netdev - Re: [Patch bpf-next v4 1/5] bpf: clean up sockmap related Kconfigs

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Date:   Fri, 19 Feb 2021 19:25:22 +0100
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        duanxiongchun@...edance.com, wangdongdong.6@...edance.com,
        jiang.wang@...edance.com, Cong Wang <cong.wang@...edance.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Lorenz Bauer <lmb@...udflare.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [Patch bpf-next v4 1/5] bpf: clean up sockmap related Kconfigs

On Tue, Feb 16, 2021 at 07:42 AM CET, Cong Wang wrote:
> From: Cong Wang <cong.wang@...edance.com>
>
> As suggested by John, clean up sockmap related Kconfigs:
>
> Reduce the scope of CONFIG_BPF_STREAM_PARSER down to TCP stream
> parser, to reflect its name.
>
> Make the rest sockmap code simply depend on CONFIG_BPF_SYSCALL.
> And leave CONFIG_NET_SOCK_MSG untouched, as it is used by
> non-sockmap cases.
>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> Cc: Jakub Sitnicki <jakub@...udflare.com>
> Reviewed-by: Lorenz Bauer <lmb@...udflare.com>
> Acked-by: John Fastabend <john.fastabend@...il.com>
> Signed-off-by: Cong Wang <cong.wang@...edance.com>
> ---

Sorry for the delay. There's a lot happening here. Took me a while to
dig through it.

I have a couple of nit-picks, which easily can be addressed as
follow-ups, and one comment.

sock_map_prog_update and sk_psock_done_strp are only used in
net/core/sock_map.c and can be static.

[...]

> diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
> index bc7d2a586e18..b2c4865eb39b 100644
> --- a/net/ipv4/tcp_bpf.c
> +++ b/net/ipv4/tcp_bpf.c
> @@ -229,7 +229,6 @@ int tcp_bpf_sendmsg_redir(struct sock *sk, struct sk_msg *msg,
>  }
>  EXPORT_SYMBOL_GPL(tcp_bpf_sendmsg_redir);
>
> -#ifdef CONFIG_BPF_STREAM_PARSER
>  static bool tcp_bpf_stream_read(const struct sock *sk)
>  {
>  	struct sk_psock *psock;
> @@ -561,8 +560,10 @@ static void tcp_bpf_rebuild_protos(struct proto prot[TCP_BPF_NUM_CFGS],
>  				   struct proto *base)
>  {
>  	prot[TCP_BPF_BASE]			= *base;
> +#if defined(CONFIG_BPF_SYSCALL)
>  	prot[TCP_BPF_BASE].unhash		= sock_map_unhash;
>  	prot[TCP_BPF_BASE].close		= sock_map_close;
> +#endif
>  	prot[TCP_BPF_BASE].recvmsg		= tcp_bpf_recvmsg;
>  	prot[TCP_BPF_BASE].stream_memory_read	= tcp_bpf_stream_read;
>
> @@ -629,4 +630,3 @@ void tcp_bpf_clone(const struct sock *sk, struct sock *newsk)
>  	if (prot == &tcp_bpf_prots[family][TCP_BPF_BASE])
>  		newsk->sk_prot = sk->sk_prot_creator;
>  }
> -#endif /* CONFIG_BPF_STREAM_PARSER */

net/core/sock_map.o now is built only when CONFIG_BPF_SYSCALL is set.
While tcp_bpf_get_proto is only called from net/core/sock_map.o.

Seems there is no sense in compiling tcp_bpf_get_proto, and everything
it depends on which was enclosed by CONFIG_BPF_STREAM_PARSER check, when
CONFIG_BPF_SYSCALL is unset.

> diff --git a/net/ipv4/udp_bpf.c b/net/ipv4/udp_bpf.c
> index 7a94791efc1a..e635ccc175ca 100644
> --- a/net/ipv4/udp_bpf.c
> +++ b/net/ipv4/udp_bpf.c
> @@ -18,8 +18,10 @@ static struct proto udp_bpf_prots[UDP_BPF_NUM_PROTS];
>  static void udp_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
>  {
>  	*prot        = *base;
> +#if defined(CONFIG_BPF_SYSCALL)
>  	prot->unhash = sock_map_unhash;
>  	prot->close  = sock_map_close;
> +#endif
>  }
>
>  static void udp_bpf_check_v6_needs_rebuild(struct proto *ops)

Same situation here but for udp_bpf_get_proto.