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Cherry-pick Multi-AP commits from uptream: 9c06f0f6a hostapd: Add Multi-AP protocol support 5abc7823b wpa_supplicant: Add Multi-AP backhaul STA support a1debd338 tests: Refactor test_multi_ap bfcdac1c8 Multi-AP: Don't reject backhaul STA on fronthaul BSS cb3c156e7 tests: Update multi_ap_fronthaul_on_ap to match implementation 56a2d788f WPS: Add multi_ap_subelem to wps_build_wfa_ext() 83ebf5586 wpa_supplicant: Support Multi-AP backhaul STA onboarding with WPS 66819b07b hostapd: Support Multi-AP backhaul STA onboarding with WPS 8682f384c hostapd: Add README-MULTI-AP b1daf498a tests: Multi-AP WPS provisioning Add support for Multi-AP to the UCI configuration. Every wifi-iface gets an option 'multi_ap'. For APs, its value can be 0 (multi-AP support disabled), 1 (backhaul AP), 2 (fronthaul AP), or 3 (fronthaul + backhaul AP). For STAs, it can be 0 (not a backhaul STA) or 1 (backhaul STA, can only associate with backhaul AP). Also add new optional parameter to wps_start ubus call of wpa_supplicant to indicate that a Multi-AP backhaul link is required. Signed-off-by: Daniel Golle <daniel@makrotopia.org> Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
182 lines
8.8 KiB
Diff
182 lines
8.8 KiB
Diff
From bd733055a22c8ca3bcd7648bf716da2713b3d9f1 Mon Sep 17 00:00:00 2001
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From: "Arnout Vandecappelle (Essensium/Mind)" <arnout@mind.be>
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Date: Mon, 21 Jan 2019 16:44:06 +0100
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Subject: [PATCH] hostapd: add README-MULTI-AP
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Document what hostapd and wpa_supplicant do for Multi-AP.
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This is only included in hostapd, since a Multi-AP device is always an
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access point so it should have hostapd.
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Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
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---
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v4: wps_pbc has multi_ap as a parameter instead of config option.
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---
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hostapd/README-MULTI-AP | 160 ++++++++++++++++++++++++++++++++++++++++
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1 file changed, 160 insertions(+)
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create mode 100644 hostapd/README-MULTI-AP
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--- /dev/null
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+++ b/hostapd/README-MULTI-AP
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@@ -0,0 +1,160 @@
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+hostapd, wpa_supplicant and the Multi-AP Specification
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+======================================================
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+
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+This document describes how hostapd and wpa_supplicant can be configured to
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+support the Multi-AP Specification.
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+
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+Introduction to Multi-AP
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+------------------------
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+
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+The Wi-Fi Alliance Multi-AP Specification is the technical specification for
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+Wi-Fi CERTIFIED EasyMesh(TM) [1], the Wi-Fi Alliance® certification program for
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+Multi-AP. It defines control protocols between Wi-Fi® access points (APs) to
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+join them into a network with centralized control and operation. It is targeted
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+only at routers (repeaters, gateways, ...), not at clients. Clients are not
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+involved at all in the protocols.
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+
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+Most of the Multi-AP specification falls outside of the scope of
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+hostapd/wpa_supplicant. hostapd/wpa_supplicant is only involved for the items
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+summarized below. The rest of the protocol must be implemented by a separate
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+daemon, e.g. prplMesh [2]. That daemon also needs to communicate with hostapd,
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+e.g. to get a list of associated clients, but this can be done using the normal
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+hostapd interfaces.
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+
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+hostapd/wpa_supplicant needs to be configured specifically to support:
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+- the WPS onboarding process;
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+- configuring backhaul links.
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+
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+The text below refers to "Multi-AP Specification v1.0" [3].
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+
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+
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+Fronthaul and backhaul links
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+----------------------------
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+
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+In a Multi-AP network, the central controller can configure the SSIDs on the
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+devices that are joined into the network. These are called fronthaul SSIDs.
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+From the point of view of hostapd, there is nothing special about these
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+fronthaul SSIDs.
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+
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+In addition to fronthaul SSIDs, the controller can also configure backhaul
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+links. A backhaul link is a link between two access point devices, giving
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+internet access to access point devices that don't have a wired link. The
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+Multi-AP specification doesn't dictate this, but typically the backhaul link
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+will be bridged into a LAN together with (one of) the fronthaul SSID(s) and the
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+wired Ethernet ports.
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+
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+A backhaul link must be treated specially by hostapd and wpa_supplicant. One
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+side of the backhaul link is configured through the Multi-AP protocol as the
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+"backhaul STA", i.e. the client side of the link. A backhaul STA is like any
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+station and is handled appropriately by wpa_supplicant, but two additional
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+features are required. It must send an additional information element in each
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+(Re-)Association Request ([3], section 5.2, paragraph 4). In addition, it must
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+use 4-address mode for all frames sent over this link ([3], section 14).
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+Therefore, wpa_supplicant must be configured explicitly as the backhaul STA
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+role, by setting 'multi_ap_backhaul_sta=1' in the network configuration block
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+or when configuring the SSID through the client socket. When
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+'multi_ap_backhaul_sta=1', wpa_supplicant includes the Multi-AP IE in
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+(Re-)Association Request messages and verifies that it is included in the
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+(Re-)Association Response. If it is not, association fails. If it is,
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+wpa_supplicant sets 4-address mode for this interface through a driver
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+callback.
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+
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+The AP side of the backhaul link is called a "backhaul SSID". Such an SSID must
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+be handled specially by hostapd, because it must add an additional information
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+element in each (Re-)Association Response, but only to stations that have
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+identified themselves as backhaul stations ([3], section 5.2, paragraph 5-6).
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+This is important because it is possible to use the same BSS and SSID for
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+fronthaul and backhaul at the same time. The additional information element must
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+only be used for frames sent to a backhaul STA, not to a normal STA. Also,
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+frames sent to a backhaul STA must use 4-address mode, while frames sent to a
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+normal STA (fronthaul, when it's a fronthaul and backhaul SSID) must use
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+3-address mode.
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+
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+An SSID is configured in Multi-AP mode in hostapd by setting the 'multi_ap'
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+configuration option to 1 (backhaul SSID), 2 (fronthaul SSID) or 3
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+(simultaneous backhaul and fronthaul SSID). If this option is set, hostapd
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+parses the Multi-AP information element in the Association Request. If the
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+station is a backhaul STA and the SSID is configured as a backhaul SSID,
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+hostapd sets up 4-address mode. Since there may be multiple stations connected
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+simultaneously, and each of them has a different RA (receiver address), a VLAN
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+is created for each backhaul STA and it is automatically added to a bridge.
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+This is the same behavior as for WDS, and the relevant option ('bridge' or
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+'wds_bridge') applies here as well.
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+
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+If 'multi_ap' is 1 (backhaul SSID only), any station that tries to associate
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+without the Multi-AP information element will be denied.
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+
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+If 'multi_ap' is 2 (fronthaul SSID only), any station that tries to associate
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+with the Multi-AP information element will be denied. That is also the only
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+difference with 'multi_ap' set to 0: in the latter case, the Multi-AP
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+information element is simply ignored.
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+
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+In summary, this is the end-to-end behaviour for a backhaul BSS (i.e.,
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+multi_ap_backhaul_sta=1 in wpa_supplicant on STA, and multi_ap=1 or 3 in
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+hostapd on AP). Note that point 1 means that hostapd must not be configured
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+with WPS support on the backhaul BSS (multi_ap=1). hostapd does not check for
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+that.
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+
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+1. Backhaul BSS beacons do not advertise WPS support (other than that, nothing
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+ multi-ap specific).
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+2. STA sends authentication req (nothing multi-ap specific).
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+3. AP sends authentication resp (nothing multi-ap specific).
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+4. STA sends association req with Multi-AP IE.
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+5. AP send association resp with Multi-AP IE.
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+6. STA and AP both use 4-address mode for data.
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+
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+
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+WPS support
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+-----------
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+
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+WPS requires more special handling. WPS must only be advertised on fronthaul
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+SSIDs, not on backhaul SSIDs, so WPS should not be enabled on a backhaul-only
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+SSID in hostapd.conf. The WPS configuration purely works on the fronthaul SSID.
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+When a WPS M1 message has an additional subelement that indicates a request for
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+a multi-AP backhaul link, hostapd must not respond with the normal fronthaul
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+SSID credentials; instead, it should respond with the (potentially different)
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+backhaul SSID credentials.
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+
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+To support this, hostapd has the 'multi_ap_backhaul_ssid',
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+'multi_ap_backhaul_wpa_psk' and 'multi_ap_backhaul_wpa_passphrase' options.
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+When these are set on an SSID with WPS, they are used instead of the normal
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+credentials when hostapd receives a WPS M1 message with the Multi-AP IE. Only
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+WPA2 Personal is supported in the Multi-AP specification, so there is no need
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+to specify authentication or encryption options. For the backhaul credentials,
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+per-device PSK is not supported.
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+
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+If the SSID is a simultaneous backhaul and fronthaul SSID, there is no need to
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+specify the backhaul credentials, since the backhaul and fronthaul credentials
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+are identical.
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+
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+To enable the Multi-AP backhaul STA feature when it performs WPS, a new
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+parameter has been introduced to the WPS_PBC control interface call.
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+When this option is set, it adds the multi-AP backhaul subelement to
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+the association and M1 messages. It then configures the new SSID with
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+'multi_ap_backhaul_sta=1'. Note that this means that if the AP does not
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+follow the Multi-AP specification, wpa_supplicant will fail to
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+associate.
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+
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+In summary, this is the end-to-end behaviour for WPS of a backhaul link (i.e.,
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+multi_ap=1 option is given in the wps_pbc call on the STA side, and multi_ap=2
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+and multi_ap_backhaul_ssid and either multi_ap_backhaul_wpa_psk or
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+multi_ap_backhaul_wpa_passphrase are set to the credentials of a backhaul SSID
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+in hostapd on registrar AP).
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+
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+1. Fronthaul BSS beacons advertise WPS support (nothing multi-ap specific).
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+2. Enrollee sends authentication req (nothing multi-ap specific).
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+3. AP sends authentication resp (nothing multi-ap specific).
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+4. Enrollee sends association req with Multi-AP IE.
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+5. AP send association resp with Multi-AP IE.
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+6. Enrollee sends M1 with additional Multi-AP subelement
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+7. AP sends M8 with backhaul instead of fronthaul credentials.
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+8. Enrollee sends Deauth.
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+
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+
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+References
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+----------
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+
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+[1] https://www.wi-fi.org/discover-wi-fi/wi-fi-easymesh
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+[2] https://github.com/prplfoundation/prplMesh
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+[3] https://www.wi-fi.org/file/multi-ap-specification-v10
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+ (requires registration)
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