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 20:27:47 +0900
From:   Yoshiki Komachi <komachi.yoshiki@...il.com>
To:     David Ahern <dsahern@...il.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


> 2020/08/01 2:15、David Ahern <dsahern@...il.com>のメール:
> 
> On 7/30/20 10:44 PM, Yoshiki Komachi wrote:
>> 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
>> @@ -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;
> 
> I need to look at the details more closely, but on first reading 2
> things caught me eye:
> 1. you need to make sure flags is 0 since there are no supported flags
> at the moment, and

Thanks for your initial comments!

I will make sure whether this flag is required or not.

>> +
>> +	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);
> 
> 2. this needs to be done via netdev ops to avoid referencing bridge code
> which can be compiled as a module. I suspect the build robots will id
> this part soon.

I guess that no build errors will occur because the API is allowed when
CONFIG_BRIDGE is enabled.

I successfully build my kernel applying this patch, and I don’t receive any
messages from build robots for now.

Thanks & Best regards,


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