pcap-bpf.c

用来监视网络通信数据的源代码和应用程序,方便网络程序底层开发.

/*
 * 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 1.67.2.5 2004/09/15 08:02:39 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 <odmi.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

#ifdef HAVE_REMOTE
#include <pcap-remote.h>
#endif /* HAVE_REMOTE */

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

static int pcap_setfilter_bpf(pcap_t *p, struct bpf_program *fp);
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;
	struct bpf_insn *fcode;

	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;
	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;
		/*
		 * Short-circuit evaluation: if using BPF filter
		 * in kernel, no need to do it now.
		 */
		if (fcode == NULL ||
		    bpf_filter(fcode, bp + hdrlen, bhp->bh_datalen, caplen)) {
#ifdef _AIX
			/*
			 * AIX's BPF returns seconds/nanoseconds time
			 * stamps, not seconds/microseconds time stamps.
			 *
			 * XXX - I'm guessing here that it's a "struct
			 * timestamp"; if not, this code won't compile,
			 * but, if not, you want to send us a bug report
			 * and fall back on using DLPI.  It's not as if
			 * BPF used to work right on AIX before this
			 * change; this change attempts to fix the fact
			 * that it didn't....
			 */
			bhp->bh_tstamp.tv_usec = bhp->bh_tstamp.tv_usec/1000;
#endif
			/*
			 * 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);
			}
		} else {
			/*
			 * Skip this packet.
			 */
			bp += BPF_WORDALIGN(caplen + hdrlen);
		}
	}
#undef bhp
	p->cc = 0;
	return (n);
}

#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++);