calc_checksum() should be passed the length of the block to be

checksummed, which is the length of the TPDU, not that length + 1.

Calculate the TPDU length correctly - use
tvb_reported_length_remaining(), not tvb_length_remaining() (we want the
*actual* length, not the amount of captured data we have), and take the
offset handed to the dissector routine into account.  Don't take the
length indicator into account for TPDUs with user data, as they run to
the end of the lower-level packet containing the TPDU(s).  The CLTP UD
TPDU contains user data.

Note that this dissects both COTP *and* CLTP (that's why it's
"packet-ositp.c", not "packet-cotp.c").

Separate some groups of #includes with blank lines.

svn path=/trunk/; revision=47745

1 files changed, 42 insertions, 11 deletions

diff --git a/epan/dissectors/packet-ositp.c b/epan/dissectors/packet-ositp.c
index 9dadf134d5..d33d6854f8 100644
--- a/epan/dissectors/packet-ositp.c
+++ b/epan/dissectors/packet-ositp.c
@@ -1,5 +1,6 @@
 /* packet-ositp.c
- * Routines for ISO/OSI transport protocol packet disassembly
+ * Routines for ISO/OSI transport protocol (connection-oriented
+ * and connectionless) packet disassembly
  *
  * $Id$
  * Laurent Deniel <laurent.deniel@free.fr>
@@ -25,7 +26,9 @@
  */
 
 #include "config.h"
+
 #include <ctype.h>
+
 #include <glib.h>
 #include <epan/prefs.h>
 #include <epan/packet.h>
@@ -688,7 +691,7 @@ 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_len + 1, tvb_get_ntohs(tvb, offset));
+      cksum_status = calc_checksum(tvb, 0, tpdu_len, tvb_get_ntohs(tvb, offset));
       switch (cksum_status) {
 
       default:
@@ -829,12 +832,15 @@ static int ositp_decode_DR(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   guint16 dst_ref, src_ref;
   guchar  reason;
   const char *str;
-  guint tpdu_len = li + tvb_length_remaining(tvb, li ); /* according to ISO/IEC 8073 13.5.1 DR may have up to 64 octects of user data  */
+  guint   tpdu_len;
 
   /* ATN TPDU's tend to be larger than normal OSI, so nothing to do with respect to LI checks */
   if (li < LI_MIN_DR)
     return -1;
 
+  /* DR TPDUs can have user data, so they run to the end of the containing PDU */
+  tpdu_len = tvb_reported_length_remaining(tvb, offset);
+
   dst_ref = tvb_get_ntohs(tvb, offset + P_DST_REF);
 
   src_ref = tvb_get_ntohs(tvb, offset + P_SRC_REF);
@@ -922,7 +928,10 @@ static int ositp_decode_DT(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   tvbuff_t *next_tvb;
   fragment_data *fd_head;
   conversation_t *conv;
-  guint tpdu_len = li  + tvb_length_remaining(tvb, offset + li ); /* DT always has user data */
+  guint     tpdu_len;
+
+  /* DT TPDUs have user data, so they run to the end of the containing PDU */
+  tpdu_len = tvb_reported_length_remaining(tvb, offset);
 
   /* 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
@@ -1240,7 +1249,10 @@ static int ositp_decode_ED(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   guint16  dst_ref;
   guint    tpdu_nr;
   tvbuff_t *next_tvb;
-  guint tpdu_len = li  + tvb_length_remaining(tvb, li ); /* ED always has user data: tpdu_length = header + user data size */
+  guint    tpdu_len;
+
+  /* ED TPDUs have user data, so they run to the end of the containing PDU */
+  tpdu_len = tvb_reported_length_remaining(tvb, offset);
 
   /* note: in the ATN the user is up to chose between 3 different checksums: */
   /* standard OSI, 2 or 4 octet extended checksum. */
@@ -1526,7 +1538,7 @@ static int ositp_decode_CC(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   guint16 dst_ref, src_ref;
   guint8  class_option;
   tvbuff_t *next_tvb;
-  guint tpdu_len = li + tvb_length_remaining(tvb, li ); /* according to ISO/IEC 8073 13.4.1 CC may have user data: header + user data size */
+  guint   tpdu_len;
 
   src_ref = tvb_get_ntohs(tvb, offset + P_SRC_REF);
 
@@ -1534,6 +1546,9 @@ static int ositp_decode_CC(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   if (((class_option & 0xF0) >> 4) > 4) /* class 0..4 allowed */
     return -1;
 
+  /* CR and CC TPDUs can have user data, so they run to the end of the containing PDU */
+  tpdu_len = tvb_reported_length_remaining(tvb, offset);
+
   dst_ref = tvb_get_ntohs(tvb, offset + P_DST_REF);
   pinfo->clnp_srcref = src_ref;
   pinfo->clnp_dstref = dst_ref;
@@ -1642,7 +1657,7 @@ static int ositp_decode_DC(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   proto_item *ti;
   proto_item *item = NULL;
   guint16 dst_ref, src_ref;
-  guint tpdu_len = li + 1; /* according to ISO/IEC 8073 13.6.1  DC has no user data  */
+  guint   tpdu_len;
 
   /* ATN may use checksums different from OSI */
   /* which may result in different TPDU header length. */
@@ -1654,6 +1669,9 @@ static int ositp_decode_DC(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
       return -1;
   }
 
+  /* DC TPDUs have no user data, so the length indicator determines the length */
+  tpdu_len = li + 1;
+
   dst_ref = tvb_get_ntohs(tvb, offset + P_DST_REF);
   src_ref = tvb_get_ntohs(tvb, offset + P_SRC_REF);
   pinfo->clnp_dstref = dst_ref;
@@ -1707,7 +1725,7 @@ static int ositp_decode_AK(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   guint16    dst_ref;
   guint      tpdu_nr;
   gushort    cdt_in_ak;
-  guint tpdu_len = li + 1; /* according to ISO/IEC 8073 13.9.1  AK does not have user data */
+  guint      tpdu_len;
 
   if (!cotp_decode_atn) {
     if (li > LI_MAX_AK)
@@ -1717,6 +1735,9 @@ static int ositp_decode_AK(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
       return -1;
   }
 
+  /* AK TPDUs have no user data, so the length indicator determines the length */
+  tpdu_len = li + 1;
+
   /* is_LI_NORMAL_AK() works for normal ATN AK's, */
   /* for the TPDU header size may be enlarged by 2 octets */
   if (is_LI_NORMAL_AK(li)) {
@@ -1821,7 +1842,7 @@ static int ositp_decode_EA(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   gboolean is_extended;
   guint16  dst_ref;
   guint    tpdu_nr;
-  guint tpdu_len = li +1; /* according to ISO/IEC 8073 13.10.1 EA does not have user data */
+  guint    tpdu_len;
 
   /* Due to different checksums in the ATN the TPDU header sizes */
   /* as well as the checksum parameters may be different than plain OSI EA.*/
@@ -1942,6 +1963,10 @@ static int ositp_decode_EA(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
         return -1;
     }
   }
+
+  /* ER TPDUs have no user data, so the length indicator determines the length */
+  tpdu_len = li + 1;
+
   dst_ref = tvb_get_ntohs(tvb, offset + P_DST_REF);
   pinfo->clnp_dstref = dst_ref;
 
@@ -1998,7 +2023,7 @@ static int ositp_decode_ER(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   proto_item *ti;
   const char *str;
   guint16 dst_ref;
-  guint8 tpdu_len = li + 1;  /* according to ISO/IEC 8073 13.12.1 ER does not have user data */
+  guint8 tpdu_len;
 
   /* ATN: except for modified LI checking nothing to be done here */
   if (!cotp_decode_atn) {
@@ -2009,6 +2034,9 @@ static int ositp_decode_ER(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
       return -1;
   }
 
+  /* ER TPDUs have no user data, so the length indicator determines the length */
+  tpdu_len = li + 1;
+
   switch(tvb_get_guint8(tvb, offset + P_REJECT_ER)) {
     case 0 :
       str = "Reason not specified";
@@ -2059,7 +2087,10 @@ static int ositp_decode_UD(tvbuff_t *tvb, int offset, guint8 li, guint8 tpdu,
   proto_item *ti;
   proto_tree *cltp_tree = NULL;
   tvbuff_t   *next_tvb;
-  guint8 tpdu_len = li + 1;
+  guint      tpdu_len;
+
+  /* UD TPDUs have user data, so they run to the end of the containing PDU */
+  tpdu_len = tvb_reported_length_remaining(tvb, offset);
 
   col_append_str(pinfo->cinfo, COL_INFO, "UD TPDU");