From guettler:

ATN decoding fixes for CLNP and COTP dissectors (configurable by option).

ATN decoding fixes for CLNP and COTP dissectors (configurable by option).

ATN specifics may be
selected/deseleted per CLNP/COTP dissector configuration (as requested).

CLNP dissector
1) configurable decoding of "ATN security label"

COTP dissector
1) configurable decoding of ATN TPDU's 
2) checksum calculation (none,OSI,ATN 16-bit, ATN 32-bit)
3) VP decoding for DR TPDU's

https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=5622

svn path=/trunk/; revision=46043

1 files changed, 150 insertions, 0 deletions

diff --git a/epan/dissectors/packet-osi.c b/epan/dissectors/packet-osi.c
index bbe763cff4..1ea35d1b25 100644
--- a/epan/dissectors/packet-osi.c
+++ b/epan/dissectors/packet-osi.c
@@ -194,6 +194,155 @@ check_and_get_checksum( tvbuff_t *tvb, int offset, guint len, guint checksum, in
     return( CKSUM_OK );
 }
 
+/* 4 octet ATN extended checksum: ICAO doc 9705 Ed3 Volume V section 5.5.4.6.4 */
+/* It is calculated over TP4 userdata (all checksums set to zero ) and a pseudo tailer */
+/* of length SRC-NSAP, SRC-NSAP, length DST-NSAP, DST-NSAP and ATN extended checksum. */
+/* In case of a CR TPDU, the value of the ISO 8073 16-bit fletcher checksum parameter shall */
+/* be set to zero. */
+gboolean check_atn_ec_32(
+  tvbuff_t *tvb, guint tdpu_len, 
+  guint offset_ec_32_val, /* offset ATN extended checksum value, calculated at last as part of pseudo trailer */
+  guint offset_iso8073_val, /* offset ISO 8073 fletcher checksum, CR only*/
+  guint clnp_pt_len, /* length of NSAP part of pseudo trailer */
+  guint8 * clnp_pt_buffer){ /* NSAP part of pseudo trailer */
+
+  guint  i = 0;
+  guint32 c0 = 0;
+  guint32 c1 = 0;
+  guint32 c2 = 0;
+  guint32 c3 = 0;
+  guint32 sum = 0; 
+
+  /* sum accross complete TDPU  */
+  for ( i =0; i< tdpu_len; i++){
+
+     c0 += tvb_get_guint8(tvb, i) ; 
+
+     if( ( i >= offset_ec_32_val ) &&  /* ignore 32 bit ATN extended checksum value */
+         ( i < ( offset_ec_32_val + 4 ) ) ){
+       c0 -= tvb_get_guint8(tvb, i); }
+      
+     if( ( offset_iso8073_val ) && /* ignore 16 bit ISO 8073 checksum, if present*/
+         ( i >= offset_iso8073_val ) && 
+         ( i < ( offset_iso8073_val + 2 ) ) ){
+       c0 -= tvb_get_guint8(tvb, i); }  
+ 
+     if ( c0 >= 0x000000FF )
+       c0 -= 0x00000FF; 
+     c1 += c0;
+     if ( c1 >= 0x000000FF )
+       c1 -= 0x000000FF; 
+     c2 += c1;
+     if ( c2 >= 0x000000FF )
+           c2 -= 0x000000FF; 
+     c3 += c2;
+     if ( c3 >= 0x000000FF )
+           c3 -= 0x000000FF; 
+    
+  }
+  /* add NSAP part of pseudo trailer */
+  for ( i =0; i< clnp_pt_len; i++){
+     c0 += clnp_pt_buffer[i];
+     if ( c0 >= 0x000000FF )
+       c0 -= 0x000000FF; 
+     c1 += c0;
+     if ( c1 >= 0x000000FF )
+       c1 -= 0x000000FF; 
+     c2 += c1;
+     if ( c2 >= 0x000000FF )
+       c2 -= 0x000000FF; 
+     c3 += c2;
+     if ( c3 >= 0x000000FF )
+       c3 -= 0x000000FF; 
+  }
+  /* add with extended checksum as last part of the pseudo trailer */
+  for ( i = offset_ec_32_val; i< (offset_ec_32_val+4); i++){
+    c0 += tvb_get_guint8(tvb, i) ;
+
+     if ( c0 >= 0x000000FF )
+       c0 -= 0x00000FF; 
+     c1 += c0;
+     if ( c1 >= 0x000000FF )
+       c1 -= 0x000000FF; 
+     c2 += c1;
+     if ( c2 >= 0x000000FF )
+           c2 -= 0x000000FF; 
+     c3 += c2;
+     if ( c3 >= 0x000000FF )
+           c3 -= 0x000000FF; 
+  }
+  
+  sum = (c3 << 24) + (c2 << 16 ) + (c1 << 8) + c0 ; 
+
+  if(!sum)
+   return TRUE;
+  else
+   return FALSE;
+}
+
+/* 2 octet ATN extended checksum: ICAO doc 9705 Ed3 Volume V section 5.5.4.6.4 */
+/* It is calculated over TP4 userdata (all checksums set to zero ) and a pseudo tailer */
+/* of length SRC-NSAP, SRC-NSAP, length DST-NSAP, DST-NSAP and ATN extended checksum. */
+/* In case of a CR TPDU, the value of the ISO 8073 16-bit fletcher checksum parameter shall */
+/* be set to zero. */
+/* this routine is currently *untested* because of the unavailability of samples.*/
+gboolean check_atn_ec_16( 
+  tvbuff_t *tvb, 
+  guint tdpu_len,  
+  guint offset_ec_16_val,  /* offset ATN extended checksum value, calculated at last as part of pseudo trailer */
+  guint offset_iso8073_val, /* offset ISO 8073 fletcher checksum, CR only*/
+  guint clnp_pt_len, /* length of NSAP part of pseudo trailer */
+  guint8 * clnp_pt_buffer ){ /* NSAP part of pseudo trailer */
+
+  guint i = 0;
+  guint16 c0 = 0;
+  guint16 c1 = 0;
+  guint16 sum = 0; 
+
+  /* sum accross complete TDPU */
+  for ( i =0; i< tdpu_len; i++){
+
+    c0 += tvb_get_guint8(tvb, i);
+
+    if( (i >= offset_ec_16_val) && /* ignore 16 bit extended checksum */
+        (i < (offset_ec_16_val + 2) ) ) {
+      c0 -= tvb_get_guint8(tvb, i) ; }
+
+    if( (i >= offset_iso8073_val) && /* ignore 16 bit ISO 8073 checksum, if present*/
+        (i < (offset_iso8073_val + 2) ) ) {
+      c0 -= tvb_get_guint8(tvb, i) ; }
+
+    if ( c0 >= 0x00FF )
+       c0 -= 0x00FF; 
+     c1 += c0;
+     if ( c1 >= 0x00FF )
+       c1 -= 0x00FF; 
+
+  }
+  /* sum with NSAP part of the pseudo trailer */
+  for ( i =0; i< clnp_pt_len; i++){
+     c0 += clnp_pt_buffer[i] ;
+     c1 += c0;
+  }
+
+  /* add extended checksum as last part of the pseudo trailer */
+  for ( i = offset_ec_16_val; i< (offset_ec_16_val+2); i++){
+    c0 += tvb_get_guint8(tvb, i) ;
+
+     if ( c0 >= 0x00FF )
+       c0 -= 0x00FF; 
+     c1 += c0;
+     if ( c1 >= 0x00FF )
+       c1 -= 0x00FF; 
+  }
+
+  sum =  (c1 << 8) + c0 ; 
+
+  if(!sum)
+   return TRUE;
+  else
+   return FALSE;
+}
 
 
 /* main entry point */
@@ -350,5 +499,6 @@ proto_register_osi(void)
                                  "Whether segmented TPKT datagrams should be reassembled",
                                  &tpkt_desegment);
 
+																 
 }