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Correctly compute the OSI checksum. 

Have "calc_checksum()" just return an indication of the status of the
checksum.

Check the CLNP header checksum, and put display its status.

svn path=/trunk/; revision=3514
This commit is contained in:
Guy Harris 2001-06-05 09:06:19 +00:00
parent 2851b7ef76
commit f2e04def43
4 changed files with 112 additions and 29 deletions
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39
packet-clnp.c
View File

@ -1,14 +1,13 @@
/* packet-clnp.c
* Routines for ISO/OSI network and transport protocol packet disassembly
*
* $Id: packet-clnp.c,v 1.28 2001/05/27 04:14:52 guy Exp $
* $Id: packet-clnp.c,v 1.29 2001/06/05 09:06:19 guy Exp $
* Laurent Deniel <deniel@worldnet.fr>
* Ralf Schneider <Ralf.Schneider@t-online.de>
*
* Ethereal - Network traffic analyzer
* By Gerald Combs <gerald@zing.org>
* By Gerald Combs <gerald@ethereal.com>
* Copyright 1998 Gerald Combs
*
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@ -1675,10 +1674,42 @@ static void dissect_clnp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
proto_tree_add_uint(clnp_tree, hf_clnp_pdu_length, tvb, P_CLNP_SEGLEN, 2,
segment_length);
cnf_cksum = tvb_get_ntohs(tvb, P_CLNP_CKSUM);
proto_tree_add_uint_format(clnp_tree, hf_clnp_checksum, tvb, P_CLNP_CKSUM, 2,
switch (calc_checksum(tvb, 0, cnf_hdr_len, cnf_cksum)) {
default:
/*
* No checksum present, or not enough of the header present to
* checksum it.
*/
proto_tree_add_uint_format(clnp_tree, hf_clnp_checksum, tvb,
P_CLNP_CKSUM, 2,
cnf_cksum,
"Checksum : 0x%04x",
cnf_cksum);
break;
case CKSUM_OK:
/*
* Checksum is correct.
*/
proto_tree_add_uint_format(clnp_tree, hf_clnp_checksum, tvb,
P_CLNP_CKSUM, 2,
cnf_cksum,
"Checksum : 0x%04x (correct)",
cnf_cksum);
break;
case CKSUM_NOT_OK:
/*
* Checksum is not correct.
*/
proto_tree_add_uint_format(clnp_tree, hf_clnp_checksum, tvb,
P_CLNP_CKSUM, 2,
cnf_cksum,
"Checksum : 0x%04x (incorrect)",
cnf_cksum);
break;
}
opt_len -= 9; /* Fixed part of Hesder */
} /* tree */

32
packet-esis.c
View File

@ -2,13 +2,12 @@
* Routines for ISO/OSI End System to Intermediate System
* Routeing Exchange Protocol ISO 9542.
*
* $Id: packet-esis.c,v 1.14 2001/03/30 10:51:50 guy Exp $
* $Id: packet-esis.c,v 1.15 2001/06/05 09:06:19 guy Exp $
* Ralf Schneider <Ralf.Schneider@t-online.de>
*
* Ethereal - Network traffic analyzer
* By Gerald Combs <gerald@zing.org>
* By Gerald Combs <gerald@ethereal.com>
* Copyright 1998 Gerald Combs
*
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@ -292,6 +291,7 @@ dissect_esis(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) {
proto_tree *esis_tree = NULL;
int variable_len = 0;
u_int tmp_uint = 0;
char *cksum_status;
if (check_col(pinfo->fd, COL_PROTOCOL))
col_set_str(pinfo->fd, COL_PROTOCOL, "ESIS");
@ -337,11 +337,31 @@ dissect_esis(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) {
tmp_uint = pntohs( ehdr.esis_checksum );
switch (calc_checksum( tvb, 0, ehdr.esis_length, tmp_uint )) {
case NO_CKSUM:
cksum_status = "Not Used";
break;
case DATA_MISSING:
cksum_status = "Not checkable - not all of packet was captured";
break;
case CKSUM_OK:
cksum_status = "Is good";
break;
case CKSUM_NOT_OK:
cksum_status = "Is wrong";
break;
default:
cksum_status = NULL;
g_assert_not_reached();
}
proto_tree_add_uint_format( esis_tree, hf_esis_checksum, tvb, 7, 2,
tmp_uint, "Checksum : 0x%x ( %s )",
tmp_uint, calc_checksum( tvb, 0,
ehdr.esis_length ,
tmp_uint ) );
tmp_uint, cksum_status );
}

56
packet-osi.c
View File

@ -2,14 +2,13 @@
* Routines for ISO/OSI network and transport protocol packet disassembly
* Main entrance point and common functions
*
* $Id: packet-osi.c,v 1.44 2001/04/16 10:04:30 guy Exp $
* $Id: packet-osi.c,v 1.45 2001/06/05 09:06:19 guy Exp $
* Laurent Deniel <deniel@worldnet.fr>
* Ralf Schneider <Ralf.Schneider@t-online.de>
*
* Ethereal - Network traffic analyzer
* By Gerald Combs <gerald@zing.org>
* By Gerald Combs <gerald@ethereal.com>
* Copyright 1998 Gerald Combs
*
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@ -49,29 +48,56 @@
#include "packet-esis.h"
gchar *calc_checksum( tvbuff_t *tvb, int offset, u_int len, u_int checksum) {
u_int calc_sum = 0;
u_int count = 0;
cksum_status_t
calc_checksum( tvbuff_t *tvb, int offset, u_int len, u_int checksum) {
const gchar *buffer;
guint available_len;
const guint8 *p;
guint32 c0, c1;
u_int seglen;
int i;
if ( 0 == checksum )
return( "Not Used" );
return( NO_CKSUM );
available_len = tvb_length_remaining( tvb, offset );
if ( available_len < len )
return( "Not checkable - not all of packet was captured" );
return( DATA_MISSING );
buffer = tvb_get_ptr( tvb, offset, len );
for ( count = 0; count < len; count++ ) {
calc_sum += (u_int) buffer[count];
/*
* The maximum values of c0 and c1 will occur if all bytes have the
* value 255; if so, then c0 will be len*255 and c1 will be
* (len*255 + (len-1)*255 + ... + 255), which is
* (len + (len - 1) + ... + 1)*255, or 255*(len*(len + 1))/2.
* This means it can overflow if "len" is 5804 or greater.
*
* (A+B) mod 255 = ((A mod 255) + (B mod 255) mod 255, so
* we can solve this by taking c0 and c1 mod 255 every
* 5803 bytes.
*/
p = buffer;
c0 = 0;
c1 = 0;
while (len != 0) {
seglen = len;
if (seglen > 5803)
seglen = 5803;
for (i = 0; i < seglen; i++) {
c0 = c0 + *(p++);
c1 += c0;
}
c0 = c0 % 255;
c1 = c1 % 255;
len -= seglen;
}
calc_sum %= 255; /* modulo 255 divison */
if ( 0 == calc_sum )
return( "Is good" );
if (c0 != 0 || c1 != 0)
return( CKSUM_NOT_OK ); /* XXX - what should the checksum be? */
else
return( "Is wrong" ); /* XXX - what should the checksum be? */
return( CKSUM_OK );
}

14
packet-osi.h
View File

@ -1,11 +1,10 @@
/* packet-osi.h
*
* $Id: packet-osi.h,v 1.7 2001/04/01 05:48:14 hagbard Exp $
* $Id: packet-osi.h,v 1.8 2001/06/05 09:06:19 guy Exp $
*
* Ethereal - Network traffic analyzer
* By Gerald Combs <gerald@zing.org>
* By Gerald Combs <gerald@ethereal.com>
* Copyright 1998 Gerald Combs
*
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@ -85,6 +84,13 @@ dissector_table_t osinl_subdissector_table;
* published API functions
*/
extern gchar *calc_checksum ( tvbuff_t *, int, u_int, u_int );
typedef enum {
NO_CKSUM, /* checksum field is 0 */
DATA_MISSING, /* not all the data covered by the checksum was captured */
CKSUM_OK, /* checksum is OK */
CKSUM_NOT_OK /* checksum is not OK */
} cksum_status_t;
extern cksum_status_t calc_checksum(tvbuff_t *, int, u_int, u_int);
#endif /* _PACKET_OSI_H */