netdev - Re: [PATCH v3 net] bpf: add bpf_sk_netns

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Date:   Tue, 07 Feb 2017 00:39:03 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Alexei Starovoitov <ast@...com>,
        "David S . Miller" <davem@...emloft.net>
CC:     David Ahern <dsa@...ulusnetworks.com>, Tejun Heo <tj@...nel.org>,
        Andy Lutomirski <luto@...capital.net>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        netdev@...r.kernel.org
Subject: Re: [PATCH v3 net] bpf: add bpf_sk_netns_id() helper

On 02/04/2017 04:34 AM, Alexei Starovoitov wrote:
[...]
> +BPF_CALL_1(bpf_skb_netns_id, struct sk_buff *, skb)
> +{
> +	struct net_device *dev = skb->dev;
> +
> +	if (!dev)
> +		return 0;
> +	return proc_get_ns_devid_inum(&dev_net(dev)->ns);
> +}
> +
> +static const struct bpf_func_proto bpf_skb_netns_id_proto = {
> +	.func		= bpf_skb_netns_id,
> +	.gpl_only	= false,
> +	.ret_type	= RET_INTEGER,
> +	.arg1_type	= ARG_PTR_TO_CTX,
> +};
> +
>   static const struct bpf_func_proto *
>   sk_filter_func_proto(enum bpf_func_id func_id)
>   {
> @@ -2620,6 +2649,8 @@ sk_filter_func_proto(enum bpf_func_id func_id)
>   	case BPF_FUNC_trace_printk:
>   		if (capable(CAP_SYS_ADMIN))
>   			return bpf_get_trace_printk_proto();
> +	case BPF_FUNC_sk_netns_id:
> +		return &bpf_skb_netns_id_proto;
>   	default:
>   		return NULL;
>   	}

Btw, I think here's an oversight that would still need to be
fixed. Above would mean that trace printk from unprivileged would
fall through and use &bpf_skb_netns_id_proto as proto now instead
of NULL. So BPF_FUNC_sk_netns_id needs to be placed above the
BPF_FUNC_trace_printk case, not in its fall-through path. Looks
like Chenbo in his get_socket_cookie missed this, too. Other than
that BPF bits seem good to me.

> @@ -2700,6 +2731,17 @@ xdp_func_proto(enum bpf_func_id func_id)
>   }