[Etherboot-developers] [RFC] Multicast reception....

[<ebi...@ln...>]

When booting large numbers of clients the reception of boot images,
(if you only have one tftp server) has been show to be a bottleneck.

To address that address that I am implemeting a reliable multicast
download protocol in etherboot.

Transmitting multicast packets is trivial and I have completed the
implemetation in 10 lines of code.  Receiving multicast packets is
more interesting.

Implementing IGMP and filtering for multicast addresses we are waiting
for looks like about the same amount of work as ARP.

My understanding of the guts of NIC is limited, so please check me.  I
believe NICs have a hardware filter that allows them to receive just
broadcast packets, and packets to their own mac address.  So to
receive multicast packets I need open up or disable the filter all
together.  The simplest solution appears to be disabling the hardware
filter and go into promiscous mode, and then replace the hardware
filter with a software filter in await_reply.  

Does anyone know if there is any communication between NICs and
switches about what a NIC is listening for that would make promiscous
mode a bad state to put NICs into?

Eric