap_snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
		  "Can't parse urb length from '%s'", string);
		return -1;
	}
	string += cnt;

	/* urb tag is not present if urb length is 0, so we can stop here
	 * text parsing */
	pkth.len = urb_len+pkth.caplen;
	uhdr->urb_len = urb_len;
	uhdr->data_flag = 1;
	data_len = 0;
	if (uhdr->urb_len == 0)
		goto got;

	/* check for data presence; data is present if and only if urb tag is '=' */
	if (sscanf(string, " %c", &urb_tag) != 1)
	{
		pcap_snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
			"Can't parse urb tag from '%s'", string);
		return -1;
	}

	if (urb_tag != '=')
		goto got;

	/* skip urb tag and following space */
	string += 3;

	/* if we reach this point we got some urb data*/
	uhdr->data_flag = 0;

	/* read all urb data; if urb length is greater then the usbmon internal
	 * buffer length used by the kernel to spool the URB, we get only
	 * a partial information.
	 * At least until linux 2.6.17 there is no way to set usbmon intenal buffer
	 * length and default value is 130. */
	while ((string[0] != 0) && (string[1] != 0) && (pkth.caplen < (bpf_u_int32)handle->snapshot))
	{
		rawdata[0] = ascii_to_int(string[0]) * 16 + ascii_to_int(string[1]);
		rawdata++;
		string+=2;
		if (string[0] == ' ')
			string++;
		pkth.caplen++;
		data_len++;
	}

got:
	uhdr->data_len = data_len;
	if (pkth.caplen > (bpf_u_int32)handle->snapshot)
		pkth.caplen = (bpf_u_int32)handle->snapshot;

	if (handle->fcode.bf_insns == NULL ||
	    bpf_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 */
}

static int
usb_inject_linux(pcap_t *handle, const void *buf _U_, size_t size _U_)
{
	pcap_snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
	    "Packet injection is not supported on USB devices");
	return (-1);
}

static int
usb_stats_linux(pcap_t *handle, struct pcap_stat *stats)
{
	struct pcap_usb_linux *handlep = handle->priv;
	int dummy, ret, consumed, cnt;
	char string[USB_LINE_LEN];
	char token[USB_LINE_LEN];
	char * ptr = string;
	int fd;

	pcap_snprintf(string, USB_LINE_LEN, USB_TEXT_DIR"/%ds", handlep->bus_index);
	fd = open(string, O_RDONLY, 0);
	if (fd < 0)
	{
		if (errno == ENOENT)
		{
			/*
			 * Not found at the new location; try the old
			 * location.
			 */
			pcap_snprintf(string, USB_LINE_LEN, USB_TEXT_DIR_OLD"/%ds", handlep->bus_index);
			fd = open(string, O_RDONLY, 0);
		}
		if (fd < 0) {
			pcap_fmt_errmsg_for_errno(handle->errbuf,
			    PCAP_ERRBUF_SIZE, errno,
			    "Can't open USB stats file %s", string);
			return -1;
		}
	}

	/* read stats line */
	do {
		ret = read(fd, string, USB_LINE_LEN-1);
	} while ((ret == -1) && (errno == EINTR));
	close(fd);

	if (ret < 0)
	{
		pcap_snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
			"Can't read stats from fd %d ", fd);
		return -1;
	}
	string[ret] = 0;

	stats->ps_recv = handlep->packets_read;
	stats->ps_drop = 0;	/* unless we find text_lost */
	stats->ps_ifdrop = 0;

	/* extract info on dropped urbs */
	for (consumed=0; consumed < ret; ) {
		/* from the sscanf man page:
 		 * The C standard says: "Execution of a %n directive does
 		 * not increment the assignment count returned at the completion
		 * of  execution" but the Corrigendum seems to contradict this.
		 * Do not make any assumptions on the effect of %n conversions
		 * on the return value and explicitly check for cnt assignmet*/
		int ntok;

		cnt = -1;
		ntok = sscanf(ptr, "%s%n", token, &cnt);
		if ((ntok < 1) || (cnt < 0))
			break;
		consumed += cnt;
		ptr += cnt;
		if (strcmp(token, "text_lost") == 0)
			ntok = sscanf(ptr, "%d%n", &stats->ps_drop, &cnt);
		else
			ntok = sscanf(ptr, "%d%n", &dummy, &cnt);
		if ((ntok != 1) || (cnt < 0))
			break;
		consumed += cnt;
		ptr += cnt;
	}

	return 0;
}

static int
usb_setdirection_linux(pcap_t *p, pcap_direction_t d)
{
	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)
	{
		pcap_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 = (u_char *)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 */

		pcap_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 on-the-wire 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 on-the-wire 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 = info.hdr->ts_sec;
	pkth.ts.tv_usec = info.hdr->ts_usec;

	if (handle->fcode.bf_insns == NULL ||
	    bpf_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;
	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 = max_packets - packets;
		if (limit <= 0)
			limit = VEC_SIZE;
		if (limit > VEC_SIZE)
			limit = VEC_SIZE;

		/* try to fetch as many events as possible*/
		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 */

			pcap_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) {
			/* discard filler */
			hdr = (pcap_usb_header_mmapped*) &handlep->mmapbuf[vec[i]];
			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 on-the-wire length
				 * on hdr->data_len (so that it's >= the
				 * captured length).
				 */
				pkth.len = sizeof(pcap_usb_header_mmapped) +
				    hdr->data_len;
			} else {
				/*
				 * We got data; base the on-the-wire length
				 * on 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_mmapped) +
				    (hdr->ndesc * sizeof (usb_isodesc)) + hdr->urb_len;
			}
			pkth.ts.tv_sec = hdr->ts_sec;
			pkth.ts.tv_usec = hdr->ts_usec;

			if (handle->fcode.bf_insns == NULL ||
			    bpf_filter(handle->fcode.bf_insns, (u_char*) hdr,
			      pkth.len, pkth.caplen)) {
				handlep->packets_read++;
				callback(user, &pkth, (u_char*) hdr);
				packets++;
			}
		}

		/* with max_packets specifying "unlimited" we stop afer 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) {
		pcap_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;
	}
	pcap_cleanup_live_common(handle);
}