netdev - Re: [PATCH bpf-next v4 1/7] bpf: add bpf_skc_to_mptcp_sock

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Date:   Mon, 16 May 2022 18:07:30 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Geliang Tang <geliang.tang@...e.com>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org, ast@...nel.org,
        daniel@...earbox.net, andrii@...nel.org, mptcp@...ts.linux.dev,
        Nicolas Rybowski <nicolas.rybowski@...sares.net>,
        Matthieu Baerts <matthieu.baerts@...sares.net>
Subject: Re: [PATCH bpf-next v4 1/7] bpf: add bpf_skc_to_mptcp_sock_proto

On Fri, May 13, 2022 at 03:48:21PM -0700, Mat Martineau wrote:
[ ... ]

> diff --git a/include/net/mptcp.h b/include/net/mptcp.h
> index 8b1afd6f5cc4..2ba09de955c7 100644
> --- a/include/net/mptcp.h
> +++ b/include/net/mptcp.h
> @@ -284,4 +284,10 @@ static inline int mptcpv6_init(void) { return 0; }
>  static inline void mptcpv6_handle_mapped(struct sock *sk, bool mapped) { }
>  #endif
>  
> +#if defined(CONFIG_MPTCP) && defined(CONFIG_BPF_SYSCALL)
> +struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk);
Can this be inline ?

> +#else
> +static inline struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk) { return NULL; }
> +#endif
> +
>  #endif /* __NET_MPTCP_H */

[ ... ]

> diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c
> new file mode 100644
> index 000000000000..535602ba2582
> --- /dev/null
> +++ b/net/mptcp/bpf.c
> @@ -0,0 +1,22 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Multipath TCP
> + *
> + * Copyright (c) 2020, Tessares SA.
> + * Copyright (c) 2022, SUSE.
> + *
> + * Author: Nicolas Rybowski <nicolas.rybowski@...sares.net>
> + */
> +
> +#define pr_fmt(fmt) "MPTCP: " fmt
> +
> +#include <linux/bpf.h>
> +#include "protocol.h"
> +
> +struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk)
> +{
> +	if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP && sk_is_mptcp(sk))
> +		return mptcp_sk(mptcp_subflow_ctx(sk)->conn);
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL(bpf_mptcp_sock_from_subflow);
Is EXPORT_SYMBOL needed ?