wifi: mac80211: add strict mode disabling workarounds

Add a strict mode where we disable certain workarounds and have
additional checks such as, for now, that VHT capabilities from
association response match those from beacon/probe response. We
can extend the checks in the future.

Make it an opt-in setting by the driver so it can be set there
in some driver-specific way, for example. Also allow setting
this one hw flag through the hwflags debugfs, by writing a new
strict=0 or strict=1 value.

Signed-off-by: Johannes Berg <[e-mail]>
Reviewed-by: Ilan Peer <[e-mail]>
Signed-off-by: Miri Korenblit <[e-mail]>
Link: https://patch.msgid.link/20250205110958.5cecb0469479.I4a69617dc60ba0d6308416ffbc3102cfd08ba068@changeid
Signed-off-by: Johannes Berg <[e-mail]>

include/net/mac80211.h

···
  *	implements MLO, so operation can continue on other links when one
  *	link is switching.
  *
+ * @IEEE80211_HW_STRICT: strictly enforce certain things mandated by the spec
+ *	but otherwise ignored/worked around for interoperability. This is a
+ *	HW flag so drivers can opt in according to their own control, e.g. in
+ *	testing.
+ *
  * @NUM_IEEE80211_HW_FLAGS: number of hardware flags, used for sizing arrays
  */
 enum ieee80211_hw_flags {
···
 	IEEE80211_HW_DISALLOW_PUNCTURING,
 	IEEE80211_HW_DISALLOW_PUNCTURING_5GHZ,
 	IEEE80211_HW_HANDLES_QUIET_CSA,
+	IEEE80211_HW_STRICT,
 
 	/* keep last, obviously */
 	NUM_IEEE80211_HW_FLAGS

net/mac80211/debugfs.c

···
 	FLAG(DISALLOW_PUNCTURING),
 	FLAG(DISALLOW_PUNCTURING_5GHZ),
 	FLAG(HANDLES_QUIET_CSA),
+	FLAG(STRICT),
 #undef FLAG
 };
 
···
 	kfree(buf);
 	return rv;
 }
+
+static ssize_t hwflags_write(struct file *file, const char __user *user_buf,
+			     size_t count, loff_t *ppos)
+{
+	struct ieee80211_local *local = file->private_data;
+	char buf[100];
+	int val;
+
+	if (count >= sizeof(buf))
+		return -EINVAL;
+
+	if (copy_from_user(buf, user_buf, count))
+		return -EFAULT;
+
+	if (count && buf[count - 1] == '\n')
+		buf[count - 1] = '\0';
+	else
+		buf[count] = '\0';
+
+	if (sscanf(buf, "strict=%d", &val) == 1) {
+		switch (val) {
+		case 0:
+			ieee80211_hw_set(&local->hw, STRICT);
+			return count;
+		case 1:
+			__clear_bit(IEEE80211_HW_STRICT, local->hw.flags);
+			return count;
+		default:
+			return -EINVAL;
+		}
+	}
+
+	return -EINVAL;
+}
+
+static const struct file_operations hwflags_ops = {
+	.open = simple_open,
+	.read = hwflags_read,
+	.write = hwflags_write,
+};
 
 static ssize_t misc_read(struct file *file, char __user *user_buf,
 			 size_t count, loff_t *ppos)
···
 	return simple_read_from_buffer(user_buf, count, ppos, buf, res);
 }
 
-DEBUGFS_READONLY_FILE_OPS(hwflags);
 DEBUGFS_READONLY_FILE_OPS(queues);
 DEBUGFS_READONLY_FILE_OPS(misc);
 
···
 #ifdef CONFIG_PM
 	DEBUGFS_ADD_MODE(reset, 0200);
 #endif
-	DEBUGFS_ADD(hwflags);
+	DEBUGFS_ADD_MODE(hwflags, 0600);
 	DEBUGFS_ADD(user_power);
 	DEBUGFS_ADD(power);
 	DEBUGFS_ADD(hw_conf);

net/mac80211/mlme.c

···
 	bool no_vht = false;
 	u32 ht_cfreq;
 
+	if (ieee80211_hw_check(&sdata->local->hw, STRICT))
+		ignore_ht_channel_mismatch = false;
+
 	*chandef = (struct cfg80211_chan_def) {
 		.chan = channel,
 		.width = NL80211_CHAN_WIDTH_20_NOHT,
···
 	 * zeroes, which is nonsense, and completely inconsistent with itself
 	 * (it doesn't have 8 streams). Accept the settings in this case anyway.
 	 */
-	if (!ap_min_req_set)
+	if (!ieee80211_hw_check(&sdata->local->hw, STRICT) && !ap_min_req_set)
 		return true;
 
 	/* make sure the AP is consistent with itself
···
 	 * zeroes, which is nonsense, and completely inconsistent with itself
 	 * (it doesn't have 8 streams). Accept the settings in this case anyway.
 	 */
-	if (!ap_min_req_set)
+	if (!ieee80211_hw_check(&sdata->local->hw, STRICT) && !ap_min_req_set)
 		return true;
 
 	/* Need to go over for 80MHz, 160MHz and for 80+80 */
···
 	 * Some APs apparently get confused if our capabilities are better
 	 * than theirs, so restrict what we advertise in the assoc request.
 	 */
-	if (!(ap_vht_cap->vht_cap_info &
-			cpu_to_le32(IEEE80211_VHT_CAP_SU_BEAMFORMER_CAPABLE)))
-		cap &= ~(IEEE80211_VHT_CAP_SU_BEAMFORMEE_CAPABLE |
-			 IEEE80211_VHT_CAP_MU_BEAMFORMEE_CAPABLE);
-	else if (!(ap_vht_cap->vht_cap_info &
-			cpu_to_le32(IEEE80211_VHT_CAP_MU_BEAMFORMER_CAPABLE)))
-		cap &= ~IEEE80211_VHT_CAP_MU_BEAMFORMEE_CAPABLE;
+	if (!ieee80211_hw_check(&local->hw, STRICT)) {
+		if (!(ap_vht_cap->vht_cap_info &
+				cpu_to_le32(IEEE80211_VHT_CAP_SU_BEAMFORMER_CAPABLE)))
+			cap &= ~(IEEE80211_VHT_CAP_SU_BEAMFORMEE_CAPABLE |
+				 IEEE80211_VHT_CAP_MU_BEAMFORMEE_CAPABLE);
+		else if (!(ap_vht_cap->vht_cap_info &
+				cpu_to_le32(IEEE80211_VHT_CAP_MU_BEAMFORMER_CAPABLE)))
+			cap &= ~IEEE80211_VHT_CAP_MU_BEAMFORMEE_CAPABLE;
+	}
 
 	/*
 	 * If some other vif is using the MU-MIMO capability we cannot associate
···
 	return mu_mimo_owner;
 }
 
-static void ieee80211_assoc_add_rates(struct sk_buff *skb,
+static void ieee80211_assoc_add_rates(struct ieee80211_local *local,
+				      struct sk_buff *skb,
 				      enum nl80211_chan_width width,
 				      struct ieee80211_supported_band *sband,
 				      struct ieee80211_mgd_assoc_data *assoc_data)
 {
 	u32 rates;
 
-	if (assoc_data->supp_rates_len) {
+	if (assoc_data->supp_rates_len &&
+	    !ieee80211_hw_check(&local->hw, STRICT)) {
 		/*
 		 * Get all rates supported by the device and the AP as
 		 * some APs don't like getting a superset of their rates
···
 		*capab |= WLAN_CAPABILITY_SPECTRUM_MGMT;
 
 	if (sband->band != NL80211_BAND_S1GHZ)
-		ieee80211_assoc_add_rates(skb, width, sband, assoc_data);
+		ieee80211_assoc_add_rates(local, skb, width, sband, assoc_data);
 
 	if (*capab & WLAN_CAPABILITY_SPECTRUM_MGMT ||
 	    *capab & WLAN_CAPABILITY_RADIO_MEASURE) {
···
 	 * for some reason check it and want it to be set, set the bit for all
 	 * pre-EHT connections as we used to do.
 	 */
-	if (link->u.mgd.conn.mode < IEEE80211_CONN_MODE_EHT)
+	if (link->u.mgd.conn.mode < IEEE80211_CONN_MODE_EHT &&
+	    !ieee80211_hw_check(&local->hw, STRICT))
 		capab |= WLAN_CAPABILITY_ESS;
 
 	/* add the elements for the assoc (main) link */
···
 	 * 2G/3G/4G wifi routers, reported models include the "Onda PN51T",
 	 * "Vodafone PocketWiFi 2", "ZTE MF60" and a similar T-Mobile device.
 	 */
-	if (!is_6ghz &&
+	if (!ieee80211_hw_check(&local->hw, STRICT) && !is_6ghz &&
 	    ((assoc_data->wmm && !elems->wmm_param) ||
 	     (link->u.mgd.conn.mode >= IEEE80211_CONN_MODE_HT &&
 	      (!elems->ht_cap_elem || !elems->ht_operation)) ||
···
 						  ies->data, ies->len);
 			if (elem && elem->datalen >= sizeof(*bss_vht_cap))
 				bss_vht_cap = (const void *)elem->data;
+		}
+
+		if (ieee80211_hw_check(&local->hw, STRICT) &&
+		    (!bss_vht_cap || memcmp(bss_vht_cap, elems->vht_cap_elem,
+					    sizeof(*bss_vht_cap)))) {
+			rcu_read_unlock();
+			ret = false;
+			link_info(link, "VHT capabilities mismatch\n");
+			goto out;
 		}
 
 		ieee80211_vht_cap_ie_to_sta_vht_cap(sdata, sband,