Logo Search packages:      
Sourcecode: nmap version File versions

pcap-bpf.c

/*
 * Copyright (c) 1993, 1994, 1995, 1996, 1998
 *    The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that: (1) source code distributions
 * retain the above copyright notice and this paragraph in its entirety, (2)
 * distributions including binary code include the above copyright notice and
 * this paragraph in its entirety in the documentation or other materials
 * provided with the distribution, and (3) all advertising materials mentioning
 * features or use of this software display the following acknowledgement:
 * ``This product includes software developed by the University of California,
 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
 * the University nor the names of its contributors may be used to endorse
 * or promote products derived from this software without specific prior
 * written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */
#ifndef lint
static const char rcsid[] _U_ =
    "@(#) $Header: /tcpdump/master/libpcap/pcap-bpf.c,v 1.86.2.8 2005/07/10 10:55:31 guy Exp $ (LBL)";
#endif

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <sys/param.h>              /* optionally get BSD define */
#include <sys/time.h>
#include <sys/timeb.h>
#include <sys/socket.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <sys/utsname.h>

#include <net/if.h>

#ifdef _AIX

/*
 * Make "pcap.h" not include "pcap-bpf.h"; we are going to include the
 * native OS version, as we need "struct bpf_config" from it.
 */
#define PCAP_DONT_INCLUDE_PCAP_BPF_H

#include <sys/types.h>

/*
 * Prevent bpf.h from redefining the DLT_ values to their
 * IFT_ values, as we're going to return the standard libpcap
 * values, not IBM's non-standard IFT_ values.
 */
#undef _AIX
#include <net/bpf.h>
#define _AIX

#include <net/if_types.h>           /* for IFT_ values */
#include <sys/sysconfig.h>
#include <sys/device.h>
#include <sys/cfgodm.h>
#include <cf.h>

#ifdef __64BIT__
#define domakedev makedev64
#define getmajor major64
#define bpf_hdr bpf_hdr32
#else /* __64BIT__ */
#define domakedev makedev
#define getmajor major
#endif /* __64BIT__ */

#define BPF_NAME "bpf"
#define BPF_MINORS 4
#define DRIVER_PATH "/usr/lib/drivers"
#define BPF_NODE "/dev/bpf"
static int bpfloadedflag = 0;
static int odmlockid = 0;

#else /* _AIX */

#include <net/bpf.h>

#endif /* _AIX */

#include <ctype.h>
#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "pcap-int.h"

#ifdef HAVE_DAG_API
#include "pcap-dag.h"
#endif /* HAVE_DAG_API */

#ifdef HAVE_OS_PROTO_H
#include "os-proto.h"
#endif

#include "gencode.h"    /* for "no_optimize" */

static int pcap_setfilter_bpf(pcap_t *p, struct bpf_program *fp);
static int pcap_setdirection_bpf(pcap_t *, pcap_direction_t);
static int pcap_set_datalink_bpf(pcap_t *p, int dlt);

static int
pcap_stats_bpf(pcap_t *p, struct pcap_stat *ps)
{
      struct bpf_stat s;

      /*
       * "ps_recv" counts packets handed to the filter, not packets
       * that passed the filter.  This includes packets later dropped
       * because we ran out of buffer space.
       *
       * "ps_drop" counts packets dropped inside the BPF device
       * because we ran out of buffer space.  It doesn't count
       * packets dropped by the interface driver.  It counts
       * only packets that passed the filter.
       *
       * Both statistics include packets not yet read from the kernel
       * by libpcap, and thus not yet seen by the application.
       */
      if (ioctl(p->fd, BIOCGSTATS, (caddr_t)&s) < 0) {
            snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCGSTATS: %s",
                pcap_strerror(errno));
            return (-1);
      }

      ps->ps_recv = s.bs_recv;
      ps->ps_drop = s.bs_drop;
      return (0);
}

static int
pcap_read_bpf(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
{
      int cc;
      int n = 0;
      register u_char *bp, *ep;
      u_char *datap;
      struct bpf_insn *fcode;
#ifdef PCAP_FDDIPAD
      register int pad;
#endif

      fcode = p->md.use_bpf ? NULL : p->fcode.bf_insns;
 again:
      /*
       * Has "pcap_breakloop()" been called?
       */
      if (p->break_loop) {
            /*
             * Yes - clear the flag that indicates that it
             * has, and return -2 to indicate that we were
             * told to break out of the loop.
             */
            p->break_loop = 0;
            return (-2);
      }
      cc = p->cc;
      if (p->cc == 0) {
            cc = read(p->fd, (char *)p->buffer, p->bufsize);
            if (cc < 0) {
                  /* Don't choke when we get ptraced */
                  switch (errno) {

                  case EINTR:
                        goto again;

#ifdef _AIX
                  case EFAULT:
                        /*
                         * Sigh.  More AIX wonderfulness.
                         *
                         * For some unknown reason the uiomove()
                         * operation in the bpf kernel extension
                         * used to copy the buffer into user 
                         * space sometimes returns EFAULT. I have
                         * no idea why this is the case given that
                         * a kernel debugger shows the user buffer 
                         * is correct. This problem appears to 
                         * be mostly mitigated by the memset of 
                         * the buffer before it is first used. 
                         * Very strange.... Shaun Clowes
                         *
                         * In any case this means that we shouldn't 
                         * treat EFAULT as a fatal error; as we
                         * don't have an API for returning
                         * a "some packets were dropped since
                         * the last packet you saw" indication,
                         * we just ignore EFAULT and keep reading.
                         */
                        goto again;
#endif 
  
                  case EWOULDBLOCK:
                        return (0);
#if defined(sun) && !defined(BSD)
                  /*
                   * Due to a SunOS bug, after 2^31 bytes, the kernel
                   * file offset overflows and read fails with EINVAL.
                   * The lseek() to 0 will fix things.
                   */
                  case EINVAL:
                        if (lseek(p->fd, 0L, SEEK_CUR) +
                            p->bufsize < 0) {
                              (void)lseek(p->fd, 0L, SEEK_SET);
                              goto again;
                        }
                        /* fall through */
#endif
                  }
                  snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "read: %s",
                      pcap_strerror(errno));
                  return (-1);
            }
            bp = p->buffer;
      } else
            bp = p->bp;

      /*
       * Loop through each packet.
       */
#define bhp ((struct bpf_hdr *)bp)
      ep = bp + cc;
#ifdef PCAP_FDDIPAD
      pad = p->fddipad;
#endif
      while (bp < ep) {
            register int caplen, hdrlen;

            /*
             * Has "pcap_breakloop()" been called?
             * If so, return immediately - if we haven't read any
             * packets, clear the flag and return -2 to indicate
             * that we were told to break out of the loop, otherwise
             * leave the flag set, so that the *next* call will break
             * out of the loop without having read any packets, and
             * return the number of packets we've processed so far.
             */
            if (p->break_loop) {
                  if (n == 0) {
                        p->break_loop = 0;
                        return (-2);
                  } else {
                        p->bp = bp;
                        p->cc = ep - bp;
                        return (n);
                  }
            }

            caplen = bhp->bh_caplen;
            hdrlen = bhp->bh_hdrlen;
            datap = bp + hdrlen;
            /*
             * Short-circuit evaluation: if using BPF filter
             * in kernel, no need to do it now.
             *
#ifdef PCAP_FDDIPAD
             * Note: the filter code was generated assuming
             * that p->fddipad was the amount of padding
             * before the header, as that's what's required
             * in the kernel, so we run the filter before
             * skipping that padding.
#endif
             */
            if (fcode == NULL ||
                bpf_filter(fcode, datap, bhp->bh_datalen, caplen)) {
                  struct pcap_pkthdr pkthdr;

                  pkthdr.ts.tv_sec = bhp->bh_tstamp.tv_sec;
#ifdef _AIX
                  /*
                   * AIX's BPF returns seconds/nanoseconds time
                   * stamps, not seconds/microseconds time stamps.
                   */
                  pkthdr.ts.tv_usec = bhp->bh_tstamp.tv_usec/1000;
#else
                  pkthdr.ts.tv_usec = bhp->bh_tstamp.tv_usec;
#endif
#ifdef PCAP_FDDIPAD
                  if (caplen > pad)
                        pkthdr.caplen = caplen - pad;
                  else
                        pkthdr.caplen = 0;
                  if (bhp->bh_datalen > pad)
                        pkthdr.len = bhp->bh_datalen - pad;
                  else
                        pkthdr.len = 0;
                  datap += pad;
#else
                  pkthdr.caplen = caplen;
                  pkthdr.len = bhp->bh_datalen;
#endif
                  (*callback)(user, &pkthdr, datap);
                  bp += BPF_WORDALIGN(caplen + hdrlen);
                  if (++n >= cnt && cnt > 0) {
                        p->bp = bp;
                        p->cc = ep - bp;
                        return (n);
                  }
            } else {
                  /*
                   * Skip this packet.
                   */
                  bp += BPF_WORDALIGN(caplen + hdrlen);
            }
      }
#undef bhp
      p->cc = 0;
      return (n);
}

static int
pcap_inject_bpf(pcap_t *p, const void *buf, size_t size)
{
      int ret;

      ret = write(p->fd, buf, size);
#ifdef __APPLE__
      if (ret == -1 && errno == EAFNOSUPPORT) {
            /*
             * In Mac OS X, there's a bug wherein setting the
             * BIOCSHDRCMPLT flag causes writes to fail; see,
             * for example:
             *
             *    http://cerberus.sourcefire.com/~jeff/archives/patches/macosx/BIOCSHDRCMPLT-10.3.3.patch
             *
             * So, if, on OS X, we get EAFNOSUPPORT from the write, we
             * assume it's due to that bug, and turn off that flag
             * and try again.  If we succeed, it either means that
             * somebody applied the fix from that URL, or other patches
             * for that bug from
             *
             *    http://cerberus.sourcefire.com/~jeff/archives/patches/macosx/
             *
             * and are running a Darwin kernel with those fixes, or
             * that Apple fixed the problem in some OS X release.
             */
            u_int spoof_eth_src = 0;

            if (ioctl(p->fd, BIOCSHDRCMPLT, &spoof_eth_src) == -1) {
                  (void)snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                      "send: can't turn off BIOCSHDRCMPLT: %s",
                      pcap_strerror(errno));
                  return (-1);
            }

            /*
             * Now try the write again.
             */
            ret = write(p->fd, buf, size);
      }
#endif /* __APPLE__ */
      if (ret == -1) {
            snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "send: %s",
                pcap_strerror(errno));
            return (-1);
      }
      return (ret);
}

#ifdef _AIX
static int 
bpf_odminit(char *errbuf)
{
      char *errstr;

      if (odm_initialize() == -1) {
            if (odm_err_msg(odmerrno, &errstr) == -1)
                  errstr = "Unknown error";
            snprintf(errbuf, PCAP_ERRBUF_SIZE,
                "bpf_load: odm_initialize failed: %s",
                errstr);
            return (-1);
      }

      if ((odmlockid = odm_lock("/etc/objrepos/config_lock", ODM_WAIT)) == -1) {
            if (odm_err_msg(odmerrno, &errstr) == -1)
                  errstr = "Unknown error";
            snprintf(errbuf, PCAP_ERRBUF_SIZE,
                "bpf_load: odm_lock of /etc/objrepos/config_lock failed: %s",
                errstr);
            return (-1);
      }

      return (0);
}

static int 
bpf_odmcleanup(char *errbuf)
{
      char *errstr;

      if (odm_unlock(odmlockid) == -1) {
            if (odm_err_msg(odmerrno, &errstr) == -1)
                  errstr = "Unknown error";
            snprintf(errbuf, PCAP_ERRBUF_SIZE,
                "bpf_load: odm_unlock failed: %s",
                errstr);
            return (-1);
      }

      if (odm_terminate() == -1) {
            if (odm_err_msg(odmerrno, &errstr) == -1)
                  errstr = "Unknown error";
            snprintf(errbuf, PCAP_ERRBUF_SIZE,
                "bpf_load: odm_terminate failed: %s",
                errstr);
            return (-1);
      }

      return (0);
}

static int
bpf_load(char *errbuf)
{
      long major;
      int *minors;
      int numminors, i, rc;
      char buf[1024];
      struct stat sbuf;
      struct bpf_config cfg_bpf;
      struct cfg_load cfg_ld;
      struct cfg_kmod cfg_km;

      /*
       * This is very very close to what happens in the real implementation
       * but I've fixed some (unlikely) bug situations.
       */
      if (bpfloadedflag)
            return (0);

      if (bpf_odminit(errbuf) != 0)
            return (-1);

      major = genmajor(BPF_NAME);
      if (major == -1) {
            snprintf(errbuf, PCAP_ERRBUF_SIZE,
                "bpf_load: genmajor failed: %s", pcap_strerror(errno));
            return (-1);
      }

      minors = getminor(major, &numminors, BPF_NAME);
      if (!minors) {
            minors = genminor("bpf", major, 0, BPF_MINORS, 1, 1);
            if (!minors) {
                  snprintf(errbuf, PCAP_ERRBUF_SIZE,
                      "bpf_load: genminor failed: %s",
                      pcap_strerror(errno));
                  return (-1);
            }
      }

      if (bpf_odmcleanup(errbuf))
            return (-1);

      rc = stat(BPF_NODE "0", &sbuf);
      if (rc == -1 && errno != ENOENT) {
            snprintf(errbuf, PCAP_ERRBUF_SIZE,
                "bpf_load: can't stat %s: %s",
                BPF_NODE "0", pcap_strerror(errno));
            return (-1);
      }

      if (rc == -1 || getmajor(sbuf.st_rdev) != major) {
            for (i = 0; i < BPF_MINORS; i++) {
                  sprintf(buf, "%s%d", BPF_NODE, i);
                  unlink(buf);
                  if (mknod(buf, S_IRUSR | S_IFCHR, domakedev(major, i)) == -1) {
                        snprintf(errbuf, PCAP_ERRBUF_SIZE,
                            "bpf_load: can't mknod %s: %s",
                            buf, pcap_strerror(errno));
                        return (-1);
                  }
            }
      }

      /* Check if the driver is loaded */
      memset(&cfg_ld, 0x0, sizeof(cfg_ld));
      cfg_ld.path = buf;
      sprintf(cfg_ld.path, "%s/%s", DRIVER_PATH, BPF_NAME);
      if ((sysconfig(SYS_QUERYLOAD, (void *)&cfg_ld, sizeof(cfg_ld)) == -1) ||
          (cfg_ld.kmid == 0)) {
            /* Driver isn't loaded, load it now */
            if (sysconfig(SYS_SINGLELOAD, (void *)&cfg_ld, sizeof(cfg_ld)) == -1) {
                  snprintf(errbuf, PCAP_ERRBUF_SIZE,
                      "bpf_load: could not load driver: %s",
                      strerror(errno));
                  return (-1);
            }
      }

      /* Configure the driver */
      cfg_km.cmd = CFG_INIT;
      cfg_km.kmid = cfg_ld.kmid;
      cfg_km.mdilen = sizeof(cfg_bpf);
      cfg_km.mdiptr = (void *)&cfg_bpf; 
      for (i = 0; i < BPF_MINORS; i++) {
            cfg_bpf.devno = domakedev(major, i);
            if (sysconfig(SYS_CFGKMOD, (void *)&cfg_km, sizeof(cfg_km)) == -1) {
                  snprintf(errbuf, PCAP_ERRBUF_SIZE,
                      "bpf_load: could not configure driver: %s",
                      strerror(errno));
                  return (-1);
            }
      }
      
      bpfloadedflag = 1;

      return (0);
}
#endif

static inline int
bpf_open(pcap_t *p, char *errbuf)
{
      int fd;
      int n = 0;
      char device[sizeof "/dev/bpf0000000000"];

#ifdef _AIX
      /*
       * Load the bpf driver, if it isn't already loaded,
       * and create the BPF device entries, if they don't
       * already exist.
       */
      if (bpf_load(errbuf) == -1)
            return (-1);
#endif

      /*
       * Go through all the minors and find one that isn't in use.
       */
      do {
            (void)snprintf(device, sizeof(device), "/dev/bpf%d", n++);
            /*
             * Initially try a read/write open (to allow the inject
             * method to work).  If that fails due to permission
             * issues, fall back to read-only.  This allows a
             * non-root user to be granted specific access to pcap
             * capabilities via file permissions.
             *
             * XXX - we should have an API that has a flag that
             * controls whether to open read-only or read-write,
             * so that denial of permission to send (or inability
             * to send, if sending packets isn't supported on
             * the device in question) can be indicated at open
             * time.
             */
            fd = open(device, O_RDWR);
            if (fd == -1 && errno == EACCES)
                  fd = open(device, O_RDONLY);
      } while (fd < 0 && errno == EBUSY);

      /*
       * XXX better message for all minors used
       */
      if (fd < 0)
            snprintf(errbuf, PCAP_ERRBUF_SIZE, "(no devices found) %s: %s",
                device, pcap_strerror(errno));

      return (fd);
}

/*
 * We include the OS's <net/bpf.h>, not our "pcap-bpf.h", so we probably
 * don't get DLT_DOCSIS defined.
 */
#ifndef DLT_DOCSIS
#define DLT_DOCSIS      143
#endif

pcap_t *
pcap_open_live(const char *device, int snaplen, int promisc, int to_ms,
    char *ebuf)
{
      int fd;
      struct ifreq ifr;
      struct bpf_version bv;
#ifdef BIOCGDLTLIST
      struct bpf_dltlist bdl;
#endif
#if defined(BIOCGHDRCMPLT) && defined(BIOCSHDRCMPLT)
      u_int spoof_eth_src = 1;
#endif
      u_int v;
      pcap_t *p;
      struct bpf_insn total_insn;
      struct bpf_program total_prog;
      struct utsname osinfo;

#ifdef HAVE_DAG_API
      if (strstr(device, "dag")) {
            return dag_open_live(device, snaplen, promisc, to_ms, ebuf);
      }
#endif /* HAVE_DAG_API */

#ifdef BIOCGDLTLIST
      memset(&bdl, 0, sizeof(bdl));
#endif

      p = (pcap_t *)malloc(sizeof(*p));
      if (p == NULL) {
            snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s",
                pcap_strerror(errno));
            return (NULL);
      }
      memset(p, 0, sizeof(*p));
      fd = bpf_open(p, ebuf);
      if (fd < 0)
            goto bad;

      p->fd = fd;
      p->snapshot = snaplen;

      if (ioctl(fd, BIOCVERSION, (caddr_t)&bv) < 0) {
            snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCVERSION: %s",
                pcap_strerror(errno));
            goto bad;
      }
      if (bv.bv_major != BPF_MAJOR_VERSION ||
          bv.bv_minor < BPF_MINOR_VERSION) {
            snprintf(ebuf, PCAP_ERRBUF_SIZE,
                "kernel bpf filter out of date");
            goto bad;
      }

      /*
       * Try finding a good size for the buffer; 32768 may be too
       * big, so keep cutting it in half until we find a size
       * that works, or run out of sizes to try.  If the default
       * is larger, don't make it smaller.
       *
       * XXX - there should be a user-accessible hook to set the
       * initial buffer size.
       */
      if ((ioctl(fd, BIOCGBLEN, (caddr_t)&v) < 0) || v < 32768)
            v = 32768;
      for ( ; v != 0; v >>= 1) {
            /* Ignore the return value - this is because the call fails
             * on BPF systems that don't have kernel malloc.  And if
             * the call fails, it's no big deal, we just continue to
             * use the standard buffer size.
             */
            (void) ioctl(fd, BIOCSBLEN, (caddr_t)&v);

            (void)strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
            if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) >= 0)
                  break;      /* that size worked; we're done */

            if (errno != ENOBUFS) {
                  snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCSETIF: %s: %s",
                      device, pcap_strerror(errno));
                  goto bad;
            }
      }

      if (v == 0) {
            snprintf(ebuf, PCAP_ERRBUF_SIZE,
                   "BIOCSBLEN: %s: No buffer size worked", device);
            goto bad;
      }

      /* Get the data link layer type. */
      if (ioctl(fd, BIOCGDLT, (caddr_t)&v) < 0) {
            snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGDLT: %s",
                pcap_strerror(errno));
            goto bad;
      }
#ifdef _AIX
      /*
       * AIX's BPF returns IFF_ types, not DLT_ types, in BIOCGDLT.
       */
      switch (v) {

      case IFT_ETHER:
      case IFT_ISO88023:
            v = DLT_EN10MB;
            break;

      case IFT_FDDI:
            v = DLT_FDDI;
            break;

      case IFT_ISO88025:
            v = DLT_IEEE802;
            break;

      case IFT_LOOP:
            v = DLT_NULL;
            break;

      default:
            /*
             * We don't know what to map this to yet.
             */
            snprintf(ebuf, PCAP_ERRBUF_SIZE, "unknown interface type %u",
                v);
            goto bad;
      }
#endif
#if _BSDI_VERSION - 0 >= 199510
      /* The SLIP and PPP link layer header changed in BSD/OS 2.1 */
      switch (v) {

      case DLT_SLIP:
            v = DLT_SLIP_BSDOS;
            break;

      case DLT_PPP:
            v = DLT_PPP_BSDOS;
            break;

      case 11:    /*DLT_FR*/
            v = DLT_FRELAY;
            break;

      case 12:    /*DLT_C_HDLC*/
            v = DLT_CHDLC;
            break;
      }
#endif
#ifdef PCAP_FDDIPAD
      if (v == DLT_FDDI)
            p->fddipad = PCAP_FDDIPAD;
      else
            p->fddipad = 0;
#endif
      p->linktype = v;

#ifdef BIOCGDLTLIST
      /*
       * We know the default link type -- now determine all the DLTs
       * this interface supports.  If this fails with EINVAL, it's
       * not fatal; we just don't get to use the feature later.
       */
      if (ioctl(fd, BIOCGDLTLIST, (caddr_t)&bdl) == 0) {
            u_int i;
            int is_ethernet;

            bdl.bfl_list = (u_int *) malloc(sizeof(u_int) * bdl.bfl_len + 1);
            if (bdl.bfl_list == NULL) {
                  (void)snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s",
                      pcap_strerror(errno));
                  goto bad;
            }

            if (ioctl(fd, BIOCGDLTLIST, (caddr_t)&bdl) < 0) {
                  (void)snprintf(ebuf, PCAP_ERRBUF_SIZE,
                      "BIOCGDLTLIST: %s", pcap_strerror(errno));
                  free(bdl.bfl_list);
                  goto bad;
            }

            /*
             * OK, for real Ethernet devices, add DLT_DOCSIS to the
             * list, so that an application can let you choose it,
             * in case you're capturing DOCSIS traffic that a Cisco
             * Cable Modem Termination System is putting out onto
             * an Ethernet (it doesn't put an Ethernet header onto
             * the wire, it puts raw DOCSIS frames out on the wire
             * inside the low-level Ethernet framing).
             *
             * A "real Ethernet device" is defined here as a device
             * that has a link-layer type of DLT_EN10MB and that has
             * no alternate link-layer types; that's done to exclude
             * 802.11 interfaces (which might or might not be the
             * right thing to do, but I suspect it is - Ethernet <->
             * 802.11 bridges would probably badly mishandle frames
             * that don't have Ethernet headers).
             */
            if (p->linktype == DLT_EN10MB) {
                  is_ethernet = 1;
                  for (i = 0; i < bdl.bfl_len; i++) {
                        if (bdl.bfl_list[i] != DLT_EN10MB) {
                              is_ethernet = 0;
                              break;
                        }
                  }
                  if (is_ethernet) {
                        /*
                         * We reserved one more slot at the end of
                         * the list.
                         */
                        bdl.bfl_list[bdl.bfl_len] = DLT_DOCSIS;
                        bdl.bfl_len++;
                  }
            }
            p->dlt_count = bdl.bfl_len;
            p->dlt_list = bdl.bfl_list;
      } else {
            if (errno != EINVAL) {
                  (void)snprintf(ebuf, PCAP_ERRBUF_SIZE,
                      "BIOCGDLTLIST: %s", pcap_strerror(errno));
                  goto bad;
            }
      }
#endif

      /*
       * If this is an Ethernet device, and we don't have a DLT_ list,
       * give it a list with DLT_EN10MB and DLT_DOCSIS.  (That'd give
       * 802.11 interfaces DLT_DOCSIS, which isn't the right thing to
       * do, but there's not much we can do about that without finding
       * some other way of determining whether it's an Ethernet or 802.11
       * device.)
       */
      if (p->linktype == DLT_EN10MB && p->dlt_count == 0) {
            p->dlt_list = (u_int *) malloc(sizeof(u_int) * 2);
            /*
             * If that fails, just leave the list empty.
             */
            if (p->dlt_list != NULL) {
                  p->dlt_list[0] = DLT_EN10MB;
                  p->dlt_list[1] = DLT_DOCSIS;
                  p->dlt_count = 2;
            }
      }
            
#if defined(BIOCGHDRCMPLT) && defined(BIOCSHDRCMPLT)
      /*
       * Do a BIOCSHDRCMPLT, if defined, to turn that flag on, so
       * the link-layer source address isn't forcibly overwritten.
       * (Should we ignore errors?  Should we do this only if
       * we're open for writing?)
       *
       * XXX - I seem to remember some packet-sending bug in some
       * BSDs - check CVS log for "bpf.c"?
       */
      if (ioctl(fd, BIOCSHDRCMPLT, &spoof_eth_src) == -1) {
            (void)snprintf(ebuf, PCAP_ERRBUF_SIZE,
                "BIOCSHDRCMPLT: %s", pcap_strerror(errno));
            goto bad;
      }
#endif
      /* set timeout */
      if (to_ms != 0) {
            /*
             * XXX - is this seconds/nanoseconds in AIX?
             * (Treating it as such doesn't fix the timeout
             * problem described below.)
             */
            struct timeval to;
            to.tv_sec = to_ms / 1000;
            to.tv_usec = (to_ms * 1000) % 1000000;
            if (ioctl(p->fd, BIOCSRTIMEOUT, (caddr_t)&to) < 0) {
                  snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCSRTIMEOUT: %s",
                      pcap_strerror(errno));
                  goto bad;
            }
      }

#ifdef _AIX
#ifdef      BIOCIMMEDIATE
      /*
       * Darren Reed notes that
       *
       *    On AIX (4.2 at least), if BIOCIMMEDIATE is not set, the
       *    timeout appears to be ignored and it waits until the buffer
       *    is filled before returning.  The result of not having it
       *    set is almost worse than useless if your BPF filter
       *    is reducing things to only a few packets (i.e. one every
       *    second or so).
       *
       * so we turn BIOCIMMEDIATE mode on if this is AIX.
       *
       * We don't turn it on for other platforms, as that means we
       * get woken up for every packet, which may not be what we want;
       * in the Winter 1993 USENIX paper on BPF, they say:
       *
       *    Since a process might want to look at every packet on a
       *    network and the time between packets can be only a few
       *    microseconds, it is not possible to do a read system call
       *    per packet and BPF must collect the data from several
       *    packets and return it as a unit when the monitoring
       *    application does a read.
       *
       * which I infer is the reason for the timeout - it means we
       * wait that amount of time, in the hopes that more packets
       * will arrive and we'll get them all with one read.
       *
       * Setting BIOCIMMEDIATE mode on FreeBSD (and probably other
       * BSDs) causes the timeout to be ignored.
       *
       * On the other hand, some platforms (e.g., Linux) don't support
       * timeouts, they just hand stuff to you as soon as it arrives;
       * if that doesn't cause a problem on those platforms, it may
       * be OK to have BIOCIMMEDIATE mode on BSD as well.
       *
       * (Note, though, that applications may depend on the read
       * completing, even if no packets have arrived, when the timeout
       * expires, e.g. GUI applications that have to check for input
       * while waiting for packets to arrive; a non-zero timeout
       * prevents "select()" from working right on FreeBSD and
       * possibly other BSDs, as the timer doesn't start until a
       * "read()" is done, so the timer isn't in effect if the
       * application is blocked on a "select()", and the "select()"
       * doesn't get woken up for a BPF device until the buffer
       * fills up.)
       */
      v = 1;
      if (ioctl(p->fd, BIOCIMMEDIATE, &v) < 0) {
            snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCIMMEDIATE: %s",
                pcap_strerror(errno));
            goto bad;
      }
#endif      /* BIOCIMMEDIATE */
#endif      /* _AIX */

      if (promisc) {
            /* set promiscuous mode, okay if it fails */
            if (ioctl(p->fd, BIOCPROMISC, NULL) < 0) {
                  snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCPROMISC: %s",
                      pcap_strerror(errno));
            }
      }

      if (ioctl(fd, BIOCGBLEN, (caddr_t)&v) < 0) {
            snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGBLEN: %s",
                pcap_strerror(errno));
            goto bad;
      }
      p->bufsize = v;
      p->buffer = (u_char *)malloc(p->bufsize);
      if (p->buffer == NULL) {
            snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s",
                pcap_strerror(errno));
            goto bad;
      }
#ifdef _AIX
      /* For some strange reason this seems to prevent the EFAULT 
       * problems we have experienced from AIX BPF. */
      memset(p->buffer, 0x0, p->bufsize);
#endif

      /*
       * If there's no filter program installed, there's
       * no indication to the kernel of what the snapshot
       * length should be, so no snapshotting is done.
       *
       * Therefore, when we open the device, we install
       * an "accept everything" filter with the specified
       * snapshot length.
       */
      total_insn.code = (u_short)(BPF_RET | BPF_K);
      total_insn.jt = 0;
      total_insn.jf = 0;
      total_insn.k = snaplen;

      total_prog.bf_len = 1;
      total_prog.bf_insns = &total_insn;
      if (ioctl(p->fd, BIOCSETF, (caddr_t)&total_prog) < 0) {
            snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCSETF: %s",
                pcap_strerror(errno));
            goto bad;
      }

      /*
       * On most BPF platforms, either you can do a "select()" or
       * "poll()" on a BPF file descriptor and it works correctly,
       * or you can do it and it will return "readable" if the
       * hold buffer is full but not if the timeout expires *and*
       * a non-blocking read will, if the hold buffer is empty
       * but the store buffer isn't empty, rotate the buffers
       * and return what packets are available.
       *
       * In the latter case, the fact that a non-blocking read
       * will give you the available packets means you can work
       * around the failure of "select()" and "poll()" to wake up
       * and return "readable" when the timeout expires by using
       * the timeout as the "select()" or "poll()" timeout, putting
       * the BPF descriptor into non-blocking mode, and read from
       * it regardless of whether "select()" reports it as readable
       * or not.
       *
       * However, in FreeBSD 4.3 and 4.4, "select()" and "poll()"
       * won't wake up and return "readable" if the timer expires
       * and non-blocking reads return EWOULDBLOCK if the hold
       * buffer is empty, even if the store buffer is non-empty.
       *
       * This means the workaround in question won't work.
       *
       * Therefore, on FreeBSD 4.3 and 4.4, we set "p->selectable_fd"
       * to -1, which means "sorry, you can't use 'select()' or 'poll()'
       * here".  On all other BPF platforms, we set it to the FD for
       * the BPF device; in NetBSD, OpenBSD, and Darwin, a non-blocking
       * read will, if the hold buffer is empty and the store buffer
       * isn't empty, rotate the buffers and return what packets are
       * there (and in sufficiently recent versions of OpenBSD
       * "select()" and "poll()" should work correctly).
       *
       * XXX - what about AIX?
       */
      p->selectable_fd = p->fd;     /* assume select() works until we know otherwise */
      if (uname(&osinfo) == 0) {
            /*
             * We can check what OS this is.
             */
            if (strcmp(osinfo.sysname, "FreeBSD") == 0) {
                  if (strncmp(osinfo.release, "4.3-", 4) == 0 ||
                       strncmp(osinfo.release, "4.4-", 4) == 0)
                        p->selectable_fd = -1;
            }
      }

      p->read_op = pcap_read_bpf;
      p->inject_op = pcap_inject_bpf;
      p->setfilter_op = pcap_setfilter_bpf;
      p->setdirection_op = pcap_setdirection_bpf;
      p->set_datalink_op = pcap_set_datalink_bpf;
      p->getnonblock_op = pcap_getnonblock_fd;
      p->setnonblock_op = pcap_setnonblock_fd;
      p->stats_op = pcap_stats_bpf;
      p->close_op = pcap_close_common;

      return (p);
 bad:
      (void)close(fd);
      if (p->dlt_list != NULL)
            free(p->dlt_list);
      free(p);
      return (NULL);
}

int
pcap_platform_finddevs(pcap_if_t **alldevsp, char *errbuf)
{
#ifdef HAVE_DAG_API
      if (dag_platform_finddevs(alldevsp, errbuf) < 0)
            return (-1);
#endif /* HAVE_DAG_API */

      return (0);
}

static int
pcap_setfilter_bpf(pcap_t *p, struct bpf_program *fp)
{
      /*
       * It looks that BPF code generated by gen_protochain() is not
       * compatible with some of kernel BPF code (for example BSD/OS 3.1).
       * Take a safer side for now.
       */
      if (no_optimize) {
            /*
             * XXX - what if we already have a filter in the kernel?
             */
            if (install_bpf_program(p, fp) < 0)
                  return (-1);
            p->md.use_bpf = 0;      /* filtering in userland */
            return (0);
      }

      /*
       * Free any user-mode filter we might happen to have installed.
       */
      pcap_freecode(&p->fcode);

      /*
       * Try to install the kernel filter.
       */
      if (ioctl(p->fd, BIOCSETF, (caddr_t)fp) < 0) {
            snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSETF: %s",
                pcap_strerror(errno));
            return (-1);
      }
      p->md.use_bpf = 1;      /* filtering in the kernel */

      /*
       * Discard any previously-received packets, as they might have
       * passed whatever filter was formerly in effect, but might
       * not pass this filter (BIOCSETF discards packets buffered
       * in the kernel, so you can lose packets in any case).
       */
      p->cc = 0;
      return (0);
}

/*
 * Set direction flag: Which packets do we accept on a forwarding
 * single device? IN, OUT or both?
 */
static int
pcap_setdirection_bpf(pcap_t *p, pcap_direction_t d)
{
#ifdef BIOCSSEESENT
      u_int seesent;
#endif

      /*
       * We don't support PCAP_D_OUT.
       */
      if (d == PCAP_D_OUT) {
            snprintf(p->errbuf, sizeof(p->errbuf),
                "Setting direction to PCAP_D_OUT is not supported on BPF");
            return -1;
      }
#ifdef BIOCSSEESENT
      seesent = (d == PCAP_D_INOUT);
      if (ioctl(p->fd, BIOCSSEESENT, &seesent) == -1) {
            (void) snprintf(p->errbuf, sizeof(p->errbuf),
                "Cannot set direction to %s: %s",
                    (d == PCAP_D_INOUT) ? "PCAP_D_INOUT" : "PCAP_D_IN",
                  strerror(errno));
            return (-1);
      }
      return (0);
#else
      (void) snprintf(p->errbuf, sizeof(p->errbuf),
          "This system doesn't support BIOCSSEESENT, so the direction can't be set");
      return (-1);
#endif
}

static int
pcap_set_datalink_bpf(pcap_t *p, int dlt)
{
#ifdef BIOCSDLT
      if (ioctl(p->fd, BIOCSDLT, &dlt) == -1) {
            (void) snprintf(p->errbuf, sizeof(p->errbuf),
                "Cannot set DLT %d: %s", dlt, strerror(errno));
            return (-1);
      }
#endif
      return (0);
}

Generated by  Doxygen 1.6.0   Back to index