netdev - Re: [PATCH iproute2] devlink: Ignore unknown attributes

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Date:   Fri, 19 Jan 2018 16:00:36 -0800
From:   David Ahern <dsahern@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     Arkadi Sharshevsky <arkadis@...lanox.com>, netdev@...r.kernel.org,
        davem@...emloft.net, mlxsw@...lanox.com
Subject: Re: [PATCH iproute2] devlink: Ignore unknown attributes

On 1/19/18 3:40 PM, Stephen Hemminger wrote:
>> mnl_attr_type_valid calls mnl_attr_get_type which does attr->nla_type &
>> NLA_TYPE_MASK. Since you are no longer acknowledging the return code of
>> mnl_attr_type_valid, you don't care about its checks so you might as
>> well not call it. I don't see anything in libmnl that checks that
>> mnl_attr_type_valid is invoked on an attr, so hence my question -- given
>> the change above why call it all?

ok. I see the error in my thinking.

>  The part that matters is:
> 
> static int attr_cb(const struct nlattr *attr, void *data)
> {
> 	const struct nlattr **tb = data;
> 	int type;
> 
> 	if (mnl_attr_type_valid(attr, DEVLINK_ATTR_MAX) < 0)         << makes sure that type < DEVLINK_ATTR_MAX
> 		return MNL_CB_OK;
> 
> 	type = mnl_attr_get_type(attr);
> 	if (mnl_attr_validate(attr, devlink_policy[type]) < 0)        << this part doesn't matter really
> 		return MNL_CB_ERROR;
> 
> 	tb[type] = attr;					<< necessary so that tb[] is filled in.
> 	return MNL_CB_OK;
> }