The Tcpdump Group git mirrors - tcpdump/blob - print-cip.c

   1 /*
   2  * Marko Kiiskila carnil@cs.tut.fi
   3  *
   4  * Tampere University of Technology - Telecommunications Laboratory
   5  *
   6  * Permission to use, copy, modify and distribute this
   7  * software and its documentation is hereby granted,
   8  * provided that both the copyright notice and this
   9  * permission notice appear in all copies of the software,
  10  * derivative works or modified versions, and any portions
  11  * thereof, that both notices appear in supporting
  12  * documentation, and that the use of this software is
  13  * acknowledged in any publications resulting from using
  14  * the software.
  15  *
  16  * TUT ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  17  * CONDITION AND DISCLAIMS ANY LIABILITY OF ANY KIND FOR
  18  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS
  19  * SOFTWARE.
  20  *
  21  */
  22
  23 /* \summary: Linux Classical IP over ATM printer */
  24
  25 #ifdef HAVE_CONFIG_H
  26 #include <config.h>
  27 #endif
  28
  29 #include <string.h>
  30
  31 #include "netdissect-stdinc.h"
  32
  33 #include "netdissect.h"
  34 #include "addrtoname.h"
  35
  36 static const unsigned char rfcllc[] = {
  37         0xaa,   /* DSAP: non-ISO */
  38         0xaa,   /* SSAP: non-ISO */
  39         0x03,   /* Ctrl: Unnumbered Information Command PDU */
  40         0x00,   /* OUI: EtherType */
  41         0x00,
  42         0x00 };
  43
  44 static void
  45 cip_print(netdissect_options *ndo, u_int length)
  46 {
  47         /*
  48          * There is no MAC-layer header, so just print the length.
  49          */
  50         ND_PRINT("%u: ", length);
  51 }
  52
  53 /*
  54  * This is the top level routine of the printer.  'p' points
  55  * to the LLC/SNAP or raw header of the packet, 'h->ts' is the timestamp,
  56  * 'h->len' is the length of the packet off the wire, and 'h->caplen'
  57  * is the number of bytes actually captured.
  58  */
  59 void
  60 cip_if_print(netdissect_options *ndo, const struct pcap_pkthdr *h, const u_char *p)
  61 {
  62         u_int caplen = h->caplen;
  63         u_int length = h->len;
  64         size_t cmplen;
  65         int llc_hdrlen;
  66
  67         ndo->ndo_protocol = "cip";
  68         cmplen = sizeof(rfcllc);
  69         if (cmplen > caplen)
  70                 cmplen = caplen;
  71         if (cmplen > length)
  72                 cmplen = length;
  73
  74         if (ndo->ndo_eflag)
  75                 cip_print(ndo, length);
  76
  77         if (cmplen == 0) {
  78                 nd_print_trunc(ndo);
  79                 return;
  80         }
  81         if (memcmp(rfcllc, p, cmplen) == 0) {
  82                 /*
  83                  * LLC header is present.  Try to print it & higher layers.
  84                  */
  85                 llc_hdrlen = llc_print(ndo, p, length, caplen, NULL, NULL);
  86                 if (llc_hdrlen < 0) {
  87                         /* packet type not known, print raw packet */
  88                         if (!ndo->ndo_suppress_default_print)
  89                                 ND_DEFAULTPRINT(p, caplen);
  90                         llc_hdrlen = -llc_hdrlen;
  91                 }
  92         } else {
  93                 /*
  94                  * LLC header is absent; treat it as just IP.
  95                  */
  96                 llc_hdrlen = 0;
  97                 ip_print(ndo, p, length);
  98         }
  99
 100         ndo->ndo_ll_hdr_len += llc_hdrlen;
 101 }