["Alex Rozin" <Arozin@xxxxxxx>]

Thank you, Guy.
But I'm afraid, that the issue is more difficult...
After perusal of 802.1s once more I came to the conclusion
that this document mistakenly allows double meaning of the
field "Version 3 Length" (octets 37-38) :(

IMHO, the correct one is "is the number of octets taken by the parameters
that follow in the BPDU..." (14.6.q and Figure 14-1-MST BPDU parameters
and format). Clive A Stubbings used this meaning.

I had been confused with item 14.4.e.3: "...a Version 3
length representing an integral number, from 0 to 64 inclusive,
of MSTI Configuration Messages...".

I don't consider this my mistake as an awful shame, because CISCO
did the same one, at least C3550 Software (C3550-I5Q3L2-M), Version 12.1(12c)EA1

Attached is a patch for your last check in. It allows to parse both types of formats;
Ethereal warns about incorrect one, as far as I see.

I am going to ask IEEE for the clarification about this field.

Best regards, Alex

P.S. Could you explain, why Ethereal-dev doesn't
operate? I cannot subscribe myself and read last messages from the
archive (last archived message is *On Thu, 01 Jan 2004*) "

On Monday, January 05, 2004 7:28 PM Guy Harris wrote:
> On Mon, Jan 05, 2004 at 08:42:55AM +0200, Alex Rozin wrote:
Alex > > I tried to debug my MSTP implementation by Ethereal and
Alex > > saw, that my MST BPDUs are considered as *malformed
Alex > > packets*.
Alex > > I investigated a problem, exploring the code.
Alex > > It seems, that a current version has a bug in packet-bpdu.c
Alex > > I fixed it as far as I could; attached is a patch for ethereal-0.10.0

Guy > Checked in, with "length" set to
Guy > "tvb_reported_length_remaining(tvb, offset)"
Guy > after setting "offset" to BPDU_MSTI; that's a bit simpler,
Guy > and also uses
Guy > the reported length of the tvbuff (i.e., the packet length)
Guy > rather than
Guy > the data length (i.e., the amount of packet data captured), so that
Guy > BPDUs are marked as short frames if captured with a snapshot
Guy > length that
Guy > doesn't capture all the packet data.
Guy >
Guy > I also updated your e-mail address.

--- packet-bpdu.gui.c	Wed Jan  7 09:46:30 2004
+++ packet-bpdu.c	Wed Jan  7 11:32:21 2004
@@ -339,9 +339,13 @@
       case BPDU_TYPE_RST:
 	if (protocol_version_identifier == 3) {
 	    version_3_length = tvb_get_ntohs(tvb, BPDU_VERSION_3_LENGTH);
+            if (version_3_length < VERSION_3_STATIC_LENGTH - 2) {
 	    set_actual_length(tvb, RST_BPDU_SIZE +
                                    VERSION_3_STATIC_LENGTH +
                                    version_3_length * MSTI_MESSAGE_SIZE);
+            } else {
+              set_actual_length(tvb, RST_BPDU_SIZE + 2 + version_3_length);
+            }
 	} else
 	    set_actual_length(tvb, RST_BPDU_SIZE);
         break;
@@ -481,6 +485,15 @@
 
 		mstp_item = proto_tree_add_uint(bpdu_tree, hf_bpdu_version_3_length, tvb,
 			BPDU_VERSION_3_LENGTH, 2, version_3_length);
+                if (version_3_length < VERSION_3_STATIC_LENGTH - 2) {
+                  proto_item_append_text (mstp_item,
+                                          " (Malformed: number of MSTI messages !!! Must be %d)",
+                                          (int) (VERSION_3_STATIC_LENGTH - 2 + version_3_length * MSTI_MESSAGE_SIZE));
+                } else {
+                  proto_item_append_text (mstp_item,
+                                          " (Number of MSTI messages: %d)",
+                                          (int) ((version_3_length - VERSION_3_STATIC_LENGTH + 2) / MSTI_MESSAGE_SIZE));
+                }
 		mstp_tree = proto_item_add_subtree(mstp_item, ett_mstp);
 
 		mst_config_format_selector = tvb_get_guint8(tvb, BPDU_MST_CONFIG_FORMAT_SELECTOR);