nl80211: add feature for BSS selection support

Introducing a new feature that the driver can use to
indicate the driver/firmware supports configuration of BSS
selection criteria upon CONNECT command. This can be useful
when multiple BSS-es are found belonging to the same ESS,
ie. Infra-BSS with same SSID. The criteria can then be used to
offload selection of a preferred BSS.

Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Lei Zhang <leizh@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
[move wiphy support check into parse_bss_select()]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

2 files changed, 118 insertions, 0 deletions

diff --git a/net/wireless/core.c b/net/wireless/core.c
index 9f1c4aa851ef..5327e4b974fa 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -626,6 +626,13 @@ int wiphy_register(struct wiphy *wiphy)
 		     !rdev->ops->set_mac_acl)))
 		return -EINVAL;
 
+	/* assure only valid behaviours are flagged by driver
+	 * hence subtract 2 as bit 0 is invalid.
+	 */
+	if (WARN_ON(wiphy->bss_select_support &&
+		    (wiphy->bss_select_support & ~(BIT(__NL80211_BSS_SELECT_ATTR_AFTER_LAST) - 2))))
+		return -EINVAL;
+
 	if (wiphy->addresses)
 		memcpy(wiphy->perm_addr, wiphy->addresses[0].addr, ETH_ALEN);
 
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 1b43f7839eeb..d6c6449c0389 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -402,6 +402,7 @@ static const struct nla_policy nl80211_policy[NUM_NL80211_ATTR] = {
 	[NL80211_ATTR_SCHED_SCAN_DELAY] = { .type = NLA_U32 },
 	[NL80211_ATTR_REG_INDOOR] = { .type = NLA_FLAG },
 	[NL80211_ATTR_PBSS] = { .type = NLA_FLAG },
+	[NL80211_ATTR_BSS_SELECT] = { .type = NLA_NESTED },
 };
 
 /* policy for the key attributes */
@@ -486,6 +487,15 @@ nl80211_plan_policy[NL80211_SCHED_SCAN_PLAN_MAX + 1] = {
 	[NL80211_SCHED_SCAN_PLAN_ITERATIONS] = { .type = NLA_U32 },
 };
 
+static const struct nla_policy
+nl80211_bss_select_policy[NL80211_BSS_SELECT_ATTR_MAX + 1] = {
+	[NL80211_BSS_SELECT_ATTR_RSSI] = { .type = NLA_FLAG },
+	[NL80211_BSS_SELECT_ATTR_BAND_PREF] = { .type = NLA_U32 },
+	[NL80211_BSS_SELECT_ATTR_RSSI_ADJUST] = {
+		.len = sizeof(struct nl80211_bss_select_rssi_adjust)
+	},
+};
+
 static int nl80211_prepare_wdev_dump(struct sk_buff *skb,
 				     struct netlink_callback *cb,
 				     struct cfg80211_registered_device **rdev,
@@ -1731,6 +1741,25 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *rdev,
 			    rdev->wiphy.ext_features))
 			goto nla_put_failure;
 
+		if (rdev->wiphy.bss_select_support) {
+			struct nlattr *nested;
+			u32 bss_select_support = rdev->wiphy.bss_select_support;
+
+			nested = nla_nest_start(msg, NL80211_ATTR_BSS_SELECT);
+			if (!nested)
+				goto nla_put_failure;
+
+			i = 0;
+			while (bss_select_support) {
+				if ((bss_select_support & 1) &&
+				    nla_put_flag(msg, i))
+					goto nla_put_failure;
+				i++;
+				bss_select_support >>= 1;
+			}
+			nla_nest_end(msg, nested);
+		}
+
 		/* done */
 		state->split_start = 0;
 		break;
@@ -5758,6 +5787,73 @@ static int validate_scan_freqs(struct nlattr *freqs)
 	return n_channels;
 }
 
+static bool is_band_valid(struct wiphy *wiphy, enum ieee80211_band b)
+{
+	return b < IEEE80211_NUM_BANDS && wiphy->bands[b];
+}
+
+static int parse_bss_select(struct nlattr *nla, struct wiphy *wiphy,
+			    struct cfg80211_bss_selection *bss_select)
+{
+	struct nlattr *attr[NL80211_BSS_SELECT_ATTR_MAX + 1];
+	struct nlattr *nest;
+	int err;
+	bool found = false;
+	int i;
+
+	/* only process one nested attribute */
+	nest = nla_data(nla);
+	if (!nla_ok(nest, nla_len(nest)))
+		return -EINVAL;
+
+	err = nla_parse(attr, NL80211_BSS_SELECT_ATTR_MAX, nla_data(nest),
+			nla_len(nest), nl80211_bss_select_policy);
+	if (err)
+		return err;
+
+	/* only one attribute may be given */
+	for (i = 0; i <= NL80211_BSS_SELECT_ATTR_MAX; i++) {
+		if (attr[i]) {
+			if (found)
+				return -EINVAL;
+			found = true;
+		}
+	}
+
+	bss_select->behaviour = __NL80211_BSS_SELECT_ATTR_INVALID;
+
+	if (attr[NL80211_BSS_SELECT_ATTR_RSSI])
+		bss_select->behaviour = NL80211_BSS_SELECT_ATTR_RSSI;
+
+	if (attr[NL80211_BSS_SELECT_ATTR_BAND_PREF]) {
+		bss_select->behaviour = NL80211_BSS_SELECT_ATTR_BAND_PREF;
+		bss_select->param.band_pref =
+			nla_get_u32(attr[NL80211_BSS_SELECT_ATTR_BAND_PREF]);
+		if (!is_band_valid(wiphy, bss_select->param.band_pref))
+			return -EINVAL;
+	}
+
+	if (attr[NL80211_BSS_SELECT_ATTR_RSSI_ADJUST]) {
+		struct nl80211_bss_select_rssi_adjust *adj_param;
+
+		adj_param = nla_data(attr[NL80211_BSS_SELECT_ATTR_RSSI_ADJUST]);
+		bss_select->behaviour = NL80211_BSS_SELECT_ATTR_RSSI_ADJUST;
+		bss_select->param.adjust.band = adj_param->band;
+		bss_select->param.adjust.delta = adj_param->delta;
+		if (!is_band_valid(wiphy, bss_select->param.adjust.band))
+			return -EINVAL;
+	}
+
+	/* user-space did not provide behaviour attribute */
+	if (bss_select->behaviour == __NL80211_BSS_SELECT_ATTR_INVALID)
+		return -EINVAL;
+
+	if (!(wiphy->bss_select_support & BIT(bss_select->behaviour)))
+		return -EINVAL;
+
+	return 0;
+}
+
 static int nl80211_parse_random_mac(struct nlattr **attrs,
 				    u8 *mac_addr, u8 *mac_addr_mask)
 {
@@ -8001,6 +8097,21 @@ static int nl80211_connect(struct sk_buff *skb, struct genl_info *info)
 		return -EOPNOTSUPP;
 	}
 
+	if (info->attrs[NL80211_ATTR_BSS_SELECT]) {
+		/* bss selection makes no sense if bssid is set */
+		if (connect.bssid) {
+			kzfree(connkeys);
+			return -EINVAL;
+		}
+
+		err = parse_bss_select(info->attrs[NL80211_ATTR_BSS_SELECT],
+				       wiphy, &connect.bss_select);
+		if (err) {
+			kzfree(connkeys);
+			return err;
+		}
+	}
+
 	wdev_lock(dev->ieee80211_ptr);
 	err = cfg80211_connect(rdev, dev, &connect, connkeys, NULL);
 	wdev_unlock(dev->ieee80211_ptr);