netdev - Re: [PATCH bpf-next 3/4] bpf: Support socket lookup in CGROUP_SOCK

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Date:   Fri, 9 Nov 2018 17:24:27 +0000
From:   Martin Lau <kafai@...com>
To:     Andrey Ignatov <rdna@...com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "joe@...d.net.nz" <joe@...d.net.nz>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH bpf-next 3/4] bpf: Support socket lookup in
 CGROUP_SOCK_ADDR progs

On Thu, Nov 08, 2018 at 08:54:24AM -0800, Andrey Ignatov wrote:
> Make bpf_sk_lookup_tcp, bpf_sk_lookup_udp and bpf_sk_release helpers
> available in programs of type BPF_PROG_TYPE_CGROUP_SOCK_ADDR.
> 
> Such programs operate on sockets and have access to socket and struct
> sockaddr passed by user to system calls such as sys_bind, sys_connect,
> sys_sendmsg.
> 
> It's useful to be able to lookup other sockets from these programs.
> E.g. sys_connect may lookup IP:port endpoint and if there is a server
> socket bound to that endpoint ("server" can be defined by saddr & sport
> being zero), redirect client connection to it by rewriting IP:port in
> sockaddr passed to sys_connect.
> 
> Signed-off-by: Andrey Ignatov <rdna@...com>
> Acked-by: Alexei Starovoitov <ast@...nel.org>
> ---
>  net/core/filter.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index dc0f86a707b7..2e8575a34a1e 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -4971,6 +4971,51 @@ static const struct bpf_func_proto bpf_sk_release_proto = {
>  	.ret_type	= RET_INTEGER,
>  	.arg1_type	= ARG_PTR_TO_SOCKET,
>  };
> +
> +static unsigned long
> +bpf_sock_addr_sk_lookup(struct sock *sk, struct bpf_sock_tuple *tuple, u32 len,
> +			u8 proto, u64 netns_id, u64 flags)
Nit. This func looks unnecessary. as good as directly calling __bpf_sk_lookup().

Others LGTM.

> +{
> +	return __bpf_sk_lookup(NULL, tuple, len, proto, netns_id, sock_net(sk),
> +			       0, flags);
> +}
> +
> +BPF_CALL_5(bpf_sock_addr_sk_lookup_tcp, struct bpf_sock_addr_kern *, ctx,
> +	   struct bpf_sock_tuple *, tuple, u32, len, u64, netns_id, u64, flags)
> +{
> +	return bpf_sock_addr_sk_lookup(ctx->sk, tuple, len, IPPROTO_TCP,
> +				       netns_id, flags);
> +}
> +
> +static const struct bpf_func_proto bpf_sock_addr_sk_lookup_tcp_proto = {
> +	.func		= bpf_sock_addr_sk_lookup_tcp,
> +	.gpl_only	= false,
> +	.ret_type	= RET_PTR_TO_SOCKET_OR_NULL,
> +	.arg1_type	= ARG_PTR_TO_CTX,
> +	.arg2_type	= ARG_PTR_TO_MEM,
> +	.arg3_type	= ARG_CONST_SIZE,
> +	.arg4_type	= ARG_ANYTHING,
> +	.arg5_type	= ARG_ANYTHING,
> +};
> +
> +BPF_CALL_5(bpf_sock_addr_sk_lookup_udp, struct bpf_sock_addr_kern *, ctx,
> +	   struct bpf_sock_tuple *, tuple, u32, len, u64, netns_id, u64, flags)
> +{
> +	return bpf_sock_addr_sk_lookup(ctx->sk, tuple, len, IPPROTO_UDP,
> +				       netns_id, flags);
> +}
> +
> +static const struct bpf_func_proto bpf_sock_addr_sk_lookup_udp_proto = {
> +	.func		= bpf_sock_addr_sk_lookup_udp,
> +	.gpl_only	= false,
> +	.ret_type	= RET_PTR_TO_SOCKET_OR_NULL,
> +	.arg1_type	= ARG_PTR_TO_CTX,
> +	.arg2_type	= ARG_PTR_TO_MEM,
> +	.arg3_type	= ARG_CONST_SIZE,
> +	.arg4_type	= ARG_ANYTHING,
> +	.arg5_type	= ARG_ANYTHING,
> +};
> +
>  #endif /* CONFIG_INET */
>  
>  bool bpf_helper_changes_pkt_data(void *func)
> @@ -5077,6 +5122,14 @@ sock_addr_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>  		return &bpf_get_socket_cookie_sock_addr_proto;
>  	case BPF_FUNC_get_local_storage:
>  		return &bpf_get_local_storage_proto;
> +#ifdef CONFIG_INET
> +	case BPF_FUNC_sk_lookup_tcp:
> +		return &bpf_sock_addr_sk_lookup_tcp_proto;
> +	case BPF_FUNC_sk_lookup_udp:
> +		return &bpf_sock_addr_sk_lookup_udp_proto;
> +	case BPF_FUNC_sk_release:
> +		return &bpf_sk_release_proto;
> +#endif /* CONFIG_INET */
>  	default:
>  		return bpf_base_func_proto(func_id);
>  	}
> -- 
> 2.17.1
>