Re: [RFC] mac80211: advertise supported interface types for sw encryption

On 2018-03-21 13:23, Johannes Berg wrote:

On Fri, 2018-03-09 at 11:57 +0530, mpubbise@codeaurora.org wrote:

quoted

From: Manikanta Pubbisetty <redacted>

Extending SW_CRYPTO_CONTROL interface so that drivers can advertise
the interface types on which they can support software encryption.
Driver's job is not done by advertising the supported vif types alone,
they should also return -EOPNOTSUPP from set_key.

Mac80211 will make the fallback decision to sw ecryption based
on the return type of set_key callback and the driver's support for
software encryption.

This change is done with the sole reason of adding the support of
VLANs for drivers which enable SW_CRYPTO_CONTROL(ex:ath10k).

With the current logic, configuring GTKs for specific VLAN groups will
always fail with the drivers enabling SW_CRYPTO_CONTROL. I understand
that the driver can return 1 from set_key to enable software 
encryption
in mac80211, but GTKs for VLANs are never passed down to the driver.
Since the return value is initialized to -EOPNOTSUPP, with this 
approach,
we get away with the failure.

Is there much value in having this control to start with, rather than
saying it's *always* allowed for AP_VLAN interfaces?

I mean - if the driver wants to support (encryption on) AP_VLAN
interfaces with SW_CRYPTO_CONTROL it basically has to set this to allow
it, which is kinda pointless - it's hard to imagine a driver that wants
to support AP_VLAN only for unencrypted, so if it doesn't support this
it might as well just disable AP_VLAN support entirely.

So IMHO - just get rid of the bitmap and hard-code AP_VLAN.

I agree with you only partially.

Today, I do not see any driver advertising SW_CRYPTO_CONTROL other than 
ath10k. There could be some driver which would want to advertise 
SW_CRYPTO_CONTROL and do not support the software encryption for VLAN 
devices. In that case, hard-coding doesn't seem to solve the problem 
completely right? No?

In some way driver has to advertise that it supports encryption on 
AP_VLANs, No?
Or you meant to say that driver should advertise the support for 
AP_VLANs only if it can support encryption on AP_VLAN devices? If this 
the case, then I could see some code in ieee80211_register_hw which says 
this,

         /* if low-level driver supports AP, we also support VLAN */
         if (local->hw.wiphy->interface_modes & BIT(NL80211_IFTYPE_AP)) {
                 hw->wiphy->interface_modes |= 
BIT(NL80211_IFTYPE_AP_VLAN);
                 hw->wiphy->software_iftypes |= 
BIT(NL80211_IFTYPE_AP_VLAN);
         }

Please correct if I misinterpreted your comment.


--
mkp