SCSI is fairly unique among the ethereal protocols in that it is sometimes normal for a PDU we receive back froma device to be truncated.

(report luns with allocation length 8 for example)

Therefore it is a bit wrong to mark these packets as [malformed packets]
Since they are truncated by scsi   and this is NOTY an error condition.


Add a new exception type  :  ScsiBoundsError
If this exception is caught by packet-frame, then print an appropriate message
instead of [malformed packet]

For SCSI, add helper macros TRY_SCSI_SHORT_PACKET   and END_...


If the packet was not short in the normal sense (snaplen < packetlen) then intercept the exception for BoundsError and rethrow it as ScsiBoundsError instead.





svn path=/trunk/; revision=17611

3 files changed, 70 insertions, 1 deletions

diff --git a/epan/dissectors/packet-frame.c b/epan/dissectors/packet-frame.c
index 3929956a4c..28d869ceeb 100644
--- a/epan/dissectors/packet-frame.c
+++ b/epan/dissectors/packet-frame.c
@@ -333,6 +333,17 @@ show_exception(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
 
 	switch (exception) {
 
+	case ScsiBoundsError:
+		if (check_col(pinfo->cinfo, COL_INFO))
+			col_append_str(pinfo->cinfo, COL_INFO, "[SCSI transfer limited due to allocation_length too small]");
+		/*item =*/ proto_tree_add_protocol_format(tree, proto_short, tvb, 0, 0,
+				"SCSI transfer limited due to allocation_length too small: %s truncated]", pinfo->current_proto);
+		/* Don't record ScsiBoundsError exceptions as expert events - they merely
+		 * reflect a normal SCSI condition.
+		 * (any case where it's caused by something else is a bug). */
+		/* expert_add_info_format(pinfo, item, PI_MALFORMED, PI_ERROR, "Packet size limited");*/
+		break;
+
 	case BoundsError:
 		if (check_col(pinfo->cinfo, COL_INFO))
 			col_append_str(pinfo->cinfo, COL_INFO, "[Packet size limited during capture]");
diff --git a/epan/dissectors/packet-scsi.c b/epan/dissectors/packet-scsi.c
index 1f2299e78a..2c7cc543d5 100644
--- a/epan/dissectors/packet-scsi.c
+++ b/epan/dissectors/packet-scsi.c
@@ -319,6 +319,48 @@ static int hf_ssc3_locate16_loid = -1;
 static gint ett_scsi         = -1;
 static gint ett_scsi_page    = -1;
 
+
+/* These two defines are used to handle cases where data coming back from
+ * the device is truncated due to a too short allocation_length specified
+ * in the command CDB.
+ * This is semi-common in SCSI and it would be wrong to mark these packets
+ * as [malformed packets].
+ * These macros will reset the reported length to what the data pdu specified
+ * and if a BoundsError is generated we will instead throw ScsiBoundsError
+ *
+ * Please see dissect_mmc4_getconfiguration() for an example how to use these
+ * macros.
+ */
+#define TRY_SCSI_SHORT_TRANSFER(tvb, length)				\
+    {									\
+	gboolean short_packet;						\
+	tvbuff_t *new_tvb;						\
+									\
+	short_packet=tvb_length(tvb) < tvb_reported_length(tvb);	\
+	new_tvb=tvb_new_subset(tvb, offset, tvb_length_remaining(tvb, offset), length);\
+	tvb=new_tvb;							\
+	offset=0;							\
+	TRY {
+
+#define END_TRY_SCSI_SHORT_TRANSFER 					\
+	    } /* TRY */							\
+	CATCH(BoundsError) {						\
+		if(short_packet){					\
+			/* this was a short packet */			\
+			RETHROW;					\
+		} else {						\
+			/* this packet was not really short but limited	\
+			 * due to a short SCSI allocation length	\
+			 */						\
+			THROW(ScsiBoundsError);				\
+		}							\
+	    }								\
+	CATCH_ALL {							\
+		RETHROW;						\
+	}								\
+	ENDTRY;								\
+    }
+
 typedef guint32 scsi_cmnd_type;
 typedef guint32 scsi_device_type;
 
@@ -4060,7 +4102,10 @@ dissect_mmc4_getconfiguration (tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree
     }
     if(tree && (!isreq)) {
         len=tvb_get_ntohl(tvb, offset+0);
-        proto_tree_add_item (tree, hf_scsi_data_length, tvb, offset+0, 4, 0);
+
+	TRY_SCSI_SHORT_TRANSFER(tvb, len); /* offset is reset to 0 */
+
+        proto_tree_add_item (tree, hf_scsi_data_length, tvb, offset, 4, 0);
         proto_tree_add_item (tree, hf_scsi_getconf_current_profile, tvb, offset+6, 2, 0);
 	offset+=8;
         len-=4;
@@ -4153,6 +4198,7 @@ dissect_mmc4_getconfiguration (tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree
                 old_offset+=additional_length;
                 len-=4+additional_length;
         }
+	END_TRY_SCSI_SHORT_TRANSFER;
     }
 }
 
diff --git a/epan/exceptions.h b/epan/exceptions.h
index a3d814cba9..92cf9a7ced 100644
--- a/epan/exceptions.h
+++ b/epan/exceptions.h
@@ -56,6 +56,18 @@
 **/
 #define DissectorError		4	
 
+/**
+    Index is out of range.
+    An attempt was made to read past the end of a buffer.
+    This error is specific to SCSI data transfers where for some CDBs
+    it is normal that the data PDU might be short.
+    I.e. ReportLuns initially called with allocation_length=8, just enough
+    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	
+
+
 /* Usage:
  *
  * TRY {