Ethereal-dev: Re: [Ethereal-dev] Comments and traces regarding new dissector - packet-extreme.
On Mon, Aug 15, 2005 at 01:30:51AM -0400, Jim Young wrote:
> 1) The "Info element" TLV values for the "edp.info.slot" and
> "edp.info.port" fields are currently off by a value of one. To
> correctly display these values it appears that the raw values
> must be incremented by one. In the attached file edp1.trace,
> my network monitor was physically connected to interface "8:60"
> but the "edp" packets are currently reported as the values
> "slot 7" and "port 59".
Fixed in my local copy. Thanks for the report!
> 2) The "Null" TLV I believe is actually used to explicitly mark the
> end of the Extreme PDU. In my own prototype extreme dissector
> I had been referring to this as the "End of EPDU" TLV. In my traces
> I have seen this TLV in virtually every EPDU, and it has always
> been the last TLV. Instead of referring to this as the "Null" TLV
> would it be better to call it the "End of EPDU" or perhaps
> "End OF TLVs" or something similar?
I wrote the dissector based on information from the Extreme knowledge
base (esupport, partner access required), so I use the conventions
from that document. The Null TVL is indeed an "end of edp" indicator.
> 3) Instead of dissecting the TLV header as three fields: marker
> (one octet), type (one octet) and length (two octets), would it
> be better to simply dissect the header as two fields: type (two octets)
> and length (2 octets)? The TLV types would then be referenced
> as a 16 bit value (i.e. 0x9900, 0x9901, 0x9902, etc).
As above, I'd like to stick with the conventions found on the Extreme
web page. What I could do if there is some interest is to generate a
summary line like I did with the version field, so it would use onle
one line in unexpanded state. Let me know what you think.
> 4) Regarding the flag bit 0x80 seen in some VLAN TLVs. I
> believe this bit is set when the advertised VLAN is actually defined
> to traverse current interface.
If you look into the source, you'll find the following lines:
/* FIXME: properly decode the bit(s):
bit 2^7 = 1 -> has ip interface
bit 2^0 = ? */
proto_tree_add_item(tree, hf_edp_vlan_flags, tvb, offset, 1,
FALSE);
So your analysis seems correct.
OK, I've added the remaining stuff from the KB to my local copy.
I've just committed the documentation and slot/port update (rev 15358).
Further feedback is welcome!
ciao
Joerg
--
Joerg Mayer <jmayer@xxxxxxxxx>
We are stuck with technology when what we really want is just stuff that
works. Some say that should read Microsoft instead of technology.
