pcap-bpf.c   [plain text]

/*
 * 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: /cvs/Darwin/Libraries/Other/libpcap/libpcap/pcap-bpf.c,v 1.1.1.1 2001/07/07 00:41:36 bbraun 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) {
		if (install_bpf_program(p, fp) < 0)
			return (-1);
	} else if (p->sf.rfile != NULL) {
		if (install_bpf_program(p, fp) < 0)
			return (-1);
	} 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);
}