On 2018-08-16 13:57, Johannes Berg wrote:
On Tue, 2018-08-14 at 18:23 +0530, Manikanta Pubbisetty wrote:
> I don't think that makes sense. If we split the capability of AP_VLAN
> and AP_VLAN_FOR_4ADDR at the "root", then we don't need to play with all
> these things. Yes, this is slightly awkward for userspace, and perhaps
> with the interface combination checks, but I'd like you to look at that.
I was working on splitting the 4-addr functionality from AP/VLAN
iftype;
I have introduced a new iftype NL80211_IFTYPE_AP_4ADDR and moved the
4-addr handling from AP/VLAN to this new iftype. But this approach
breaks the backward compatibility with older userspace applications.
Yeah ...
I'm confused and no longer sure what I was thinking, nor even what
we're
trying to achieve here...
I had introduced a change db3bdcb9c3ff (" mac80211: allow AP_VLAN
operation on crypto controlled devices ") for supporting VLAN
functionality on ath10k devices; this commit has broken 4 addr support
on ath10k devices as I was advertising the AP/VLAN support
conditionally. Since 4 addr operation is tied to AP/VLAN support, with
this change, only the chips which support VLAN functionality can support
4 addr operation but other ath10k chips don't.
From what I can understand from our previous discussions, we had to
separate the 4addr support from the AP/VLAN iftype but doing so could
lead to backward compatibility issues. I have the code which separates
the 4addr functionality from AP/VLAN but the bigger problem is the
backward compatibility.
I am hoping that now I have set the context correctly :)
Since I am completely moving the 4-addr handling to the new type,
older
applications which do not understand this new type will simply fail
and
4-addr mode will be completely broken.
Currently, whenever a 4-addr client attempts a connection, hostapd
just
creates a AP/VLAN interface and moves the 4-addr client to the AP/VLAN
iface; there are no other checks. I had no other option other than
going
with a new iftype for 4-addr handling.
Is there a way we can maintain backward compatibility with this
approach? Retaining the 4-addr handling in AP/VLAN and duplicating the
same functionality to the new iftype seems will work but I am not sure
if this is the right approach.
I think we have to keep the 4-addr handling in AP_VLAN iftype either
way, to not break existing hostapd. We could introduce a separate
AP_VLAN_NO_4ADDR and then require updating hostapd to get non-4addr
VLAN, but that also seems awkward.
Since hostapd doesn't currently check anything...
Ok, no, I'm confused now. If we just clear WIPHY_FLAG_4ADDR_AP, don't
we
get what we want? 4-addr AP_VLAN interfaces would no longer be
permitted
to be created?
As I explained above, the agenda is to provide the driver (in this case,
ath10k) a better control for advertising the device capabilities; only
few ath10k chips can support VLAN functionality but all of them can
support 4 addr operation.
Manikanta
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