wifi: mac80211_hwsim: add control to skip beacons

To test certain beacon loss scenarios it can be useful to
simply not send a couple of beacons. Add a simple debugfs
file (per vif) to skip sending the beacons. They're still
fully prepared etc. so their DTIM count etc. will appear
as if they were simply corrupt over the air or otherwise
not received.
Reviewed-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://msgid.link/20240129200001.a267383709e6.I36f427d17c3478a7df46e205716f5ebc9b35a918@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/virtual/mac80211_hwsim.c

@@ -213,6 +213,7 @@ static const struct ieee80211_regdomain *hwsim_world_regdom_custom[] = {
 
 struct hwsim_vif_priv {
 	u32 magic;
+	u32 skip_beacons;
 	u8 bssid[ETH_ALEN];
 	bool assoc;
 	bool bcn_en;
@@ -2128,6 +2129,16 @@ static int mac80211_hwsim_add_interface(struct ieee80211_hw *hw,
 	return 0;
 }
 
+#ifdef CONFIG_MAC80211_DEBUGFS
+static void mac80211_hwsim_vif_add_debugfs(struct ieee80211_hw *hw,
+					   struct ieee80211_vif *vif)
+{
+	struct hwsim_vif_priv *vp = (void *)vif->drv_priv;
+
+	debugfs_create_u32("skip_beacons", 0600, vif->debugfs_dir,
+			   &vp->skip_beacons);
+}
+#endif
 
 static int mac80211_hwsim_change_interface(struct ieee80211_hw *hw,
 					   struct ieee80211_vif *vif,
@@ -2193,12 +2204,19 @@ static void __mac80211_hwsim_beacon_tx(struct ieee80211_bss_conf *link_conf,
 				       struct ieee80211_vif *vif,
 				       struct sk_buff *skb)
 {
+	struct hwsim_vif_priv *vp = (void *)vif->drv_priv;
 	struct ieee80211_tx_info *info;
 	struct ieee80211_rate *txrate;
 	struct ieee80211_mgmt *mgmt;
 	/* TODO: get MCS */
 	int bitrate = 100;
 
+	if (vp->skip_beacons) {
+		vp->skip_beacons--;
+		dev_kfree_skb(skb);
+		return;
+	}
+
 	info = IEEE80211_SKB_CB(skb);
 	if (ieee80211_hw_check(hw, SUPPORTS_RC_TABLE))
 		ieee80211_get_tx_rates(vif, NULL, skb,
@@ -3857,6 +3875,13 @@ static int hwsim_pmsr_report_nl(struct sk_buff *msg, struct genl_info *info)
 	return err;
 }
 
+#ifdef CONFIG_MAC80211_DEBUGFS
+#define HWSIM_DEBUGFS_OPS					\
+	.vif_add_debugfs = mac80211_hwsim_vif_add_debugfs,
+#else
+#define HWSIM_DEBUGFS_OPS
+#endif
+
 #define HWSIM_COMMON_OPS					\
 	.tx = mac80211_hwsim_tx,				\
 	.wake_tx_queue = ieee80211_handle_wake_tx_queue,	\
@@ -3881,7 +3906,8 @@ static int hwsim_pmsr_report_nl(struct sk_buff *msg, struct genl_info *info)
 	.get_et_stats = mac80211_hwsim_get_et_stats,		\
 	.get_et_strings = mac80211_hwsim_get_et_strings,	\
 	.start_pmsr = mac80211_hwsim_start_pmsr,		\
-	.abort_pmsr = mac80211_hwsim_abort_pmsr,
+	.abort_pmsr = mac80211_hwsim_abort_pmsr,		\
+	HWSIM_DEBUGFS_OPS
 
 #define HWSIM_NON_MLO_OPS					\
 	.sta_add = mac80211_hwsim_sta_add,			\