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

[Daniel Borkmann]

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@xxxxxxxxxxxx>
> ---
>   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)