netdev - Re: [PATCH net-next v2 1/3] net: bridge: add support for user-controlled bool options

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Date:   Sat, 24 Nov 2018 17:25:41 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     nikolay@...ulusnetworks.com
Cc:     netdev@...r.kernel.org, roopa@...ulusnetworks.com,
        davem@...emloft.net, bridge@...ts.linux-foundation.org
Subject: Re: [PATCH net-next v2 1/3] net: bridge: add support for
 user-controlled bool options

On Sat, Nov 24, 2018 at 06:18:33PM +0200, nikolay@...ulusnetworks.com wrote:
> On 24 November 2018 18:10:41 EET, Andrew Lunn <andrew@...n.ch> wrote:
> >> +int br_boolopt_toggle(struct net_bridge *br, enum br_boolopt_id opt,
> >bool on,
> >> +		      struct netlink_ext_ack *extack)
> >> +{
> >> +	switch (opt) {
> >> +	default:
> >> +		/* shouldn't be called with unsupported options */
> >> +		WARN_ON(1);
> >> +		break;
> >
> >So you return 0 here, meaning the br_debug() lower down will not
> >happen. Maybe return -EOPNOTSUPP?
> >
> 
> No, the idea here is that some option in the future might return an error. 
> This function cannot be called with unsupported option thus the warn. 

O.K, i was trying to make it easier to see which option caused it to
happen.

> >> +	}
> >> +
> >> +	return 0;
> >> +}
> >> +
> >
> >> +int br_boolopt_multi_toggle(struct net_bridge *br,
> >> +			    struct br_boolopt_multi *bm,
> >> +			    struct netlink_ext_ack *extack)
> >> +{
> >> +	unsigned long bitmap = bm->optmask;
> >> +	int err = 0;
> >> +	int opt_id;
> >> +
> >> +	for_each_set_bit(opt_id, &bitmap, BR_BOOLOPT_MAX) {
> >> +		bool on = !!(bm->optval & BIT(opt_id));
> >> +
> >> +		err = br_boolopt_toggle(br, opt_id, on, extack);
> >> +		if (err) {
> >> +			br_debug(br, "boolopt multi-toggle error: option: %d current: %d
> >new: %d error: %d\n",
> >> +				 opt_id, br_boolopt_get(br, opt_id), on, err);
> >> +			break;
> >> +		}
> >> +	}
> >
> >Does the semantics of extack allow you to return something even when
> >there is no error? If there are bits > BR_BOOLOPT_MAX you could return
> >0, but also add a warning in extack that some bits where not supported
> >by this kernel.
> 
> If we return 0 there's no reason to check extack. 

Well, the caller can check to see if extack is present, even on
success. This is extack, not extnack after all...

	 Andrew