[ 76/85] ipv4: introduce rt_uses_gateway

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

3.6-stable review patch.  If anyone has any objections, please let me know.

------------------


From: Julian Anastasov <ja@ssi.bg>

[ Upstream commit 155e8336c373d14d87a7f91e356d85ef4b93b8f9 ]

Add new flag to remember when route is via gateway.
We will use it to allow rt_gateway to contain address of
directly connected host for the cases when DST_NOCACHE is
used or when the NH exception caches per-destination route
without DST_NOCACHE flag, i.e. when routes are not used for
other destinations. By this way we force the neighbour
resolving to work with the routed destination but we
can use different address in the packet, feature needed
for IPVS-DR where original packet for virtual IP is routed
via route to real IP.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/net/route.h             |    3 +-
 net/ipv4/inet_connection_sock.c |    4 +--
 net/ipv4/ip_forward.c           |    2 -
 net/ipv4/ip_output.c            |    4 +--
 net/ipv4/route.c                |   48 +++++++++++++++++++++-------------------
 net/ipv4/xfrm4_policy.c         |    1 
 6 files changed, 34 insertions(+), 28 deletions(-)

--- a/include/net/route.h
+++ b/include/net/route.h
@@ -48,7 +48,8 @@ struct rtable {
 	int			rt_genid;
 	unsigned int		rt_flags;
 	__u16			rt_type;
-	__u16			rt_is_input;
+	__u8			rt_is_input;
+	__u8			rt_uses_gateway;
 
 	int			rt_iif;
 
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -386,7 +386,7 @@ struct dst_entry *inet_csk_route_req(str
 	rt = ip_route_output_flow(net, fl4, sk);
 	if (IS_ERR(rt))
 		goto no_route;
-	if (opt && opt->opt.is_strictroute && rt->rt_gateway)
+	if (opt && opt->opt.is_strictroute && rt->rt_uses_gateway)
 		goto route_err;
 	return &rt->dst;
 
@@ -422,7 +422,7 @@ struct dst_entry *inet_csk_route_child_s
 	rt = ip_route_output_flow(net, fl4, sk);
 	if (IS_ERR(rt))
 		goto no_route;
-	if (opt && opt->opt.is_strictroute && rt->rt_gateway)
+	if (opt && opt->opt.is_strictroute && rt->rt_uses_gateway)
 		goto route_err;
 	rcu_read_unlock();
 	return &rt->dst;
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -85,7 +85,7 @@ int ip_forward(struct sk_buff *skb)
 
 	rt = skb_rtable(skb);
 
-	if (opt->is_strictroute && rt->rt_gateway)
+	if (opt->is_strictroute && rt->rt_uses_gateway)
 		goto sr_failed;
 
 	if (unlikely(skb->len > dst_mtu(&rt->dst) && !skb_is_gso(skb) &&
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -193,7 +193,7 @@ static inline int ip_finish_output2(stru
 	}
 
 	rcu_read_lock_bh();
-	nexthop = rt->rt_gateway ? rt->rt_gateway : ip_hdr(skb)->daddr;
+	nexthop = (__force u32) rt_nexthop(rt, ip_hdr(skb)->daddr);
 	neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
 	if (unlikely(!neigh))
 		neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
@@ -371,7 +371,7 @@ int ip_queue_xmit(struct sk_buff *skb, s
 	skb_dst_set_noref(skb, &rt->dst);
 
 packet_routed:
-	if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_gateway)
+	if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
 		goto no_route;
 
 	/* OK, we know where to send it, allocate and build IP header. */
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1129,7 +1129,7 @@ static unsigned int ipv4_mtu(const struc
 	mtu = dst->dev->mtu;
 
 	if (unlikely(dst_metric_locked(dst, RTAX_MTU))) {
-		if (rt->rt_gateway && mtu > 576)
+		if (rt->rt_uses_gateway && mtu > 576)
 			mtu = 576;
 	}
 
@@ -1180,7 +1180,9 @@ static bool rt_bind_exception(struct rta
 		if (fnhe->fnhe_gw) {
 			rt->rt_flags |= RTCF_REDIRECTED;
 			rt->rt_gateway = fnhe->fnhe_gw;
-		}
+			rt->rt_uses_gateway = 1;
+		} else if (!rt->rt_gateway)
+			rt->rt_gateway = daddr;
 
 		orig = rcu_dereference(fnhe->fnhe_rth);
 		rcu_assign_pointer(fnhe->fnhe_rth, rt);
@@ -1189,13 +1191,6 @@ static bool rt_bind_exception(struct rta
 
 		fnhe->fnhe_stamp = jiffies;
 		ret = true;
-	} else {
-		/* Routes we intend to cache in nexthop exception have
-		 * the DST_NOCACHE bit clear.  However, if we are
-		 * unsuccessful at storing this route into the cache
-		 * we really need to set it.
-		 */
-		rt->dst.flags |= DST_NOCACHE;
 	}
 	spin_unlock_bh(&fnhe_lock);
 
@@ -1218,15 +1213,8 @@ static bool rt_cache_route(struct fib_nh
 	if (prev == orig) {
 		if (orig)
 			rt_free(orig);
-	} else {
-		/* Routes we intend to cache in the FIB nexthop have
-		 * the DST_NOCACHE bit clear.  However, if we are
-		 * unsuccessful at storing this route into the cache
-		 * we really need to set it.
-		 */
-		rt->dst.flags |= DST_NOCACHE;
+	} else
 		ret = false;
-	}
 
 	return ret;
 }
@@ -1287,8 +1275,10 @@ static void rt_set_nexthop(struct rtable
 	if (fi) {
 		struct fib_nh *nh = &FIB_RES_NH(*res);
 
-		if (nh->nh_gw && nh->nh_scope == RT_SCOPE_LINK)
+		if (nh->nh_gw && nh->nh_scope == RT_SCOPE_LINK) {
 			rt->rt_gateway = nh->nh_gw;
+			rt->rt_uses_gateway = 1;
+		}
 		dst_init_metrics(&rt->dst, fi->fib_metrics, true);
 #ifdef CONFIG_IP_ROUTE_CLASSID
 		rt->dst.tclassid = nh->nh_tclassid;
@@ -1297,8 +1287,18 @@ static void rt_set_nexthop(struct rtable
 			cached = rt_bind_exception(rt, fnhe, daddr);
 		else if (!(rt->dst.flags & DST_NOCACHE))
 			cached = rt_cache_route(nh, rt);
-	}
-	if (unlikely(!cached))
+		if (unlikely(!cached)) {
+			/* Routes we intend to cache in nexthop exception or
+			 * FIB nexthop have the DST_NOCACHE bit clear.
+			 * However, if we are unsuccessful at storing this
+			 * route into the cache we really need to set it.
+			 */
+			rt->dst.flags |= DST_NOCACHE;
+			if (!rt->rt_gateway)
+				rt->rt_gateway = daddr;
+			rt_add_uncached_list(rt);
+		}
+	} else
 		rt_add_uncached_list(rt);
 
 #ifdef CONFIG_IP_ROUTE_CLASSID
@@ -1366,6 +1366,7 @@ static int ip_route_input_mc(struct sk_b
 	rth->rt_iif	= 0;
 	rth->rt_pmtu	= 0;
 	rth->rt_gateway	= 0;
+	rth->rt_uses_gateway = 0;
 	INIT_LIST_HEAD(&rth->rt_uncached);
 	if (our) {
 		rth->dst.input= ip_local_deliver;
@@ -1435,7 +1436,6 @@ static int __mkroute_input(struct sk_buf
 		return -EINVAL;
 	}
 
-
 	err = fib_validate_source(skb, saddr, daddr, tos, FIB_RES_OIF(*res),
 				  in_dev->dev, in_dev, &itag);
 	if (err < 0) {
@@ -1491,6 +1491,7 @@ static int __mkroute_input(struct sk_buf
 	rth->rt_iif 	= 0;
 	rth->rt_pmtu	= 0;
 	rth->rt_gateway	= 0;
+	rth->rt_uses_gateway = 0;
 	INIT_LIST_HEAD(&rth->rt_uncached);
 
 	rth->dst.input = ip_forward;
@@ -1658,6 +1659,7 @@ local_input:
 	rth->rt_iif	= 0;
 	rth->rt_pmtu	= 0;
 	rth->rt_gateway	= 0;
+	rth->rt_uses_gateway = 0;
 	INIT_LIST_HEAD(&rth->rt_uncached);
 	if (res.type == RTN_UNREACHABLE) {
 		rth->dst.input= ip_error;
@@ -1826,6 +1828,7 @@ static struct rtable *__mkroute_output(c
 	rth->rt_iif	= orig_oif ? : 0;
 	rth->rt_pmtu	= 0;
 	rth->rt_gateway = 0;
+	rth->rt_uses_gateway = 0;
 	INIT_LIST_HEAD(&rth->rt_uncached);
 
 	RT_CACHE_STAT_INC(out_slow_tot);
@@ -2104,6 +2107,7 @@ struct dst_entry *ipv4_blackhole_route(s
 		rt->rt_flags = ort->rt_flags;
 		rt->rt_type = ort->rt_type;
 		rt->rt_gateway = ort->rt_gateway;
+		rt->rt_uses_gateway = ort->rt_uses_gateway;
 
 		INIT_LIST_HEAD(&rt->rt_uncached);
 
@@ -2182,7 +2186,7 @@ static int rt_fill_info(struct net *net,
 		if (nla_put_be32(skb, RTA_PREFSRC, fl4->saddr))
 			goto nla_put_failure;
 	}
-	if (rt->rt_gateway &&
+	if (rt->rt_uses_gateway &&
 	    nla_put_be32(skb, RTA_GATEWAY, rt->rt_gateway))
 		goto nla_put_failure;
 
--- a/net/ipv4/xfrm4_policy.c
+++ b/net/ipv4/xfrm4_policy.c
@@ -91,6 +91,7 @@ static int xfrm4_fill_dst(struct xfrm_ds
 					      RTCF_LOCAL);
 	xdst->u.rt.rt_type = rt->rt_type;
 	xdst->u.rt.rt_gateway = rt->rt_gateway;
+	xdst->u.rt.rt_uses_gateway = rt->rt_uses_gateway;
 	xdst->u.rt.rt_pmtu = rt->rt_pmtu;
 	INIT_LIST_HEAD(&xdst->u.rt.rt_uncached);