netdev - Re: [PATCH bpf-next v9 1/4] bpf: make common crypto API for TC/XDP programs

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Message-ID: <1a9240ba-7279-405d-be37-2cdacb518579@linux.dev>
Date: Mon, 22 Apr 2024 14:42:11 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
 Vadim Fedorenko <vadfed@...a.com>
Cc: Jakub Kicinski <kuba@...nel.org>, Andrii Nakryiko <andrii@...nel.org>,
 Alexei Starovoitov <ast@...nel.org>, Mykola Lysenko <mykolal@...com>,
 Herbert Xu <herbert@...dor.apana.org.au>, netdev@...r.kernel.org,
 linux-crypto@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next v9 1/4] bpf: make common crypto API for TC/XDP
 programs

On 4/19/24 5:24 PM, Vadim Fedorenko wrote:
>>> +/**
>>> + * bpf_crypto_ctx_create() - Create a mutable BPF crypto context.
>>> + *
>>> + * Allocates a crypto context that can be used, acquired, and released by
>>> + * a BPF program. The crypto context returned by this function must either
>>> + * be embedded in a map as a kptr, or freed with bpf_crypto_ctx_release().
>>> + * As crypto API functions use GFP_KERNEL allocations, this function can
>>> + * only be used in sleepable BPF programs.
>>> + *
>>> + * bpf_crypto_ctx_create() allocates memory for crypto context.
>>> + * It may return NULL if no memory is available.
>>> + * @params: pointer to struct bpf_crypto_params which contains all the
>>> + *          details needed to initialise crypto context.
>>> + * @err:    integer to store error code when NULL is returned.
>>> + */
>>> +__bpf_kfunc struct bpf_crypto_ctx *
>>> +bpf_crypto_ctx_create(const struct bpf_crypto_params *params, int *err)
>>
>> Add a "u32 params__sz" arg in case that the params struct will have addition.
>> Take a look at how opts__sz is checked in nf_conntrack_bpf.c.
>>
> 
> nf_conntrack uses hard-coded value, while xfrm code uses
> sizeof(struct bpf_xfrm_state_opts), which one is better?

If it is about the enum NF_BPF_CT_OPTS_SZ in nf_conntrack, I don't think it is a 
must have. bpf_core_type_size() should have the same effect to figure out the 
sizeof a struct in the running kernel.

afaik, sizeof() should do.