The BPF code is generated using pcap_fddipad, so if we have to evaluate

[libpcap] / 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 1.89 2004-12-15 00:05:48 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;
        struct bpf_insn *fcode;
        register int cc, n, buflen, inc;
        register struct enstamp *sp;
#ifdef LBL_ALIGN
        struct enstamp stamp;
#endif
#ifdef PCAP_FDDIPAD
        register int pad;
#endif

        fcode = pc->md.use_bpf ? NULL : pc->fcode.bf_insns;
 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
        if (pc->linktype == DLT_FDDI)
                pad = pcap_fddipad;
        else
                pad = 0;
#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.
                 *
#ifdef PCAP_FDDIPAD
                 * Note: the filter code was generated assuming
                 * that pcap_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, 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

pcap_t *
pcap_open_live(const char *device, int snaplen, int promisc, int to_ms,
    char *ebuf)
{
        pcap_t *p;
        short enmode;
        int backlog = -1;       /* request the most */
        struct enfilter Filter;
        struct endevp devparams;

        p = (pcap_t *)malloc(sizeof(*p));
        if (p == NULL) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE,
                    "pcap_open_live: %s", pcap_strerror(errno));
                return (0);
        }
        memset(p, 0, sizeof(*p));
        /*
         * 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(device, O_RDWR);
        if (p->fd == -1 && errno == EACCES)
                p->fd = pfopen(device, O_RDONLY);
        if (p->fd < 0) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "pf open: %s: %s\n\
your system may not be properly configured; see the packetfilter(4) man page\n",
                        device, pcap_strerror(errno));
                goto bad;
        }
        p->md.OrigMissed = -1;
        enmode = ENTSTAMP|ENBATCH|ENNONEXCL;
        if (promisc)
                enmode |= ENPROMISC;
        if (ioctl(p->fd, EIOCMBIS, (caddr_t)&enmode) < 0) {
                snprintf(ebuf, 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(ebuf, PCAP_ERRBUF_SIZE, "EIOCSETW: %s",
                    pcap_strerror(errno));
                goto bad;
        }
        /* discover interface type */
        if (ioctl(p->fd, EIOCDEVP, (caddr_t)&devparams) < 0) {
                snprintf(ebuf, 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(ebuf, PCAP_ERRBUF_SIZE, "unknown data-link type %u",
                    devparams.end_dev_type);
                goto bad;
        }
        /* set truncation */
#ifdef PCAP_FDDIPAD
        if (p->linktype == DLT_FDDI)
                /* packetfilter includes the padding in the snapshot */
                snaplen += pcap_fddipad;
#endif
        if (ioctl(p->fd, EIOCTRUNCATE, (caddr_t)&snaplen) < 0) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "EIOCTRUNCATE: %s",
                    pcap_strerror(errno));
                goto bad;
        }
        p->snapshot = snaplen;
        /* 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(ebuf, PCAP_ERRBUF_SIZE, "EIOCSETF: %s",
                    pcap_strerror(errno));
                goto bad;
        }

        if (to_ms != 0) {
                struct timeval timeout;
                timeout.tv_sec = to_ms / 1000;
                timeout.tv_usec = (to_ms * 1000) % 1000000;
                if (ioctl(p->fd, EIOCSRTIMEOUT, (caddr_t)&timeout) < 0) {
                        snprintf(ebuf, 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(ebuf, 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->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;
        p->close_op = pcap_close_common;

        return (p);
 bad:
        if (p->fd >= 0)
                close(p->fd);
        /*
         * Get rid of any link-layer type list we allocated.
         */
        if (p->dlt_list != NULL)
                free(p->dlt_list);
        free(p);
        return (NULL);
}

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;
                        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);
}