netdev - Re: [PATCH bpf v4 2/2] bpf, sockmap: sk_prot needs inuse

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Message-ID: <87zguqr6yq.fsf@cloudflare.com>
Date:   Tue, 13 Jul 2021 09:47:09 +0200
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     ast@...nel.org, daniel@...earbox.net, andriin@...com,
        xiyou.wangcong@...il.com, bpf@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH bpf v4 2/2] bpf, sockmap: sk_prot needs inuse_idx set
 for proc stats

On Mon, Jul 12, 2021 at 09:55 PM CEST, John Fastabend wrote:
> Proc socket stats use sk_prot->inuse_idx value to record inuse sock stats.
> We currently do not set this correctly from sockmap side. The result is
> reading sock stats '/proc/net/sockstat' gives incorrect values. The
> socket counter is incremented correctly, but because we don't set the
> counter correctly when we replace sk_prot we may omit the decrement.
>
> To get the correct inuse_idx value move the core_initcall that initializes
> the tcp/udp proto handlers to late_initcall. This way it is initialized
> after TCP/UDP has the chance to assign the inuse_idx value from the
> register protocol handler.
>
> Suggested-by: Jakub Sitnicki <jakub@...udflare.com>
> Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface")
> Signed-off-by: John Fastabend <john.fastabend@...il.com>
> ---
>  net/ipv4/tcp_bpf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
> index f26916a62f25..d3e9386b493e 100644
> --- a/net/ipv4/tcp_bpf.c
> +++ b/net/ipv4/tcp_bpf.c
> @@ -503,7 +503,7 @@ static int __init tcp_bpf_v4_build_proto(void)
>  	tcp_bpf_rebuild_protos(tcp_bpf_prots[TCP_BPF_IPV4], &tcp_prot);
>  	return 0;
>  }
> -core_initcall(tcp_bpf_v4_build_proto);
> +late_initcall(tcp_bpf_v4_build_proto);
>
>  static int tcp_bpf_assert_proto_ops(struct proto *ops)
>  {

Respective change for udp_bpf is missing. I've posted it separately [1]
to save us an iteration. Hope you don't mind.

[1] https://lore.kernel.org/bpf/20210713074401.475209-1-jakub@cloudflare.com/