[net80211] Add a method to return the vap's ifname.

This removes the requirement to know what's in the ifp.

(If someone wants a quick clean-up task, it'd be nice to convert instances
of ifp dereferencing for if_xname over to this method.)

sys/net80211/ieee80211_freebsd.c

@@ -1033,6 +1033,20 @@ wlan_iflladdr(void *arg __unused, struct ifnet *ifp)
 	}
 }
 
+/*
+ * Fetch the VAP name.
+ *
+ * This returns a const char pointer suitable for debugging,
+ * but don't expect it to stick around for much longer.
+ */
+const char *
+ieee80211_get_vap_ifname(struct ieee80211vap *vap)
+{
+	if ((vap->iv_ifp == NULL) || (vap->iv_ifp->if_xname == NULL))
+		return "(none)";
+	return vap->iv_ifp->if_xname;
+}
+
 /*
  * Module glue.
  *

sys/net80211/ieee80211_freebsd.h

@@ -245,6 +245,7 @@ void	ieee80211_drain_ifq(struct ifqueue *);
 void	ieee80211_flush_ifq(struct ifqueue *, struct ieee80211vap *);
 
 void	ieee80211_vap_destroy(struct ieee80211vap *);
+const char *	ieee80211_get_vap_ifname(struct ieee80211vap *);
 
 #define	IFNET_IS_UP_RUNNING(_ifp) \
 	(((_ifp)->if_flags & IFF_UP) && \