Re: [PATCH RFC 0/9] socket filtering using nf_tables
From: Alexei Starovoitov
Date: Sat Mar 15 2014 - 15:19:28 EST
On Sat, Mar 15, 2014 at 12:03 PM, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote:
> On Fri, Mar 14, 2014 at 09:04:50PM -0700, Alexei Starovoitov wrote:
> [...]
>> In the patches I sent, ebpf is _not_ exposed to the user.
>
> From your last patch: http://patchwork.ozlabs.org/patch/329713/
>
> diff --git a/include/uapi/linux/filter.h b/include/uapi/linux/filter.h
> index 8eb9ccaa5b48..4e98fe16ba88 100644
> --- a/include/uapi/linux/filter.h
> +++ b/include/uapi/linux/filter.h
> @@ -1,5 +1,6 @@
> /*
> * Linux Socket Filter Data Structures
> + * Extended BPF is Copyright (c) 2011-2014, PLUMgrid, http://plumgrid.com
> */
>
> #ifndef _UAPI__LINUX_FILTER_H__
> @@ -19,7 +20,7 @@
> * Try and keep these values and structures similar to BSD,
> * especially
> * the BPF code definitions which need to match so you can share
> * filters
> */
> -
> +
> struct sock_filter { /* Filter block */
> __u16 code; /* Actual filter code */
> __u8 jt; /* Jump true */
> @@ -27,6 +28,14 @@ struct sock_filter { /* Filter block */
> __u32 k; /* Generic multiuse field */
> };
>
> +struct sock_filter_ext {
> + __u8 code; /* opcode */
> + __u8 a_reg:4; /* dest register */
> + __u8 x_reg:4; /* source register */
> + __s16 off; /* signed offset */
> + __s32 imm; /* signed immediate constant */
> +};
> +
> struct sock_fprog { /* Required for SO_ATTACH_FILTER. */
> unsigned short len; /* Number of filter blocks */
> struct sock_filter __user *filter;
>
> That sock_filter_ext structure is exposed to userspace as well as many
> other new BPF_* macros that you have defined.
For the first few versions of the patchset they were in linux/bpf.h,
but then it was suggested to put them into uapi/linux/filter.h
to make the whole thing consistent with existing sock_filter structure.
So yes, uapi header is changed as:
include/uapi/linux/filter.h | 33 ++++++++++++++++++++++++++-------
1 file changed, 26 insertions(+), 7 deletions(-)
but there is no way to use these #define from user space at present.
As I said I think it's safe to expose it, because these defines won't change,
but if there is a concern I can move it back into linux/bpf.h
Thanks
Alexei
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