On 11/20/18 7:18 AM, Pavel Popa wrote: > Hi all, > > I've implemented a XDP forwarding program using the bpf_fib_lookup() > helper, and loaded it in the kernel as XDP driver mode (i.e. executed > at the virtio_net driver level). The only problem is that the > receiving virtio network interface seems to drop the XDP packet after > successfully executing my XDP program. > Kernel: 4.18.10 > > my_xdp_fwd_kern.c: > /* made sure this returns 0 (i.e. BPF_FIB_LKUP_RET_SUCCESS) */ > rc = bpf_fib_lookup(ctx, &fib_params, sizeof(fib_params), > BPF_FIB_LOOKUP_DIRECT); > /* made sure this returns 4 (i.e. XDP_REDIRECT) */ > rc = bpf_redirect_map(&dev_map, fib_params.ifindex, 0); > return rc; > > I checked that rc is indeed XDP_REDIRECT and that fib_params.ifindex > is the correct dev index from FIB lookup. > dev_map is setup by the userspace my_xdp_fwd_user.c component as follows: > for (i = 1; i < 64; i++) > bpf_map_update_elem(devmap_fd, &i, &i, BPF_ANY); > > I'm passing the following to the qemu cmd line for the 2 devices I > want to run XDP on (as stated here > https://marc.info/?l=xdp-newbies&m=149486931113651&w=2): > -device virtio-net-pci,mq=on,vectors=18,rx_queue_size=1024,tx_queue_size=512, > ... ,gso=off,guest_tso4=off,guest_tso6=off,guest_ecn=off,guest_ufo=off > \ > -device virtio-net-pci,mq=on,vectors=18,rx_queue_size=1024,tx_queue_size=512, > ... ,gso=off,guest_tso4=off,guest_tso6=off,guest_ecn=off,guest_ufo=off > \ > > In the guest enabling also the MultiQueue feature, as stated here > https://www.linux-kvm.org/page/Multiqueue#Enable_MQ_feature. > What I'm left with is debugging the virtio_net kernel module by adding > a bunch of printk() and see what happens, especially here > https://elixir.bootlin.com/linux/v4.18.10/source/drivers/net/virtio_net.c#L667. > > Am I doing something wrong here? What I'm missing? > I believe at this point you can drop the gso,tso,ufo and ecn args. I use virtio for development and these days start my VMs with only: ...,mq=on,guest_csum=off,... After that are you installing the xdp program on all interfaces that can be used for forwarding? ie., if it transmits a packet in XDP mode it needs the xdp program loaded. For example I use: xdp_fwd eth1 eth2 eth3 eth4 >From there: echo 1 > /sys/kernel/debug/tracing/events/xdp/enable cat /sys/kernel/debug/tracing/trace_pipe
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