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

[Vadim Fedorenko <vadim.fedorenko@linux.dev>]

On 27/10/2023 02:35, Jakub Kicinski wrote:
> On Fri, 27 Oct 2023 00:29:29 +0100 Vadim Fedorenko wrote:
>>> Does anything prevent them from being used simultaneously
>>> by difference CPUs?
>>
>> The algorithm configuration and the key can be used by different CPUs
>> simultaneously
> 
> Makes sense, got confused ctx vs req. You allocate req on the fly.
> 
>>>> +	case BPF_DYNPTR_TYPE_SKB:
>>>> +		return skb_pointer_if_linear(ptr->data, ptr->offset, __bpf_dynptr_size(ptr));
>>>
>>> dynptr takes care of checking if skb can be written to?
>>
>> dynptr is used to take care of size checking, but this particular part is used
>> to provide plain buffer from skb. I'm really sure if we can (or should) encrypt
>> or decrypt in-place, so API now assumes that src and dst are different buffers.
> 
> Not sure this answers my question. What I'm asking is basically whether
> for destination we need to call __bpf_dynptr_is_rdonly() or something
> already checks that.

Well, I actually went to simpler implementation. As it's only needed for
dst buffer, move __bpf_dynptr_is_rdonly to helpers and use it to check
dst only and break earlier in case of error. If there will be other
customers of __bpf_dynptr_data_ptr helper, I'll implement it other way.