netdev - Re: [PATCH v3 3/6] bpf: add BPF_PROG_ATTACH and BPF_PROG

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Date:   Mon, 5 Sep 2016 14:56:20 +0200
From:   Daniel Mack <daniel@...que.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     htejun@...com, daniel@...earbox.net, ast@...com,
        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 3/6] bpf: add BPF_PROG_ATTACH and BPF_PROG_DETACH
 commands

On 08/27/2016 02:08 AM, Alexei Starovoitov wrote:
> On Fri, Aug 26, 2016 at 09:58:49PM +0200, Daniel Mack wrote:

>> +
>> +	struct { /* anonymous struct used by BPF_PROG_ATTACH/DETACH commands */
>> +		__u32		target_fd;	/* container object to attach to */
>> +		__u32		attach_bpf_fd;	/* eBPF program to attach */
>> +		__u32		attach_type;	/* BPF_ATTACH_TYPE_* */
>> +		__u64		attach_flags;
>> +	};
> 
> there is a 4 byte hole in this struct. Can we pack it differently?

Okay - I swapped "type" and "flags" to repair this.

>> +	switch (attr->attach_type) {
>> +	case BPF_ATTACH_TYPE_CGROUP_INET_INGRESS:
>> +	case BPF_ATTACH_TYPE_CGROUP_INET_EGRESS: {
>> +		struct cgroup *cgrp;
>> +
>> +		prog = bpf_prog_get_type(attr->attach_bpf_fd,
>> +					 BPF_PROG_TYPE_CGROUP_SOCKET_FILTER);
>> +		if (IS_ERR(prog))
>> +			return PTR_ERR(prog);
>> +
>> +		cgrp = cgroup_get_from_fd(attr->target_fd);
>> +		if (IS_ERR(cgrp)) {
>> +			bpf_prog_put(prog);
>> +			return PTR_ERR(cgrp);
>> +		}
>> +
>> +		cgroup_bpf_update(cgrp, prog, attr->attach_type);
>> +		cgroup_put(cgrp);
>> +
>> +		break;
>> +	}
> 
> this } formatting style is confusing. The above } looks
> like it matches 'switch () {'.
> May be move 'struct cgroup *cgrp' to the top to avoid that?

I kept it local to its users, but you're right, it's not worth it. Will
change.


Thanks,
Daniel