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>

5 files changed, 14 insertions, 0 deletions

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 4bbf5007799b..5608f6c68413 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -323,6 +323,8 @@ static void sta_set_sinfo(struct sta_info *sta, struct station_info *sinfo)
 {
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
 
+	sinfo->generation = sdata->local->sta_generation;
+
 	sinfo->filled = STATION_INFO_INACTIVE_TIME |
 			STATION_INFO_RX_BYTES |
 			STATION_INFO_TX_BYTES |
@@ -909,6 +911,8 @@ static void mpath_set_pinfo(struct mesh_path *mpath, u8 *next_hop,
 	else
 		memset(next_hop, 0, ETH_ALEN);
 
+	pinfo->generation = mesh_paths_generation;
+
 	pinfo->filled = MPATH_INFO_FRAME_QLEN |
 			MPATH_INFO_DSN |
 			MPATH_INFO_METRIC |
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 989591787aee..99433222bc5c 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -678,6 +678,7 @@ struct ieee80211_local {
 	struct list_head sta_list;
 	struct sta_info *sta_hash[STA_HASH_SIZE];
 	struct timer_list sta_cleanup;
+	int sta_generation;
 
 	struct sk_buff_head pending[IEEE80211_MAX_QUEUES];
 	struct tasklet_struct tx_pending_tasklet;
diff --git a/net/mac80211/mesh.h b/net/mac80211/mesh.h
index 2a2ed182cb7e..ce538814b9bd 100644
--- a/net/mac80211/mesh.h
+++ b/net/mac80211/mesh.h
@@ -265,6 +265,8 @@ void mesh_path_discard_frame(struct sk_buff *skb,
 void mesh_path_quiesce(struct ieee80211_sub_if_data *sdata);
 void mesh_path_restart(struct ieee80211_sub_if_data *sdata);
 
+extern int mesh_paths_generation;
+
 #ifdef CONFIG_MAC80211_MESH
 extern int mesh_allocated;
 
diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index 04b9e4d61b8e..431865a58622 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -38,6 +38,8 @@ struct mpath_node {
 static struct mesh_table *mesh_paths;
 static struct mesh_table *mpp_paths; /* Store paths for MPP&MAP */
 
+int mesh_paths_generation;
+
 /* This lock will have the grow table function as writer and add / delete nodes
  * as readers. When reading the table (i.e. doing lookups) we are well protected
  * by RCU
@@ -243,6 +245,8 @@ int mesh_path_add(u8 *dst, struct ieee80211_sub_if_data *sdata)
 		mesh_paths->mean_chain_len * (mesh_paths->hash_mask + 1))
 		grow = 1;
 
+	mesh_paths_generation++;
+
 	spin_unlock(&mesh_paths->hashwlock[hash_idx]);
 	read_unlock(&pathtbl_resize_lock);
 	if (grow) {
@@ -484,6 +488,7 @@ int mesh_path_del(u8 *addr, struct ieee80211_sub_if_data *sdata)
 
 	err = -ENXIO;
 enddel:
+	mesh_paths_generation++;
 	spin_unlock(&mesh_paths->hashwlock[hash_idx]);
 	read_unlock(&pathtbl_resize_lock);
 	return err;
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index a360bceeba59..eec001491e66 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -349,6 +349,7 @@ int sta_info_insert(struct sta_info *sta)
 		goto out_free;
 	}
 	list_add(&sta->list, &local->sta_list);
+	local->sta_generation++;
 	local->num_sta++;
 	sta_info_hash_add(local, sta);
 
@@ -485,6 +486,7 @@ static void __sta_info_unlink(struct sta_info **sta)
 	}
 
 	local->num_sta--;
+	local->sta_generation++;
 
 	if (local->ops->sta_notify) {
 		if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)