121 lines
4.4 KiB
C
121 lines
4.4 KiB
C
/*
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* Copyright (c) 1990, 1991, 1993, 1994, 1995, 1996, 1997
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that: (1) source code distributions
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* retain the above copyright notice and this paragraph in its entirety, (2)
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* distributions including binary code include the above copyright notice and
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* this paragraph in its entirety in the documentation or other materials
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* provided with the distribution, and (3) all advertising materials mentioning
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* features or use of this software display the following acknowledgement:
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* ``This product includes software developed by the University of California,
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* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
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* the University nor the names of its contributors may be used to endorse
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* or promote products derived from this software without specific prior
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* written permission.
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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*/
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/* \summary: PPP Van Jacobson compression printer */
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/* specification: RFC 1144 */
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <netdissect-stdinc.h>
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#include "netdissect.h"
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#include "slcompress.h"
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#include "ppp.h"
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/*
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* XXX - for BSD/OS PPP, what packets get supplied with a PPP header type
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* of PPP_VJC and what packets get supplied with a PPP header type of
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* PPP_VJNC? PPP_VJNC is for "UNCOMPRESSED_TCP" packets, and PPP_VJC
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* is for COMPRESSED_TCP packets (PPP_IP is used for TYPE_IP packets).
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*
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* RFC 1144 implies that, on the wire, the packet type is *not* needed
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* for PPP, as different PPP protocol types can be used; it only needs
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* to be put on the wire for SLIP.
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*
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* It also indicates that, for compressed SLIP:
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*
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* If the COMPRESSED_TCP bit is set in the first byte, it's
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* a COMPRESSED_TCP packet; that byte is the change byte, and
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* the COMPRESSED_TCP bit, 0x80, isn't used in the change byte.
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*
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* If the upper 4 bits of the first byte are 7, it's an
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* UNCOMPRESSED_TCP packet; that byte is the first byte of
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* the UNCOMPRESSED_TCP modified IP header, with a connection
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* number in the protocol field, and with the version field
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* being 7, not 4.
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*
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* Otherwise, the packet is an IPv4 packet (where the upper 4 bits
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* of the packet are 4).
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*
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* So this routine looks as if it's sort-of intended to handle
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* compressed SLIP, although it doesn't handle UNCOMPRESSED_TCP
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* correctly for that (it doesn't fix the version number and doesn't
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* do anything to the protocol field), and doesn't check for COMPRESSED_TCP
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* packets correctly for that (you only check the first bit - see
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* B.1 in RFC 1144).
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*
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* But it's called for BSD/OS PPP, not SLIP - perhaps BSD/OS does weird
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* things with the headers?
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*
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* Without a BSD/OS VJC-compressed PPP trace, or knowledge of what the
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* BSD/OS VJC code does, we can't say what's the case.
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*
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* We therefore leave "proto" - which is the PPP protocol type - in place,
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* *not* marked as unused, for now, so that GCC warnings about the
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* unused argument remind us that we should fix this some day.
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*
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* XXX - also, it fetches the TCP checksum field in COMPRESSED_TCP
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* packets directly, rather than with EXTRACT_16BITS(); RFC 1144 says
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* it's "the unmodified TCP checksum", which would imply that it's
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* big-endian, but perhaps, on the platform where this was developed,
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* the packets were munged by the networking stack before being handed
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* to the packet capture mechanism.
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*/
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int
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vjc_print(netdissect_options *ndo, register const char *bp, u_short proto _U_)
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{
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int i;
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switch (bp[0] & 0xf0) {
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case TYPE_IP:
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if (ndo->ndo_eflag)
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ND_PRINT((ndo, "(vjc type=IP) "));
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return PPP_IP;
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case TYPE_UNCOMPRESSED_TCP:
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if (ndo->ndo_eflag)
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ND_PRINT((ndo, "(vjc type=raw TCP) "));
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return PPP_IP;
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case TYPE_COMPRESSED_TCP:
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if (ndo->ndo_eflag)
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ND_PRINT((ndo, "(vjc type=compressed TCP) "));
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for (i = 0; i < 8; i++) {
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if (bp[1] & (0x80 >> i))
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ND_PRINT((ndo, "%c", "?CI?SAWU"[i]));
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}
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if (bp[1])
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ND_PRINT((ndo, " "));
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ND_PRINT((ndo, "C=0x%02x ", bp[2]));
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ND_PRINT((ndo, "sum=0x%04x ", *(const u_short *)&bp[3]));
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return -1;
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case TYPE_ERROR:
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if (ndo->ndo_eflag)
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ND_PRINT((ndo, "(vjc type=error) "));
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return -1;
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default:
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if (ndo->ndo_eflag)
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ND_PRINT((ndo, "(vjc type=0x%02x) ", bp[0] & 0xf0));
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return -1;
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}
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}
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