netdev - Re: [PATCH v3 bpf-next 1/2] bpf: af_unix: Implement BPF iterator for UNIX domain socket.

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Date:   Thu, 5 Aug 2021 09:53:40 -0700
From:   Yonghong Song <yhs@...com>
To:     Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>
CC:     Benjamin Herrenschmidt <benh@...zon.com>,
        Kuniyuki Iwashima <kuni1840@...il.com>, <bpf@...r.kernel.org>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH v3 bpf-next 1/2] bpf: af_unix: Implement BPF iterator for
 UNIX domain socket.



On 8/4/21 12:08 AM, Kuniyuki Iwashima wrote:
> This patch implements the BPF iterator for the UNIX domain socket and
> exports some functions under GPL for the CONFIG_UNIX=m case.
> 
> Currently, the batch optimization introduced for the TCP iterator in the
> commit 04c7820b776f ("bpf: tcp: Bpf iter batching and lock_sock") is not
> applied.  It will require replacing the big lock for the hash table with
> small locks for each hash list not to block other processes.
> 
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.co.jp>
> ---
>   fs/proc/proc_net.c      |  2 +
>   include/linux/btf_ids.h |  3 +-
>   kernel/bpf/bpf_iter.c   |  3 ++
>   net/core/filter.c       |  1 +
>   net/unix/af_unix.c      | 93 +++++++++++++++++++++++++++++++++++++++++
>   5 files changed, 101 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
> index 15c2e55d2ed2..887a8102da9f 100644
> --- a/fs/proc/proc_net.c
> +++ b/fs/proc/proc_net.c
> @@ -91,6 +91,7 @@ int bpf_iter_init_seq_net(void *priv_data, struct bpf_iter_aux_info *aux)
>   #endif
>   	return 0;
>   }
> +EXPORT_SYMBOL_GPL(bpf_iter_init_seq_net);

bpf_iter does not support modules for now as it is implemented before 
module btf support. It needs some changes.
For example, currently bpf_iter only caches/uses the vmlinux btf_id
and module obj_id and module btf_id is not used.
One example is ipv6 and bpf_iter is guarded with IS_BUILTIN(CONFIG_IPV6).

So you could (1) add btf_iter support module btf in this patch set, or
(2). check IS_BUILTIN(CONFIG_UNIX). (2) might be easier and you can have
a subsequent patch set to add module support for bpf_iter. But it is
up to you.

>   
>   void bpf_iter_fini_seq_net(void *priv_data)
>   {
> @@ -100,6 +101,7 @@ void bpf_iter_fini_seq_net(void *priv_data)
>   	put_net(p->net);
>   #endif
[...]