On Fri, Jul 13, 2018 at 2:55 AM Paolo Abeni <pab...@redhat.com> wrote: > > When mirred is invoked from the ingress path, and it wants to redirect > the processed packet, it can now use the ACT_REDIRECT action, > filling the tcf_result accordingly. > > This avoids a skb_clone() in the TC S/W data path giving a ~10% > improvement in forwarding performances. Overall TC S/W performances > are now comparable to the kernel openswitch datapath.
Avoiding skb_clone() for redirection is cool, but why need to use skb_do_redirect() here? There is a subtle difference here: skb_do_redirect() calls __bpf_rx_skb() which calls dev_forward_skb(). while the current mirred action doesn't scrub packets when redirecting to ingress (from egress). Although I forget if it is intentionally. Also, skb->skb_iif is unset in skb_do_redirect() when redirecting to ingress, I recall we have to set it correctly for input routing. Probably yet another reason why we can't scrub it, unless my memory goes wrong. :) Thanks!
