Allow remote RADIUS authentication with local VLAN management

Allow remote RADIUS authentication with local VLAN management

The documentation in the hostapd.conf file says that the dynamic_vlan
variable is used to control whether VLAN assignments are accepted from a
RADIUS server. The implication seems to be that a static VLAN assignment
will come from the accept_mac_file if dynamic_vlan is set to 0, and a
dynamic assignment will come from the RADIUS server if dynamic_vlan is
set to 1. Instead, I'm seeing that the static settings from the
accept_mac_file are ignored if dynamic_vlan is set to 0, but used if
dynamic_vlan is set to 1. If dynamic_vlan is set to 1 and the RADIUS
server does not provide a VLAN, then the accept_mac_file assignment is
overridden and the STA is assigned to the default non-VLANed interface.

If my understanding of the expected behavior is correct, then I believe
the problem is in ap_sta_set_vlan(). That routine checks the
dynamic_vlan setting, but has no way of determining whether the incoming
vlan_desc is static (i.e., from accept_mac_file) or dynamic (i.e., from
a RADIUS server).

I've attached a patch that gets hostapd working as I believe it's meant
to, and updates the documentation to make the implicit behavior
explicit.

The functional changes are:

- hostapd_allowed_address() will always extract the vlan_id from the
  accept_macs file. It will not update the vlan_id from the RADIUS cache
  if dynamic_vlan is DISABLED.

- hostapd_acl_recv_radius() will not update the cached vlan_id if
  dynamic_vlan is DISABLED.

- ieee802_1x_receive_auth() will not update the vlan_id if dynamic_vlan
  is DISABLED.

More cosmetic:

Most of the delta is just moving code out of ieee802_1x_receive_auth()
into a new ieee802_1x_update_vlan() routine. While I initially did this
because the new DISABLED check introduced excessive indentation, it has
the added advantage of eliminating the vlan_description allocation and
os_memset() call for all DYNAMIC_VLAN_DISABLED configs.

I've done a couple rounds of review offline with Michael Braun (who has
done much of the work in this part of the code) and incorporated his
feedback.

If dynamic_vlan=0 (disabled), vlan assignments will be managed using the
local accept_mac_file ACL file, even if a RADIUS server is being used
for user authentication. This allows us to manage users and devices
independently.

Signed-off-by: Nils Nieuwejaar <nils.nieuwejaar@gmail.com>