On Tue, 20 Nov 2018 16:47:19 +0100 Pavel Popa <pashinho1990@xxxxxxxxx> wrote: > Well, here's the output from the `ip link` cmd: > 3: eth3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 xdp qdisc mq state UP > link/ether 52:54:fc:47:e2:d3 brd ff:ff:ff:ff:ff:ff > prog/xdp id 1 tag 1cd982ef22273bda jited > 4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 xdp qdisc mq state UP > link/ether 52:54:55:d3:50:ee brd ff:ff:ff:ff:ff:ff > prog/xdp id 1 tag 1cd982ef22273bda jited > > As you can see, there's the XDP program ID 1 executing on them. > However, there's definitely something interesting happening when > bpf_fib_lookup() returns BPF_FIB_LKUP_RET_NO_NEIGH, for which my XDP > program just returns XDP_PASS while the following line gets printed in > kern.log: > eth3: bad gso: type: 164, size: 256 > > No idea what's wrong here. > Also, when bpf_fib_lookup() returns BPF_FIB_LKUP_RET_SUCCESS, for > which my XDP program executes bpf_redirect_map(&dev_map, > fib_params.ifindex, 0), the following gets printed in > > /sys/kernel/debug/tracing/trace_pipe: > xdp_redirect_map_err: prog_id=1 action=REDIRECT ifindex=3 > to_ifindex=0 err=-14 map_id=0 map_index=4 The err=-14 is -EFAULT. Notice "ifindex=3" but "to_ifindex=0", which is the problem. The "map_index=4" is correct, but "to_ifindex" does a lookup in the map for the net_device->ifindex stored in this map. It is fairly unlikely that you added device with ifindex=0 to map index 4, I presume? Then I was thinking, maybe the "map_index=4" doesn't contain anything, but reading the code, that will return err=-22 (#define EINVAL 22), which it not the case. Assuming that map_index=4 does contain a valid net_device. Following the code via __bpf_tx_xdp_map -> dev_map_enqueue, I simply cannot find an -EFAULT err return value. --Jesper > I feel this last one to be somewhat related to the comment here > https://elixir.bootlin.com/linux/v4.18.10/source/samples/bpf/xdp_fwd_kern.c#L107. > Is it correct? If so, what does this precisely mean? Is there any way > to get around with this? Because what I'm doing is simply using the > BPF_MAP_TYPE_DEVMAP with the bpf_redirect_map() helper to forward > packets between "XDP ports". > > Il giorno mar 20 nov 2018 alle ore 15:39 David Ahern > <dsahern@xxxxxxxxx> ha scritto: > > > > 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 > > -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
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