cfg80211: support an active monitor interface flag

An active monitor interface is one that is used for communication (via
injection). It is expected to ACK incoming unicast packets. This is
useful for running various 802.11 testing utilities that associate to an
AP via injection and manage the state in user space.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

3 files changed, 16 insertions, 0 deletions

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index b3b076a46d50..13b247d26544 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -961,6 +961,7 @@ struct station_info {
  * @MONITOR_FLAG_CONTROL: pass control frames
  * @MONITOR_FLAG_OTHER_BSS: disable BSSID filtering
  * @MONITOR_FLAG_COOK_FRAMES: report frames after processing
+ * @MONITOR_FLAG_ACTIVE: active monitor, ACKs frames on its MAC address
  */
 enum monitor_flags {
         MONITOR_FLAG_FCSFAIL            = 1<<NL80211_MNTR_FLAG_FCSFAIL,
@@ -968,6 +969,7 @@ enum monitor_flags {
         MONITOR_FLAG_CONTROL            = 1<<NL80211_MNTR_FLAG_CONTROL,
         MONITOR_FLAG_OTHER_BSS          = 1<<NL80211_MNTR_FLAG_OTHER_BSS,
         MONITOR_FLAG_COOK_FRAMES        = 1<<NL80211_MNTR_FLAG_COOK_FRAMES,
+        MONITOR_FLAG_ACTIVE             = 1<<NL80211_MNTR_FLAG_ACTIVE,
 };
 
 /**
diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
index 32b060ea5266..5920715278c2 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -2428,6 +2428,8 @@ enum nl80211_survey_info {
  * @NL80211_MNTR_FLAG_OTHER_BSS: disable BSSID filtering
  * @NL80211_MNTR_FLAG_COOK_FRAMES: report frames after processing.
  *      overrides all other flags.
+ * @NL80211_MNTR_FLAG_ACTIVE: use the configured MAC address
+ *      and ACK incoming unicast packets.
  *
  * @__NL80211_MNTR_FLAG_AFTER_LAST: internal use
  * @NL80211_MNTR_FLAG_MAX: highest possible monitor flag
@@ -2439,6 +2441,7 @@ enum nl80211_mntr_flags {
         NL80211_MNTR_FLAG_CONTROL,
         NL80211_MNTR_FLAG_OTHER_BSS,
         NL80211_MNTR_FLAG_COOK_FRAMES,
+        NL80211_MNTR_FLAG_ACTIVE,
 
         /* keep last */
         __NL80211_MNTR_FLAG_AFTER_LAST,
@@ -3595,6 +3598,7 @@ enum nl80211_feature_flags {
         NL80211_FEATURE_ADVERTISE_CHAN_LIMITS           = 1 << 14,
         NL80211_FEATURE_FULL_AP_CLIENT_STATE            = 1 << 15,
         NL80211_FEATURE_USERSPACE_MPM                   = 1 << 16,
+        NL80211_FEATURE_ACTIVE_MONITOR                  = 1 << 17,
 };
 
 /**
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index fb6abcb359a1..31d265f36d2c 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -2227,6 +2227,7 @@ static const struct nla_policy mntr_flags_policy[NL80211_MNTR_FLAG_MAX + 1] = {
         [NL80211_MNTR_FLAG_CONTROL] = { .type = NLA_FLAG },
         [NL80211_MNTR_FLAG_OTHER_BSS] = { .type = NLA_FLAG },
         [NL80211_MNTR_FLAG_COOK_FRAMES] = { .type = NLA_FLAG },
+        [NL80211_MNTR_FLAG_ACTIVE] = { .type = NLA_FLAG },
 };
 
 static int parse_monitor_flags(struct nlattr *nla, u32 *mntrflags)
@@ -2338,6 +2339,10 @@ static int nl80211_set_interface(struct sk_buff *skb, struct genl_info *info)
                 change = true;
         }
 
+        if (flags && (*flags & NL80211_MNTR_FLAG_ACTIVE) &&
+            !(rdev->wiphy.features & NL80211_FEATURE_ACTIVE_MONITOR))
+                return -EOPNOTSUPP;
+
         if (change)
                 err = cfg80211_change_iface(rdev, dev, ntype, flags, &params);
         else
@@ -2395,6 +2400,11 @@ static int nl80211_new_interface(struct sk_buff *skb, struct genl_info *info)
         err = parse_monitor_flags(type == NL80211_IFTYPE_MONITOR ?
                                   info->attrs[NL80211_ATTR_MNTR_FLAGS] : NULL,
                                   &flags);
+
+        if (!err && (flags & NL80211_MNTR_FLAG_ACTIVE) &&
+            !(rdev->wiphy.features & NL80211_FEATURE_ACTIVE_MONITOR))
+                return -EOPNOTSUPP;
+
         wdev = rdev_add_virtual_intf(rdev,
                                 nla_data(info->attrs[NL80211_ATTR_IFNAME]),
                                 type, err ? NULL : &flags, &params);