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Subject: Re: [PATCH bpf-next v3 1/2] bpf: add skcipher API support to TC/XDP
 programs
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To: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
 linux-crypto@vger.kernel.org, Jakub Kicinski <kuba@kernel.org>,
 Andrii Nakryiko <andrii@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
 Mykola Lysenko <mykolal@fb.com>, Vadim Fedorenko <vadfed@meta.com>,
 "David S. Miller" <davem@davemloft.net>,
 Herbert Xu <herbert@gondor.apana.org.au>
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 <dac97b74-5ff1-172b-9cd5-4cdcf07386ec@linux.dev>
 <91a6d5a7-7b18-48a2-9a74-7c00509467f8@linux.dev>
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From: Martin KaFai Lau <martin.lau@linux.dev>
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On 11/1/23 3:50 PM, Vadim Fedorenko wrote:
>>> +static void *__bpf_dynptr_data_ptr(const struct bpf_dynptr_kern *ptr)
>>> +{
>>> +    enum bpf_dynptr_type type;
>>> +
>>> +    if (!ptr->data)
>>> +        return NULL;
>>> +
>>> +    type = bpf_dynptr_get_type(ptr);
>>> +
>>> +    switch (type) {
>>> +    case BPF_DYNPTR_TYPE_LOCAL:
>>> +    case BPF_DYNPTR_TYPE_RINGBUF:
>>> +        return ptr->data + ptr->offset;
>>> +    case BPF_DYNPTR_TYPE_SKB:
>>> +        return skb_pointer_if_linear(ptr->data, ptr->offset, 
>>> __bpf_dynptr_size(ptr));
>>> +    case BPF_DYNPTR_TYPE_XDP:
>>> +    {
>>> +        void *xdp_ptr = bpf_xdp_pointer(ptr->data, ptr->offset, 
>>> __bpf_dynptr_size(ptr));
>>
>> I suspect what it is doing here (for skb and xdp in particular) is very 
>> similar to bpf_dynptr_slice. Please check if bpf_dynptr_slice(ptr, 0, NULL, 
>> sz) will work.
>>
> 
> Well, yes, it's simplified version of bpf_dynptr_slice. The problem is
> that bpf_dynptr_slice bpf_kfunc which cannot be used in another
> bpf_kfunc. Should I refactor the code to use it in both places? Like

Sorry, scrolled too fast in my earlier reply :(

I am not aware of this limitation. What error does it have?
The bpf_dynptr_slice_rdwr kfunc() is also calling the bpf_dynptr_slice() kfunc.

> create __bpf_dynptr_slice() which will be internal part of bpf_kfunc?