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>

1 files changed, 105 insertions, 0 deletions

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 4dc139cdba5c..5c8b3bfada4b 100644
--- a/net/wireless/nl80211.c
+++ b/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",