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Message-ID: <9420fbc2-3139-f23e-fb6b-e3d28b9bee5f@iogearbox.net>
Date: Fri, 31 Jul 2020 23:12:27 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: Yoshiki Komachi <komachi.yoshiki@...il.com>,
"David S. Miller" <davem@...emloft.net>,
Alexei Starovoitov <ast@...nel.org>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
Jakub Kicinski <kuba@...nel.org>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
Andrii Nakryiko <andriin@...com>,
KP Singh <kpsingh@...omium.org>,
Roopa Prabhu <roopa@...ulusnetworks.com>,
Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
David Ahern <dsahern@...nel.org>
Cc: netdev@...r.kernel.org, bridge@...ts.linux-foundation.org,
bpf@...r.kernel.org
Subject: Re: [RFC PATCH bpf-next 2/3] bpf: Add helper to do forwarding lookups
in kernel FDB table
On 7/31/20 6:44 AM, Yoshiki Komachi wrote:
> This patch adds a new bpf helper to access FDB in the kernel tables
> from XDP programs. The helper enables us to find the destination port
> of master bridge in XDP layer with high speed. If an entry in the
> tables is successfully found, egress device index will be returned.
>
> In cases of failure, packets will be dropped or forwarded to upper
> networking stack in the kernel by XDP programs. Multicast and broadcast
> packets are currently not supported. Thus, these will need to be
> passed to upper layer on the basis of XDP_PASS action.
>
> The API uses destination MAC and VLAN ID as keys, so XDP programs
> need to extract these from forwarded packets.
>
> Signed-off-by: Yoshiki Komachi <komachi.yoshiki@...il.com>
Few initial comments below:
> ---
> include/uapi/linux/bpf.h | 28 +++++++++++++++++++++
> net/core/filter.c | 45 ++++++++++++++++++++++++++++++++++
> scripts/bpf_helpers_doc.py | 1 +
> tools/include/uapi/linux/bpf.h | 28 +++++++++++++++++++++
> 4 files changed, 102 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 54d0c886e3ba..f2e729dd1721 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -2149,6 +2149,22 @@ union bpf_attr {
> * * > 0 one of **BPF_FIB_LKUP_RET_** codes explaining why the
> * packet is not forwarded or needs assist from full stack
> *
> + * long bpf_fdb_lookup(void *ctx, struct bpf_fdb_lookup *params, int plen, u32 flags)
> + * Description
> + * Do FDB lookup in kernel tables using parameters in *params*.
> + * If lookup is successful (ie., FDB lookup finds a destination entry),
> + * ifindex is set to the egress device index from the FDB lookup.
> + * Both multicast and broadcast packets are currently unsupported
> + * in XDP layer.
> + *
> + * *plen* argument is the size of the passed **struct bpf_fdb_lookup**.
> + * *ctx* is only **struct xdp_md** for XDP programs.
> + *
> + * Return
> + * * < 0 if any input argument is invalid
> + * * 0 on success (destination port is found)
> + * * > 0 on failure (there is no entry)
> + *
> * long bpf_sock_hash_update(struct bpf_sock_ops *skops, struct bpf_map *map, void *key, u64 flags)
> * Description
> * Add an entry to, or update a sockhash *map* referencing sockets.
> @@ -3449,6 +3465,7 @@ union bpf_attr {
> FN(get_stack), \
> FN(skb_load_bytes_relative), \
> FN(fib_lookup), \
> + FN(fdb_lookup), \
This breaks UAPI. Needs to be added to the very end of the list.
> FN(sock_hash_update), \
> FN(msg_redirect_hash), \
> FN(sk_redirect_hash), \
> @@ -4328,6 +4345,17 @@ struct bpf_fib_lookup {
> __u8 dmac[6]; /* ETH_ALEN */
> };
>
> +enum {
> + BPF_FDB_LKUP_RET_SUCCESS, /* lookup successful */
> + BPF_FDB_LKUP_RET_NOENT, /* entry is not found */
> +};
> +
> +struct bpf_fdb_lookup {
> + unsigned char addr[6]; /* ETH_ALEN */
> + __u16 vlan_id;
> + __u32 ifindex;
> +};
> +
> enum bpf_task_fd_type {
> BPF_FD_TYPE_RAW_TRACEPOINT, /* tp name */
> BPF_FD_TYPE_TRACEPOINT, /* tp name */
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 654c346b7d91..68800d1b8cd5 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -45,6 +45,7 @@
> #include <linux/filter.h>
> #include <linux/ratelimit.h>
> #include <linux/seccomp.h>
> +#include <linux/if_bridge.h>
> #include <linux/if_vlan.h>
> #include <linux/bpf.h>
> #include <linux/btf.h>
> @@ -5084,6 +5085,46 @@ static const struct bpf_func_proto bpf_skb_fib_lookup_proto = {
> .arg4_type = ARG_ANYTHING,
> };
>
> +#if IS_ENABLED(CONFIG_BRIDGE)
> +BPF_CALL_4(bpf_xdp_fdb_lookup, struct xdp_buff *, ctx,
> + struct bpf_fdb_lookup *, params, int, plen, u32, flags)
> +{
> + struct net_device *src, *dst;
> + struct net *net;
> +
> + if (plen < sizeof(*params))
> + return -EINVAL;
Given flags are not used, this needs to reject anything invalid otherwise
you're not able to extend it in future.
> + net = dev_net(ctx->rxq->dev);
> +
> + if (is_multicast_ether_addr(params->addr) ||
> + is_broadcast_ether_addr(params->addr))
> + return BPF_FDB_LKUP_RET_NOENT;
> +
> + src = dev_get_by_index_rcu(net, params->ifindex);
> + if (unlikely(!src))
> + return -ENODEV;
> +
> + dst = br_fdb_find_port_xdp(src, params->addr, params->vlan_id);
> + if (dst) {
> + params->ifindex = dst->ifindex;
> + return BPF_FDB_LKUP_RET_SUCCESS;
> + }
Currently the helper description says nothing that this is /only/ limited to
bridges. I think it would be better to also name the helper bpf_br_fdb_lookup()
as well if so to avoid any confusion.
> + return BPF_FDB_LKUP_RET_NOENT;
> +}
> +
> +static const struct bpf_func_proto bpf_xdp_fdb_lookup_proto = {
> + .func = bpf_xdp_fdb_lookup,
> + .gpl_only = true,
> + .ret_type = RET_INTEGER,
> + .arg1_type = ARG_PTR_TO_CTX,
> + .arg2_type = ARG_PTR_TO_MEM,
> + .arg3_type = ARG_CONST_SIZE,
> + .arg4_type = ARG_ANYTHING,
> +};
> +#endif
This should also have a tc pendant (similar as done in routing lookup helper)
in case native XDP is not available. This will be useful for those that have
the same code compilable for both tc/XDP.
> #if IS_ENABLED(CONFIG_IPV6_SEG6_BPF)
> static int bpf_push_seg6_encap(struct sk_buff *skb, u32 type, void *hdr, u32 len)
> {
> @@ -6477,6 +6518,10 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> return &bpf_xdp_adjust_tail_proto;
> case BPF_FUNC_fib_lookup:
> return &bpf_xdp_fib_lookup_proto;
> +#if IS_ENABLED(CONFIG_BRIDGE)
> + case BPF_FUNC_fdb_lookup:
> + return &bpf_xdp_fdb_lookup_proto;
> +#endif
> #ifdef CONFIG_INET
> case BPF_FUNC_sk_lookup_udp:
> return &bpf_xdp_sk_lookup_udp_proto;
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