Index: sys/net/if.c
===================================================================
--- sys/net/if.c
+++ sys/net/if.c
@@ -1857,8 +1857,17 @@
 void
 ifa_ref(struct ifaddr *ifa)
 {
+	u_int old;
 
-	refcount_acquire(&ifa->ifa_refcnt);
+	old = refcount_acquire(&ifa->ifa_refcnt);
+	KASSERT(old > 0, ("%s: ifa %p has 0 refs", __func__, ifa));
+}
+
+int
+ifa_try_ref(struct ifaddr *ifa)
+{
+
+	return (refcount_acquire_if_not_zero(&ifa->ifa_refcnt));
 }
 
 static void
Index: sys/net/if_var.h
===================================================================
--- sys/net/if_var.h
+++ sys/net/if_var.h
@@ -577,6 +577,7 @@
 struct ifaddr *	ifa_alloc(size_t size, int flags);
 void	ifa_free(struct ifaddr *ifa);
 void	ifa_ref(struct ifaddr *ifa);
+int	ifa_try_ref(struct ifaddr *ifa);
 
 /*
  * Multicast address structure.  This is analogous to the ifaddr