nl80211: add generation number to all dumps

In order for userspace to be able to figure out whether
it obtained a consistent snapshot of data or not when
using netlink dumps, we need to have a generation number
in each dump message that indicates whether the list has
changed or not -- its value is arbitrary.

This patch adds such a number to all dumps, this needs
some mac80211 involvement to keep track of a generation
number to start with when adding/removing mesh paths or
stations.

The wiphy and netdev lists can be fully handled within
cfg80211, of course, but generation numbers need to be
stored there as well.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

4 files changed, 29 insertions, 10 deletions

diff --git a/net/wireless/core.c b/net/wireless/core.c
index 1e18930..62e1ac0 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -32,6 +32,7 @@ MODULE_DESCRIPTION("wireless configuration support");
  * only read the list, and that can happen quite
  * often because we need to do it for each command */
 LIST_HEAD(cfg80211_rdev_list);
+int cfg80211_rdev_list_generation;
 
 /*
  * This is used to protect the cfg80211_rdev_list
@@ -511,6 +512,7 @@ int wiphy_register(struct wiphy *wiphy)
 	wiphy_update_regulatory(wiphy, NL80211_REGDOM_SET_BY_CORE);
 
 	list_add(&rdev->list, &cfg80211_rdev_list);
+	cfg80211_rdev_list_generation++;
 
 	mutex_unlock(&cfg80211_mutex);
 
@@ -593,6 +595,7 @@ void wiphy_unregister(struct wiphy *wiphy)
 	reg_device_remove(wiphy);
 
 	list_del(&rdev->list);
+	cfg80211_rdev_list_generation++;
 	device_del(&rdev->wiphy.dev);
 	debugfs_remove(rdev->wiphy.debugfsdir);
 
@@ -653,6 +656,7 @@ static int cfg80211_netdev_notifier_call(struct notifier_block * nb,
 		spin_lock_init(&wdev->event_lock);
 		mutex_lock(&rdev->devlist_mtx);
 		list_add(&wdev->list, &rdev->netdev_list);
+		rdev->devlist_generation++;
 		/* can only change netns with wiphy */
 		dev->features |= NETIF_F_NETNS_LOCAL;
 
@@ -733,6 +737,7 @@ static int cfg80211_netdev_notifier_call(struct notifier_block * nb,
 		if (!list_empty(&wdev->list)) {
 			sysfs_remove_link(&dev->dev.kobj, "phy80211");
 			list_del_init(&wdev->list);
+			rdev->devlist_generation++;
 			mutex_destroy(&wdev->mtx);
 #ifdef CONFIG_WIRELESS_EXT
 			kfree(wdev->wext.keys);
diff --git a/net/wireless/core.h b/net/wireless/core.h
index 92e0492..639db52 100644
--- a/net/wireless/core.h
+++ b/net/wireless/core.h
@@ -49,6 +49,7 @@ struct cfg80211_registered_device {
 	/* associate netdev list */
 	struct mutex devlist_mtx;
 	struct list_head netdev_list;
+	int devlist_generation;
 
 	/* BSSes/scanning */
 	spinlock_t bss_lock;
@@ -101,6 +102,7 @@ bool wiphy_idx_valid(int wiphy_idx)
 
 extern struct mutex cfg80211_mutex;
 extern struct list_head cfg80211_rdev_list;
+extern int cfg80211_rdev_list_generation;
 
 #define assert_cfg80211_lock() WARN_ON(!mutex_is_locked(&cfg80211_mutex))
 
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 2ff7376..b3d5c1d 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -408,6 +408,9 @@ static int nl80211_send_wiphy(struct sk_buff *msg, u32 pid, u32 seq, int flags,
 	NLA_PUT_U32(msg, NL80211_ATTR_WIPHY, dev->wiphy_idx);
 	NLA_PUT_STRING(msg, NL80211_ATTR_WIPHY_NAME, wiphy_name(&dev->wiphy));
 
+	NLA_PUT_U32(msg, NL80211_ATTR_GENERATION,
+		    cfg80211_rdev_list_generation);
+
 	NLA_PUT_U8(msg, NL80211_ATTR_WIPHY_RETRY_SHORT,
 		   dev->wiphy.retry_short);
 	NLA_PUT_U8(msg, NL80211_ATTR_WIPHY_RETRY_LONG,
@@ -825,6 +828,11 @@ static int nl80211_send_iface(struct sk_buff *msg, u32 pid, u32 seq, int flags,
 	NLA_PUT_U32(msg, NL80211_ATTR_WIPHY, rdev->wiphy_idx);
 	NLA_PUT_STRING(msg, NL80211_ATTR_IFNAME, dev->name);
 	NLA_PUT_U32(msg, NL80211_ATTR_IFTYPE, dev->ieee80211_ptr->iftype);
+
+	NLA_PUT_U32(msg, NL80211_ATTR_GENERATION,
+		    rdev->devlist_generation ^
+			(cfg80211_rdev_list_generation << 2));
+
 	return genlmsg_end(msg, hdr);
 
  nla_put_failure:
@@ -838,12 +846,12 @@ static int nl80211_dump_interface(struct sk_buff *skb, struct netlink_callback *
 	int if_idx = 0;
 	int wp_start = cb->args[0];
 	int if_start = cb->args[1];
-	struct cfg80211_registered_device *dev;
+	struct cfg80211_registered_device *rdev;
 	struct wireless_dev *wdev;
 
 	mutex_lock(&cfg80211_mutex);
-	list_for_each_entry(dev, &cfg80211_rdev_list, list) {
-		if (!net_eq(wiphy_net(&dev->wiphy), sock_net(skb->sk)))
+	list_for_each_entry(rdev, &cfg80211_rdev_list, list) {
+		if (!net_eq(wiphy_net(&rdev->wiphy), sock_net(skb->sk)))
 			continue;
 		if (wp_idx < wp_start) {
 			wp_idx++;
@@ -851,21 +859,21 @@ static int nl80211_dump_interface(struct sk_buff *skb, struct netlink_callback *
 		}
 		if_idx = 0;
 
-		mutex_lock(&dev->devlist_mtx);
-		list_for_each_entry(wdev, &dev->netdev_list, list) {
+		mutex_lock(&rdev->devlist_mtx);
+		list_for_each_entry(wdev, &rdev->netdev_list, list) {
 			if (if_idx < if_start) {
 				if_idx++;
 				continue;
 			}
 			if (nl80211_send_iface(skb, NETLINK_CB(cb->skb).pid,
 					       cb->nlh->nlmsg_seq, NLM_F_MULTI,
-					       dev, wdev->netdev) < 0) {
-				mutex_unlock(&dev->devlist_mtx);
+					       rdev, wdev->netdev) < 0) {
+				mutex_unlock(&rdev->devlist_mtx);
 				goto out;
 			}
 			if_idx++;
 		}
-		mutex_unlock(&dev->devlist_mtx);
+		mutex_unlock(&rdev->devlist_mtx);
 
 		wp_idx++;
 	}
@@ -1616,6 +1624,8 @@ static int nl80211_send_station(struct sk_buff *msg, u32 pid, u32 seq,
 	NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, dev->ifindex);
 	NLA_PUT(msg, NL80211_ATTR_MAC, ETH_ALEN, mac_addr);
 
+	NLA_PUT_U32(msg, NL80211_ATTR_GENERATION, sinfo->generation);
+
 	sinfoattr = nla_nest_start(msg, NL80211_ATTR_STA_INFO);
 	if (!sinfoattr)
 		goto nla_put_failure;
@@ -2101,6 +2111,8 @@ static int nl80211_send_mpath(struct sk_buff *msg, u32 pid, u32 seq,
 	NLA_PUT(msg, NL80211_ATTR_MAC, ETH_ALEN, dst);
 	NLA_PUT(msg, NL80211_ATTR_MPATH_NEXT_HOP, ETH_ALEN, next_hop);
 
+	NLA_PUT_U32(msg, NL80211_ATTR_GENERATION, pinfo->generation);
+
 	pinfoattr = nla_nest_start(msg, NL80211_ATTR_MPATH_INFO);
 	if (!pinfoattr)
 		goto nla_put_failure;
@@ -3090,8 +3102,7 @@ static int nl80211_send_bss(struct sk_buff *msg, u32 pid, u32 seq, int flags,
 	if (!hdr)
 		return -1;
 
-	NLA_PUT_U32(msg, NL80211_ATTR_SCAN_GENERATION,
-		    rdev->bss_generation);
+	NLA_PUT_U32(msg, NL80211_ATTR_GENERATION, rdev->bss_generation);
 	NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, wdev->netdev->ifindex);
 
 	bss = nla_nest_start(msg, NL80211_ATTR_BSS);
diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 0ccf3a0..1bcb131 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -562,6 +562,7 @@ void cfg80211_unlink_bss(struct wiphy *wiphy, struct cfg80211_bss *pub)
 	spin_lock_bh(&dev->bss_lock);
 
 	list_del(&bss->list);
+	dev->bss_generation++;
 	rb_erase(&bss->rbn, &dev->bss_tree);
 
 	spin_unlock_bh(&dev->bss_lock);