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 1e189306560d..62e1ac00879b 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 92e0492b0e4d..639db52eeff7 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 2ff7376f35a3..b3d5c1df08dd 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 0ccf3a07dc02..1bcb1312bd94 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);