Re: mmap/munmap bug

[Arjan van de Ven <arjan@infradead.org>]

On Tue, 2005-03-22 at 10:23 +0200, Hayim Shaul wrote:
> >> Does it support zero copy not only for send but also for receive? Can we
> >> receive packets directly to userspace buffers?
> >
> > that it can't currently, but without some major protocol stack rework
> > that's not going to be easy. If you want to help do that work,
> > excellent! Be sure to contact the people on net-dev mailinglist since
> > they are the ones having looked at this previously.
> 
> My case is simpler, as the application I attend it to is similar to a NAT. 
> A packet comes in, a little alternation of the headers and off it goes 
> again. So there's no TCP-stack or anything.
> 
> What I thought of doing, is map the skbuff to user-space. Have the 
> user-application alter the headers. Send the (same) skbuff from 
> kernel-space.
> 
> Does there exist anything equivalent?

yes; netfilter has facilities for this actually afaik.
tcpdump also uses something like this (but only in one direction), it
mmaps some ringbuffer with incomming packets.