Firwalls Gurus,
I'm trying to set up some packet filtering, on a fairly primitive box. I can
use it get the value of a field at a particular offset, but am unable to
calculate an offset to use - it has to be an explicit constant value.
The IHL field in the IP header indicates the length of that header - so if,
for instance, I need to get to the TCP destination port field within the
packet, I should calculate the offset of it based upon the value of the IHL.
So my question is, is it valid to reject packets which have an IHL value of
something other than 5, since I can't find a way to index into packets with
a different value
thanx in advance
chris newton
network security
sandpiper software consulting
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