Re: [colorforth] IPv4

[Oninoshiko <oninoshiko@xxxxxxxxxxxxxxxxxxxx>]

On Sun, 9 May 2004, Oninoshiko wrote:

> > This is true. The IPv4 code assumes no options, no fragmentation. From
> > observation of tcpdump these seem to hold. It is important that code is
> > protected from malicious packets however, I have not yet investigated the
> > security in case assumptions fail.
> 
> the obvious solution (for the options) is to  shift the header into the 
> space occuppied by the options, blasting them into oblivion. then 
> everuthing works. this is what i plan on doing in my copy, so im gonna 
> make the same assumption when writing the checksumming code for my IPv4 
> implimentation.
> 

after some disscussion and consideration this plan is getting replaced bu 
simply ovewriting the end of the IP header with the psudo-header specified 
in "RFC 793: TRANSMISSION CONTROL PROTOCOL." this seems to contain any 
information needed by any higher level protocols, sets the TCP header up 
for easy computation of the checksum, and solves any problems which could 
be caused by variabe length headers


Oninoshiko


"A Pax, a pax, a pax upon thee"

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