cfg80211: return channel noise via survey API

This patch implements the NL80211_CMD_GET_SURVEY command and an get_survey()
ops that a driver can implement. The goal of this command is to allow a
drivers to report channel survey data (e.g. channel noise, channel
occupation).

For now, only the mechanism to report back channel noise has been
implemented.

In future, there will either be a survey-trigger command --- or the existing
scan-trigger command will be enhanced. This will allow user-space to
request survey for arbitrary channels.

Note: any driver that cannot report channel noise should not report
any value at all, e.g. made-up -92 dBm.
Signed-off-by: Holger Schurig <holgerschurig@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/linux/nl80211.h

@@ -160,6 +160,11 @@
  * @NL80211_CMD_SCAN_ABORTED: scan was aborted, for unspecified reasons,
  *	partial scan results may be available
  *
+ * @NL80211_CMD_GET_SURVEY: get survey resuls, e.g. channel occupation
+ *      or noise level
+ * @NL80211_CMD_NEW_SURVEY_RESULTS: survey data notification (as a reply to
+ *	NL80211_CMD_GET_SURVEY and on the "scan" multicast group)
+ *
  * @NL80211_CMD_REG_CHANGE: indicates to userspace the regulatory domain
  * 	has been changed and provides details of the request information
  * 	that caused the change such as who initiated the regulatory request
@@ -341,6 +346,9 @@ enum nl80211_commands {
 
 	NL80211_CMD_SET_WIPHY_NETNS,
 
+	NL80211_CMD_GET_SURVEY,
+	NL80211_CMD_NEW_SURVEY_RESULTS,
+
 	/* add new commands above here */
 
 	/* used to define NL80211_CMD_MAX below */
@@ -586,6 +594,10 @@ enum nl80211_commands {
  *
  * @NL80211_ATTR_4ADDR: Use 4-address frames on a virtual interface
  *
+ * @NL80211_ATTR_SURVEY_INFO: survey information about a channel, part of
+ *      the survey response for %NL80211_CMD_GET_SURVEY, nested attribute
+ *      containing info as possible, see &enum survey_info.
+ *
  * @NL80211_ATTR_MAX: highest attribute number currently defined
  * @__NL80211_ATTR_AFTER_LAST: internal use
  */
@@ -718,6 +730,8 @@ enum nl80211_attrs {
 
 	NL80211_ATTR_4ADDR,
 
+	NL80211_ATTR_SURVEY_INFO,
+
 	/* add attributes here, update the policy in nl80211.c */
 
 	__NL80211_ATTR_AFTER_LAST,
@@ -1120,6 +1134,26 @@ enum nl80211_reg_rule_flags {
 	NL80211_RRF_NO_IBSS		= 1<<8,
 };
 
+/**
+ * enum nl80211_survey_info - survey information
+ *
+ * These attribute types are used with %NL80211_ATTR_SURVEY_INFO
+ * when getting information about a survey.
+ *
+ * @__NL80211_SURVEY_INFO_INVALID: attribute number 0 is reserved
+ * @NL80211_SURVEY_INFO_FREQUENCY: center frequency of channel
+ * @NL80211_SURVEY_INFO_NOISE: noise level of channel (u8, dBm)
+ */
+enum nl80211_survey_info {
+	__NL80211_SURVEY_INFO_INVALID,
+	NL80211_SURVEY_INFO_FREQUENCY,
+	NL80211_SURVEY_INFO_NOISE,
+
+	/* keep last */
+	__NL80211_SURVEY_INFO_AFTER_LAST,
+	NL80211_SURVEY_INFO_MAX = __NL80211_SURVEY_INFO_AFTER_LAST - 1
+};
+
 /**
  * enum nl80211_mntr_flags - monitor configuration flags
  *

include/net/cfg80211.h

@@ -234,6 +234,35 @@ struct key_params {
 	u32 cipher;
 };
 
+/**
+ * enum survey_info_flags - survey information flags
+ *
+ * Used by the driver to indicate which info in &struct survey_info
+ * it has filled in during the get_survey().
+ */
+enum survey_info_flags {
+	SURVEY_INFO_NOISE_DBM = 1<<0,
+};
+
+/**
+ * struct survey_info - channel survey response
+ *
+ * Used by dump_survey() to report back per-channel survey information.
+ *
+ * @channel: the channel this survey record reports, mandatory
+ * @filled: bitflag of flags from &enum survey_info_flags
+ * @noise: channel noise in dBm. This and all following fields are
+ *     optional
+ *
+ * This structure can later be expanded with things like
+ * channel duty cycle etc.
+ */
+struct survey_info {
+	struct ieee80211_channel *channel;
+	u32 filled;
+	s8 noise;
+};
+
 /**
  * struct beacon_parameters - beacon parameters
  *
@@ -944,6 +973,8 @@ struct cfg80211_bitrate_mask {
  * @rfkill_poll: polls the hw rfkill line, use cfg80211 reporting
  *	functions to adjust rfkill hw state
  *
+ * @dump_survey: get site survey information.
+ *
  * @testmode_cmd: run a test mode command
  */
 struct cfg80211_ops {
@@ -1063,6 +1094,9 @@ struct cfg80211_ops {
 				    const u8 *peer,
 				    const struct cfg80211_bitrate_mask *mask);
 
+	int	(*dump_survey)(struct wiphy *wiphy, struct net_device *netdev,
+			int idx, struct survey_info *info);
+
 	/* some temporary stuff to finish wext */
 	int	(*set_power_mgmt)(struct wiphy *wiphy, struct net_device *dev,
 				  bool enabled, int timeout);

net/wireless/nl80211.c

@@ -3245,6 +3245,106 @@ static int nl80211_dump_scan(struct sk_buff *skb,
 	return err;
 }
 
+static int nl80211_send_survey(struct sk_buff *msg, u32 pid, u32 seq,
+				int flags, struct net_device *dev,
+				struct survey_info *survey)
+{
+	void *hdr;
+	struct nlattr *infoattr;
+
+	/* Survey without a channel doesn't make sense */
+	if (!survey->channel)
+		return -EINVAL;
+
+	hdr = nl80211hdr_put(msg, pid, seq, flags,
+			     NL80211_CMD_NEW_SURVEY_RESULTS);
+	if (!hdr)
+		return -ENOMEM;
+
+	NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, dev->ifindex);
+
+	infoattr = nla_nest_start(msg, NL80211_ATTR_SURVEY_INFO);
+	if (!infoattr)
+		goto nla_put_failure;
+
+	NLA_PUT_U32(msg, NL80211_SURVEY_INFO_FREQUENCY,
+		    survey->channel->center_freq);
+	if (survey->filled & SURVEY_INFO_NOISE_DBM)
+		NLA_PUT_U8(msg, NL80211_SURVEY_INFO_NOISE,
+			    survey->noise);
+
+	nla_nest_end(msg, infoattr);
+
+	return genlmsg_end(msg, hdr);
+
+ nla_put_failure:
+	genlmsg_cancel(msg, hdr);
+	return -EMSGSIZE;
+}
+
+static int nl80211_dump_survey(struct sk_buff *skb,
+			struct netlink_callback *cb)
+{
+	struct survey_info survey;
+	struct cfg80211_registered_device *dev;
+	struct net_device *netdev;
+	int ifidx = cb->args[0];
+	int survey_idx = cb->args[1];
+	int res;
+
+	if (!ifidx)
+		ifidx = nl80211_get_ifidx(cb);
+	if (ifidx < 0)
+		return ifidx;
+	cb->args[0] = ifidx;
+
+	rtnl_lock();
+
+	netdev = __dev_get_by_index(sock_net(skb->sk), ifidx);
+	if (!netdev) {
+		res = -ENODEV;
+		goto out_rtnl;
+	}
+
+	dev = cfg80211_get_dev_from_ifindex(sock_net(skb->sk), ifidx);
+	if (IS_ERR(dev)) {
+		res = PTR_ERR(dev);
+		goto out_rtnl;
+	}
+
+	if (!dev->ops->dump_survey) {
+		res = -EOPNOTSUPP;
+		goto out_err;
+	}
+
+	while (1) {
+		res = dev->ops->dump_survey(&dev->wiphy, netdev, survey_idx,
+					    &survey);
+		if (res == -ENOENT)
+			break;
+		if (res)
+			goto out_err;
+
+		if (nl80211_send_survey(skb,
+				NETLINK_CB(cb->skb).pid,
+				cb->nlh->nlmsg_seq, NLM_F_MULTI,
+				netdev,
+				&survey) < 0)
+			goto out;
+		survey_idx++;
+	}
+
+ out:
+	cb->args[1] = survey_idx;
+	res = skb->len;
+ out_err:
+	cfg80211_unlock_rdev(dev);
+ out_rtnl:
+	rtnl_unlock();
+
+	return res;
+}
+
 static bool nl80211_valid_auth_type(enum nl80211_auth_type auth_type)
 {
 	return auth_type <= NL80211_AUTHTYPE_MAX;
@@ -4322,6 +4422,11 @@ static struct genl_ops nl80211_ops[] = {
 		.policy = nl80211_policy,
 		.flags = GENL_ADMIN_PERM,
 	},
+	{
+		.cmd = NL80211_CMD_GET_SURVEY,
+		.policy = nl80211_policy,
+		.dumpit = nl80211_dump_survey,
+	},
 };
 static struct genl_multicast_group nl80211_mlme_mcgrp = {
 	.name = "mlme",