nl80211: reduce non-split wiphy dump size

When wiphy dumps cannot be split, such as in events or with
older userspace that doesn't support it, the size can today
be too big.

Reduce it, by doing two things:

 1) remove data that couldn't have been present before the
    split capability was introduced since it's new, such as
    HE capabilities

 2) as suggested by Martin Willi, remove management frame
    subtypes from the split dumps, as just (1) isn't even
    enough due to other new code capabilities. This is fine
    as old consumers (really just wpa_supplicant) didn't
    check this data before they got support for split dumps.

Reported-by: Martin Willi <martin@strongswan.org>
Suggested-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Tested-by: Martin Willi <martin@strongswan.org>
Link: https://lore.kernel.org/r/20200928130655.53bce7873164.I71f06c9a221cd0630429a1a56eeae68a13beca61@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/nl80211.c

@@ -984,6 +984,8 @@ static int nl80211_msg_put_channel(struct sk_buff *msg, struct wiphy *wiphy,
 	if (!large && chan->flags &
 	    (IEEE80211_CHAN_NO_10MHZ | IEEE80211_CHAN_NO_20MHZ))
 		return 0;
+	if (!large && chan->freq_offset)
+		return 0;
 
 	if (nla_put_u32(msg, NL80211_FREQUENCY_ATTR_FREQ,
 			chan->center_freq))
@@ -1676,7 +1678,8 @@ nl80211_send_iftype_data(struct sk_buff *msg,
 }
 
 static int nl80211_send_band_rateinfo(struct sk_buff *msg,
-				      struct ieee80211_supported_band *sband)
+				      struct ieee80211_supported_band *sband,
+				      bool large)
 {
 	struct nlattr *nl_rates, *nl_rate;
 	struct ieee80211_rate *rate;
@@ -1704,7 +1707,7 @@ static int nl80211_send_band_rateinfo(struct sk_buff *msg,
 			 sband->vht_cap.cap)))
 		return -ENOBUFS;
 
-	if (sband->n_iftype_data) {
+	if (large && sband->n_iftype_data) {
 		struct nlattr *nl_iftype_data =
 			nla_nest_start_noflag(msg,
 					      NL80211_BAND_ATTR_IFTYPE_DATA);
@@ -1732,7 +1735,7 @@ static int nl80211_send_band_rateinfo(struct sk_buff *msg,
 	}
 
 	/* add EDMG info */
-	if (sband->edmg_cap.channels &&
+	if (large && sband->edmg_cap.channels &&
 	    (nla_put_u8(msg, NL80211_BAND_ATTR_EDMG_CHANNELS,
 		       sband->edmg_cap.channels) ||
 	    nla_put_u8(msg, NL80211_BAND_ATTR_EDMG_BW_CONFIG,
@@ -2150,13 +2153,7 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *rdev,
 		    nla_put_u16(msg, NL80211_ATTR_MAX_SCHED_SCAN_IE_LEN,
 				rdev->wiphy.max_sched_scan_ie_len) ||
 		    nla_put_u8(msg, NL80211_ATTR_MAX_MATCH_SETS,
-			       rdev->wiphy.max_match_sets) ||
-		    nla_put_u32(msg, NL80211_ATTR_MAX_NUM_SCHED_SCAN_PLANS,
-				rdev->wiphy.max_sched_scan_plans) ||
-		    nla_put_u32(msg, NL80211_ATTR_MAX_SCAN_PLAN_INTERVAL,
-				rdev->wiphy.max_sched_scan_plan_interval) ||
-		    nla_put_u32(msg, NL80211_ATTR_MAX_SCAN_PLAN_ITERATIONS,
-				rdev->wiphy.max_sched_scan_plan_iterations))
+			       rdev->wiphy.max_match_sets))
 			goto nla_put_failure;
 
 		if ((rdev->wiphy.flags & WIPHY_FLAG_IBSS_RSN) &&
@@ -2246,6 +2243,10 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *rdev,
 		     band < NUM_NL80211_BANDS; band++) {
 			struct ieee80211_supported_band *sband;
 
+			/* omit higher bands for ancient software */
+			if (band > NL80211_BAND_5GHZ && !state->split)
+				break;
+
 			sband = rdev->wiphy.bands[band];
 
 			if (!sband)
@@ -2257,7 +2258,8 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *rdev,
 
 			switch (state->chan_start) {
 			case 0:
-				if (nl80211_send_band_rateinfo(msg, sband))
+				if (nl80211_send_band_rateinfo(msg, sband,
+							       state->split))
 					goto nla_put_failure;
 				state->chan_start++;
 				if (state->split)
@@ -2359,8 +2361,6 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *rdev,
 		    nla_put_flag(msg, NL80211_ATTR_OFFCHANNEL_TX_OK))
 			goto nla_put_failure;
 
-		if (nl80211_send_mgmt_stypes(msg, mgmt_stypes))
-			goto nla_put_failure;
 		state->split_start++;
 		if (state->split)
 			break;
@@ -2431,6 +2431,17 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *rdev,
 		state->split_start++;
 		break;
 	case 9:
+		if (nl80211_send_mgmt_stypes(msg, mgmt_stypes))
+			goto nla_put_failure;
+
+		if (nla_put_u32(msg, NL80211_ATTR_MAX_NUM_SCHED_SCAN_PLANS,
+				rdev->wiphy.max_sched_scan_plans) ||
+		    nla_put_u32(msg, NL80211_ATTR_MAX_SCAN_PLAN_INTERVAL,
+				rdev->wiphy.max_sched_scan_plan_interval) ||
+		    nla_put_u32(msg, NL80211_ATTR_MAX_SCAN_PLAN_ITERATIONS,
+				rdev->wiphy.max_sched_scan_plan_iterations))
+			goto nla_put_failure;
+
 		if (rdev->wiphy.extended_capabilities &&
 		    (nla_put(msg, NL80211_ATTR_EXT_CAPA,
 			     rdev->wiphy.extended_capabilities_len,