[libpcap] / 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[] =
    "@(#) $Header: /tcpdump/master/libpcap/pcap-bpf.c,v 1.43 2000-10-12 03:53:58 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 <net/if.h>

#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_OS_PROTO_H
#include "os-proto.h"
#endif

#include "gencode.h"

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

        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);
}

int
pcap_read(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
{
        int cc;
        int n = 0;
        register u_char *bp, *ep;

 again:
        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;

                        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;
        while (bp < ep) {
                register int caplen, hdrlen;
                caplen = bhp->bh_caplen;
                hdrlen = bhp->bh_hdrlen;
                /*
                 * XXX A bpf_hdr matches a pcap_pkthdr.
                 */
                (*callback)(user, (struct pcap_pkthdr*)bp, bp + hdrlen);
                bp += BPF_WORDALIGN(caplen + hdrlen);
                if (++n >= cnt && cnt > 0) {
                        p->bp = bp;
                        p->cc = ep - bp;
                        return (n);
                }
        }
#undef bhp
        p->cc = 0;
        return (n);
}

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

        /*
         * Go through all the minors and find one that isn't in use.
         */
        do {
                (void)snprintf(device, sizeof(device), "/dev/bpf%d", n++);
                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);
}

pcap_t *
pcap_open_live(char *device, int snaplen, int promisc, int to_ms, char *ebuf)
{
        int fd;
        struct ifreq ifr;
        struct bpf_version bv;
        u_int v;
        pcap_t *p;

        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.
         *
         * XXX - there should be a user-accessible hook to set the
         * initial buffer size.
         */
        for (v = 32768; 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 __OpenBSD__
        switch (v) {
        case DLT_LOOP:
                /*
                 * XXX - DLT_LOOP has a network-byte-order, rather than
                 * a host-byte-order, AF_ value as the link-layer
                 * header; will the BPF code generator handle that
                 * correctly on little-endian machines?
                 */
                v = DLT_NULL;
                break;
        }
#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_RAW;    /*XXX*/
                break;

        case 12:        /*DLT_C_HDLC*/
                v = DLT_CHDLC;
                break;
        }
#endif
        p->linktype = v;

        /* set timeout */
        if (to_ms != 0) {
                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 */
                (void)ioctl(p->fd, BIOCPROMISC, NULL);

        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;
        }

        return (p);
 bad:
        (void)close(fd);
        free(p);
        return (NULL);
}

int
pcap_setfilter(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)
                p->fcode = *fp;
        else if (p->sf.rfile != NULL)
                p->fcode = *fp;
        else if (ioctl(p->fd, BIOCSETF, (caddr_t)fp) < 0) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSETF: %s",
                    pcap_strerror(errno));
                return (-1);
        }
        return (0);
}