netdev - Re: [PATCH v3 4/6] net: filter: run cgroup eBPF ingress programs

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Date:   Tue, 30 Aug 2016 01:15:16 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Daniel Mack <daniel@...que.org>, htejun@...com, ast@...com
CC:     davem@...emloft.net, kafai@...com, fw@...len.de,
        pablo@...filter.org, harald@...hat.com, netdev@...r.kernel.org,
        sargun@...gun.me
Subject: Re: [PATCH v3 4/6] net: filter: run cgroup eBPF ingress programs

On 08/26/2016 09:58 PM, Daniel Mack wrote:
> If the cgroup associated with the receiving socket has an eBPF
> programs installed, run them from sk_filter_trim_cap().
>
> eBPF programs used in this context are expected to either return 1 to
> let the packet pass, or != 1 to drop them. The programs have access to
> the full skb, including the MAC headers.
>
> Note that cgroup_bpf_run_filter() is stubbed out as static inline nop
> for !CONFIG_CGROUP_BPF, and is otherwise guarded by a static key if
> the feature is unused.
>
> Signed-off-by: Daniel Mack <daniel@...que.org>
> ---
>   net/core/filter.c | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/net/core/filter.c b/net/core/filter.c
> index bc04e5c..163f75b 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -78,6 +78,11 @@ int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap)
>   	if (skb_pfmemalloc(skb) && !sock_flag(sk, SOCK_MEMALLOC))
>   		return -ENOMEM;
>
> +	err = cgroup_bpf_run_filter(sk, skb,
> +				    BPF_ATTACH_TYPE_CGROUP_INET_INGRESS);

Maybe just BPF_CGROUP_INET_{IN,E}GRESS (seems less cluttered, and we know
these were set via bpf(2) as attach_type anyway)?

> +	if (err)
> +		return err;
> +
>   	err = security_sock_rcv_skb(sk, skb);
>   	if (err)
>   		return err;
>