When we're dissecting the beginning of a fragmented packet that we

haven't reassembled, we're probably moving sequentially through the
packet, which means that we'll run past the end of the fragment rather
than past the end of what would have been the reassembled packet had we
reassembled it.

I.e., there's little reason to care whether we're past the end of the
fragment but not past the end of the packet, or whether we're past the
end of the packet; in either case, we're past the end of the fragment,
and if somebody wants to know whether the packet is malformed by
stopping short of certain fields, they should enable reassembly.

So we get rid of the explicit fragment length in tvbuffs and, instead,
have a "this is a fragment" flag; if that flag is set, we throw
FragmentBoundsError rather than ReportedBoundsError if we run past the
end of the reported data.

(This also means we could flag the tvbuff even if we don't know how
large the reassembled packet will be, e.g. when doing IP reassembly.)

Replace tvb_new_subset_length_fragment() with tvb_new_subset_length()
and a new "set the "this is a fragment flag"" routine.

svn path=/trunk/; revision=48940

1 files changed, 13 insertions, 19 deletions

diff --git a/epan/tvbuff.h b/epan/tvbuff.h
index 21abf5ecf7..8950feb68b 100644
--- a/epan/tvbuff.h
+++ b/epan/tvbuff.h
@@ -81,10 +81,10 @@ typedef struct tvbuff tvbuff_t;
  * A dissector:
  *  - Can chain new tvbs (subset, real, composite) to the
  *    tvb handed to the dissector using tvb_new_subset(),
- *    tvb_new_subset_remaining(), tvb_new_child_real_data(),
- *    tvb_set_child_real_data_tvbuff(), tvb_composite_finalize(), and
- *    tvb_child_uncompress(). (Composite tvbs should reference
- *    only tvbs which are already part of the chain).
+ *    tvb_new_subset_length(), tvb_new_subset_remaining(),
+ *    tvb_new_child_real_data(), tvb_set_child_real_data_tvbuff(),
+ *    tvb_composite_finalize(), and tvb_child_uncompress(). (Composite
+ *    tvbs should reference only tvbs which are already part of the chain).
  *  - Must not save for later use (e.g., when dissecting another frame) a
  *    pointer to a tvb handed to the dissector; (A higher level function
  *    may very well free the chain thus leaving a dangling pointer).
@@ -181,24 +181,14 @@ WS_DLL_PUBLIC tvbuff_t* tvb_new_real_data(const guint8* data, const guint length
 WS_DLL_PUBLIC tvbuff_t* tvb_new_subset(tvbuff_t* backing,
 		const gint backing_offset, const gint backing_length, const gint reported_length);
 
-/*
-* Similar to tvb_new_subset() but with captured length calculated
+/**
+ * Similar to tvb_new_subset() but with captured length calculated
  * to fit within the existing captured length and the specified
- * backing length (which is used as both the fragment and reported
- * length).
+ * backing length (which is used as the reported length).
  * Can throw ReportedBoundsError. */
 WS_DLL_PUBLIC tvbuff_t* tvb_new_subset_length(tvbuff_t *backing,
 		const gint backing_offset, const gint backing_length);
 
-/** Similar to tvb_new_subset() but with fragment and reported length
- * set as specified and captured length calculated to fit within
- * the existing captured length and the specified fragment and
- * reported lengths.
- * Can throw ReportedBoundsError. */
-extern tvbuff_t* tvb_new_subset_length_fragment(tvbuff_t *backing,
-		const gint backing_offset, const gint fragment_length,
-		const gint reported_length);
-
 /** Similar to tvb_new_subset() but with backing_length and reported_length set to -1.
  * Can throw ReportedBoundsError. */
 WS_DLL_PUBLIC tvbuff_t* tvb_new_subset_remaining(tvbuff_t* backing,
@@ -267,6 +257,12 @@ WS_DLL_PUBLIC guint tvb_offset_from_real_beginning(const tvbuff_t *tvb);
 /* Returns the offset from the first byte of real data. */
 WS_DLL_PUBLIC gint tvb_raw_offset(tvbuff_t *tvb);
 
+/** Set the "this is a fragment" flag. */
+WS_DLL_PUBLIC void tvb_set_fragment(tvbuff_t *tvb);
+
+WS_DLL_PUBLIC struct tvbuff *tvb_get_ds_tvb(tvbuff_t *tvb);
+
+
 /************** START OF ACCESSORS ****************/
 /* All accessors will throw an exception if appropriate */
 
@@ -678,8 +674,6 @@ typedef struct dgt_set_t
 dgt_set_t;
 
 WS_DLL_PUBLIC const gchar *tvb_bcd_dig_to_ep_str(tvbuff_t *tvb, const gint offset, const gint len, dgt_set_t *dgt, gboolean skip_first);
-WS_DLL_PUBLIC
-struct tvbuff *tvb_get_ds_tvb(tvbuff_t *tvb);
 
 /** Locate a sub-tvbuff within another tvbuff, starting at position
  * 'haystack_offset'. Returns the index of the beginning of 'needle' within