netdev - Re: [PATCH] Support for nlattr and nested_nlattr attribute search in EBPF filter

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Message-ID: <a7d6f51f-8c5c-9242-97a1-8fdea9fdbb7b@iogearbox.net>
Date:   Thu, 23 Jan 2020 16:57:39 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Kalimuthu Velappan <kalimuthu.velappan@...adcom.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Stanislav Fomichev <sdf@...gle.com>,
        Quentin Monnet <quentin.monnet@...ronome.com>,
        Andrey Ignatov <rdna@...com>,
        "open list:BPF (Safe dynamic programs and tools)" 
        <netdev@...r.kernel.org>,
        "open list:BPF (Safe dynamic programs and tools)" 
        <bpf@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Support for nlattr and nested_nlattr attribute search in
 EBPF filter

On 1/23/20 2:08 PM, Kalimuthu Velappan wrote:
> Added attribute search and nested attribute support in EBPF filter
> functionality.

Your commit describes what the code does, but not the rationale why it's needed
resp. the use-case you're trying to solve with this.

Also, why it cannot be resolved in native BPF?

> Signed-off-by: Kalimuthu Velappan <kalimuthu.velappan@...adcom.com>
> ---
>   include/uapi/linux/bpf.h       |  5 ++++-
>   net/core/filter.c              | 22 ++++++++++++++++++++++
>   tools/include/uapi/linux/bpf.h |  4 +++-
>   3 files changed, 29 insertions(+), 2 deletions(-)
> 
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index dbbcf0b..ac9794c 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -2938,7 +2938,10 @@ union bpf_attr {
>   	FN(probe_read_user),		\
>   	FN(probe_read_kernel),		\
>   	FN(probe_read_user_str),	\
> -	FN(probe_read_kernel_str),
> +	FN(probe_read_kernel_str),  \
> +	FN(skb_get_nlattr),     \
> +	FN(skb_get_nlattr_nest),
> +

This is not on latest bpf-next tree.

>   /* integer value in 'imm' field of BPF_CALL instruction selects which helper
>    * function eBPF program intends to call
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 538f6a7..56a87e1 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -2699,6 +2699,24 @@ static const struct bpf_func_proto bpf_set_hash_invalid_proto = {
>   	.arg1_type	= ARG_PTR_TO_CTX,
>   };
>   
> +static const struct bpf_func_proto bpf_skb_get_nlattr_proto = {
> +	.func		= bpf_skb_get_nlattr,
> +	.gpl_only	= false,
> +	.ret_type	= RET_INTEGER,
> +	.arg1_type	= ARG_PTR_TO_CTX,
> +	.arg2_type  = ARG_ANYTHING,
> +	.arg3_type  = ARG_ANYTHING,
> +};
> +
> +static const struct bpf_func_proto skb_get_nlattr_nest_proto = {
> +	.func		= bpf_skb_get_nlattr_nest,
> +	.gpl_only	= false,
> +	.ret_type	= RET_INTEGER,
> +	.arg1_type	= ARG_PTR_TO_CTX,
> +	.arg2_type  = ARG_ANYTHING,
> +	.arg3_type  = ARG_ANYTHING,
> +};
> +
>   BPF_CALL_2(bpf_set_hash, struct sk_buff *, skb, u32, hash)