netdev - Re: [PATCH net-next 2/3] bpf: Add new cgroups prog type to enable sock modifications

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Date:   Wed, 26 Oct 2016 10:41:55 +0200
From:   Thomas Graf <tgraf@...g.ch>
To:     David Ahern <dsa@...ulusnetworks.com>
Cc:     netdev@...r.kernel.org, daniel@...que.org, ast@...com,
        daniel@...earbox.net
Subject: Re: [PATCH net-next 2/3] bpf: Add new cgroups prog type to enable
 sock modifications

On 10/25/16 at 03:30pm, David Ahern wrote:
> @@ -171,6 +177,9 @@ int __cgroup_bpf_run_filter(struct sock *sk,
>  		case BPF_CGROUP_INET_EGRESS:
>  			ret = __cgroup_bpf_run_filter_skb(skb, prog);
>  			break;
> +		case BPF_CGROUP_INET_SOCK_CREATE:
> +			ret = __cgroup_bpf_run_filter_sk_create(sk, prog);
> +			break;
>  		/* make gcc happy else complains about missing enum value */
>  		default:
>  			return 0;

Thinking further ahead of your simple example. Instead of adding yet
another prog type for the same hook, we can make this compatible with
BPF_CGROUP_INET_EGRESS instead which would then provide a ctx which
contains both, the sk and skb.

The ctx concept is very flexible. We can keep the existing dummy skb
representation and add sk_ fields which are only valid for BPF at
socket layer, e.g skb->sk_bound_dev_if would translate to
sk->bound_dev_if.