[PATCH] wifi: brcmfmac: leave the AP 4-way handshake to the host on Apple chips

[Andre Eikmeyer <dev@deq.rocks>]

The Apple firmware for the BCM4364 and BCM4377 lists "idauth" in its
capabilities, so brcmfmac enables BRCMF_FEAT_FWAUTH and advertises
NL80211_EXT_FEATURE_4WAY_HANDSHAKE_AP_PSK. hostapd and wpa_supplicant
then pass the PSK to the driver and leave the AP side of the 4-way
handshake to the firmware. On the BCM4364 that handshake never
completes. The client associates, no EAPOL-Key frame is sent, and the
firmware removes the station after about 8 s.

Measured on a MacBookPro15,1 (BCM4364/3, firmware 9.30.514.0.32.5.94,
FWID 01-47278712) with a WPA2-PSK access point and a Samsung Galaxy
S22 Ultra as client:

  offload advertised:  NEW_STATION, DEL_STATION 7.8 s later, no EAPOL
  offload not advertised: 4-way handshake by wpa_supplicant completes,
                          AP-STA-CONNECTED, DHCP lease, traffic flows

Clear BRCMF_FEAT_FWAUTH on the chips in Apple's T2 Macs, so the host
runs the handshake.

Tested-by: Yossef Osman <Yossef.Osman@proton.me>
Tested-by: Aditya Garg <aditya.garg@linux.dev>
Signed-off-by: Andre Eikmeyer <dev@deq.rocks>
---
The KaiT2en community runs this patch with its kernels, no regression
was reported.

 .../wireless/broadcom/brcm80211/brcmfmac/feature.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/feature.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/feature.c
index 488364e..05e9750 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/feature.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/feature.c
@@ -318,6 +318,20 @@ void brcmf_feat_attach(struct brcmf_pub *drvr)
 					BIT(BRCMF_FEAT_WOWL_GTK);
 		}
 	}
+	/* The Apple firmware for these chips lists "idauth", but in AP mode
+	 * its authenticator never completes the 4-way handshake and the
+	 * station is dropped after about 8 s. Leave the handshake to the host.
+	 */
+	switch (drvr->bus_if->chip) {
+	case BRCM_CC_4355_CHIP_ID:
+	case BRCM_CC_4364_CHIP_ID:
+	case BRCM_CC_4377_CHIP_ID:
+		ifp->drvr->feat_flags &= ~BIT(BRCMF_FEAT_FWAUTH);
+		break;
+	default:
+		break;
+	}
+
 	/* MBSS does not work for all chips */
 	switch (drvr->bus_if->chip) {
 	case BRCM_CC_4330_CHIP_ID:
-- 
2.56.0