Move show_exception() and show_reported_bounds_error() to

epan/show_exception.c, as it's used outside
epan/dissectors/packet-frame.c.  Update their callers to include
<epan/show_exception.h> to get their declaration.

Add a CATCH_NONFATAL_ERRORS macro that catches all exceptions that, if
there's more stuff in the packet to dissect after the dissector call
that threw the exception, doesn't mean you shouldn't go ahead and
dissect that stuff.  Use it in all those cases, including ones where
BoundsError was inappropriately being caught (you want those passed up
to the top level, so that the packet is reported as having been cut
short in the capture process).

Add a CATCH_BOUNDS_ERRORS macro that catches all exceptions that
correspond to running past the end of the data for a tvbuff; use it
rather than explicitly catching those exceptions individually, and
rather than just catching all exceptions (the only place that
DissectorError should be caught, for example, is at the top level, so
dissector bugs show up in the protocol tree).

Don't catch and then immediately rethrow exceptions without doing
anything else; just let the exceptions go up to the final catcher.

Use show_exception() to report non-fatal errors, rather than doing it
yourself.
 
If a dissector is called from Lua, catch all non-fatal errors and use
show_exception() to report them rather than catching only
ReportedBoundsError and adding a proto_malformed item.

Don't catch exceptions when constructing a trailer tvbuff in
packet-ieee8023.c - just construct it after the payload has been
dissected, and let whatever exceptions that throws be handled at the top
level.

Avoid some TRY/CATCH/ENDTRY cases by using checks such as
tvb_bytes_exist() before even looking in the tvbuff.

svn path=/trunk/; revision=47924

1 files changed, 22 insertions, 34 deletions

diff --git a/epan/dissectors/packet-ieee8023.c b/epan/dissectors/packet-ieee8023.c
index bd9b473ae7..89d1e14b25 100644
--- a/epan/dissectors/packet-ieee8023.c
+++ b/epan/dissectors/packet-ieee8023.c
@@ -27,9 +27,9 @@
 #include <glib.h>
 #include <epan/packet.h>
 #include <epan/expert.h>
+#include <epan/show_exception.h>
 #include "packet-ieee8023.h"
 #include "packet-eth.h"
-#include "packet-frame.h"
 
 static dissector_handle_t ipx_handle;
 static dissector_handle_t llc_handle;
@@ -43,7 +43,7 @@ dissect_802_3(volatile int length, gboolean is_802_2, tvbuff_t *tvb,
 {
   proto_item		*length_it;
   tvbuff_t		*volatile next_tvb = NULL;
-  tvbuff_t		*volatile trailer_tvb = NULL;
+  tvbuff_t		*trailer_tvb = NULL;
   const char		*saved_proto;
   gint			captured_length, reported_length;
   void			*pd_save;
@@ -74,20 +74,6 @@ dissect_802_3(volatile int length, gboolean is_802_2, tvbuff_t *tvb,
   if (captured_length > length)
     captured_length = length;
   next_tvb = tvb_new_subset(tvb, offset_after_length, captured_length, length);
-  TRY {
-    trailer_tvb = tvb_new_subset_remaining(tvb, offset_after_length + length);
-  }
-  CATCH2(BoundsError, ReportedBoundsError) {
-    /* The packet has exactly "length" bytes worth of captured data
-       left in it, so the "tvb_new_subset()" creating "trailer_tvb"
-       threw an exception.
-
-       This means that all the data in the frame is within the length
-       value (assuming our offset isn't past the end of the tvb), so
-       we give all the data to the next protocol and have no trailer. */
-    trailer_tvb = NULL;
-  }
-  ENDTRY;
 
   /* Dissect the payload either as IPX or as an LLC frame.
      Catch BoundsError and ReportedBoundsError, so that if the
@@ -109,31 +95,33 @@ dissect_802_3(volatile int length, gboolean is_802_2, tvbuff_t *tvb,
         call_dissector(ccsds_handle, next_tvb, pinfo, tree);
     }
   }
-  CATCH(BoundsError) {
-   /* Somebody threw BoundsError, which means that dissecting the payload
-      found that the packet was cut off by a snapshot length before the
-      end of the payload.  The trailer comes after the payload, so *all*
-      of the trailer is cut off - don't bother adding the trailer, just
-      rethrow the exception so it gets reported. */
-   RETHROW;
-  }
-  CATCH_ALL {
-    /* Well, somebody threw an exception other than BoundsError.
-       Show the exception, and then drive on to show the trailer,
-       restoring the protocol value that was in effect before we
-       called the subdissector. */
+  CATCH_NONFATAL_ERRORS {
+    /* Somebody threw an exception that means that there was a problem
+       dissecting the payload; that means that a dissector was found,
+       so we don't need to dissect the payload as data or update the
+       protocol or info columns.
 
-    /*  Restore the private_data structure in case one of the
-     *  called dissectors modified it (and, due to the exception,
-     *  was unable to restore it).
-     */
+       Just show the exception and then drive on to show the trailer,
+       after noting that a dissector was found and restoring the
+       protocol value that was in effect before we called the subdissector. */
     pinfo->private_data = pd_save;
 
     show_exception(next_tvb, pinfo, tree, EXCEPT_CODE, GET_MESSAGE);
-    pinfo->current_proto = saved_proto;
   }
   ENDTRY;
 
+  /* Restore the protocol value, so that any exception thrown by
+     tvb_new_subset_remaining() refers to the protocol for which
+     this is a trailer, and restore the private_data structure in
+     case one of the called dissectors modified it. */
+  pinfo->private_data = pd_save;
+  pinfo->current_proto = saved_proto;
+
+  /* Construct a tvbuff for the trailer; if the trailer is past the
+     end of the captured data, this will throw a BoundsError, which
+     is what we want, as it'll report that the packet was cut short. */
+  trailer_tvb = tvb_new_subset_remaining(tvb, offset_after_length + length);
+
   add_ethernet_trailer(pinfo, tree, fh_tree, trailer_id, tvb, trailer_tvb, fcs_len);
 }