[RFC, v3] cfg80211: first stab at channel survey

[RFC, v3] cfg80211: first stab at channel survey

[Holger Schurig]

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
driver to report back channel survey data (e.g. channel noise, channel
occupation) back to cfg80211 and thus via nl80211 to user-space.

In future, they will either be a survey-trigger command --- or the existing
scan-trigger command will be enhanced. However, the get_survey() operation
is usable even in absence of this: a driver can report the channel noise in
mBm with the implemented mechanism.

get_survey() is currently modelled like get_key(). I hope that's right.

struct survey_info is modelled like struct station_info. This allows different
drivers to fill in different fields.

Signed-off-by: Holger Schurig <holgerschurig@gmail.com>

---
v2: * channel is mandatory (by way of callback-parameter)
    * switched to .dump operation, e.g. nl80211_dump_survey() is now
      similar to nl80211_dump_stations() and nl80211_send_survey()
      is similar to nl80211_send_station().
    * this also means that the cfg80211_ops dump_survey() now caries
      an idx. A possible implementation (sketched, not compile-tested)
      for libertas could be:

v3: * own name-space for survey parameters
    * added sample to mac80211_hwsim

int lbs_dump_survey(struct wiphy *wiphy, struct net_device *netdev,
	int idx, struct survey_info *info)
{
	struct lbs_private *priv = wiphy_priv(wiphy);

	if (idx != 0)
		return -ENOENT;

	info->channel = priv->channel;
	info->filled = SURVEY_INFO_NOISE_MBM;
	info->noise = CAL_NF(...);
	return 0;
}

but other drives would use idx to iterate over stored survey information and
return the according information.
    

--- linux-wl.orig/include/linux/nl80211.h
+++ linux-wl/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 @@
 
 	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 */
@@ -584,6 +592,10 @@
  *	changed then the list changed and the dump should be repeated
  *	completely from scratch.
  *
+ * @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
  */
@@ -714,6 +726,8 @@
 
 	NL80211_ATTR_PID,
 
+	NL80211_ATTR_SURVEY_INFO,
+
 	/* add attributes here, update the policy in nl80211.c */
 
 	__NL80211_ATTR_AFTER_LAST,
@@ -1117,6 +1131,26 @@
 };
 
 /**
+ * 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_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_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
  *
  * Monitor configuration flags.
--- linux-wl.orig/include/net/cfg80211.h
+++ linux-wl/include/net/cfg80211.h
@@ -233,6 +233,35 @@
 };
 
 /**
+ * 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
  *
  * Used to configure the beacon for an interface.
@@ -941,6 +970,8 @@
  * @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 {
@@ -1060,6 +1091,9 @@
 				    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);
--- linux-wl.orig/net/wireless/nl80211.c
+++ linux-wl/net/wireless/nl80211.c
@@ -3229,6 +3229,108 @@
 	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 -1;
+
+	hdr = nl80211hdr_put(msg, pid, seq, flags,
+			     NL80211_CMD_NEW_SURVEY_RESULTS);
+	if (!hdr)
+		return -1;
+
+	NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, dev->ifindex);
+
+	infoattr = nla_nest_start(msg, NL80211_ATTR_SURVEY_INFO);
+	if (!infoattr)
+		goto nla_put_failure;
+
+	/* I could possibly use nl80211_msg_put_channel() and nest this into my
+	 * own NL80211_SURVEY_FREQUENCY. Would that be a better interface or
+	 * would all those regulatory fields distract us? */
+	NLA_PUT_U32(msg, NL80211_SURVEY_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 err;
+
+	if (!ifidx)
+		ifidx = nl80211_get_ifidx(cb);
+	if (ifidx < 0)
+		return ifidx;
+
+	rtnl_lock();
+
+	netdev = __dev_get_by_index(sock_net(skb->sk), ifidx);
+	if (!netdev) {
+		err = -ENODEV;
+		goto out_rtnl;
+	}
+
+	dev = cfg80211_get_dev_from_ifindex(sock_net(skb->sk), ifidx);
+	if (IS_ERR(dev)) {
+		err = PTR_ERR(dev);
+		goto out_rtnl;
+	}
+
+	if (!dev->ops->dump_survey) {
+		err = -EOPNOTSUPP;
+		goto out_err;
+	}
+
+	while (1) {
+		err = dev->ops->dump_survey(&dev->wiphy, netdev, survey_idx,
+					    &survey);
+		if (err == -ENOENT)
+			break;
+		if (err)
+			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;
+	err = skb->len;
+ out_err:
+	cfg80211_unlock_rdev(dev);
+ out_rtnl:
+	rtnl_unlock();
+
+	return err;
+}
+
 static bool nl80211_valid_auth_type(enum nl80211_auth_type auth_type)
 {
 	return auth_type <= NL80211_AUTHTYPE_MAX;
@@ -4306,6 +4408,11 @@
 		.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",

-- 
http://www.holgerschurig.de

Re: [RFC, v3] cfg80211: first stab at channel survey

[Johannes Berg]

[-- Attachment #1: Type: text/plain, Size: 1105 bytes --]

On Tue, 2009-11-10 at 17:23 +0100, Holger Schurig wrote:
> 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
> driver to report back channel survey data (e.g. channel noise, channel
> occupation) back to cfg80211 and thus via nl80211 to user-space.
> 
> In future, they will either be a survey-trigger command --- or the existing
> scan-trigger command will be enhanced. However, the get_survey() operation
> is usable even in absence of this: a driver can report the channel noise in
> mBm with the implemented mechanism.
> 
> get_survey() is currently modelled like get_key(). I hope that's right.

I don't think this last sentence is true any more?

> struct survey_info is modelled like struct station_info. This allows different
> drivers to fill in different fields.

Guess the details don't really belong into the commit log anyway.

Anyway, apart from the two things we talked about on IRC (error codes
and missing "cb->args[0] = ifidx;") it looks good, thanks.

johannes

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