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Subject: Re: [PATCH v3] {nl,mac}80211: allow 4addr AP operation on crypto
 controlled devices
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Manikanta Pubbisetty <mpubbise@codeaurora.org>
Cc:     linux-wireless@vger.kernel.org
Date:   Tue, 14 May 2019 10:38:59 +0200
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On Wed, 2019-05-08 at 14:55 +0530, Manikanta Pubbisetty wrote:
> 
> +++ b/net/mac80211/util.c
> @@ -3795,7 +3795,9 @@ int ieee80211_check_combinations(struct ieee80211_sub_if_data *sdata,
>  	}
>  
>  	/* Always allow software iftypes */
> -	if (local->hw.wiphy->software_iftypes & BIT(iftype)) {
> +	if (local->hw.wiphy->software_iftypes & BIT(iftype) ||
> +	    (iftype == NL80211_IFTYPE_AP_VLAN &&
> +	     local->hw.wiphy->flags & WIPHY_FLAG_4ADDR_AP)) {
>  		if (radar_detect)
>  			return -EINVAL;

Shouldn't this check if 4addr is actually enabled too, like here:

>  	case NETDEV_PRE_UP:
> -		if (!(wdev->wiphy->interface_modes & BIT(wdev->iftype)))
> +		if (!(wdev->wiphy->interface_modes & BIT(wdev->iftype)) &&
> +		    !(wdev->iftype == NL80211_IFTYPE_AP_VLAN &&
> +		      rdev->wiphy.flags & WIPHY_FLAG_4ADDR_AP &&
> +		      wdev->use_4addr))
>  			return notifier_from_errno(-EOPNOTSUPP);

?
Or is there some reason it doesn't matter?

> @@ -3439,6 +3438,11 @@ static int nl80211_new_interface(struct sk_buff *skb, struct genl_info *info)
>  			return err;
>  	}
>  
> +	if (!(rdev->wiphy.interface_modes & (1 << type)) &&
> +	    !(type == NL80211_IFTYPE_AP_VLAN && params.use_4addr &&
> +	      rdev->wiphy.flags & WIPHY_FLAG_4ADDR_AP))
> +		return -EOPNOTSUPP;
> +

I also wonder if we shouldn't go "all in" and actually make the check
something like

  check_interface_allowed(iftype, 4addr):
    if (iftype == AP_VLAN && 4addr)
      return wiphy.flags & WIPHY_FLAG_4ADDR_AP;

    else return wiphy.interface_modes & BIT(iftype);

i.e. make it "you must have WIPHY_FLAG_4ADDR_AP to use 4-addr AP_VLAN
interfaces", rather than "also allow it in this case".

That would seem like the clearer semantics to me?

johannes