--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -784,7 +784,8 @@ static int ieee80211_set_monitor_channel
 			ret = ieee80211_vif_use_channel(sdata, chandef,
 					IEEE80211_CHANCTX_EXCLUSIVE);
 		}
-	} else if (local->open_count == local->monitors) {
+       // Patch: Always allow channel change, even if a normal virtual interface is present
+       } else /*if (local->open_count == local->monitors)*/ {
 		local->_oper_chandef = *chandef;
 		ieee80211_hw_config(local, 0);
 	}
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -810,11 +810,19 @@
 
 	/*
 	 * Packet injection may want to control the sequence
-	 * number, if we have no matching interface then we
-	 * neither assign one ourselves nor ask the driver to.
+	 * number, so if an injected packet is found, skip
+	 * renumbering it. Also make the packet NO_ACK to avoid
+	 * excessive retries (ACKing and retrying should be
+	 * handled by the injecting application).
+	 * FIXME This may break hostapd and some other injectors.
+	 * This should be done using a radiotap flag.
 	 */
-	if (unlikely(info->control.vif->type == NL80211_IFTYPE_MONITOR))
+	if (unlikely((info->flags & IEEE80211_TX_CTL_INJECTED) &&
+	   !(tx->sdata->u.mntr.flags & MONITOR_FLAG_COOK_FRAMES))) {
+		if (!ieee80211_has_morefrags(hdr->frame_control))
+			info->flags |= IEEE80211_TX_CTL_NO_ACK;
 		return TX_CONTINUE;
+	}
 
 	if (unlikely(ieee80211_is_ctl(hdr->frame_control)))
 		return TX_CONTINUE;
@@ -2011,7 +2019,10 @@
 		}
 	}
 
-	ieee80211_set_qos_hdr(sdata, skb);
+	// Don't overwrite QoS header in monitor mode
+	if (likely(info->control.vif->type != NL80211_IFTYPE_MONITOR)) {
+		ieee80211_set_qos_hdr(sdata, skb);
+	}
 	ieee80211_tx(sdata, sta, skb, false);
 }
 
--- a/net/wireless/chan.c
+++ b/net/wireless/chan.c
@@ -1148,8 +1148,10 @@ int cfg80211_set_monitor_channel(struct
 {
 	if (!rdev->ops->set_monitor_channel)
 		return -EOPNOTSUPP;
-	if (!cfg80211_has_monitors_only(rdev))
-		return -EBUSY;
+	// Always allow user to change channel, even if there is another normal
+	// virtual interface using the device.
+	//if (!cfg80211_has_monitors_only(rdev))
+	//	return -EBUSY;
 
 	return rdev_set_monitor_channel(rdev, chandef);
 }