Subject: Re: [PATCH v3 net] bpf: add bpf_sk_netns_id() helper

From: Alexei Starovoitov <[email-masked]>
Date: Mon, 6 Feb 2017 16:02:55 -0800

On 2/6/17 3:39 PM, Daniel Borkmann wrote:
> 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.

Ahh, right. Good catch.
I'll add 'else return NULL;' otherwise somebody might step on it again.
Thanks Daniel!

Eric,
still waiting for your review of nsfs.c bits.