Subject: [dhcwg] RFC3925 heads-up

From: "David W. Hankins" <[email-masked]>
Date: Wed, 17 Sep 2008 12:01:45 -0700

There seems to be at least one incompatible interpretation of the
format of the VIVCO option.

  http://marc.info/?l=dhcp-users&m=122167258025515&w=2

My interpretation of that tcpdump is that the vendor (Broadcom if
the enterprise-id is to be believed, but "AVI_WLAN" appears in the
vendor-class-identifier) is only sending a 4-octet enterprise id, and
no length octet.  Our software interprets the next data octet (0x01)
as a length octet, which causes it to fail to frame the vendor's data
properly.

It looks rather like someone thought the DHCPv4 VIVSO option was
formatted identically to the DHCPv6 VSIO option, which does not
utilize a length field...

I'm sending this in the event the vendors in question are monitoring
this list, or in the event that anyone else might have made a similar
mistake.

-- 
Ash bugud-gul durbatuluk agh burzum-ishi krimpatul.
Why settle for the lesser evil?	 https://secure.isc.org/store/t-shirt/
-- 
David W. Hankins	"If you don't do it right the first time,
Software Engineer		     you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins
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From: Josh Littlefield <[email-masked]>
Date: Wed, 17 Sep 2008 15:28:21 -0400

You are correct in your interpretation, and the RFC is very clear about 
this.  The length byte is in there after the enterprise ID to support 
option concatenation, which is the by-product of having multiple option 
125s in the packet.  Without the length, there would be no way to have 
multiple enterprise IDs in the (concatenated resulting) option 125.

-josh

David W. Hankins wrote:
> ------------------------------------------------------------------------
>

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Josh Littlefield                                  Cisco Systems, Inc.
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