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pcap-pf.c

/*
 * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996
 *    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.
 *
 * packet filter subroutines for tcpdump
 *    Extraction/creation by Jeffrey Mogul, DECWRL
 */

#ifndef lint
static const char rcsid[] _U_ =
    "@(#) $Header: /tcpdump/master/libpcap/pcap-pf.c,v 1.94.2.3 2008-04-14 20:41:52 guy Exp $ (LBL)";
#endif

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

#include <sys/types.h>
#include <sys/time.h>
#include <sys/timeb.h>
#include <sys/socket.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <net/pfilt.h>

struct mbuf;
struct rtentry;
#include <net/if.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/if_ether.h>
#include <netinet/ip_var.h>
#include <netinet/udp.h>
#include <netinet/udp_var.h>
#include <netinet/tcp.h>
#include <netinet/tcpip.h>

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

/*
 * Make "pcap.h" not include "pcap/bpf.h"; we are going to include the
 * native OS version, as we need various BPF ioctls from it.
 */
#define PCAP_DONT_INCLUDE_PCAP_BPF_H
#include <net/bpf.h>

#include "pcap-int.h"

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

static int pcap_setfilter_pf(pcap_t *, struct bpf_program *);

/*
 * BUFSPACE is the size in bytes of the packet read buffer.  Most tcpdump
 * applications aren't going to need more than 200 bytes of packet header
 * and the read shouldn't return more packets than packetfilter's internal
 * queue limit (bounded at 256).
 */
#define BUFSPACE (200 * 256)

static int
pcap_read_pf(pcap_t *pc, int cnt, pcap_handler callback, u_char *user)
{
      register u_char *p, *bp;
      register int cc, n, buflen, inc;
      register struct enstamp *sp;
#ifdef LBL_ALIGN
      struct enstamp stamp;
#endif
#ifdef PCAP_FDDIPAD
      register int pad;
#endif

 again:
      cc = pc->cc;
      if (cc == 0) {
            cc = read(pc->fd, (char *)pc->buffer + pc->offset, pc->bufsize);
            if (cc < 0) {
                  if (errno == EWOULDBLOCK)
                        return (0);
                  if (errno == EINVAL &&
                      lseek(pc->fd, 0L, SEEK_CUR) + pc->bufsize < 0) {
                        /*
                         * Due to a kernel bug, after 2^31 bytes,
                         * the kernel file offset overflows and
                         * read fails with EINVAL. The lseek()
                         * to 0 will fix things.
                         */
                        (void)lseek(pc->fd, 0L, SEEK_SET);
                        goto again;
                  }
                  snprintf(pc->errbuf, sizeof(pc->errbuf), "pf read: %s",
                        pcap_strerror(errno));
                  return (-1);
            }
            bp = pc->buffer + pc->offset;
      } else
            bp = pc->bp;
      /*
       * Loop through each packet.
       */
      n = 0;
#ifdef PCAP_FDDIPAD
      pad = pc->fddipad;
#endif
      while (cc > 0) {
            /*
             * 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 (pc->break_loop) {
                  if (n == 0) {
                        pc->break_loop = 0;
                        return (-2);
                  } else {
                        pc->cc = cc;
                        pc->bp = bp;
                        return (n);
                  }
            }
            if (cc < sizeof(*sp)) {
                  snprintf(pc->errbuf, sizeof(pc->errbuf),
                      "pf short read (%d)", cc);
                  return (-1);
            }
#ifdef LBL_ALIGN
            if ((long)bp & 3) {
                  sp = &stamp;
                  memcpy((char *)sp, (char *)bp, sizeof(*sp));
            } else
#endif
                  sp = (struct enstamp *)bp;
            if (sp->ens_stamplen != sizeof(*sp)) {
                  snprintf(pc->errbuf, sizeof(pc->errbuf),
                      "pf short stamplen (%d)",
                      sp->ens_stamplen);
                  return (-1);
            }

            p = bp + sp->ens_stamplen;
            buflen = sp->ens_count;
            if (buflen > pc->snapshot)
                  buflen = pc->snapshot;

            /* Calculate inc before possible pad update */
            inc = ENALIGN(buflen + sp->ens_stamplen);
            cc -= inc;
            bp += inc;
            pc->md.TotPkts++;
            pc->md.TotDrops += sp->ens_dropped;
            pc->md.TotMissed = sp->ens_ifoverflows;
            if (pc->md.OrigMissed < 0)
                  pc->md.OrigMissed = pc->md.TotMissed;

            /*
             * Short-circuit evaluation: if using BPF filter
             * in kernel, no need to do it now - we already know
             * the packet passed the filter.
             *
#ifdef PCAP_FDDIPAD
             * Note: the filter code was generated assuming
             * that pc->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 (pc->md.use_bpf ||
                bpf_filter(pc->fcode.bf_insns, p, sp->ens_count, buflen)) {
                  struct pcap_pkthdr h;
                  pc->md.TotAccepted++;
                  h.ts = sp->ens_tstamp;
#ifdef PCAP_FDDIPAD
                  h.len = sp->ens_count - pad;
#else
                  h.len = sp->ens_count;
#endif
#ifdef PCAP_FDDIPAD
                  p += pad;
                  buflen -= pad;
#endif
                  h.caplen = buflen;
                  (*callback)(user, &h, p);
                  if (++n >= cnt && cnt > 0) {
                        pc->cc = cc;
                        pc->bp = bp;
                        return (n);
                  }
            }
      }
      pc->cc = 0;
      return (n);
}

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

      ret = write(p->fd, buf, size);
      if (ret == -1) {
            snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "send: %s",
                pcap_strerror(errno));
            return (-1);
      }
      return (ret);
}                           

static int
pcap_stats_pf(pcap_t *p, struct pcap_stat *ps)
{

      /*
       * If packet filtering is being done in the kernel:
       *
       *    "ps_recv" counts only packets that passed the filter.
       *    This does not include packets dropped because we
       *    ran out of buffer space.  (XXX - perhaps it should,
       *    by adding "ps_drop" to "ps_recv", for compatibility
       *    with some other platforms.  On the other hand, on
       *    some platforms "ps_recv" counts only packets that
       *    passed the filter, and on others it counts packets
       *    that didn't pass the filter....)
       *
       *    "ps_drop" counts packets that passed the kernel filter
       *    (if any) but were dropped because the input queue was
       *    full.
       *
       *    "ps_ifdrop" counts packets dropped by the network
       *    inteface (regardless of whether they would have passed
       *    the input filter, of course).
       *
       * If packet filtering is not being done in the kernel:
       *
       *    "ps_recv" counts only packets that passed the filter.
       *
       *    "ps_drop" counts packets that were dropped because the
       *    input queue was full, regardless of whether they passed
       *    the userland filter.
       *
       *    "ps_ifdrop" counts packets dropped by the network
       *    inteface (regardless of whether they would have passed
       *    the input filter, of course).
       *
       * These statistics don't include packets not yet read from
       * the kernel by libpcap, but they may include packets not
       * yet read from libpcap by the application.
       */
      ps->ps_recv = p->md.TotAccepted;
      ps->ps_drop = p->md.TotDrops;
      ps->ps_ifdrop = p->md.TotMissed - p->md.OrigMissed;
      return (0);
}

/*
 * 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

static int
pcap_activate_pf(pcap_t *p)
{
      short enmode;
      int backlog = -1; /* request the most */
      struct enfilter Filter;
      struct endevp devparams;

      /*
       * 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.
       *
       * XXX - we assume here that "pfopen()" does not, in fact, modify
       * its argument, even though it takes a "char *" rather than a
       * "const char *" as its first argument.  That appears to be
       * the case, at least on Digital UNIX 4.0.
       */
      p->fd = pfopen(p->opt.source, O_RDWR);
      if (p->fd == -1 && errno == EACCES)
            p->fd = pfopen(p->opt.source, O_RDONLY);
      if (p->fd < 0) {
            snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "pf open: %s: %s\n\
your system may not be properly configured; see the packetfilter(4) man page\n",
                  p->opt.source, pcap_strerror(errno));
            goto bad;
      }
      p->md.OrigMissed = -1;
      enmode = ENTSTAMP|ENBATCH|ENNONEXCL;
      if (p->opt.promisc)
            enmode |= ENPROMISC;
      if (ioctl(p->fd, EIOCMBIS, (caddr_t)&enmode) < 0) {
            snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "EIOCMBIS: %s",
                pcap_strerror(errno));
            goto bad;
      }
#ifdef      ENCOPYALL
      /* Try to set COPYALL mode so that we see packets to ourself */
      enmode = ENCOPYALL;
      (void)ioctl(p->fd, EIOCMBIS, (caddr_t)&enmode);/* OK if this fails */
#endif
      /* set the backlog */
      if (ioctl(p->fd, EIOCSETW, (caddr_t)&backlog) < 0) {
            snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "EIOCSETW: %s",
                pcap_strerror(errno));
            goto bad;
      }
      /* discover interface type */
      if (ioctl(p->fd, EIOCDEVP, (caddr_t)&devparams) < 0) {
            snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "EIOCDEVP: %s",
                pcap_strerror(errno));
            goto bad;
      }
      /* HACK: to compile prior to Ultrix 4.2 */
#ifndef     ENDT_FDDI
#define     ENDT_FDDI   4
#endif
      switch (devparams.end_dev_type) {

      case ENDT_10MB:
            p->linktype = DLT_EN10MB;
            p->offset = 2;
            /*
             * This is (presumably) a real Ethernet capture; give it a
             * link-layer-type list with DLT_EN10MB and DLT_DOCSIS, 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).
             */
            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;
            }
            break;

      case ENDT_FDDI:
            p->linktype = DLT_FDDI;
            break;

#ifdef ENDT_SLIP
      case ENDT_SLIP:
            p->linktype = DLT_SLIP;
            break;
#endif

#ifdef ENDT_PPP
      case ENDT_PPP:
            p->linktype = DLT_PPP;
            break;
#endif

#ifdef ENDT_LOOPBACK
      case ENDT_LOOPBACK:
            /*
             * It appears to use Ethernet framing, at least on
             * Digital UNIX 4.0.
             */
            p->linktype = DLT_EN10MB;
            p->offset = 2;
            break;
#endif

#ifdef ENDT_TRN
      case ENDT_TRN:
            p->linktype = DLT_IEEE802;
            break;
#endif

      default:
            /*
             * XXX - what about ENDT_IEEE802?  The pfilt.h header
             * file calls this "IEEE 802 networks (non-Ethernet)",
             * but that doesn't specify a specific link layer type;
             * it could be 802.4, or 802.5 (except that 802.5 is
             * ENDT_TRN), or 802.6, or 802.11, or....  That's why
             * DLT_IEEE802 was hijacked to mean Token Ring in various
             * BSDs, and why we went along with that hijacking.
             *
             * XXX - what about ENDT_HDLC and ENDT_NULL?
             * Presumably, as ENDT_OTHER is just "Miscellaneous
             * framing", there's not much we can do, as that
             * doesn't specify a particular type of header.
             */
            snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                "unknown data-link type %u", devparams.end_dev_type);
            goto bad;
      }
      /* set truncation */
#ifdef PCAP_FDDIPAD
      if (p->linktype == DLT_FDDI) {
            p->fddipad = PCAP_FDDIPAD;

            /* packetfilter includes the padding in the snapshot */
            p->snapshot += PCAP_FDDIPAD;
      } else
            p->fddipad = 0;
#endif
      if (ioctl(p->fd, EIOCTRUNCATE, (caddr_t)&p->snapshot) < 0) {
            snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "EIOCTRUNCATE: %s",
                pcap_strerror(errno));
            goto bad;
      }
      /* accept all packets */
      memset(&Filter, 0, sizeof(Filter));
      Filter.enf_Priority = 37;     /* anything > 2 */
      Filter.enf_FilterLen = 0;     /* means "always true" */
      if (ioctl(p->fd, EIOCSETF, (caddr_t)&Filter) < 0) {
            snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "EIOCSETF: %s",
                pcap_strerror(errno));
            goto bad;
      }

      if (p->md.timeout != 0) {
            struct timeval timeout;
            timeout.tv_sec = p->md.timeout / 1000;
            timeout.tv_usec = (p->md.timeout * 1000) % 1000000;
            if (ioctl(p->fd, EIOCSRTIMEOUT, (caddr_t)&timeout) < 0) {
                  snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "EIOCSRTIMEOUT: %s",
                        pcap_strerror(errno));
                  goto bad;
            }
      }

      p->bufsize = BUFSPACE;
      p->buffer = (u_char*)malloc(p->bufsize + p->offset);
      if (p->buffer == NULL) {
            strlcpy(p->errbuf, pcap_strerror(errno), PCAP_ERRBUF_SIZE);
            goto bad;
      }

      /*
       * "select()" and "poll()" work on packetfilter devices.
       */
      p->selectable_fd = p->fd;

      p->read_op = pcap_read_pf;
      p->inject_op = pcap_inject_pf;
      p->setfilter_op = pcap_setfilter_pf;
      p->setdirection_op = NULL;    /* Not implemented. */
      p->set_datalink_op = NULL;    /* can't change data link type */
      p->getnonblock_op = pcap_getnonblock_fd;
      p->setnonblock_op = pcap_setnonblock_fd;
      p->stats_op = pcap_stats_pf;

      return (0);
 bad:
      return (PCAP_ERROR);
}

pcap_t *
pcap_create(const char *device, char *ebuf)
{
      pcap_t *p;

      p = pcap_create_common(device, ebuf);
      if (p == NULL)
            return (NULL);

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

int
pcap_platform_finddevs(pcap_if_t **alldevsp, char *errbuf)
{
      return (0);
}

static int
pcap_setfilter_pf(pcap_t *p, struct bpf_program *fp)
{
      struct bpf_version bv;

      /*
       * See if BIOCVERSION works.  If not, we assume the kernel doesn't
       * support BPF-style filters (it's not documented in the bpf(7)
       * or packetfiler(7) man pages, but the code used to fail if
       * BIOCSETF worked but BIOCVERSION didn't, and I've seen it do
       * kernel filtering in DU 4.0, so presumably BIOCVERSION works
       * there, at least).
       */
      if (ioctl(p->fd, BIOCVERSION, (caddr_t)&bv) >= 0) {
            /*
             * OK, we have the version of the BPF interpreter;
             * is it the same major version as us, and the same
             * or better minor version?
             */
            if (bv.bv_major == BPF_MAJOR_VERSION &&
                bv.bv_minor >= BPF_MINOR_VERSION) {
                  /*
                   * Yes.  Try to install the filter.
                   */
                  if (ioctl(p->fd, BIOCSETF, (caddr_t)fp) < 0) {
                        snprintf(p->errbuf, sizeof(p->errbuf),
                            "BIOCSETF: %s", pcap_strerror(errno));
                        return (-1);
                  }

                  /*
                   * OK, that succeeded.  We're doing filtering in
                   * the kernel.  (We assume we don't have a
                   * userland filter installed - that'd require
                   * a previous version check to have failed but
                   * this one to succeed.)
                   *
                   * XXX - this message should be supplied to the
                   * application as a warning of some sort,
                   * except that if it's a GUI application, it's
                   * not clear that it should be displayed in
                   * a window to annoy the user.
                   */
                  fprintf(stderr, "tcpdump: Using kernel BPF filter\n");
                  p->md.use_bpf = 1;

                  /*
                   * 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);
            }

            /*
             * We can't use the kernel's BPF interpreter; don't give
             * up, just log a message and be inefficient.
             *
             * XXX - this should really be supplied to the application
             * as a warning of some sort.
             */
            fprintf(stderr,
          "tcpdump: Requires BPF language %d.%d or higher; kernel is %d.%d\n",
                BPF_MAJOR_VERSION, BPF_MINOR_VERSION,
                bv.bv_major, bv.bv_minor);
      }

      /*
       * We couldn't do filtering in the kernel; do it in userland.
       */
      if (install_bpf_program(p, fp) < 0)
            return (-1);

      /*
       * XXX - this message should be supplied by the application as
       * a warning of some sort.
       */
      fprintf(stderr, "tcpdump: Filtering in user process\n");
      p->md.use_bpf = 0;
      return (0);
}

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