commit 6980269662ec2b601e3346ee23e82baa11c4a7c9
Author: Ryota Ozaki <ozaki-r@iij.ad.jp>
Date:   Tue Apr 12 14:39:18 2016 +0900

    Get rid of meaningless RTF_UP check
    
    The check is meaningless because
    - An obtained rtentry is ensured that it's always RTF_UP
      by rtcache, rtalloc1 and rtlookup. If the rtentry isn't changed
      (RTF_UP gets dropped) during processing, the check should be
      unnecessary
    - Even If not, i.e., an obtained rtentry can be changed during
      processing, checking only at the point doesn't help; the rtentry
      can be changed after the check
    
    Instead we have to ensure that RTF_UP isn't dropped if someone
    is using it somehow. Note that we already ensure that a rtentry
    being used isn't freed by rt_refcnt.

diff --git a/sys/netinet/ip_output.c b/sys/netinet/ip_output.c
index db23198..2c719a0 100644
--- a/sys/netinet/ip_output.c
+++ b/sys/netinet/ip_output.c
@@ -202,50 +202,20 @@ klock_if_output(struct ifnet * const ifp, struct mbuf * const m,
  * calling ifp's output routine.
  */
 int
-ip_hresolv_output(struct ifnet * const ifp0, struct mbuf * const m,
-    const struct sockaddr * const dst, struct rtentry *rt00)
+ip_hresolv_output(struct ifnet * const ifp, struct mbuf * const m,
+    const struct sockaddr * const dst, struct rtentry *rt0)
 {
 	int error = 0;
-	struct ifnet *ifp = ifp0;
-	struct rtentry *rt, *rt0, *gwrt;
+	struct rtentry *rt = rt0, *gwrt;
 
 #define RTFREE_IF_NEEDED(_rt) \
-	if ((_rt) != NULL && (_rt) != rt00) \
+	if ((_rt) != NULL && (_rt) != rt0) \
 		rtfree((_rt));
 
-	rt0 = rt00;
-retry:
-	if (!ip_hresolv_needed(ifp)) {
-		rt = rt0;
+	if (!ip_hresolv_needed(ifp))
 		goto out;
-	}
 
-	if (rt0 == NULL) {
-		rt = NULL;
-		goto out;
-	}
-
-	rt = rt0;
-
-	/*
-	 * The following block is highly questionable.  How did we get here
-	 * with a !RTF_UP route?  Does rtalloc1() always return an RTF_UP
-	 * route?
-	 */
-	if ((rt->rt_flags & RTF_UP) == 0) {
-		rt = rtalloc1(dst, 1);
-		if (rt == NULL) {
-			error = EHOSTUNREACH;
-			goto bad;
-		}
-		rt0 = rt;
-		if (rt->rt_ifp != ifp) {
-			ifp = rt->rt_ifp;
-			goto retry;
-		}
-	}
-
-	if ((rt->rt_flags & RTF_GATEWAY) == 0)
+	if (rt == NULL || (rt->rt_flags & RTF_GATEWAY) == 0)
 		goto out;
 
 	gwrt = rt_get_gwroute(rt);