[PATCH v2 1/3] cfg80211: support an active monitor interface flag

[Felix Fietkau <nbd@openwrt.org>]

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>
---
 include/net/cfg80211.h       |  1 +
 include/uapi/linux/nl80211.h |  4 ++++
 net/wireless/nl80211.c       | 10 ++++++++++
 3 files changed, 15 insertions(+)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 26b5b69..489821f 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -954,6 +954,7 @@ 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 d1e48b5..7b4b101 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -2413,6 +2413,8 @@ 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
@@ -2424,6 +2426,7 @@ 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,
@@ -3575,6 +3578,7 @@ 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 dfdb5e6..27c9f5c 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -2279,6 +2279,7 @@ 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)
@@ -2390,6 +2391,10 @@ static int nl80211_set_interface(struct sk_buff *skb, struct genl_info *info)
 		change = true;
 	}
 
+	if ((*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
@@ -2447,6 +2452,11 @@ 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);
-- 
1.8.0.2