Re: Packet forwarding in XDP

[Anmol Panda <anmol07.visitor@xxxxxxxxxxxxxx>]

On 12.11.2017 17:30, Jesper Dangaard Brouer wrote:
> On Sun, 12 Nov 2017 14:27:25 +0530
> Anmol Panda <anmol07.visitor@xxxxxxxxxxxxxx> wrote:
>
> > Dear all,
> >      We are trying to write a program that receives a packet from a
> > client and is supposed to return the packet to the source. We tried to
> > swap the source and dest and send it using the XDP_TX action. But it
> > doesn't work.
> >
> >     We have compiled a new kernel and bound the NIC to xdp 
> > successfully.
> > After binding, the system stops responding to ping and other packet
> > generating scripts (like sendip). We are using kernel  4.13.12 (Ubuntu
> > 17.10) from the main linux kernel tree and binding with Intel I217-LM
> > NIC. This NIC is using e1000e driver. Can xdp / eBPF be used for this
> > NIC? Moreover, do we need to patch the driver for additional support?
>
> Not all drivers have "native' XDP support. See slide 11 of [1]
>
> [1]
> http://people.netfilter.org/hawk/presentations/driving-IT2017/driving-IT-2017_XDP_eBPF_technology_Jesper_Brouer.pdf
>
> There is something called "Generic" XDP (v4.12) for ease of
> development. It allow you to attach an XDP program any net_device. I
> call it --skb-mode in my sample programs. See [2]
>
> [2]
> https://prototype-kernel.readthedocs.io/en/latest/blogposts/xdp25_eval_generic_xdp_tx.html
>
> >      Our aim is to benchmark various forwarding applications (L2 , L3,
> > etc.) run using xdp. Please point to some code samples to achieve 
> > this.
> > We will be truly grateful.
>
> Kernel have directory: samples/bpf/
>
> I maintain some more example programs here:
>  
> https://github.com/netoptimizer/prototype-kernel/tree/master/kernel/samples/bpf
>
>
> Do notice that e1000e is only 1Gbit/s (which is very slow).  The normal
> Linux kernel can handle 1Gbit/s without any issues... I hope you are
> planning to use something faster, else it does not make sense to use 
> XDP.

Hello,
   Thank you Jesper for your quick response.
   We are trying to run the programs ~/linux-4.13.12/samples/bpf/ and we 
get the following error (also attached as a snapshot):

'
root@compute5:~/workspace/XDP/kernel/linux-4.13.12/samples/bpf# 
./tc_l2_redirect.sh
l2_to_ipip ingress: Note: 8 bytes struct bpf_elf_map fixup performed due 
to size mismatch!
No bpf syscall, kernel headers too old?
No bpf syscall, kernel headers too old?
Map object 'tun_iface' rejected: Function not implemented (38)!
 - Type:         2
 - Identifier:   0
 - Pinning:      2
 - Size key:     4
 - Size value:   4
 - Max elems:    1
 - Flags:        0

Error loading maps into kernel!
Error fetching ELF ancillary data!
'
    We are now using the Intel x520 dual port NICs (total 40 Gbps b/w). 
Please guide us regarding the error above.

Thanks,
Sincerely,