Add to tvbuffs a "fragment length" field; if the tvbuff represents the

first fragment of a non-reassembled packet, and we know the length the
packet would have if it were reassembled, this field holds the length of
the fragment, and the "reported length" field shows the length the
packet would have if it were reassembled, so going past the end of the
fragment but staying within the length of the reassembled packet can be
reported as "dissection would have worked if the packet had been
reassembled" rather than "the packet is too short, so it was probably
malformed".

Add a FragmentBoundsError exception, thrown in the "dissection would
have worked if the packet had been reassembled" case.

Add a new tvb_new_subset_length_fragment() routine to create a new
subset tvb with specified fragment and reported lengths.  Use it in the
CLNP dissector.

Add some more sanity checks in the CLNP dissector.

svn path=/trunk/; revision=48917

1 files changed, 61 insertions, 16 deletions

diff --git a/epan/exceptions.h b/epan/exceptions.h
index 938115e622..601206e986 100644
--- a/epan/exceptions.h
+++ b/epan/exceptions.h
@@ -52,20 +52,19 @@
     code constructed the packet and put it on the wire didn't put enough
     data into it.  It is therefore currently reported as a "Malformed
     packet".
-    However, it also happens in some cases where the packet was fragmented
-    and the fragments weren't reassembled.  We need to add another length
-    field to a tvbuff, so that "length of the packet from the link layer"
-    and "length of the packet were it fully reassembled" are different,
-    and going past the first of those without going past the second would
-    throw a different exception, which would be reported as an "Unreassembled
-    packet" rather than a "Malformed packet".
 **/
 #define ReportedBoundsError	2
 
 /**
+    Index is beyond fragment length but not reported length.
+    This means that the packet wasn't reassembled.
+**/
+#define FragmentBoundsError	3
+
+/**
     During dfilter parsing
 **/
-#define TypeError		3
+#define TypeError		4
 
 /**
     A bug was detected in a dissector.
@@ -76,7 +75,7 @@
 
     Instead, use the DISSECTOR_ASSERT(), etc. macros in epan/proto.h.
 **/
-#define DissectorError		4
+#define DissectorError		5
 
 /**
     Index is out of range.
@@ -87,13 +86,13 @@
     to get the "size" of lun list back after which the initiator will
     reissue the command with an allocation_length that is big enough.
 **/
-#define ScsiBoundsError		5
+#define ScsiBoundsError		6
 
 /**
     Running out of memory.
     A dissector tried to allocate memory but that failed.
 **/
-#define OutOfMemoryError	6
+#define OutOfMemoryError	7
 
 /**
     The reassembly state machine was passed a bad fragment offset,
@@ -102,7 +101,7 @@
     contains a bad fragment offset, the dissector shouldn't have to figure
     that out by itself since that's what the reassembly machine is for.
 **/
-#define ReassemblyError         7
+#define ReassemblyError         8
 
 /*
  * Catch errors that, if you're calling a subdissector and catching
@@ -110,9 +109,14 @@
  * stuff after the subdissector returns or fails, mean it makes
  * sense to continue dissecting:
  *
- * BoundsError indicates a configuration problem; there's no point in
+ * BoundsError indicates a configuration problem (the capture was
+ * set up to throw away data, and it did); there's no point in
  * trying to dissect any more data, as there's no more data to dissect.
  *
+ * FragmentBoundsError indicates a configuration problem (reassembly
+ * wasn't enabled or couldn't be done); there's no point in trying
+ * to dissect any more data, as there's no more data to dissect.
+ *
  * OutOfMemoryError indicates what its name suggests; there's no point
  * in trying to dissect any more data, as you're probably not going to
  * have any more memory to use when dissecting them.
@@ -129,7 +133,8 @@
  * Catch all bounds-checking errors.
  */
 #define CATCH_BOUNDS_ERRORS \
-	CATCH3(BoundsError, ReportedBoundsError, ScsiBoundsError)
+	CATCH4(BoundsError, FragmentBoundsError, ReportedBoundsError, \
+	       ScsiBoundsError)
 
 /*
  * Catch all bounds-checking errors, and catch dissector bugs.
@@ -137,7 +142,8 @@
  * go all the way to the top level and get reported immediately.
  */
 #define CATCH_BOUNDS_AND_DISSECTOR_ERRORS \
-	CATCH5(BoundsError, ReportedBoundsError, ScsiBoundsError, DissectorError, ReassemblyError)
+	CATCH6(BoundsError, FragmentBoundsError, ReportedBoundsError, \
+	       ScsiBoundsError, DissectorError, ReassemblyError)
 
 /* Usage:
  *
@@ -153,7 +159,31 @@
  * 	code;
  * }
  *
- * CATCH_END_OF_DATA_ERROR {
+ * CATCH3(exception1, exception2, exception3) {
+ * 	code;
+ * }
+ *
+ * CATCH4(exception1, exception2, exception3, exception4) {
+ * 	code;
+ * }
+ *
+ * CATCH5(exception1, exception2, exception3, exception4, exception5) {
+ * 	code;
+ * }
+ *
+ * CATCH6(exception1, exception2, exception3, exception4, exception5, exception6) {
+ * 	code;
+ * }
+ *
+ * CATCH_NONFATAL_ERRORS {
+ *	code;
+ * }
+ *
+ * CATCH_BOUNDS_ERRORS {
+ *	code;
+ * }
+ *
+ * CATCH_BOUNDS_AND_DISSECTOR_ERRORS {
  *	code;
  * }
  *
@@ -191,6 +221,10 @@
  * 		caught = TRUE;
  * 		<CATCH2(3,4) code>
  * 	}
+ * 	if (!caught && (x == 5 || x == 6 || x == 7)) {
+ * 		caught = TRUE;
+ * 		<CATCH3(5,6,7) code>
+ * 	}
  * 	if (!caught && x != 0) {
  *		caught = TRUE;
  * 		<CATCH_ALL code>
@@ -306,6 +340,17 @@
 	    (except_state|=EXCEPT_CAUGHT)) \
 		/* user's code goes here */
 
+#define CATCH6(u,v,w,x,y,z) \
+	if (except_state == 0 && exc != 0 && \
+	    (exc->except_id.except_code == (u) || \
+	     exc->except_id.except_code == (v) || \
+	     exc->except_id.except_code == (w) || \
+	     exc->except_id.except_code == (x) || \
+	     exc->except_id.except_code == (y) || \
+	     exc->except_id.except_code == (z)) && \
+	    (except_state|=EXCEPT_CAUGHT)) \
+		/* user's code goes here */
+
 #define CATCH_ALL \
 	if (except_state == 0 && exc != 0 && \
 	    (except_state|=EXCEPT_CAUGHT)) \