epan: Separate fragment_head and fragment_item

Separate fragment_head and fragment_item into two
different types of structs.

Remove "offset" from fragment_head, which was unused,
making fragment heads 4 bytes smaller.

Remove fragment_nr_offset, datalen, reassembled_in,
reas_in_layer_num, and error from fragment_item,
making them 24 bytes smaller.

Change a few dissectors which were using fragment_head
and fragment_item indistinguishably.

Ping #17311

1 files changed, 25 insertions, 17 deletions

diff --git a/epan/reassemble.h b/epan/reassemble.h
index 14a41ebff5..9e97d9bc07 100644
--- a/epan/reassemble.h
+++ b/epan/reassemble.h
@@ -51,13 +51,25 @@
 
 typedef struct _fragment_item {
 	struct _fragment_item *next;
-	guint32 frame;			/* XXX - does this apply to reassembly heads? */
-	guint32	offset;			/* XXX - does this apply to reassembly heads? */
-	guint32	len;			/* XXX - does this apply to reassembly heads? */
+	guint32 frame;			/**< frame number where the fragment is from */
+	guint32	offset;			/**< fragment number for FD_BLOCKSEQUENCE, byte
+					 * offset otherwise */
+	guint32	len;			/**< fragment length */
+	guint32 flags;			/**< XXX - do some of these apply only to reassembly
+					 * heads and others only to fragments within
+					 * a reassembly? */
+	tvbuff_t *tvb_data;
+} fragment_item;
+
+typedef struct _fragment_head {
+	struct _fragment_item *next;
+	guint32 frame;			/**< maximum of all frame numbers added to reassembly */
+	guint32	len;			/**< When flags&FD_BLOCKSEQUENCE and FD_DEFRAGMENTED
+					 * are set, the number of bytes of the full datagram.
+					 * Otherwise not valid. */
 	guint32 fragment_nr_offset;	/**< offset for frame numbering, for sequences, where the
 					 * provided fragment number of the first fragment does
-					 * not start with 0
-					 * XXX - does this apply only to reassembly heads? */
+					 * not start with 0 */
 	guint32 datalen;		/**< When flags&FD_BLOCKSEQUENCE is set, the
 					 * index of the last block (segments in
 					 * datagram + 1); otherwise the number of
@@ -65,11 +77,11 @@ typedef struct _fragment_item {
 					 * the first item of the fragments list when
 					 * flags&FD_DATALEN is set.*/
 	guint32 reassembled_in;		/**< frame where this PDU was reassembled,
-					 * only valid in the first item of the list
-					 * and when FD_DEFRAGMENTED is set*/
-	guint8 reas_in_layer_num;	/**< The current "depth" or layer number in the current frame where reassembly was completed.
-					 * Example: in SCTP there can be several data chunks and we want the reassemblied tvb for the final
-					 * segment only. */
+					 * only valid when FD_DEFRAGMENTED is set */
+	guint8 reas_in_layer_num;	/**< The current "depth" or layer number in the current
+					 * frame where reassembly was completed.
+					 * Example: in SCTP there can be several data chunks and
+					 * we want the reassemblied tvb for the final segment only. */
 	guint32 flags;			/**< XXX - do some of these apply only to reassembly
 					 * heads and others only to fragments within
 					 * a reassembly? */
@@ -77,14 +89,9 @@ typedef struct _fragment_item {
 	/**
 	 * Null if the reassembly had no error; non-null if it had
 	 * an error, in which case it's the string for the error.
-	 *
-	 * XXX - this is wasted in all but the reassembly head; we
-	 * should probably have separate data structures for a
-	 * reassembly and for the fragments in a reassembly.
 	 */
 	const char *error;
-} fragment_item, fragment_head;
-
+} fragment_head;
 
 /*
  * Flags for fragment_add_seq_*
@@ -359,7 +366,8 @@ fragment_start_seq_check(reassembly_table *table, const packet_info *pinfo,
  * Mark end of reassembly and returns the reassembled fragment (if completed).
  * Use it when fragments were added with "more_flags" set while you discovered
  * that no more fragments have to be added.
- * XXX rename to fragment_finish as it works also for fragment_add?
+ * This is for fragments added with add_seq_next; it doesn't check for gaps,
+ * and doesn't set datalen correctly for the fragment_add family.
  */
 WS_DLL_PUBLIC fragment_head *
 fragment_end_seq_next(reassembly_table *table, const packet_info *pinfo,