netdev - Re: [PATCH net-next 1/8] bpf: Recursively apply cgroup sock filters

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Date:   Wed, 23 Aug 2017 09:33:09 -0700
From:   David Ahern <dsahern@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     netdev@...r.kernel.org, daniel@...earbox.net, ast@...nel.org,
        tj@...nel.org, davem@...emloft.net
Subject: Re: [PATCH net-next 1/8] bpf: Recursively apply cgroup sock filters

On 8/22/17 6:40 PM, Alexei Starovoitov wrote:
>> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
>> index df2e0f14a95d..7480cebab073 100644
>> --- a/kernel/cgroup/cgroup.c
>> +++ b/kernel/cgroup/cgroup.c
>> @@ -5186,4 +5186,22 @@ int cgroup_bpf_update(struct cgroup *cgrp, struct bpf_prog *prog,
>>  	mutex_unlock(&cgroup_mutex);
>>  	return ret;
>>  }
>> +
>> +int cgroup_bpf_run_filter_sk(struct sock *sk,
>> +			     enum bpf_attach_type type)
>> +{
>> +	struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
>> +	int ret = 0;
>> +
>> +	while (cgrp) {
>> +		ret = __cgroup_bpf_run_filter_sk(cgrp, sk, type);
>> +		if (ret < 0)
>> +			break;
>> +
>> +		cgrp = cgroup_parent(cgrp);
>> +	}
> 
> I think this walk changes semantics for existing setups, so we cannot do it
> by default and have to add new attach flag.

I can add a flag similar to the override.

> Also why break on (ret < 0) ?

Because __cgroup_bpf_run_filter_sk returns either 0 or -EPERM.

> The caller of this does:
>   err = BPF_CGROUP_RUN_PROG_INET_SOCK(sk);
>   if (err) {
>           sk_common_release(sk);
> so we should probably break out of the loop on if (ret) too.
> 

I'll do that in v2.