Handle the pseudo-trailer for the ATN extended checksums by passing in

the source and destination address lengths and data, and adding them in,
rather than by copying those fields to a fixed-size static buffer - that
gets rid of a global variable (global variables considered harmful), and
also means that we don't try to copy 24 bytes of length+address from
packets that don't *have* 24 bytes of length+address (which caused
exceptions to be thrown on some OSI captures I have).

Construct some LI #defines out of other LI #defines, to make it a bit
clearer why they have the values they do.

Support the "additional information related to the clearing of the
connection" variable part parameter of the COTP DR packet (which just
means giving it a name, as its contents are user-defined - some HP-UX
OSI stack appears to just stick in a string saying that it's said
stack).

Make the code that decodes the variable part of a DR packet look like
the code that decodes the variable part of most other packets.

For COTP CR packets, determine the class up front by checking whether
the length is > 2.  (At some point we might want to associate a class
indication with the COTP connection, if we see the connection setup,
and, if we have that indication, use it in preference to the
heuristics.)

Make the code to handle various length indicator values in the ATN case
more like the code in the non-ATN case.

Dissect the variable part of COTP ER packets.

Fix tpyos (TDPU->TPDU, tdpu->tpdu) and typpoes (accross->across).

Clean up white space.

svn path=/trunk/; revision=46060

4 files changed, 231 insertions, 181 deletions

diff --git a/epan/dissectors/packet-clnp.c b/epan/dissectors/packet-clnp.c
index c621a9ae02..7e6faa58e4 100644
--- a/epan/dissectors/packet-clnp.c
+++ b/epan/dissectors/packet-clnp.c
@@ -38,12 +38,6 @@
 #include <epan/nlpid.h>
 #include <epan/ipproto.h>
 
-/* pseudo-trailer for ATN extended checksums on TP4 layer*/
-/* the checksum is calculated from the TPDU as well als */
-/* dst  NSAP length, dst  NSAP, src  NSAP length and src NSAP as encoded in CLNP PDU*/
-guint     clnp_pt_len ;        
-guint8    clnp_pt_buffer[42]; 
-
 /* protocols and fields */
 
 static int  proto_clnp         = -1;
@@ -68,8 +62,8 @@ static int hf_clnp_dest_length = -1;
 static int hf_clnp_dest        = -1;
 static int hf_clnp_src_length  = -1;
 static int hf_clnp_src         = -1;
-       int hf_clnp_atntt			 = -1; /* as referenced in packet-osi-options.c */
-			 int hf_clnp_atnsc			 = -1; /* as referenced in packet-osi-options.c */
+       int hf_clnp_atntt       = -1; /* as referenced in packet-osi-options.c */
+       int hf_clnp_atnsc       = -1; /* as referenced in packet-osi-options.c */
 static int hf_clnp_segments    = -1;
 static int hf_clnp_segment     = -1;
 static int hf_clnp_segment_overlap          = -1;
@@ -363,10 +357,6 @@ dissect_clnp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
   src_len  = tvb_get_guint8(tvb, offset + dst_len + 1);
   src_addr = tvb_get_ptr(tvb, offset + dst_len + 2, src_len);
 
-  /* store src & dst address parts for ATN extended checksum calculation in ositp.c */
-  clnp_pt_len = dst_len + src_len + 2;
-  tvb_memcpy(tvb, &clnp_pt_buffer, offset, sizeof(clnp_pt_buffer));	
-	
   if (tree) {
     proto_tree_add_uint(clnp_tree, hf_clnp_dest_length, tvb, offset, 1,
                         dst_len);
@@ -688,10 +678,6 @@ proto_register_clnp(void)
                                  "Decode ATN security label",
                                  "Whether ATN security label should be decoded",
                                  &clnp_decode_atn_options);
-	
-	/* init src & dst address parts for ATN extended checksum calculation in ositp.c */
-	memset(clnp_pt_buffer, 0, sizeof(clnp_pt_buffer));
-  clnp_pt_len = 0;
 }
 
 void
diff --git a/epan/dissectors/packet-osi.c b/epan/dissectors/packet-osi.c
index 1ea35d1b25..9d53d3a473 100644
--- a/epan/dissectors/packet-osi.c
+++ b/epan/dissectors/packet-osi.c
@@ -200,12 +200,14 @@ check_and_get_checksum( tvbuff_t *tvb, int offset, guint len, guint checksum, in
 /* 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 */
+  tvbuff_t *tvb, guint tpdu_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 clnp_dst_len,       /* length of DST-NSAP */
+  const guint8 *clnp_dst,   /* DST-NSAP */
+  guint clnp_src_len,       /* length of SRC-NSAP */
+  const guint8 *clnp_src)   /* SRC-NSAP */
+{
   guint  i = 0;
   guint32 c0 = 0;
   guint32 c1 = 0;
@@ -213,71 +215,109 @@ gboolean check_atn_ec_32(
   guint32 c3 = 0;
   guint32 sum = 0; 
 
-  /* sum accross complete TDPU  */
-  for ( i =0; i< tdpu_len; i++){
-
-     c0 += tvb_get_guint8(tvb, i) ; 
+  /* sum across complete TPDU  */
+  for ( i =0; i< tpdu_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( ( 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( ( 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; 
-    
+    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 NSAP parts of pseudo trailer */
+  c0 += clnp_dst_len;
+  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; 
+  for ( i =0; i< clnp_dst_len; i++){
+    c0 += clnp_dst[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 */
+  c0 += clnp_src_len;
+  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; 
+  for ( i =0; i< clnp_src_len; i++){
+    c0 += clnp_src[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 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; 
+    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;
+    return TRUE;
   else
-   return FALSE;
+    return FALSE;
 }
 
 /* 2 octet ATN extended checksum: ICAO doc 9705 Ed3 Volume V section 5.5.4.6.4 */
@@ -288,60 +328,86 @@ gboolean check_atn_ec_32(
 /* 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 tpdu_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 clnp_dst_len,       /* length of DST-NSAP */
+  const guint8 *clnp_dst,   /* DST-NSAP */
+  guint clnp_src_len,       /* length of SRC-NSAP */
+  const guint8 *clnp_src)   /* SRC-NSAP */
+{
   guint i = 0;
   guint16 c0 = 0;
   guint16 c1 = 0;
   guint16 sum = 0; 
 
-  /* sum accross complete TDPU */
-  for ( i =0; i< tdpu_len; i++){
+  /* sum across complete TPDU */
+  for ( i =0; i< tpdu_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) ; }
+      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) ; }
+      c0 -= tvb_get_guint8(tvb, i) ;
+    }
 
     if ( c0 >= 0x00FF )
        c0 -= 0x00FF; 
-     c1 += c0;
-     if ( c1 >= 0x00FF )
-       c1 -= 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 NSAP parts of pseudo trailer */
+  c0 += clnp_dst_len;
+  if ( c0 >= 0x00FF )
+    c0 -= 0x00FF; 
+  c1 += c0;
+  if ( c1 >= 0x00FF )
+    c1 -= 0x00FF; 
+  for ( i =0; i< clnp_dst_len; i++){
+    c0 += clnp_dst[i];
+    if ( c0 >= 0x00FF )
+      c0 -= 0x00FF; 
+    c1 += c0;
+    if ( c1 >= 0x00FF )
+      c1 -= 0x00FF; 
+  }
+  c0 += clnp_src_len;
+  if ( c0 >= 0x00FF )
+    c0 -= 0x00FF; 
+  c1 += c0;
+  if ( c1 >= 0x00FF )
+    c1 -= 0x00FF; 
+  for ( i =0; i< clnp_src_len; i++){
+    c0 += clnp_src[i];
+    if ( c0 >= 0x00FF )
+      c0 -= 0x00FF; 
+    c1 += c0;
+    if ( c1 >= 0x00FF )
+      c1 -= 0x00FF; 
   }
-
   /* 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; 
+    if ( c0 >= 0x00FF )
+      c0 -= 0x00FF; 
+    c1 += c0;
+    if ( c1 >= 0x00FF )
+      c1 -= 0x00FF; 
   }
 
   sum =  (c1 << 8) + c0 ; 
 
   if(!sum)
-   return TRUE;
+    return TRUE;
   else
-   return FALSE;
+    return FALSE;
 }
 
 
diff --git a/epan/dissectors/packet-osi.h b/epan/dissectors/packet-osi.h
index 8b88d4d235..1162ea3941 100644
--- a/epan/dissectors/packet-osi.h
+++ b/epan/dissectors/packet-osi.h
@@ -86,8 +86,8 @@ typedef enum {
 } cksum_status_t;
 
 extern cksum_status_t calc_checksum(tvbuff_t *, int, guint, guint);
-extern cksum_status_t check_and_get_checksum( tvbuff_t *, int, guint, guint, int, guint16*);
-extern gboolean check_atn_ec_32(tvbuff_t *tvb, guint tdpu_len, guint offset_ec_32_val, guint offset_iso8073_val, guint clnp_pt_len, guint8 * clnp_pt_buffer);
-extern gboolean check_atn_ec_16(  tvbuff_t *tvb, guint tdpu_len, guint offset_ec_16_val, guint offset_iso8073_val, guint clnp_pt_len, guint8 * clnp_pt_buffer );
+extern cksum_status_t check_and_get_checksum(tvbuff_t *, int, guint, guint, int, guint16*);
+extern gboolean check_atn_ec_32(tvbuff_t *tvb, guint tpdu_len, guint offset_ec_32_val, guint offset_iso8073_val, guint clnp_dst_len, const guint8 *clnp_dst, guint clnp_src_len, const guint8 *clnp_src);
+extern gboolean check_atn_ec_16(tvbuff_t *tvb, guint tpdu_len, guint offset_ec_16_val, guint offset_iso8073_val, guint clnp_dst_len, const guint8 *clnp_dst, guint clnp_src_len, const guint8 *clnp_src);
 
 #endif /* _PACKET_OSI_H */
diff --git a/epan/dissectors/packet-ositp.c b/epan/dissectors/packet-ositp.c
index db7ac9ad01..c5635aa105 100644
--- a/epan/dissectors/packet-ositp.c
+++ b/epan/dissectors/packet-ositp.c
@@ -175,17 +175,21 @@ static const value_string class_option_vals[] = {
 #define P_REASON_IN_DR 		6
 #define P_CLASS_OPTION 		6
 
-/* TPDU length indicator */
+/*
+ * TPDU length indicator values.
+ * Checksum parameter is 4 octets - 1 octet of parameter code, 1 octet
+ * of parameter length, 2 octets of checksum.
+ */
 
 #define LI_NORMAL_DT_CLASS_01		 2
-#define LI_NORMAL_DT_WITH_CHECKSUM       8
 #define LI_NORMAL_DT_WITHOUT_CHECKSUM    4
-#define LI_EXTENDED_DT_WITH_CHECKSUM     11
+#define LI_NORMAL_DT_WITH_CHECKSUM       (LI_NORMAL_DT_WITHOUT_CHECKSUM+4)
 #define LI_EXTENDED_DT_WITHOUT_CHECKSUM  7
-#define LI_NORMAL_EA_WITH_CHECKSUM       8
+#define LI_EXTENDED_DT_WITH_CHECKSUM     (LI_EXTENDED_DT_WITHOUT_CHECKSUM+4)
 #define LI_NORMAL_EA_WITHOUT_CHECKSUM    4
-#define LI_EXTENDED_EA_WITH_CHECKSUM     11
+#define LI_NORMAL_EA_WITH_CHECKSUM       (LI_NORMAL_EA_WITHOUT_CHECKSUM+4)
 #define LI_EXTENDED_EA_WITHOUT_CHECKSUM  7
+#define LI_EXTENDED_EA_WITH_CHECKSUM     (LI_EXTENDED_EA_WITHOUT_CHECKSUM+4)
 #define LI_NORMAL_RJ                     4
 #define LI_EXTENDED_RJ                   9
 #define LI_MIN_DR                        6
@@ -198,17 +202,23 @@ static const value_string class_option_vals[] = {
    number of octets? */
 #define is_LI_NORMAL_AK(p)               ((p & 0x01) == 0)
 
-/* modified TPDU length indicators due to ATN extended checksum */
-#define LI_ATN_NORMAL_DT_WITH_CHECKSUM       10 /* ATN 4 octet extended checksum adds 2 octets */
-#define LI_ATN_EXTENDED_DT_WITH_CHECKSUM     13 /* ATN 4 octet extended checksum adds 2 octets */
-#define LI_ATN_NORMAL_EA_WITH_CHECKSUM       10 /* ATN 4 octet extended checksum adds 2 octets */
-#define LI_ATN_EXTENDED_EA_WITH_CHECKSUM     13 /* ATN 4 octet extended checksum adds 2 octets */
-#define LI_ATN_NORMAL_RJ                     6  /* ATN 4 octet extended checksum adds 2 octets */
-#define LI_ATN_EXTENDED_RJ                   11 /* ATN 4 octet extended checksum adds 2 octets */
-#define LI_ATN_MAX_DC                        11 /* ATN 4 octet extended checksum adds 2 octets */
-#define LI_ATN_MAX_AK                        30 /* ATN 4 octet extended checksum adds 2 octets */
-#define LI_ATN_MAX_EA                        13 /* ATN 4 octet extended checksum adds 2 octets */
-#define LI_ATN_MAX_ER			 									 10 /* ATN 4 octet extended checksum adds 2 octets */
+/*
+ * Modified TPDU length indicator values due to ATN 4-octet extended
+ * checksum.
+ * Checksum parameter is 6 octets - 1 octet of parameter code, 1 octet
+ * of parameter length, 4 octets of checksum.  That adds 2 octets to
+ * the lengths with a 2-octet checksum.
+ */
+#define LI_ATN_NORMAL_DT_WITH_CHECKSUM       (LI_NORMAL_DT_WITH_CHECKSUM+2)
+#define LI_ATN_EXTENDED_DT_WITH_CHECKSUM     (LI_EXTENDED_DT_WITH_CHECKSUM+2)
+#define LI_ATN_NORMAL_EA_WITH_CHECKSUM       (LI_NORMAL_EA_WITH_CHECKSUM+2)
+#define LI_ATN_EXTENDED_EA_WITH_CHECKSUM     (LI_EXTENDED_EA_WITH_CHECKSUM+2)
+#define LI_ATN_NORMAL_RJ                     (LI_NORMAL_RJ+2)
+#define LI_ATN_EXTENDED_RJ                   (LI_EXTENDED_RJ+2)
+#define LI_ATN_MAX_DC                        (LI_MAX_DC+2)
+#define LI_ATN_MAX_AK                        (LI_MAX_AK+2+1) /* +1 for padding? */
+#define LI_ATN_MAX_EA                        (LI_MAX_EA+2)
+#define LI_ATN_MAX_ER                        (LI_MAX_ER+2)
 
 /* variant part */
 
@@ -228,6 +238,7 @@ static const value_string class_option_vals[] = {
 #define VP_PROTECTION   	0xC5
 #define VP_OPT_SEL      	0xC6
 #define VP_PROTO_CLASS  	0xC7
+#define VP_CLEARING_INFO	0xE0         /* in DR */
 #define VP_PREF_MAX_TPDU_SIZE  	0xF0
 #define VP_INACTIVITY_TIMER  	0xF2
 
@@ -239,12 +250,6 @@ static const value_string class_option_vals[] = {
 #define VP_ATN_EC_16              0x09         /* 2 octet ATN Extended Transport Checksum parameter */
 /* ATN end */
 
-/* pseudo-trailer for ATN extended checksums on TP4 layer*/
-/* the checksum is calculated from the TPDU as well als */
-/* dst  NSAP length, dst  NSAP, src  NSAP length and src NSAP as encoded in CLNP PDU*/
-extern guint     clnp_pt_len;           /* length of dst-len + dst-nsap + src-len + src-nsap  */
-extern guint8    clnp_pt_buffer[42];      /* buffer containing CLNP pseudoheader */
-
 static const value_string tp_vpart_type_vals[] = {
   { VP_ATN_EC_16,   "ATN extended checksum - 16 bit" },
   { VP_ATN_EC_32,   "ATN extended checksum - 32 bit" },
@@ -264,6 +269,7 @@ static const value_string tp_vpart_type_vals[] = {
   { VP_PROTECTION,		"protection" },
   { VP_OPT_SEL,			"options" },
   { VP_PROTO_CLASS,		"proto class" },
+  { VP_CLEARING_INFO,           "additional connection clearing info" },
   { VP_PREF_MAX_TPDU_SIZE,	"preferred max TPDU size" },
   { VP_INACTIVITY_TIMER,        "inactivity timer" },
   { 0,				NULL }
@@ -374,6 +380,7 @@ static gchar *print_tsap(const guchar *tsap, int length)
 
 static gboolean ositp_decode_var_part(tvbuff_t *tvb, int offset,
 				      int vp_length, int class_option,
+                                      packet_info *pinfo,
 				      proto_tree *tree)
 {
   guint8  code, length;
@@ -427,7 +434,10 @@ static gboolean ositp_decode_var_part(tvbuff_t *tvb, int offset,
             i += tmp_len;
           }
         }
-        checksum_ok = check_atn_ec_16(tvb, tpdu_length, offset, offset_iso8073_checksum, clnp_pt_len, (guint8 *) &clnp_pt_buffer);
+        checksum_ok = check_atn_ec_16(tvb, tpdu_length, offset,
+                                      offset_iso8073_checksum,
+                                      pinfo->dst.len, pinfo->dst.data,
+                                      pinfo->src.len, pinfo->src.data);
         proto_tree_add_text(tree, tvb, offset, length,
             "ATN extended checksum : 0x%04x (%s)",
                               tvb_get_ntohs(tvb, offset),
@@ -455,7 +465,10 @@ static gboolean ositp_decode_var_part(tvbuff_t *tvb, int offset,
             i += tmp_len;
           }
         }
-        checksum_ok = check_atn_ec_32(tvb, tpdu_length, offset, offset_iso8073_checksum, clnp_pt_len, (guint8 *) &clnp_pt_buffer);
+        checksum_ok = check_atn_ec_32(tvb, tpdu_length, offset,
+                                      offset_iso8073_checksum,
+                                      pinfo->dst.len, pinfo->dst.data,
+                                      pinfo->src.len, pinfo->src.data);
         proto_tree_add_text(tree, tvb, offset, length,
              "ATN extended checksum : 0x%08x (%s)",
                               tvb_get_ntohl(tvb, offset),
@@ -679,7 +692,7 @@ static gboolean ositp_decode_var_part(tvbuff_t *tvb, int offset,
 
     case VP_CHECKSUM:
       offset_iso8073_checksum = offset; /* save ISO 8073 checksum offset for ATN extended checksum calculation */
-      cksum_status = calc_checksum(tvb, 0, tpdu_length, tvb_get_ntohs(tvb, offset));
+      cksum_status = calc_checksum(tvb, 0, tvb_reported_length(tvb), tvb_get_ntohs(tvb, offset));
       switch (cksum_status) {
 
       default:
@@ -799,6 +812,7 @@ static gboolean ositp_decode_var_part(tvbuff_t *tvb, int offset,
 
     case VP_PROTECTION:           /* user-defined */
     case VP_PROTO_CLASS:          /* todo */
+    case VP_CLEARING_INFO:        /* user-defined */
     default:			  /* unknown, no decoding */
       proto_tree_add_text(tree, tvb, offset, length,
 			      "Parameter value: <not shown>");
@@ -875,13 +889,12 @@ static int ositp_decode_DR(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
     proto_tree_add_text(cotp_tree, tvb, offset +  6, 1,
 			"Cause: %s", str);
   }
+  offset += 7;
+  li -= 6;
 
-  /* decode VP */
-  if (tree) {
-    ositp_decode_var_part(tvb, offset + P_REASON_IN_DR + 1, li - P_REASON_IN_DR  , 4, cotp_tree);
-  }
-
-  offset += li + 1;
+  if (tree)
+    ositp_decode_var_part(tvb, offset, li, 4, pinfo, cotp_tree);
+  offset += li;
 
   expert_add_info_format(pinfo, ti, PI_SEQUENCE, PI_CHAT,
 	  "Disconnect Request(DR): 0x%x -> 0x%x", src_ref, dst_ref);
@@ -913,6 +926,11 @@ static int ositp_decode_DT(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   fragment_data *fd_head;
   conversation_t *conv;
 
+  /* The fixed part is 2 octets long, not including the length indicator,
+     for classes 0 and 1; it is at least 4 octets long, not including
+     the length indicator, for classes 2, 3, and 4. */
+  is_class_234 = (li > LI_NORMAL_DT_CLASS_01);
+
   /* note: in the ATN the user is up to chose between 3 different checksums: */
   /* standard OSI, 2 or 4 octet extended checksum. */
   /* The differences for DT are that the TPDU headers may be enlarged by 2 octets */
@@ -942,7 +960,6 @@ static int ositp_decode_DT(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
         else
           fragment = TRUE;
         is_extended = FALSE;
-        is_class_234 = TRUE;
         dst_ref = tvb_get_ntohs(tvb, offset + P_DST_REF);
         break;
 
@@ -958,7 +975,6 @@ static int ositp_decode_DT(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
         else
           fragment = TRUE;
         is_extended = TRUE;
-        is_class_234 = TRUE;
         dst_ref = tvb_get_ntohs(tvb, offset + P_DST_REF);
         break;
 
@@ -969,7 +985,6 @@ static int ositp_decode_DT(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
         else
           fragment = TRUE;
         is_extended = FALSE;
-        is_class_234 = FALSE;
         prev_dst_ref = p_get_proto_data (pinfo->fd, proto_clnp);
         if (!prev_dst_ref) {
           /* First COTP in frame - save previous dst_ref as offset */
@@ -1007,47 +1022,29 @@ static int ositp_decode_DT(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
     /* note: normal/extended TPDU numbering is negociable  */
     switch (li) {
 
-      case LI_NORMAL_DT_WITHOUT_CHECKSUM   :
-        tpdu_nr = tvb_get_guint8(tvb, offset + P_TPDU_NR_234);
-        if (tpdu_nr & 0x80)
-          tpdu_nr = tpdu_nr & 0x7F;
-        else
-          fragment = TRUE;
-        is_extended = FALSE;
-        is_class_234 = TRUE;
-        dst_ref = tvb_get_ntohs(tvb, offset + P_DST_REF);
-        break;
-
       /* normal DT with 2 octets of OSI or of ATN Extended Checksum */
       case LI_NORMAL_DT_WITH_CHECKSUM      :
         if (tvb_get_guint8(tvb, offset + P_VAR_PART_NDT) != VP_CHECKSUM &&
-             tvb_get_guint8(tvb, offset + P_VAR_PART_NDT) != VP_ATN_EC_16)
+            tvb_get_guint8(tvb, offset + P_VAR_PART_NDT) != VP_ATN_EC_16)
           return -1;
+        /* FALLTHROUGH */
+
+      case LI_NORMAL_DT_WITHOUT_CHECKSUM   :
         tpdu_nr = tvb_get_guint8(tvb, offset + P_TPDU_NR_234);
         if (tpdu_nr & 0x80)
           tpdu_nr = tpdu_nr & 0x7F;
         else
           fragment = TRUE;
         is_extended = FALSE;
-        is_class_234 = TRUE;
         dst_ref = tvb_get_ntohs(tvb, offset + P_DST_REF);
         break;
 
-      /* normal DT with ATN Extended Checksum (4 octets)*/
-      case LI_ATN_NORMAL_DT_WITH_CHECKSUM      :
-        if (tvb_get_guint8(tvb, offset + P_VAR_PART_NDT) != VP_ATN_EC_32)
+      /* extended DT with 2 octets of OSI or of ATN Extended Checksum */
+      case LI_EXTENDED_DT_WITH_CHECKSUM    :
+        if (tvb_get_guint8(tvb, offset + P_VAR_PART_EDT) != VP_CHECKSUM &&
+            tvb_get_guint8(tvb, offset + P_VAR_PART_EDT) != VP_ATN_EC_16)
           return -1;
-
-        tpdu_nr = tvb_get_guint8(tvb, offset + P_TPDU_NR_234);
-
-        if (tpdu_nr & 0x80)
-          tpdu_nr = tpdu_nr & 0x7F;
-        else
-          fragment = TRUE;
-        is_extended = FALSE;
-        is_class_234 = TRUE;
-        dst_ref = tvb_get_ntohs(tvb, offset + P_DST_REF);
-        break;
+        /* FALLTHROUGH */
 
       case LI_EXTENDED_DT_WITHOUT_CHECKSUM :
         tpdu_nr = tvb_get_ntohl(tvb, offset + P_TPDU_NR_234);
@@ -1056,23 +1053,21 @@ static int ositp_decode_DT(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
         else
           fragment = TRUE;
         is_extended = TRUE;
-        is_class_234 = TRUE;
         dst_ref = tvb_get_ntohs(tvb, offset + P_DST_REF);
         break;
 
-      /* extended DT with 2 octets of OSI or of ATN Extended Checksum */
-      case LI_EXTENDED_DT_WITH_CHECKSUM    :
-        if (tvb_get_guint8(tvb, offset + P_VAR_PART_EDT) != VP_CHECKSUM &&
-            tvb_get_guint8(tvb, offset + P_VAR_PART_EDT) != VP_ATN_EC_16)
+      /* normal DT with ATN Extended Checksum (4 octets)*/
+      case LI_ATN_NORMAL_DT_WITH_CHECKSUM      :
+        if (tvb_get_guint8(tvb, offset + P_VAR_PART_NDT) != VP_ATN_EC_32)
           return -1;
 
-        tpdu_nr = tvb_get_ntohl(tvb, offset + P_TPDU_NR_234);
-        if (tpdu_nr & 0x80000000)
-          tpdu_nr = tpdu_nr & 0x7FFFFFFF;
+        tpdu_nr = tvb_get_guint8(tvb, offset + P_TPDU_NR_234);
+
+        if (tpdu_nr & 0x80)
+          tpdu_nr = tpdu_nr & 0x7F;
         else
           fragment = TRUE;
-        is_extended = TRUE;
-        is_class_234 = TRUE;
+        is_extended = FALSE;
         dst_ref = tvb_get_ntohs(tvb, offset + P_DST_REF);
         break;
 
@@ -1087,7 +1082,6 @@ static int ositp_decode_DT(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
         else
           fragment = TRUE;
         is_extended = TRUE;
-        is_class_234 = TRUE;
         dst_ref = tvb_get_ntohs(tvb, offset + P_DST_REF);
         break;
 
@@ -1152,7 +1146,7 @@ static int ositp_decode_DT(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   }
 
   if (tree)
-    ositp_decode_var_part(tvb, offset, li, 4, cotp_tree);
+    ositp_decode_var_part(tvb, offset, li, 4, pinfo, cotp_tree);
   offset += li;
 
   next_tvb = tvb_new_subset_remaining(tvb, offset);
@@ -1417,7 +1411,7 @@ static int ositp_decode_ED(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   }
 
   if (tree)
-    ositp_decode_var_part(tvb, offset, li, 4, cotp_tree);
+    ositp_decode_var_part(tvb, offset, li, 4, pinfo, cotp_tree);
   offset += li;
 
   next_tvb = tvb_new_subset_remaining(tvb, offset);
@@ -1611,7 +1605,7 @@ static int ositp_decode_CC(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
 
        XXX - have TPKT know that a given session is an RDP session,
        and let us know, so we know whether to check for this stuff. */
-    ositp_decode_var_part(tvb, offset, li, class_option, cotp_tree);
+    ositp_decode_var_part(tvb, offset, li, class_option, pinfo, cotp_tree);
   }
   offset += li;
 
@@ -1686,7 +1680,7 @@ static int ositp_decode_DC(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   li -= 2;
 
   if (tree)
-    ositp_decode_var_part(tvb, offset, li, 4, cotp_tree);
+    ositp_decode_var_part(tvb, offset, li, 4, pinfo, cotp_tree);
   offset += li;
 
   expert_add_info_format(pinfo, item, PI_SEQUENCE, PI_CHAT,
@@ -1753,7 +1747,7 @@ static int ositp_decode_AK(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
     li -= 1;
 
     if (tree)
-      ositp_decode_var_part(tvb, offset, li, 4, cotp_tree);
+      ositp_decode_var_part(tvb, offset, li, 4, pinfo, cotp_tree);
     offset += li;
 
   } else { /* extended format */
@@ -1800,7 +1794,7 @@ static int ositp_decode_AK(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
     li -= 2;
 
     if (tree)
-      ositp_decode_var_part(tvb, offset, li, 4, cotp_tree);
+      ositp_decode_var_part(tvb, offset, li, 4, pinfo, cotp_tree);
     offset += li;
 
   } /* is_LI_NORMAL_AK */
@@ -1979,7 +1973,7 @@ static int ositp_decode_EA(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   }
 
   if (tree)
-    ositp_decode_var_part(tvb, offset, li, 4, cotp_tree);
+    ositp_decode_var_part(tvb, offset, li, 4, pinfo, cotp_tree);
   offset += li;
 
   return offset;
@@ -2035,8 +2029,12 @@ static int ositp_decode_ER(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
     proto_tree_add_text(cotp_tree, tvb, offset +  4, 1,
 			"Reject cause: %s", str);
   }
+  offset += 5;
+  li -= 4;
 
-  offset += li + 1;
+  if (tree)
+    ositp_decode_var_part(tvb, offset, li, 4, pinfo, cotp_tree);
+  offset += li;
 
   return offset;
 
@@ -2066,7 +2064,7 @@ static int ositp_decode_UD(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   li -= 1;
 
   if (tree)
-    ositp_decode_var_part(tvb, offset, li, 0, cltp_tree);
+    ositp_decode_var_part(tvb, offset, li, 0, pinfo, cltp_tree);
   offset += li;
 
   next_tvb = tvb_new_subset_remaining(tvb, offset);