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>

1 files changed, 12 insertions, 5 deletions

diff --git a/include/linux/nl80211.h b/include/linux/nl80211.h
index cb3dc6027fd9..a8d71ed43a0e 100644
--- a/include/linux/nl80211.h
+++ b/include/linux/nl80211.h
@@ -480,10 +480,6 @@ enum nl80211_commands {
  * @NL80211_ATTR_SCAN_FREQUENCIES: nested attribute with frequencies (in MHz)
  * @NL80211_ATTR_SCAN_SSIDS: nested attribute with SSIDs, leave out for passive
  *      scanning and include a zero-length SSID (wildcard) for wildcard scan
- * @NL80211_ATTR_SCAN_GENERATION: the scan generation increases whenever the
- *      scan result list changes (BSS expired or added) so that applications
- *      can verify that they got a single, consistent snapshot (when all dump
- *      messages carried the same generation number)
  * @NL80211_ATTR_BSS: scan result BSS
  *
  * @NL80211_ATTR_REG_INITIATOR: indicates who requested the regulatory domain
@@ -580,6 +576,14 @@ enum nl80211_commands {
  *
  * @NL80211_ATTR_PID: Process ID of a network namespace.
  *
+ * @NL80211_ATTR_GENERATION: Used to indicate consistent snapshots for
+ *      dumps. This number increases whenever the object list being
+ *      dumped changes, and as such userspace can verify that it has
+ *      obtained a complete and consistent snapshot by verifying that
+ *      all dump messages contain the same generation number. If it
+ *      changed then the list changed and the dump should be repeated
+ *      completely from scratch.
+ *
  * @NL80211_ATTR_MAX: highest attribute number currently defined
  * @__NL80211_ATTR_AFTER_LAST: internal use
  */
@@ -651,7 +655,7 @@ enum nl80211_attrs {
 
         NL80211_ATTR_SCAN_FREQUENCIES,
         NL80211_ATTR_SCAN_SSIDS,
-        NL80211_ATTR_SCAN_GENERATION,
+        NL80211_ATTR_GENERATION, /* replaces old SCAN_GENERATION */
         NL80211_ATTR_BSS,
 
         NL80211_ATTR_REG_INITIATOR,
@@ -716,6 +720,9 @@ enum nl80211_attrs {
         NL80211_ATTR_MAX = __NL80211_ATTR_AFTER_LAST - 1
 };
 
+/* source-level API compatibility */
+#define NL80211_ATTR_SCAN_GENERATION NL80211_ATTR_GENERATION
+
 /*
  * Allow user space programs to use #ifdef on new attributes by defining them
  * here