netdev - Re: [RFC PATCH bpf-next 2/3] bpf: Add helper to do forwarding lookups in kernel FDB table

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Date:   Tue, 4 Aug 2020 17:44:17 +0900
From:   Yoshiki Komachi <komachi.yoshiki@...il.com>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        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>, 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


> 2020/07/31 20:52、Maciej Fijalkowski <maciej.fijalkowski@...el.com>のメール:
> 
> On Fri, Jul 31, 2020 at 01:44:19PM +0900, 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>
>> ---
>> 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/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;
>> +
>> +	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;
> 
> small nit: you could move that validation before dev_net() call.

Thanks for your quick response.
I will try to fix it in the next version.

Best regards,

>> +
>> +	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;
>> +	}
>> +
>> +	return BPF_FDB_LKUP_RET_NOENT;
>> +}

—
Yoshiki Komachi
komachi.yoshiki@...il.com