Factorize various duplicated chunks of (old and horrible) code, checking

for the validity of a given outgoing route entry into a single function.

This change is inspired from FreeBSD r111767.  The function introduced
here, rt_checkgate(), should hopefully die in a near future.  Why should
it die?  Well, it is way too late to do such validity checks: if your
kernel can ends up in ether_output() with an invalid route, please do
not let it try to find a new one that might do the job.

Go read this function if you're wondering why you're getting messages
like:

"arpresolve: X.X.X.X: route without link local address"

Since this horrible logic has survived 20 years of copy & past and small
modifications for workarounds without a single clear commit message, let's
assume it is full of dragons and try to play safe.  This factorization is
not intended to change any behavior.

With much inputs from bluhm@, tested by weerd@ and florian@ on setups
with p2p IPv6 interfaces.

ok bluhm@, benno@, florian@

3 files changed, 56 insertions, 39 deletions

diff --git a/sys/net/if_ethersubr.c b/sys/net/if_ethersubr.c
index 27193378ab8..d9d5da16ffe 100644
--- a/sys/net/if_ethersubr.c
+++ b/sys/net/if_ethersubr.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_ethersubr.c,v 1.184 2014/12/19 17:14:39 tedu Exp $	*/
+/*	$OpenBSD: if_ethersubr.c,v 1.185 2015/01/08 14:29:18 mpi Exp $	*/
 /*	$NetBSD: if_ethersubr.c,v 1.19 1996/05/07 02:40:30 thorpej Exp $	*/
 
 /*
@@ -238,14 +238,13 @@ ether_addheader(struct mbuf **m, struct ifnet *ifp, u_int16_t etype,
  */
 int
 ether_output(struct ifnet *ifp0, struct mbuf *m0, struct sockaddr *dst,
-    struct rtentry *rt0)
+    struct rtentry *rt)
 {
 	u_int16_t etype;
 	int s, len, error = 0;
 	u_char edst[ETHER_ADDR_LEN];
 	u_char *esrc;
 	struct mbuf *m = m0;
-	struct rtentry *rt;
 	struct mbuf *mcopy = NULL;
 	struct ether_header *eh;
 	struct arpcom *ac = (struct arpcom *)ifp0;
@@ -283,38 +282,12 @@ ether_output(struct ifnet *ifp0, struct mbuf *m0, struct sockaddr *dst,
 
 	if ((ifp->if_flags & (IFF_UP|IFF_RUNNING)) != (IFF_UP|IFF_RUNNING))
 		senderr(ENETDOWN);
-	if ((rt = rt0) != NULL) {
-		if ((rt->rt_flags & RTF_UP) == 0) {
-			if ((rt0 = rt = rtalloc(dst, RT_REPORT|RT_RESOLVE,
-			    m->m_pkthdr.ph_rtableid)) != NULL)
-				rt->rt_refcnt--;
-			else
-				senderr(EHOSTUNREACH);
-		}
 
-		if (rt->rt_flags & RTF_GATEWAY) {
-			if (rt->rt_gwroute == NULL)
-				goto lookup;
-			if (((rt = rt->rt_gwroute)->rt_flags & RTF_UP) == 0) {
-				rtfree(rt);
-				rt = rt0;
-			lookup:
-				rt->rt_gwroute = rtalloc(rt->rt_gateway,
-				    RT_REPORT|RT_RESOLVE, ifp->if_rdomain);
-				if ((rt = rt->rt_gwroute) == NULL)
-					senderr(EHOSTUNREACH);
-			}
-		}
-		if (rt->rt_flags & RTF_REJECT)
-			if (rt->rt_rmx.rmx_expire == 0 ||
-			    time_second < rt->rt_rmx.rmx_expire)
-				senderr(rt == rt0 ? EHOSTDOWN : EHOSTUNREACH);
-	}
 	switch (dst->sa_family) {
-
 	case AF_INET:
-		if (!arpresolve(ac, rt, m, dst, edst))
-			return (0);	/* if not yet resolved */
+		error = arpresolve(ac, rt, m, dst, edst);
+		if (error)
+			return (error == EAGAIN ? 0 : error);
 		/* If broadcasting on a simplex interface, loopback a copy */
 		if ((m->m_flags & M_BCAST) && (ifp->if_flags & IFF_SIMPLEX) &&
 		    !m->m_pkthdr.pf.routed)
@@ -323,8 +296,9 @@ ether_output(struct ifnet *ifp0, struct mbuf *m0, struct sockaddr *dst,
 		break;
 #ifdef INET6
 	case AF_INET6:
-		if (!nd6_storelladdr(ifp, rt, m, dst, (u_char *)edst))
-			return (0); /* it must be impossible, but... */
+		error = nd6_storelladdr(ifp, rt, m, dst, (u_char *)edst);
+		if (error)
+			return (error);
 		etype = htons(ETHERTYPE_IPV6);
 		break;
 #endif
@@ -347,8 +321,9 @@ ether_output(struct ifnet *ifp0, struct mbuf *m0, struct sockaddr *dst,
 				    sizeof(edst));
 				break;
 			case AF_INET:
-				if (!arpresolve(ac, rt, m, dst, edst))
-					return (0); /* if not yet resolved */
+				error = arpresolve(ac, rt, m, dst, edst);
+				if (error)
+					return (error == EAGAIN ? 0 : error);
 				break;
 			default:
 				senderr(EHOSTUNREACH);
diff --git a/sys/net/route.c b/sys/net/route.c
index 05f56763c50..427656a13c7 100644
--- a/sys/net/route.c
+++ b/sys/net/route.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: route.c,v 1.196 2014/12/29 11:53:58 mpi Exp $	*/
+/*	$OpenBSD: route.c,v 1.197 2015/01/08 14:29:18 mpi Exp $	*/
 /*	$NetBSD: route.c,v 1.14 1996/02/13 22:00:46 christos Exp $	*/
 
 /*
@@ -1032,6 +1032,45 @@ rt_setgate(struct rtentry *rt, struct sockaddr *dst, struct sockaddr *gate,
 	return (0);
 }
 
+int
+rt_checkgate(struct ifnet *ifp, struct rtentry *rt, struct sockaddr *dst,
+    unsigned int rtableid, struct rtentry **rtp)
+{
+	struct rtentry *rt0;
+
+	KASSERT(rt != NULL);
+
+	if ((rt->rt_flags & RTF_UP) == 0) {
+		rt = rtalloc(dst, RT_REPORT|RT_RESOLVE, rtableid);
+		rt->rt_refcnt--;
+		if (rt == NULL || rt->rt_ifp != ifp)
+			return (EHOSTUNREACH);
+	}
+
+	rt0 = rt;
+
+	if (rt->rt_flags & RTF_GATEWAY) {
+		if (rt->rt_gwroute && !(rt->rt_gwroute->rt_flags & RTF_UP)) {
+			rtfree(rt->rt_gwroute);
+			rt->rt_gwroute = NULL;
+		}
+		if (rt->rt_gwroute == NULL) {
+			rt->rt_gwroute = rtalloc(rt->rt_gateway,
+			    RT_REPORT|RT_RESOLVE, rtableid);
+			if (rt->rt_gwroute == NULL)
+				return (EHOSTUNREACH);
+		}
+		rt = rt->rt_gwroute;
+	}
+
+	if (rt->rt_flags & RTF_REJECT)
+		if (rt->rt_expire == 0 || time_second < rt->rt_expire)
+			return (rt == rt0 ? EHOSTDOWN : EHOSTUNREACH);
+
+	*rtp = rt;
+	return (0);
+}
+
 void
 rt_maskedcopy(struct sockaddr *src, struct sockaddr *dst,
     struct sockaddr *netmask)
diff --git a/sys/net/route.h b/sys/net/route.h
index c48905bf4f2..6fb9659b2cf 100644
--- a/sys/net/route.h
+++ b/sys/net/route.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: route.h,v 1.101 2014/11/24 12:43:54 mpi Exp $	*/
+/*	$OpenBSD: route.h,v 1.102 2015/01/08 14:29:18 mpi Exp $	*/
 /*	$NetBSD: route.h,v 1.9 1996/02/13 22:00:49 christos Exp $	*/
 
 /*
@@ -113,7 +113,8 @@ struct rtentry {
 	u_int16_t rt_labelid;		/* route label ID */
 	u_int8_t rt_priority;		/* routing priority to use */
 };
-#define	rt_use	rt_rmx.rmx_pksent
+#define	rt_use		rt_rmx.rmx_pksent
+#define	rt_expire	rt_rmx.rmx_expire
 
 #endif /* _KERNEL */
 
@@ -360,6 +361,8 @@ void	 rt_missmsg(int, struct rt_addrinfo *, int, struct ifnet *, int,
 void	 rt_newaddrmsg(int, struct ifaddr *, int, struct rtentry *);
 int	 rt_setgate(struct rtentry *, struct sockaddr *,
 	    struct sockaddr *, u_int);
+int	 rt_checkgate(struct ifnet *, struct rtentry *, struct sockaddr *,
+	    unsigned int, struct rtentry **);
 void	 rt_setmetrics(u_long, struct rt_metrics *, struct rt_kmetrics *);
 void	 rt_getmetrics(struct rt_kmetrics *, struct rt_metrics *);