netdev - Re: [PATCH v3 bpf-next 2/4] bpf: add layer 2 encap support to bpf_skb_adjust

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Date:   Thu, 11 Apr 2019 23:24:55 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     Alan Maguire <alan.maguire@...cle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        David Miller <davem@...emloft.net>,
        Shuah Khan <shuah@...nel.org>, Martin KaFai Lau <kafai@...com>,
        songliubraving@...com, yhs@...com, quentin.monnet@...ronome.com,
        John Fastabend <john.fastabend@...il.com>, rdna@...com,
        linux-kselftest@...r.kernel.org,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH v3 bpf-next 2/4] bpf: add layer 2 encap support to
 bpf_skb_adjust_room

On 04/11/2019 11:18 PM, Willem de Bruijn wrote:
[...]
>>> diff --git a/net/core/filter.c b/net/core/filter.c
>>> index 22eb2ed..a1654ef62 100644
>>> --- a/net/core/filter.c
>>> +++ b/net/core/filter.c
>>> @@ -2969,11 +2969,14 @@ static u32 bpf_skb_net_base_len(const struct sk_buff *skb)
>>>  #define BPF_F_ADJ_ROOM_MASK          (BPF_F_ADJ_ROOM_FIXED_GSO | \
>>>                                        BPF_F_ADJ_ROOM_ENCAP_L3_MASK | \
>>>                                        BPF_F_ADJ_ROOM_ENCAP_L4_GRE | \
>>> -                                      BPF_F_ADJ_ROOM_ENCAP_L4_UDP)
>>> +                                      BPF_F_ADJ_ROOM_ENCAP_L4_UDP | \
>>> +                                      BPF_F_ADJ_ROOM_ENCAP_L2( \
>>> +                                       BPF_ADJ_ROOM_ENCAP_L2_MASK))
>>>
>>>  static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
>>>                           u64 flags)
>>>  {
>>
>> One thing that it seems missing in this but also in Willem's earlier set
>> is that we reject these flags in bpf_skb_net_shrink(). Both are called from
>> bpf_skb_adjust_room(), so if we don't support decap yet we should reject
>> such flags so we can extend in future. Could you or Willem send a follow-up?
> 
> Indeed. Thanks for bringing that up, Daniel. I only thought of that
> after submitting the original patchset, too. Will send a patch.

Great, thanks, appreciated! :)