Re: [ECOS] RedBoot: __eth_install_handler?

[Gary Thomas <gthomas@cambridge.redhat.com>]

On 22-Jan-2001 Grant Edwards wrote:
> On Mon, Jan 22, 2001 at 02:57:41PM -0600, Grant Edwards wrote:
>> 
>> > > In RedBoot's net.h file, there's a declaration for
>> > > __eth_install_handler(), which would seem from the declaration to
>> > > do exactly what I want to do: set a call-back to handle packets
>> > > with Ethernet protocol type <whatever>.
>> > > 
>> > > That functionality hasn't been implemented, so I'm about to
>> > > implement it.  
> 
> It doesn't look like the packet handler routines verify that
> the length of a received Ethernet frame is long enough to
> contain the amount of data expected.  For example, the IP
> handler doesn't check to make sure that the number of bytes in
> the Ethernet frame was was large enough to hold the amount of
> data claimed in the IP header.
> 
> The only way for that to happen would be for another host to
> intentionally send a short Ethernet frame (AFAIK). Even if that
> happens it should be caught by the checksum verification,
> right?
>

That would certainly be true - the checksum routines will try
and access the advertised length of data.  I see no way that the
computed value would match if the actual data was too short.