On Mon, 10 Dec 2007 15:32:14 +0100
Ariane Keller [off-list ref] wrote:

I finally managed to rewrite the netem trace extension to use rtnetlink 
communication for the data transfer for user space to kernel space.

The kernel patch is available here:
http://www.tcn.hypert.net/tcn_kernel_2_6_23_rtnetlink

and the iproute patch is here:
http://www.tcn.hypert.net/tcn_iproute2_2_6_23_rtnetlink

Whenever new data is needed the kernel module sends a notification to 
the user space process. Thereupon the user space process sends a data 
package to the kernel module.

I wonder if it wouldn't be possible to enhance/extend netlink
to use sendfile/splice to get the data.  It is rather more work than
needed for just this, but it would be useful for large configuration.

I had to write a new qdisc_notify function (qdisc_notify_pid) since the 
other was acquiring a lock, which we already hold in this situation.

I hope everything works as expected and I'm looking forward for your 
comments.

Thanks!
Ariane

-- 
Stephen Hemminger [off-list ref]