linux-kernel - Re: [PATCH bpf-next 1/2] bpf: Expose bpf_get_socket

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Date:   Fri, 27 Nov 2020 00:08:44 -0800
From:   Yonghong Song <yhs@...com>
To:     Florent Revest <revest@...omium.org>, <bpf@...r.kernel.org>
CC:     <ast@...nel.org>, <daniel@...earbox.net>, <andrii@...nel.org>,
        <kpsingh@...omium.org>, <revest@...gle.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next 1/2] bpf: Expose bpf_get_socket_cookie to tracing
 programs



On 11/26/20 9:02 AM, Florent Revest wrote:
> This creates a new helper proto because the existing
> bpf_get_socket_cookie_sock_proto has a ARG_PTR_TO_CTX argument and only
> works for BPF programs where the context is a sock.
> 
> This helper could also be useful to other BPF program types such as LSM.
> 
> Signed-off-by: Florent Revest <revest@...gle.com>
> ---
>   kernel/trace/bpf_trace.c | 4 ++++
>   net/core/filter.c        | 7 +++++++
>   2 files changed, 11 insertions(+)
> 
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index d255bc9b2bfa..14ad96579813 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1725,6 +1725,8 @@ raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>   	}
>   }
>   
> +extern const struct bpf_func_proto bpf_get_socket_cookie_sock_tracing_proto;
> +
>   const struct bpf_func_proto *
>   tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>   {
> @@ -1748,6 +1750,8 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>   		return &bpf_sk_storage_get_tracing_proto;
>   	case BPF_FUNC_sk_storage_delete:
>   		return &bpf_sk_storage_delete_tracing_proto;
> +	case BPF_FUNC_get_socket_cookie:
> +		return &bpf_get_socket_cookie_sock_tracing_proto;
>   #endif
>   	case BPF_FUNC_seq_printf:
>   		return prog->expected_attach_type == BPF_TRACE_ITER ?
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 2ca5eecebacf..177c4e5e529d 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -4631,6 +4631,13 @@ static const struct bpf_func_proto bpf_get_socket_cookie_sock_proto = {
>   	.arg1_type	= ARG_PTR_TO_CTX,
>   };
>   
> +const struct bpf_func_proto bpf_get_socket_cookie_sock_tracing_proto = {
> +	.func		= bpf_get_socket_cookie_sock,
> +	.gpl_only	= false,
> +	.ret_type	= RET_INTEGER,
> +	.arg1_type      = ARG_PTR_TO_BTF_ID_SOCK_COMMON,
> +};

This seems correct to me. Could you add another helper description in 
uapi bpf.h? Currently we already have:
   u64 bpf_get_socket_cookie(struct sk_buff *skb)
   u64 bpf_get_socket_cookie(struct bpf_sock_addr *ctx)
   u64 bpf_get_socket_cookie(struct bpf_sock_ops *ctx)

The btf-id based helper will be something like below
   u64 bpf_get_socket_cookie(void *sk)


> +
>   BPF_CALL_1(bpf_get_socket_cookie_sock_ops, struct bpf_sock_ops_kern *, ctx)
>   {
>   	return __sock_gen_cookie(ctx->sk);
>