ipv4: Cache input routes in fib_info nexthops.

Caching input routes is slightly simpler than output routes, since we
don't need to be concerned with nexthop exceptions.  (locally
destined, and routed packets, never trigger PMTU events or redirects
that will be processed by us).

However, we have to elide caching for the DIRECTSRC and non-zero itag
cases.

Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip_fib.h

@@ -82,6 +82,7 @@ struct fib_nh {
 	__be32			nh_saddr;
 	int			nh_saddr_genid;
 	struct rtable		*nh_rth_output;
+	struct rtable		*nh_rth_input;
 	struct fnhe_hash_bucket	*nh_exceptions;
 };
 

net/ipv4/fib_semantics.c

@@ -173,6 +173,8 @@ static void free_fib_info_rcu(struct rcu_head *head)
 			free_nh_exceptions(nexthop_nh);
 		if (nexthop_nh->nh_rth_output)
 			dst_release(&nexthop_nh->nh_rth_output->dst);
+		if (nexthop_nh->nh_rth_input)
+			dst_release(&nexthop_nh->nh_rth_input->dst);
 	} endfor_nexthops(fi);
 
 	release_net(fi->fib_net);

net/ipv4/route.c

@@ -1231,6 +1231,9 @@ static void rt_cache_route(struct fib_nh *nh, struct rtable *rt)
 {
 	struct rtable *orig, *prev, **p = &nh->nh_rth_output;
 
+	if (rt_is_input_route(rt))
+		p = &nh->nh_rth_input;
+
 	orig = *p;
 
 	prev = cmpxchg(p, orig, rt);
@@ -1241,6 +1244,11 @@ static void rt_cache_route(struct fib_nh *nh, struct rtable *rt)
 	}
 }
 
+static bool rt_cache_valid(struct rtable *rt)
+{
+	return (rt && rt->dst.obsolete == DST_OBSOLETE_FORCE_CHK);
+}
+
 static void rt_set_nexthop(struct rtable *rt, __be32 daddr,
 			   const struct fib_result *res,
 			   struct fib_nh_exception *fnhe,
@@ -1257,8 +1265,7 @@ static void rt_set_nexthop(struct rtable *rt, __be32 daddr,
 #ifdef CONFIG_IP_ROUTE_CLASSID
 		rt->dst.tclassid = nh->nh_tclassid;
 #endif
-		if (!(rt->dst.flags & DST_HOST) &&
-		    rt_is_output_route(rt))
+		if (!(rt->dst.flags & DST_HOST))
 			rt_cache_route(nh, rt);
 	}
 
@@ -1384,11 +1391,11 @@ static int __mkroute_input(struct sk_buff *skb,
 			   __be32 daddr, __be32 saddr, u32 tos,
 			   struct rtable **result)
 {
-	struct fib_nh_exception *fnhe;
 	struct rtable *rth;
 	int err;
 	struct in_device *out_dev;
 	unsigned int flags = 0;
+	bool do_cache;
 	u32 itag;
 
 	/* get a working reference to the output device */
@@ -1431,13 +1438,21 @@ static int __mkroute_input(struct sk_buff *skb,
 		}
 	}
 
-	fnhe = NULL;
-	if (res->fi)
-		fnhe = find_exception(&FIB_RES_NH(*res), daddr);
+	do_cache = false;
+	if (res->fi) {
+		if (!(flags & RTCF_DIRECTSRC) && !itag) {
+			rth = FIB_RES_NH(*res).nh_rth_input;
+			if (rt_cache_valid(rth)) {
+				dst_use(&rth->dst, jiffies);
+				goto out;
+			}
+			do_cache = true;
+		}
+	}
 
 	rth = rt_dst_alloc(out_dev->dev,
 			   IN_DEV_CONF_GET(in_dev, NOPOLICY),
-			   IN_DEV_CONF_GET(out_dev, NOXFRM), false);
+			   IN_DEV_CONF_GET(out_dev, NOXFRM), do_cache);
 	if (!rth) {
 		err = -ENOBUFS;
 		goto cleanup;
@@ -1456,8 +1471,8 @@ static int __mkroute_input(struct sk_buff *skb,
 	rth->dst.input = ip_forward;
 	rth->dst.output = ip_output;
 
-	rt_set_nexthop(rth, daddr, res, fnhe, res->fi, res->type, itag);
-
+	rt_set_nexthop(rth, daddr, res, NULL, res->fi, res->type, itag);
+out:
 	*result = rth;
 	err = 0;
  cleanup:
@@ -1509,6 +1524,7 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	struct rtable	*rth;
 	int		err = -EINVAL;
 	struct net    *net = dev_net(dev);
+	bool do_cache;
 
 	/* IP on this device is disabled. */
 
@@ -1522,6 +1538,7 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr))
 		goto martian_source;
 
+	res.fi = NULL;
 	if (ipv4_is_lbcast(daddr) || (saddr == 0 && daddr == 0))
 		goto brd_input;
 
@@ -1597,8 +1614,20 @@ out:	return err;
 	RT_CACHE_STAT_INC(in_brd);
 
 local_input:
+	do_cache = false;
+	if (res.fi) {
+		if (!(flags & RTCF_DIRECTSRC) && !itag) {
+			rth = FIB_RES_NH(res).nh_rth_input;
+			if (rt_cache_valid(rth)) {
+				dst_use(&rth->dst, jiffies);
+				goto set_and_out;
+			}
+			do_cache = true;
+		}
+	}
+
 	rth = rt_dst_alloc(net->loopback_dev,
-			   IN_DEV_CONF_GET(in_dev, NOPOLICY), false, false);
+			   IN_DEV_CONF_GET(in_dev, NOPOLICY), false, do_cache);
 	if (!rth)
 		goto e_nobufs;
 
@@ -1622,6 +1651,9 @@ out:	return err;
 		rth->dst.error= -err;
 		rth->rt_flags 	&= ~RTCF_LOCAL;
 	}
+	if (do_cache)
+		rt_cache_route(&FIB_RES_NH(res), rth);
+set_and_out:
 	skb_dst_set(skb, &rth->dst);
 	err = 0;
 	goto out;
@@ -1756,8 +1788,7 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
 		fnhe = find_exception(&FIB_RES_NH(*res), fl4->daddr);
 		if (!fnhe) {
 			rth = FIB_RES_NH(*res).nh_rth_output;
-			if (rth &&
-			    rth->dst.obsolete == DST_OBSOLETE_FORCE_CHK) {
+			if (rt_cache_valid(rth)) {
 				dst_use(&rth->dst, jiffies);
 				return rth;
 			}