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From:   Petr Machata <petrm@nvidia.com>
To:     Daniel Machon <daniel.machon@microchip.com>
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Subject: Re: [PATCH net-next 2/6] net: dcb: add new common function for
 set/del of app/rewr entries
Date:   Fri, 13 Jan 2023 15:52:27 +0100
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Daniel Machon <daniel.machon@microchip.com> writes:

> In preparation for DCB rewrite. Add a new function for setting and
> deleting both app and rewrite entries. Moving this into a separate
> function reduces duplicate code, as both type of entries requires the
> same set of checks. The function will now iterate through a configurable
> nested attribute (app or rewrite attr), validate each attribute and call
> the appropriate set- or delete function.
>
> Note that this function always checks for nla_len(attr_itr) <
> sizeof(struct dcb_app), which was only done in dcbnl_ieee_set and not in
> dcbnl_ieee_del prior to this patch. This means, that any userspace tool
> that used to shove in data < sizeof(struct dcb_app) would now receive
> -ERANGE.

Good.

> Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
> ---
>  net/dcb/dcbnl.c | 104 +++++++++++++++++++++++-------------------------
>  1 file changed, 49 insertions(+), 55 deletions(-)
>
> diff --git a/net/dcb/dcbnl.c b/net/dcb/dcbnl.c
> index a76bdf6f0198..6d19564e19a8 100644
> --- a/net/dcb/dcbnl.c
> +++ b/net/dcb/dcbnl.c
> @@ -1099,6 +1099,45 @@ static int dcbnl_getapptrust(struct net_device *netdev, struct sk_buff *skb)
>  	return err;
>  }
>  
> +/* Set or delete APP table or rewrite table entries. The APP struct is validated
> + * and the appropriate callback function is called.
> + */
> +static int dcbnl_apprewr_setdel(struct nlattr *attr, struct net_device *netdev,
> +				int (*setdel)(struct net_device *dev,
> +					      struct dcb_app *app),
> +				int (*ops_setdel)(struct net_device *dev,
> +						  struct dcb_app *app))

The name makes it look like it's rewrite-specific. Maybe make it
_app_table_? Given both DCB app and DCB rewrite use app table as the
database... Dunno. Not a big deal.

> +{
> +	struct dcb_app *app_data;
> +	enum ieee_attrs_app type;
> +	struct nlattr *attr_itr;
> +	int rem, err;
> +
> +	nla_for_each_nested(attr_itr, attr, rem) {
> +		type = nla_type(attr_itr);
> +
> +		if (!dcbnl_app_attr_type_validate(type))
> +			continue;
> +
> +		if (nla_len(attr_itr) < sizeof(struct dcb_app))
> +			return -ERANGE;
> +
> +		app_data = nla_data(attr_itr);
> +
> +		if (!dcbnl_app_selector_validate(type, app_data->selector))
> +			return -EINVAL;
> +
> +		if (ops_setdel)
> +			err = ops_setdel(netdev, app_data);
> +		else
> +			err = setdel(netdev, app_data);
> +		if (err)
> +			return err;
> +	}
> +
> +	return 0;
> +}
> +
>  /* Handle IEEE 802.1Qaz/802.1Qau/802.1Qbb GET commands. */
>  static int dcbnl_ieee_fill(struct sk_buff *skb, struct net_device *netdev)
>  {
> @@ -1568,36 +1607,11 @@ static int dcbnl_ieee_set(struct net_device *netdev, struct nlmsghdr *nlh,
>  	}
>  
>  	if (ieee[DCB_ATTR_IEEE_APP_TABLE]) {
> -		struct nlattr *attr;
> -		int rem;
> -
> -		nla_for_each_nested(attr, ieee[DCB_ATTR_IEEE_APP_TABLE], rem) {
> -			enum ieee_attrs_app type = nla_type(attr);
> -			struct dcb_app *app_data;
> -
> -			if (!dcbnl_app_attr_type_validate(type))
> -				continue;
> -
> -			if (nla_len(attr) < sizeof(struct dcb_app)) {
> -				err = -ERANGE;
> -				goto err;
> -			}
> -
> -			app_data = nla_data(attr);
> -
> -			if (!dcbnl_app_selector_validate(type,
> -							 app_data->selector)) {
> -				err = -EINVAL;
> -				goto err;
> -			}
> -
> -			if (ops->ieee_setapp)
> -				err = ops->ieee_setapp(netdev, app_data);
> -			else
> -				err = dcb_ieee_setapp(netdev, app_data);
> -			if (err)
> -				goto err;
> -		}
> +		err = dcbnl_apprewr_setdel(ieee[DCB_ATTR_IEEE_APP_TABLE],
> +					   netdev, dcb_ieee_setapp,
> +					   ops->ieee_setapp);

This could pre-resolve the callback to use and pass one pointer:

		err = dcbnl_apprewr_setdel(ieee[DCB_ATTR_IEEE_APP_TABLE], netdev,
					   ops->ieee_setapp ?: dcb_ieee_setapp);

And the same below.

> +		if (err)
> +			goto err;
>  	}
>  
>  	if (ieee[DCB_ATTR_DCB_APP_TRUST_TABLE]) {
> @@ -1684,31 +1698,11 @@ static int dcbnl_ieee_del(struct net_device *netdev, struct nlmsghdr *nlh,
>  		return err;
>  
>  	if (ieee[DCB_ATTR_IEEE_APP_TABLE]) {
> -		struct nlattr *attr;
> -		int rem;
> -
> -		nla_for_each_nested(attr, ieee[DCB_ATTR_IEEE_APP_TABLE], rem) {
> -			enum ieee_attrs_app type = nla_type(attr);
> -			struct dcb_app *app_data;
> -
> -			if (!dcbnl_app_attr_type_validate(type))
> -				continue;
> -			app_data = nla_data(attr);
> -
> -			if (!dcbnl_app_selector_validate(type,
> -							 app_data->selector)) {
> -				err = -EINVAL;
> -				goto err;
> -			}
> -
> -			if (ops->ieee_delapp)
> -				err = ops->ieee_delapp(netdev, app_data);
> -			else
> -				err = dcb_ieee_delapp(netdev, app_data);
> -			if (err)
> -				goto err;
> -		}
> +		err = dcbnl_apprewr_setdel(ieee[DCB_ATTR_IEEE_APP_TABLE],
> +					   netdev, dcb_ieee_delapp,
> +					   ops->ieee_delapp);
> +		if (err)
> +			goto err;
>  	}
>  
>  err: