Clients sending corrupt VendorClassID

Randall C Grimshaw rgrimsha at
Tue Aug 21 19:24:28 UTC 2012

  That was a world-class great idea... but in real life there doesn't seem to be anything I can do to overwrite the client provided value.

  if substring( option vendor-class-identifier, 1, 3 ) = "PS3" {
    option vendor-class-identifier "PS3";

  No effect (also tried with offset 0 just in case)
  any other ideas?

Randall Grimshaw rgrimsha at
From: at [ at] on behalf of Simon Hobson [dhcp1 at]
Sent: Tuesday, August 21, 2012 2:06 PM
To: Users of ISC DHCP
Subject: RE: Clients sending corrupt VendorClassID

Randall C Grimshaw wrote:

>I am seeing PS3 devices submit a control value that is affecting the
>log and class definitions.
>Vendor-Class Option 60, length 4: "PS3^@"

FYI, the same issue affects DNS updates when clients pad the hostname
with nulls. As you say, what's needed (if it's not already
implemented) is a filter to strip such characters from fields where
they are not legal - I'm assuming they aren't legal for a hostname.
But they could be for a Client-ID since that is "just a byte field" -
so you'd need it as a generic function to apply to any string/option.

If it's just a single value then I think you could write an if
statement to replace it with the corrected version.
Ie something along the lines of :
if vendor-class="PS3^@" then vendor-class=="PS3"

Simon Hobson

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