netdev - Re: [PATCH bpf-next v6 04/11] bpf: Support passing args to sock

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Date:   Wed, 24 Jan 2018 02:11:06 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Lawrence Brakmo <brakmo@...com>, netdev <netdev@...r.kernel.org>
Cc:     Kernel Team <kernel-team@...com>, Blake Matheny <bmatheny@...com>,
        Alexei Starovoitov <ast@...com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>
Subject: Re: [PATCH bpf-next v6 04/11] bpf: Support passing args to sock_ops
 bpf function

On 01/20/2018 02:45 AM, Lawrence Brakmo wrote:
> Adds support for passing up to 4 arguments to sock_ops bpf functions. It
> reusues the reply union, so the bpf_sock_ops structures are not
> increased in size.
> 
> Signed-off-by: Lawrence Brakmo <brakmo@...com>
> ---
>  include/linux/filter.h   |  1 +
>  include/net/tcp.h        | 64 ++++++++++++++++++++++++++++++++++++++++++++----
>  include/uapi/linux/bpf.h |  5 ++--
>  net/ipv4/tcp.c           |  2 +-
>  net/ipv4/tcp_nv.c        |  2 +-
>  net/ipv4/tcp_output.c    |  2 +-
>  6 files changed, 66 insertions(+), 10 deletions(-)
> 
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index daa5a67..20384c4 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -1003,6 +1003,7 @@ struct bpf_sock_ops_kern {
>  	struct	sock *sk;
>  	u32	op;
>  	union {
> +		u32 args[4];
>  		u32 reply;
>  		u32 replylong[4];
>  	};
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 108d16a..8e9111f 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -2005,7 +2005,7 @@ void tcp_cleanup_ulp(struct sock *sk);
>   * program loaded).
>   */
>  #ifdef CONFIG_BPF
> -static inline int tcp_call_bpf(struct sock *sk, int op)
> +static inline int tcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
>  {
>  	struct bpf_sock_ops_kern sock_ops;
>  	int ret;
> @@ -2018,6 +2018,8 @@ static inline int tcp_call_bpf(struct sock *sk, int op)
>  
>  	sock_ops.sk = sk;
>  	sock_ops.op = op;
> +	if (nargs > 0)
> +		memcpy(sock_ops.args, args, nargs*sizeof(u32));

Small nit given respin: nargs * sizeof(*args)

>  	ret = BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops);
>  	if (ret == 0)
> @@ -2026,18 +2028,70 @@ static inline int tcp_call_bpf(struct sock *sk, int op)
>  		ret = -1;
>  	return ret;
>  }
> +
> +static inline int tcp_call_bpf_1arg(struct sock *sk, int op, u32 arg)
> +{
> +	return tcp_call_bpf(sk, op, 1, &arg);
> +}
> +
> +static inline int tcp_call_bpf_2arg(struct sock *sk, int op, u32 arg1, u32 arg2)
> +{
> +	u32 args[2] = {arg1, arg2};
> +
> +	return tcp_call_bpf(sk, op, 2, args);
> +}
> +
> +static inline int tcp_call_bpf_3arg(struct sock *sk, int op, u32 arg1, u32 arg2,
> +				    u32 arg3)
> +{
> +	u32 args[3] = {arg1, arg2, arg3};
> +
> +	return tcp_call_bpf(sk, op, 3, args);
> +}
> +
> +static inline int tcp_call_bpf_4arg(struct sock *sk, int op, u32 arg1, u32 arg2,
> +				    u32 arg3, u32 arg4)
> +{
> +	u32 args[4] = {arg1, arg2, arg3, arg4};
> +
> +	return tcp_call_bpf(sk, op, 4, args);
> +}
> +
>  #else
> -static inline int tcp_call_bpf(struct sock *sk, int op)
> +static inline int tcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
>  {
>  	return -EPERM;
>  }
> +
> +static inline int tcp_call_bpf_1arg(struct sock *sk, int op, u32 arg)
> +{
> +	return -EPERM;
> +}
> +
> +static inline int tcp_call_bpf_2arg(struct sock *sk, int op, u32 arg1, u32 arg2)
> +{
> +	return -EPERM;
> +}
> +
> +static inline int tcp_call_bpf_3arg(struct sock *sk, int op, u32 arg1, u32 arg2,
> +	u32 arg3)

indent: arg3

> +{
> +	return -EPERM;
> +}
> +
> +static inline int tcp_call_bpf_4arg(struct sock *sk, int op, u32 arg1, u32 arg2,
> +				    u32 arg3, u32 arg4)
> +{
> +	return -EPERM;
> +}
> +
>  #endif

tcp_call_bpf_1arg() and tcp_call_bpf_4arg() unused for the time being?