netdev - Re: [PATCH bpf-next v3 1/2] bpf: add skcipher API support to TC/XDP programs

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Date: Thu, 2 Nov 2023 00:38:00 +0000
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org,
 linux-crypto@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
 Andrii Nakryiko <andrii@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
 Mykola Lysenko <mykolal@...com>, Vadim Fedorenko <vadfed@...a.com>
Subject: Re: [PATCH bpf-next v3 1/2] bpf: add skcipher API support to TC/XDP
 programs

On 01.11.2023 23:41, Martin KaFai Lau wrote:
> 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.
> 

Yeah, but they are in the same module. We do not declare prototypes of kfuncs in
linux/bpf.h and that's why we cannot use them outside of helpers.c.
The same problem was with bpf_dynptr_is_rdonly() I believe.

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