Re: Half Duplex and Zero Copy IP

[Jamie Lokier]

Andi Kleen wrote:
> The sniffer zero copy implementation as implemented in some libpcaps 
> does not depend on any special NIC support; it should work with any.

Do you mean mmap() on a packet socket?  Unless I am mistaken, the data
is still copied once to the mmap area, however only the capture length
is copied -- the rest of the packet is discarded.

This means that you cannot use mmap() on a packet socket to zero-copy
read whole packets.  In fact there is no way to zero-copy read whole
packets into user space, without modifying the kernel.

Am I mistaken (it would be nice)?

Thanks,
-- Jamie