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tcpdump.c

/*
 * Copyright (c) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
 *               2002, 2003, 2004
 *    Ohio University.
 *
 * ---
 * 
 * Starting with the release of tcptrace version 6 in 2001, tcptrace
 * is licensed under the GNU General Public License (GPL).  We believe
 * that, among the available licenses, the GPL will do the best job of
 * allowing tcptrace to continue to be a valuable, freely-available
 * and well-maintained tool for the networking community.
 *
 * Previous versions of tcptrace were released under a license that
 * was much less restrictive with respect to how tcptrace could be
 * used in commercial products.  Because of this, I am willing to
 * consider alternate license arrangements as allowed in Section 10 of
 * the GNU GPL.  Before I would consider licensing tcptrace under an
 * alternate agreement with a particular individual or company,
 * however, I would have to be convinced that such an alternative
 * would be to the greater benefit of the networking community.
 * 
 * ---
 *
 * This file is part of Tcptrace.
 *
 * Tcptrace was originally written and continues to be maintained by
 * Shawn Ostermann with the help of a group of devoted students and
 * users (see the file 'THANKS').  The work on tcptrace has been made
 * possible over the years through the generous support of NASA GRC,
 * the National Science Foundation, and Sun Microsystems.
 *
 * Tcptrace is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Tcptrace is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Tcptrace (in the file 'COPYING'); if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 * 
 * Author:  Shawn Ostermann
 *          School of Electrical Engineering and Computer Science
 *          Ohio University
 *          Athens, OH
 *          ostermann@cs.ohiou.edu
 *          http://www.tcptrace.org/
 */
#include "tcptrace.h"
static char const GCC_UNUSED copyright[] =
    "@(#)Copyright (c) 2004 -- Ohio University.\n";
static char const GCC_UNUSED rcsid[] =
    "@(#)$Header: /usr/local/cvs/tcptrace/tcpdump.c,v 5.22 2003/11/19 14:38:05 sdo Exp $";

#include <stdio.h>

#ifdef GROK_TCPDUMP

#include "tcpdump.h"
#include <pcap.h>




/* external ref, in case missing in older version */
extern int pcap_offline_read(void *, int, pcap_handler, u_char *);

/* global pointer, the pcap info header */
static pcap_t *pcap;


/* Interaction with pcap */
static struct ether_header eth_header;
#define EH_SIZE sizeof(struct ether_header)
static char *ip_buf;  /* [IP_MAXPACKET] */
static struct pcap_pkthdr *callback_phdr;
static void *callback_plast;


static int callback(
    char *user,
    struct pcap_pkthdr *phdr,
    char *buf)
{
    int type;
    int iplen;
    static int offset = -1;

    iplen = phdr->caplen;
    if (iplen > IP_MAXPACKET)
      iplen = IP_MAXPACKET;

    type = pcap_datalink(pcap);

    /* remember the stuff we always save */
    callback_phdr = phdr;

    /* kindof ugly, but about the only way to make them fit together :-( */
    switch (type) {
      case 100:
      /* for some reason, the windows version of tcpdump is using */
      /* this.  It looks just like ethernet to me */
      case PCAP_DLT_EN10MB:
      offset = find_ip_eth(buf); /* Here we check if we are dealing with Straight Ethernet encapsulation or PPPoE */
      memcpy(&eth_header, buf, EH_SIZE); /* save ether header */
      switch (offset)
      {
            case -1: /* Not an IP packet */
                  return (-1);
            case EH_SIZE: /* straight Ethernet encapsulation */
                  memcpy((char *)ip_buf,buf+offset,iplen);
                  callback_plast = ip_buf+iplen-offset-1;
                  break;
            case PPPOE_SIZE: /* PPPoE encapsulation */
                  /* we use a fake ether type here */
                  eth_header.ether_type = htons(ETHERTYPE_IP);
                  memcpy((char *)ip_buf,buf+offset,iplen);
                  callback_plast = ip_buf+iplen-offset-1;
                  break;
            default: /* should not be used, but we never know ... */
                  return (-1);
      }
      break;
      case PCAP_DLT_IEEE802:
      /* just pretend it's "normal" ethernet */
      offset = 14;            /* 22 bytes of IEEE cruft */
      memcpy(&eth_header,buf,EH_SIZE);  /* save ether header */
      memcpy(ip_buf,buf+offset,iplen);
      callback_plast = (char *)ip_buf+iplen-offset-1;
      break;
      case PCAP_DLT_SLIP:
      memcpy(ip_buf,buf+16,iplen);
      callback_plast = (char *)ip_buf+iplen-16-1;
      break;
      case PCAP_DLT_PPP:
      /* deals with raw PPP and also with HDLC PPP frames */
      offset = find_ip_ppp(buf);
      if (offset < 0) /* Not an IP packet */
            return (-1);
      memcpy((char *)ip_buf,buf+offset,iplen);
      callback_plast = ip_buf+iplen-offset-1;
      break;
      case PCAP_DLT_FDDI:
      if (offset < 0)
            offset = find_ip_fddi(buf,iplen);
      if (offset < 0)
            return(-1);
      memcpy((char *)ip_buf,buf+offset,iplen);
      callback_plast = ip_buf+iplen-offset-1;
      break;
      case PCAP_DLT_NULL:
      /* no phys header attached */
      offset = 4;
      memcpy((char *)ip_buf,buf+offset,iplen);
      callback_plast = ip_buf+iplen-offset-1;
      break;
      case PCAP_DLT_ATM_RFC1483:
      /* ATM RFC1483 - LLC/SNAP ecapsulated atm */
      memcpy((char*)ip_buf,buf+8,iplen);
      callback_plast = ip_buf+iplen-8-1;
      break;
      case PCAP_DLT_RAW:
      /* raw IP */
      offset = 0;
      memcpy((char *)ip_buf,buf+offset,iplen);
      callback_plast = ip_buf+iplen-offset-1;
      break;
      case PCAP_DLT_LINUX_SLL:
      /* linux cooked socket */
      offset = 16;
      memcpy((char *)ip_buf, buf+offset, iplen);
      callback_plast = ip_buf+iplen-offset-1;
      break;
      // Patch sent by Brandon Eisenamann to passby 802.11, LLC/SNAP
      // and Prism2 headers to get to the IP packet.
      case PCAP_DLT_IEEE802_11:
      offset=24+8;// 802.11 header + LLC/SNAP header
      memcpy((char *)ip_buf, buf+offset, iplen);
      callback_plast = ip_buf+iplen-offset-1;
      break;
      case PCAP_DLT_IEEE802_11_RADIO:
      offset=64+24;//WLAN header + 802.11 header
      memcpy(&eth_header,buf,EH_SIZE); // save ethernet header
      memcpy((char *)ip_buf, buf+offset, iplen);
      callback_plast = ip_buf+iplen-offset-1;
      break;
      case PCAP_DLT_PRISM2:
      offset=144+24+8; // PRISM2+IEEE 802.11+ LLC/SNAP headers
      memcpy((char *)ip_buf, buf+offset, iplen);
      callback_plast = ip_buf+iplen-offset-1;
      break;
      case PCAP_DLT_C_HDLC:
      offset=4;
      memcpy((char *)ip_buf, buf+offset, iplen);
      callback_plast = (char *)ip_buf+iplen-offset-1;
      break;
      default:
      fprintf(stderr,"Don't understand link-level format (%d)\n", type);

      exit(1);
    }
    
    return(0);
}


/* currently only works for ETHERNET and FDDI */
static int
pread_tcpdump(
    struct timeval      *ptime,
    int                 *plen,
    int                 *ptlen,
    void          **pphys,
    int                 *pphystype,
    struct ip           **ppip,
    void          **pplast)
{
    int ret;

    while (1) {
      if ((ret = pcap_offline_read(pcap,1,(pcap_handler)callback,0)) != 1) {
          /* prob EOF */

          if (ret == -1) {
            char *error;
            error = pcap_geterr(pcap);

            if (error && *error)
                fprintf(stderr,"PCAP error: '%s'\n",pcap_geterr(pcap));
            /* else, it's just EOF */
          }
          
          return(0);
      }

      /* at least one tcpdump implementation (AIX) seems to be */
      /* storing NANOseconds in the usecs field of the timestamp. */
      /* This confuses EVERYTHING.  Try to compensate. */
      {
          static Bool bogus_nanoseconds = FALSE;
          if ((callback_phdr->ts.tv_usec >= US_PER_SEC) ||
            (bogus_nanoseconds)) {
            if (!bogus_nanoseconds) {
                fprintf(stderr,
                      "tcpdump: attempting to adapt to bogus nanosecond timestamps\n");
                bogus_nanoseconds = TRUE;
            }
            callback_phdr->ts.tv_usec /= 1000;
          }
      }

      /* fill in all of the return values */
      *pphys     = &eth_header;/* everything assumed to be ethernet */
      *pphystype = PHYS_ETHER; /* everything assumed to be ethernet */
      *ppip      = (struct ip *) ip_buf;
      *pplast    = callback_plast; /* last byte in IP packet */
      /* (copying time structure in 2 steps to avoid RedHat brain damage) */
      ptime->tv_usec = callback_phdr->ts.tv_usec;
      ptime->tv_sec = callback_phdr->ts.tv_sec;
      *plen      = callback_phdr->len;
      *ptlen     = callback_phdr->caplen;

      /* if it's not IP, then skip it */
      if ((ntohs(eth_header.ether_type) != ETHERTYPE_IP) &&
          (ntohs(eth_header.ether_type) != ETHERTYPE_IPV6)) {
          if (debug > 2)
            fprintf(stderr,"pread_tcpdump: not an IP packet\n");
          continue;
      }

      return(1);
    }
}


pread_f *is_tcpdump(char *filename)
{
    char errbuf[100];
    char *physname = "<unknown>";
    int type;

#ifdef __WIN32   
      if ((pcap = pcap_open_offline(filename, errbuf)) == NULL) {
#else       
      if ((pcap = pcap_open_offline("-", errbuf)) == NULL) {
#endif /* __WIN32 */      
      if (debug > 2)
          fprintf(stderr,"PCAP said: '%s'\n", errbuf);
      rewind(stdin);
      return(NULL);
    }


    if (debug) {
      printf("Using 'pcap' version of tcpdump\n");
      if (debug > 1) {
          printf("\tversion_major: %d\n", pcap_major_version(pcap));
          printf("\tversion_minor: %d\n", pcap_minor_version(pcap));
          printf("\tsnaplen: %d\n", pcap_snapshot(pcap));
          printf("\tlinktype: %d\n", pcap_datalink(pcap));
          printf("\tswapped: %d\n", pcap_is_swapped(pcap));
      }
    }

    /* check the phys type (pretend everything is ethernet) */
    memset(&eth_header,0,EH_SIZE);
    switch (type = pcap_datalink(pcap)) {
case 100:
      case PCAP_DLT_EN10MB:
      /* OK, we understand this one */
      physname = "Ethernet";
      break;
      case PCAP_DLT_IEEE802:
      /* just pretend it's normal ethernet */
      physname = "Ethernet";
      break;
      case PCAP_DLT_SLIP:
      eth_header.ether_type = htons(ETHERTYPE_IP);
      physname = "Slip";
      break;
      case PCAP_DLT_PPP:
      eth_header.ether_type = htons(ETHERTYPE_IP);
      physname = "PPP or HDLC PPP";
      break;
      case PCAP_DLT_FDDI:
      eth_header.ether_type = htons(ETHERTYPE_IP);
      physname = "FDDI";
      break;
      case PCAP_DLT_NULL:
      eth_header.ether_type = htons(ETHERTYPE_IP);
      physname = "NULL";
      break;
      case PCAP_DLT_ATM_RFC1483:
      eth_header.ether_type = htons(ETHERTYPE_IP);
      physname = "ATM, LLC/SNAP encapsulated";
      break;
      case PCAP_DLT_RAW:
      eth_header.ether_type = htons(ETHERTYPE_IP);
      physname = "RAW_IP";
      break;
      case PCAP_DLT_LINUX_SLL:
      /* linux cooked socket type */
      eth_header.ether_type = htons(ETHERTYPE_IP);
      physname = "Linux Cooked Socket";
      break;
      case PCAP_DLT_IEEE802_11:
      eth_header.ether_type = htons(ETHERTYPE_IP);
      physname = "IEEE802_11";
      break;
      case PCAP_DLT_IEEE802_11_RADIO:
      eth_header.ether_type = htons(ETHERTYPE_IP);
      physname = "IEEE802_11_RADIO";
      break;
      case PCAP_DLT_PRISM2:
      eth_header.ether_type = htons(ETHERTYPE_IP);
      physname = "PRISM2";
      break;
      case PCAP_DLT_C_HDLC:
      eth_header.ether_type = htons(ETHERTYPE_IP);
      physname = "Cisco HDLC";
      break;
      default:
        fprintf(stderr,"tcptrace did not understand link format (%d)!\n",type);
        fprintf(stderr,
            "\t If you can give us a capture file with this link format\n\
\t or even better, a patch to decipher this format, we shall add it in, \n\
\t in a future release.\n");
      rewind(stdin);
      return(NULL);
    }

    if (debug)
      fprintf(stderr,"Tcpdump format, physical type is %d (%s)\n",
            type, physname);

    /* set up some stuff */
    ip_buf = MallocZ(IP_MAXPACKET);


    return(pread_tcpdump);
}


/* support for writing a new pcap file */

void
PcapSavePacket(
    char *filename,
    struct ip *pip,
    void *plast)
{
    static MFILE *f_savefile = NULL;
    struct pcap_pkthdr phdr;
    int wlen;

    if (f_savefile == NULL) {
      struct pcap_file_header fhdr;

      /* try to open the file */
      if ((f_savefile = Mfopen(filename, "w")) == NULL) {
          perror(filename);
          exit(-1);
      }
      
      /* make up the header info it wants */
      /* this comes from version 2.4, no pcap routine handy :-(  */
      fhdr.magic = TCPDUMP_MAGIC;
      fhdr.version_major = PCAP_VERSION_MAJOR;
      fhdr.version_minor = PCAP_VERSION_MINOR;

      fhdr.thiszone = 0;      /* don't have this info, just make it up */
      fhdr.snaplen = 1000000; /* don't have this info, just make it up */
      fhdr.linktype = PCAP_DLT_EN10MB; /* always Ethernet (10Mb) */
      fhdr.sigfigs = 0;

      /* write the header */
      Mfwrite((char *)&fhdr, sizeof(fhdr), 1, f_savefile);

      if (debug)
          fprintf(stderr,"Created pcap save file '%s'\n", filename);
    }

    /* create the packet header */
    /* (copying time structure in 2 steps to avoid RedHat brain damage) */
    phdr.ts.tv_sec = current_time.tv_sec;
    phdr.ts.tv_usec = current_time.tv_usec;
    phdr.caplen = (char *)plast - (char *)pip + 1;
    phdr.caplen += EH_SIZE;   /* add in the ether header */
    phdr.len = EH_SIZE + ntohs(PIP_LEN(pip));   /* probably this */

    /* write the packet header */
    Mfwrite(&phdr, sizeof(phdr), 1, f_savefile);

    /* write a (bogus) ethernet header */
    memset(&eth_header,0,EH_SIZE);
    eth_header.ether_type = htons(ETHERTYPE_IP);
    Mfwrite(&eth_header, sizeof(eth_header), 1, f_savefile);

    /* write the IP/TCP parts */
    wlen = phdr.caplen - EH_SIZE;   /* remove the ether header */
    Mfwrite(pip, wlen, 1, f_savefile);
}
    


#else /* GROK_TCPDUMP */

void
PcapSavePacket(
    char *filename,
    struct ip *pip,
    void *plast)
{
    fprintf(stderr,"\
Sorry, packet writing only supported with the pcap library\n\
compiled into the program (See GROK_TCPDUMP)\n");
    exit(-2);
}


#endif /* GROK_TCPDUMP */

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