Handle subset tvbuffs where the length goes past the end of the parent.

Add a "contained length" to tvbuffs.  For non-subset tvbuffs, that's the
same as the reported length.  For a subset tvbuff, that's the amount of
the reported data that was actually present in the "contained data" of
the parent tvbuff.

This is unaffected by the *captured* length of any tvbuff; that differs
from the contained length only if the capture was cut short by a
snapshot length.

If a reference is within the reported data, but not within the contained
data, a ContainedBoundsError exception is thrown.  This exception
represents a protocol error, rather than a reference past the captured
data in the packet; we treat it as such.

Change-Id: Ide87f81238eaeb89b3093f54a87bf7f715485af5
Reviewed-on: https://code.wireshark.org/review/27039
Reviewed-by: Guy Harris <guy@alum.mit.edu>

1 files changed, 19 insertions, 1 deletions

diff --git a/epan/tvbuff-int.h b/epan/tvbuff-int.h
index 6a5c1d4490..17128abdf7 100644
--- a/epan/tvbuff-int.h
+++ b/epan/tvbuff-int.h
@@ -55,7 +55,9 @@ struct tvbuff {
 	 * file.  This is the length of virtual buffer (and/or
 	 * real_data).  It may be less than the reported
 	 * length if this is from a packet that was cut short
-	 * by the capture process. */
+	 * by the capture process.
+	 *
+	 * This must never be > reported_length or contained_length. */
 	guint			length;
 
 	/** Amount of data that was reported as being in
@@ -64,6 +66,22 @@ struct tvbuff {
 	 * amount of data that's available. */
 	guint			reported_length;
 
+	/** If this was extracted from a parent tvbuff,
+	 * this is the amount of extracted data that
+	 * was reported as being in the parent tvbuff;
+	 * if this represents a blob of data in that
+	 * tvbuff that has a length specified by data
+	 * in that tvbuff, it might be greater than
+	 * the amount of data that was actually there
+	 * to extract, so it could be greater than
+	 * reported_length.
+	 *
+	 * If this wasn't extracted from a parent tvbuff,
+	 * this is the same as reported_length.
+	 *
+	 * This must never be > reported_length. */
+	guint			contained_length;
+
 	/* Offset from beginning of first "real" tvbuff. */
 	gint			raw_offset;
 };