On Sun, 26 Jan 2020 21:03:15 -0700, David Ahern wrote:

On 1/26/20 3:11 PM, Jakub Kicinski wrote:

quoted

I looked through the commit message and the cover letter again, and you
never explain why you need the egress hook. Could you please clarify
your needs?   

XDP is about efficient network processing - ie., bypassing the Linux
stack when it does not make sense for the person deploying some
solution. XDP right now is Rx centric.

Network hardware is also "Rx centric" and somehow it works..

I want to run an ebpf program in the Tx path of the NIC regardless of
how the packet arrived at the device -- as an skb or an xdp_frame. There
are options for running programs on skb-based packets (e.g., tc). There
are *zero* options for manipulating/controlling/denying xdp_frames -
e.g., one REDIRECTED from an ingress device.

Okay - so no precise use case.  You can run the same program at the 
end of whatever is doing the redirect (especially with Alexei's work 
on linking) and from cls_bpf 🤷‍♂️

I'm sure all driver authors can't wait to plough through their TX paths
:/