I really appreciate that you are working on adding this helper.
Some comments below.
On Fri, 31 Jul 2020 13:44:20 +0900
Yoshiki Komachi <komachi.yoshiki@xxxxxxxxx> wrote:
> diff --git a/samples/bpf/xdp_bridge_kern.c b/samples/bpf/xdp_bridge_kern.c
> new file mode 100644
> index 000000000000..00f802503199
> --- /dev/null
> +++ b/samples/bpf/xdp_bridge_kern.c
> @@ -0,0 +1,129 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2020 NTT Corp. All Rights Reserved.
> + *
[...]
> +
> +struct {
> + __uint(type, BPF_MAP_TYPE_DEVMAP_HASH);
> + __uint(key_size, sizeof(int));
> + __uint(value_size, sizeof(int));
> + __uint(max_entries, 64);
> +} xdp_tx_ports SEC(".maps");
> +
> +static __always_inline int xdp_bridge_proto(struct xdp_md *ctx, u16 br_vlan_proto)
> +{
> + void *data_end = (void *)(long)ctx->data_end;
> + void *data = (void *)(long)ctx->data;
> + struct bpf_fdb_lookup fdb_lookup_params;
> + struct vlan_hdr *vlan_hdr = NULL;
> + struct ethhdr *eth = data;
> + u16 h_proto;
> + u64 nh_off;
> + int rc;
> +
> + nh_off = sizeof(*eth);
> + if (data + nh_off > data_end)
> + return XDP_DROP;
> +
> + __builtin_memset(&fdb_lookup_params, 0, sizeof(fdb_lookup_params));
> +
> + h_proto = eth->h_proto;
> +
> + if (unlikely(ntohs(h_proto) < ETH_P_802_3_MIN))
> + return XDP_PASS;
> +
> + /* Handle VLAN tagged packet */
> + if (h_proto == br_vlan_proto) {
> + vlan_hdr = (void *)eth + nh_off;
> + nh_off += sizeof(*vlan_hdr);
> + if ((void *)eth + nh_off > data_end)
> + return XDP_PASS;
> +
> + fdb_lookup_params.vlan_id = ntohs(vlan_hdr->h_vlan_TCI) &
> + VLAN_VID_MASK;
> + }
> +
> + /* FIXME: Although Linux bridge provides us with vlan filtering (contains
> + * PVID) at ingress, the feature is currently unsupported in this XDP program.
> + *
> + * Two ideas to realize the vlan filtering are below:
> + * 1. usespace daemon monitors bridge vlan events and notifies XDP programs
^^
Typo: usespace -> userspace
> + * of them through BPF maps
> + * 2. introduce another bpf helper to retrieve bridge vlan information
The comment appears two times time this file.
> + *
> + *
> + * FIXME: After the vlan filtering, learning feature is required here, but
> + * it is currently unsupported as well. If another bpf helper for learning
> + * is accepted, the processing could be implemented in the future.
> + */
> +
> + memcpy(&fdb_lookup_params.addr, eth->h_dest, ETH_ALEN);
> +
> + /* Note: This program definitely takes ifindex of ingress interface as
> + * a bridge port. Linux networking devices can be stacked and physical
> + * interfaces are not necessarily slaves of bridges (e.g., bonding or
> + * vlan devices can be slaves of bridges), but stacked bridge ports are
> + * currently unsupported in this program. In such cases, XDP programs
> + * should be attached to a lower device in order to process packets with
> + * higher speed. Then, a new bpf helper to find upper devices will be
> + * required here in the future because they will be registered on FDB
> + * in the kernel.
> + */
> + fdb_lookup_params.ifindex = ctx->ingress_ifindex;
> +
> + rc = bpf_fdb_lookup(ctx, &fdb_lookup_params, sizeof(fdb_lookup_params), 0);
> + if (rc != BPF_FDB_LKUP_RET_SUCCESS) {
> + /* In cases of flooding, XDP_PASS will be returned here */
> + return XDP_PASS;
> + }
> +
> + /* FIXME: Although Linux bridge provides us with vlan filtering (contains
> + * untagged policy) at egress as well, the feature is currently unsupported
> + * in this XDP program.
> + *
> + * Two ideas to realize the vlan filtering are below:
> + * 1. usespace daemon monitors bridge vlan events and notifies XDP programs
> + * of them through BPF maps
> + * 2. introduce another bpf helper to retrieve bridge vlan information
> + */
(2nd time the comment appears)
> +
A comment about below bpf_redirect_map() would be good. Explaining
that we depend on fallback behavior, to let normal bridge code handle
other cases (e.g. flood/broadcast). And also that if lookup fails,
XDP_PASS/fallback also happens.
> + return bpf_redirect_map(&xdp_tx_ports, fdb_lookup_params.ifindex, XDP_PASS);
> +}
> +
> +SEC("xdp_bridge")
> +int xdp_bridge_prog(struct xdp_md *ctx)
> +{
> + return xdp_bridge_proto(ctx, 0);
> +}
> +
> +SEC("xdp_8021q_bridge")
> +int xdp_8021q_bridge_prog(struct xdp_md *ctx)
> +{
> + return xdp_bridge_proto(ctx, htons(ETH_P_8021Q));
> +}
> +
> +SEC("xdp_8021ad_bridge")
> +int xdp_8021ad_bridge_prog(struct xdp_md *ctx)
> +{
> + return xdp_bridge_proto(ctx, htons(ETH_P_8021AD));
> +}
> +
> +char _license[] SEC("license") = "GPL";
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
