wifi: cfg80211: add RNR with reporting AP information

If the reporting AP is part of the same MLD, then an entry in the RNR is
required in order to discover it again from the BSS generated from the
per-STA profile in the Multi-Link Probe Response.

We need this because we do not have a direct concept of an MLD AP and
just do the lookup from one to the other on the fly if needed. As such,
we need to ensure that this lookup will work both ways.

Fixes: 2481b5da ("wifi: cfg80211: handle BSS data contained in ML probe responses")
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240102213313.4cb3dbb1d84f.I7c74edec83c5d7598cdd578929fd0876d67aef7f@changeid
[roll in off-by-one fix and test updates from Benjamin]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/scan.c

@@ -2617,6 +2617,103 @@ cfg80211_tbtt_info_for_mld_ap(const u8 *ie, size_t ielen, u8 mld_id, u8 link_id,
 	return 0;
 }
 
+static struct element *
+cfg80211_gen_reporter_rnr(struct cfg80211_bss *source_bss, bool is_mbssid,
+			  bool same_mld, u8 link_id, u8 bss_change_count,
+			  gfp_t gfp)
+{
+	const struct cfg80211_bss_ies *ies;
+	struct ieee80211_neighbor_ap_info ap_info;
+	struct ieee80211_tbtt_info_ge_11 tbtt_info;
+	u32 short_ssid;
+	const struct element *elem;
+	struct element *res;
+
+	/*
+	 * We only generate the RNR to permit ML lookups. For that we do not
+	 * need an entry for the corresponding transmitting BSS, lets just skip
+	 * it even though it would be easy to add.
+	 */
+	if (!same_mld)
+		return NULL;
+
+	/* We could use tx_data->ies if we change cfg80211_calc_short_ssid */
+	rcu_read_lock();
+	ies = rcu_dereference(source_bss->ies);
+
+	ap_info.tbtt_info_len = offsetofend(typeof(tbtt_info), mld_params);
+	ap_info.tbtt_info_hdr =
+			u8_encode_bits(IEEE80211_TBTT_INFO_TYPE_TBTT,
+				       IEEE80211_AP_INFO_TBTT_HDR_TYPE) |
+			u8_encode_bits(0, IEEE80211_AP_INFO_TBTT_HDR_COUNT);
+
+	ap_info.channel = ieee80211_frequency_to_channel(source_bss->channel->center_freq);
+
+	/* operating class */
+	elem = cfg80211_find_elem(WLAN_EID_SUPPORTED_REGULATORY_CLASSES,
+				  ies->data, ies->len);
+	if (elem && elem->datalen >= 1) {
+		ap_info.op_class = elem->data[0];
+	} else {
+		struct cfg80211_chan_def chandef;
+
+		/* The AP is not providing us with anything to work with. So
+		 * make up a somewhat reasonable operating class, but don't
+		 * bother with it too much as no one will ever use the
+		 * information.
+		 */
+		cfg80211_chandef_create(&chandef, source_bss->channel,
+					NL80211_CHAN_NO_HT);
+
+		if (!ieee80211_chandef_to_operating_class(&chandef,
+							  &ap_info.op_class))
+			goto out_unlock;
+	}
+
+	/* Just set TBTT offset and PSD 20 to invalid/unknown */
+	tbtt_info.tbtt_offset = 255;
+	tbtt_info.psd_20 = IEEE80211_RNR_TBTT_PARAMS_PSD_RESERVED;
+
+	memcpy(tbtt_info.bssid, source_bss->bssid, ETH_ALEN);
+	if (cfg80211_calc_short_ssid(ies, &elem, &short_ssid))
+		goto out_unlock;
+
+	rcu_read_unlock();
+
+	tbtt_info.short_ssid = cpu_to_le32(short_ssid);
+
+	tbtt_info.bss_params = IEEE80211_RNR_TBTT_PARAMS_SAME_SSID;
+
+	if (is_mbssid) {
+		tbtt_info.bss_params |= IEEE80211_RNR_TBTT_PARAMS_MULTI_BSSID;
+		tbtt_info.bss_params |= IEEE80211_RNR_TBTT_PARAMS_TRANSMITTED_BSSID;
+	}
+
+	tbtt_info.mld_params.mld_id = 0;
+	tbtt_info.mld_params.params =
+		le16_encode_bits(link_id, IEEE80211_RNR_MLD_PARAMS_LINK_ID) |
+		le16_encode_bits(bss_change_count,
+				 IEEE80211_RNR_MLD_PARAMS_BSS_CHANGE_COUNT);
+
+	res = kzalloc(struct_size(res, data,
+				  sizeof(ap_info) + ap_info.tbtt_info_len),
+		      gfp);
+	if (!res)
+		return NULL;
+
+	/* Copy the data */
+	res->id = WLAN_EID_REDUCED_NEIGHBOR_REPORT;
+	res->datalen = sizeof(ap_info) + ap_info.tbtt_info_len;
+	memcpy(res->data, &ap_info, sizeof(ap_info));
+	memcpy(res->data + sizeof(ap_info), &tbtt_info, ap_info.tbtt_info_len);
+
+	return res;
+
+out_unlock:
+	rcu_read_unlock();
+	return NULL;
+}
+
 static void
 cfg80211_parse_ml_elem_sta_data(struct wiphy *wiphy,
 				struct cfg80211_inform_single_bss_data *tx_data,
@@ -2630,13 +2727,14 @@ cfg80211_parse_ml_elem_sta_data(struct wiphy *wiphy,
 		.source_bss = source_bss,
 		.bss_source = BSS_SOURCE_STA_PROFILE,
 	};
+	struct element *reporter_rnr = NULL;
 	struct ieee80211_multi_link_elem *ml_elem;
 	struct cfg80211_mle *mle;
 	u16 control;
 	u8 ml_common_len;
-	u8 *new_ie;
+	u8 *new_ie = NULL;
 	struct cfg80211_bss *bss;
-	int mld_id;
+	u8 mld_id, reporter_link_id, bss_change_count;
 	u16 seen_links = 0;
 	const u8 *pos;
 	u8 i;
@@ -2658,8 +2756,14 @@ cfg80211_parse_ml_elem_sta_data(struct wiphy *wiphy,
 
 	ml_common_len = ml_elem->variable[0];
 
-	/* length + MLD MAC address + link ID info + BSS Params Change Count */
-	pos = ml_elem->variable + 1 + 6 + 1 + 1;
+	/* length + MLD MAC address */
+	pos = ml_elem->variable + 1 + 6;
+
+	reporter_link_id = pos[0];
+	pos += 1;
+
+	bss_change_count = pos[0];
+	pos += 1;
 
 	if (u16_get_bits(control, IEEE80211_MLC_BASIC_PRES_MED_SYNC_DELAY))
 		pos += 2;
@@ -2690,10 +2794,21 @@ cfg80211_parse_ml_elem_sta_data(struct wiphy *wiphy,
 	if (!mle)
 		return;
 
+	/* No point in doing anything if there is no per-STA profile */
+	if (!mle->sta_prof[0])
+		goto out;
+
 	new_ie = kmalloc(IEEE80211_MAX_DATA_LEN, gfp);
 	if (!new_ie)
 		goto out;
 
+	reporter_rnr = cfg80211_gen_reporter_rnr(source_bss,
+						 u16_get_bits(control,
+							      IEEE80211_MLC_BASIC_PRES_MLD_ID),
+						 mld_id == 0, reporter_link_id,
+						 bss_change_count,
+						 gfp);
+
 	for (i = 0; i < ARRAY_SIZE(mle->sta_prof) && mle->sta_prof[i]; i++) {
 		const struct ieee80211_neighbor_ap_info *ap_info;
 		enum nl80211_band band;
@@ -2803,7 +2918,16 @@ cfg80211_parse_ml_elem_sta_data(struct wiphy *wiphy,
 
 		data.ielen += sizeof(*ml_elem) + ml_common_len;
 
-		/* TODO: Add an RNR containing only the reporting AP */
+		if (reporter_rnr && (use_for & NL80211_BSS_USE_FOR_NORMAL)) {
+			if (data.ielen + sizeof(struct element) +
+			    reporter_rnr->datalen > IEEE80211_MAX_DATA_LEN)
+				continue;
+
+			memcpy(new_ie + data.ielen, reporter_rnr,
+			       sizeof(struct element) + reporter_rnr->datalen);
+			data.ielen += sizeof(struct element) +
+				      reporter_rnr->datalen;
+		}
 
 		bss = cfg80211_inform_single_bss_data(wiphy, &data, gfp);
 		if (!bss)
@@ -2812,6 +2936,7 @@ cfg80211_parse_ml_elem_sta_data(struct wiphy *wiphy,
 	}
 
 out:
+	kfree(reporter_rnr);
 	kfree(new_ie);
 	kfree(mle);
 }

net/wireless/tests/scan.c

@@ -2,7 +2,7 @@
 /*
  * KUnit tests for inform_bss functions
  *
- * Copyright (C) 2023 Intel Corporation
+ * Copyright (C) 2023-2024 Intel Corporation
  */
 #include <linux/ieee80211.h>
 #include <net/cfg80211.h>
@@ -406,9 +406,27 @@ static struct inform_bss_ml_sta_case {
 	const char *desc;
 	int mld_id;
 	bool sta_prof_vendor_elems;
+	bool include_oper_class;
 } inform_bss_ml_sta_cases[] = {
-	{ .desc = "no_mld_id", .mld_id = 0, .sta_prof_vendor_elems = false },
-	{ .desc = "mld_id_eq_1", .mld_id = 1, .sta_prof_vendor_elems = true },
+	{
+		.desc = "zero_mld_id",
+		.mld_id = 0,
+		.sta_prof_vendor_elems = false,
+	}, {
+		.desc = "zero_mld_id_with_oper_class",
+		.mld_id = 0,
+		.sta_prof_vendor_elems = false,
+		.include_oper_class = true,
+	}, {
+		.desc = "mld_id_eq_1",
+		.mld_id = 1,
+		.sta_prof_vendor_elems = true,
+	}, {
+		.desc = "mld_id_eq_1_with_oper_class",
+		.mld_id = 1,
+		.sta_prof_vendor_elems = true,
+		.include_oper_class = true,
+	},
 };
 KUNIT_ARRAY_PARAM_DESC(inform_bss_ml_sta, inform_bss_ml_sta_cases, desc)
 
@@ -515,6 +533,12 @@ static void test_inform_bss_ml_sta(struct kunit *test)
 	skb_put_u8(input, 4);
 	skb_put_data(input, "TEST", 4);
 
+	if (params->include_oper_class) {
+		skb_put_u8(input, WLAN_EID_SUPPORTED_REGULATORY_CLASSES);
+		skb_put_u8(input, 1);
+		skb_put_u8(input, 81);
+	}
+
 	skb_put_u8(input, WLAN_EID_REDUCED_NEIGHBOR_REPORT);
 	skb_put_u8(input, sizeof(rnr));
 	skb_put_data(input, &rnr, sizeof(rnr));
@@ -582,15 +606,21 @@ static void test_inform_bss_ml_sta(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, ies->tsf, tsf + le64_to_cpu(sta_prof.tsf_offset));
 	/* Resulting length should be:
 	 * SSID (inherited) + RNR (inherited) + vendor element(s) +
+	 * operating class (if requested) +
+	 * generated RNR (if MLD ID == 0) +
 	 * MLE common info + MLE header and control
 	 */
 	if (params->sta_prof_vendor_elems)
 		KUNIT_EXPECT_EQ(test, ies->len,
 				6 + 2 + sizeof(rnr) + 2 + 160 + 2 + 165 +
+				(params->include_oper_class ? 3 : 0) +
+				(!params->mld_id ? 22 : 0) +
 				mle_basic_common_info.var_len + 5);
 	else
 		KUNIT_EXPECT_EQ(test, ies->len,
 				6 + 2 + sizeof(rnr) + 2 + 155 +
+				(params->include_oper_class ? 3 : 0) +
+				(!params->mld_id ? 22 : 0) +
 				mle_basic_common_info.var_len + 5);
 	rcu_read_unlock();