Re: [PATCH bpf-next v3 10/21] net: bpf: add netlink and ipv6_route bpf_iter targets

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Yonghong Song <yhs@fb.com>
Cc: Andrii Nakryiko <andriin@fb.com>, bpf <bpf@vger.kernel.org>,
	Martin KaFai Lau <kafai@fb.com>,
	Networking <netdev@vger.kernel.org>,
	Alexei Starovoitov <ast@fb.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH bpf-next v3 10/21] net: bpf: add netlink and ipv6_route bpf_iter targets
Date: Fri, 8 May 2020 12:17:15 -0700	[thread overview]
Message-ID: <CAEf4BzYvwCaG9sTFM-mJXRF-BosuRRe+URZpVUvrke-nXABivA@mail.gmail.com> (raw)
In-Reply-To: <20200507053926.1543403-1-yhs@fb.com>

On Wed, May 6, 2020 at 10:40 PM Yonghong Song <yhs@fb.com> wrote:
>
> This patch added netlink and ipv6_route targets, using
> the same seq_ops (except show() and minor changes for stop())
> for /proc/net/{netlink,ipv6_route}.
>
> The net namespace for these targets are the current net
> namespace at file open stage, similar to
> /proc/net/{netlink,ipv6_route} reference counting
> the net namespace at seq_file open stage.
>
> Since module is not supported for now, ipv6_route is
> supported only if the IPV6 is built-in, i.e., not compiled
> as a module. The restriction can be lifted once module
> is properly supported for bpf_iter.
>
> Signed-off-by: Yonghong Song <yhs@fb.com>
> ---

Looks correct.

Acked-by: Andrii Nakryiko <andriin@fb.com>

>  fs/proc/proc_net.c       | 19 +++++++++
>  include/linux/proc_fs.h  |  3 ++
>  net/ipv6/ip6_fib.c       | 65 +++++++++++++++++++++++++++++-
>  net/ipv6/route.c         | 37 +++++++++++++++++
>  net/netlink/af_netlink.c | 87 +++++++++++++++++++++++++++++++++++++++-
>  5 files changed, 207 insertions(+), 4 deletions(-)
>

[...]

> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 3912aac7854d..25f6d3e619d0 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -6393,6 +6393,30 @@ void __init ip6_route_init_special_entries(void)
>    #endif
>  }
>
> +#if IS_BUILTIN(CONFIG_IPV6)
> +#if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_PROC_FS)
> +DEFINE_BPF_ITER_FUNC(ipv6_route, struct bpf_iter_meta *meta, struct fib6_info *rt)
> +
> +static int __init bpf_iter_register(void)
> +{
> +       struct bpf_iter_reg reg_info = {
> +               .target                 = "ipv6_route",
> +               .seq_ops                = &ipv6_route_seq_ops,
> +               .init_seq_private       = bpf_iter_init_seq_net,
> +               .fini_seq_private       = bpf_iter_fini_seq_net,
> +               .seq_priv_size          = sizeof(struct ipv6_route_iter),
> +       };
> +
> +       return bpf_iter_reg_target(&reg_info);
> +}
> +
> +static void bpf_iter_unregister(void)
> +{
> +       bpf_iter_unreg_target("ipv6_route");

Nit. This string duplication is unfortunate. If bpf_iter_unreg_target
took same `struct bpf_iter_ret *` as bpf_iter_reg_target(), it would
be symmetrical and not dependent on magic strings anymore. That
reg_info struct would just be static const struct global variable
passed to both register/unregister.

> +}
> +#endif
> +#endif
> +

[...]