On Thu, 28 Dec 2017 21:19:26 -0800 Florian Fainelli <f.fainelli@xxxxxxxxx> wrote: > On December 28, 2017 8:34:24 PM PST, David Ahern <dsahern@xxxxxxxxx> wrote: > >On 12/28/17 9:37 PM, MD I. Islam wrote: > >> Hi > >> > >> Is XDP designed for implementing packet forwarding? Is there an > >> example of ipv4 forwarding the kernel? I don't find any example in > >> samples/bpf/ directory. > > > >samples/bpf/xdp_router_ipv4_*.c > > > >I have a POC on using new helpers that allow BPF programs to leverage > >kernel FIB and neighbor tables: > > https://github.com/dsahern/linux/commits/bpf/xdp-fwding-wip > > > >It shows a 400% increase in forwarding. A lot of issues need to be > >addressed, but it shows the intent. > > Nice! What would be uber cool is a NATP fastpath implemented using > XDP. Now that eBPF for ARM32 has landed it would enable a lot of > platforms. Yes, and we will get there. Once the OpenWRT/LEDE drivers actually implement XDP support in their drivers ;-). And more drivers support XDP_REDIRECT. That said, I would not recommend (re)implementing a NAT fastpath in XDP. It is doable, but will require an advanced eBPF prog that keep state (via maps) etc. For now I recommend falling back to Netfilter NAT for this purpose. Pure routing (no NAT) on a embedded device could be accelerated a lot with this approach. Instead of trying to re-implementing everything in XDP, I instead want you/people to think about how XDP can cooperate with and software-offload part of the Linux network stack. This is exactly what samples/bpf/xdp_router_ipv4_*.c and David Ahern is doing. Notice that these solutions leverage the existing IPv4 routing table for lookups, which means that all existing tools remains the same, while XDP can software-offload and accelerate the basic IPv4 routing step. It is important to limited the scope, IMHO advanced routing (e.g. with multiple route-tables, ToS match/routing etc) should fallback to the normal Linux network stack, and not be handled by XDP. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
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