ipv4: Delete routing cache.

The ipv4 routing cache is non-deterministic, performance wise, and is
subject to reasonably easy to launch denial of service attacks.

The routing cache works great for well behaved traffic, and the world
was a much friendlier place when the tradeoffs that led to the routing
cache's design were considered.

What it boils down to is that the performance of the routing cache is
a product of the traffic patterns seen by a system rather than being a
product of the contents of the routing tables.  The former of which is
controllable by external entitites.

Even for "well behaved" legitimate traffic, high volume sites can see
hit rates in the routing cache of only ~%10.

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

2 files changed, 13 insertions, 932 deletions

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index b832036..f277cf0 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1072,11 +1072,6 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
 		rt_cache_flush(dev_net(dev), 0);
 		break;
 	case NETDEV_UNREGISTER_BATCH:
-		/* The batch unregister is only called on the first
-		 * device in the list of devices being unregistered.
-		 * Therefore we should not pass dev_net(dev) in here.
-		 */
-		rt_cache_flush_batch(NULL);
 		break;
 	}
 	return NOTIFY_DONE;
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index d547f6f..6d6146d 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -133,10 +133,6 @@ static int ip_rt_gc_elasticity __read_mostly	= 8;
 static int ip_rt_mtu_expires __read_mostly	= 10 * 60 * HZ;
 static int ip_rt_min_pmtu __read_mostly		= 512 + 20 + 20;
 static int ip_rt_min_advmss __read_mostly	= 256;
-static int rt_chain_length_max __read_mostly	= 20;
-
-static struct delayed_work expires_work;
-static unsigned long expires_ljiffies;
 
 /*
  *	Interface to generic destination cache.
@@ -152,7 +148,6 @@ static void		 ip_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
 					   struct sk_buff *skb, u32 mtu);
 static void		 ip_do_redirect(struct dst_entry *dst, struct sock *sk,
 					struct sk_buff *skb);
-static int rt_garbage_collect(struct dst_ops *ops);
 
 static void ipv4_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
 			    int how)
@@ -172,7 +167,6 @@ static struct neighbour *ipv4_neigh_lookup(const struct dst_entry *dst,
 static struct dst_ops ipv4_dst_ops = {
 	.family =		AF_INET,
 	.protocol =		cpu_to_be16(ETH_P_IP),
-	.gc =			rt_garbage_collect,
 	.check =		ipv4_dst_check,
 	.default_advmss =	ipv4_default_advmss,
 	.mtu =			ipv4_mtu,
@@ -209,184 +203,30 @@ const __u8 ip_tos2prio[16] = {
 };
 EXPORT_SYMBOL(ip_tos2prio);
 
-/*
- * Route cache.
- */
-
-/* The locking scheme is rather straight forward:
- *
- * 1) Read-Copy Update protects the buckets of the central route hash.
- * 2) Only writers remove entries, and they hold the lock
- *    as they look at rtable reference counts.
- * 3) Only readers acquire references to rtable entries,
- *    they do so with atomic increments and with the
- *    lock held.
- */
-
-struct rt_hash_bucket {
-	struct rtable __rcu	*chain;
-};
-
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) || \
-	defined(CONFIG_PROVE_LOCKING)
-/*
- * Instead of using one spinlock for each rt_hash_bucket, we use a table of spinlocks
- * The size of this table is a power of two and depends on the number of CPUS.
- * (on lockdep we have a quite big spinlock_t, so keep the size down there)
- */
-#ifdef CONFIG_LOCKDEP
-# define RT_HASH_LOCK_SZ	256
-#else
-# if NR_CPUS >= 32
-#  define RT_HASH_LOCK_SZ	4096
-# elif NR_CPUS >= 16
-#  define RT_HASH_LOCK_SZ	2048
-# elif NR_CPUS >= 8
-#  define RT_HASH_LOCK_SZ	1024
-# elif NR_CPUS >= 4
-#  define RT_HASH_LOCK_SZ	512
-# else
-#  define RT_HASH_LOCK_SZ	256
-# endif
-#endif
-
-static spinlock_t	*rt_hash_locks;
-# define rt_hash_lock_addr(slot) &rt_hash_locks[(slot) & (RT_HASH_LOCK_SZ - 1)]
-
-static __init void rt_hash_lock_init(void)
-{
-	int i;
-
-	rt_hash_locks = kmalloc(sizeof(spinlock_t) * RT_HASH_LOCK_SZ,
-			GFP_KERNEL);
-	if (!rt_hash_locks)
-		panic("IP: failed to allocate rt_hash_locks\n");
-
-	for (i = 0; i < RT_HASH_LOCK_SZ; i++)
-		spin_lock_init(&rt_hash_locks[i]);
-}
-#else
-# define rt_hash_lock_addr(slot) NULL
-
-static inline void rt_hash_lock_init(void)
-{
-}
-#endif
-
-static struct rt_hash_bucket 	*rt_hash_table __read_mostly;
-static unsigned int		rt_hash_mask __read_mostly;
-static unsigned int		rt_hash_log  __read_mostly;
-
 static DEFINE_PER_CPU(struct rt_cache_stat, rt_cache_stat);
 #define RT_CACHE_STAT_INC(field) __this_cpu_inc(rt_cache_stat.field)
 
-static inline unsigned int rt_hash(__be32 daddr, __be32 saddr, int idx,
-				   int genid)
-{
-	return jhash_3words((__force u32)daddr, (__force u32)saddr,
-			    idx, genid)
-		& rt_hash_mask;
-}
-
 static inline int rt_genid(struct net *net)
 {
 	return atomic_read(&net->ipv4.rt_genid);
 }
 
 #ifdef CONFIG_PROC_FS
-struct rt_cache_iter_state {
-	struct seq_net_private p;
-	int bucket;
-	int genid;
-};
-
-static struct rtable *rt_cache_get_first(struct seq_file *seq)
-{
-	struct rt_cache_iter_state *st = seq->private;
-	struct rtable *r = NULL;
-
-	for (st->bucket = rt_hash_mask; st->bucket >= 0; --st->bucket) {
-		if (!rcu_access_pointer(rt_hash_table[st->bucket].chain))
-			continue;
-		rcu_read_lock_bh();
-		r = rcu_dereference_bh(rt_hash_table[st->bucket].chain);
-		while (r) {
-			if (dev_net(r->dst.dev) == seq_file_net(seq) &&
-			    r->rt_genid == st->genid)
-				return r;
-			r = rcu_dereference_bh(r->dst.rt_next);
-		}
-		rcu_read_unlock_bh();
-	}
-	return r;
-}
-
-static struct rtable *__rt_cache_get_next(struct seq_file *seq,
-					  struct rtable *r)
-{
-	struct rt_cache_iter_state *st = seq->private;
-
-	r = rcu_dereference_bh(r->dst.rt_next);
-	while (!r) {
-		rcu_read_unlock_bh();
-		do {
-			if (--st->bucket < 0)
-				return NULL;
-		} while (!rcu_access_pointer(rt_hash_table[st->bucket].chain));
-		rcu_read_lock_bh();
-		r = rcu_dereference_bh(rt_hash_table[st->bucket].chain);
-	}
-	return r;
-}
-
-static struct rtable *rt_cache_get_next(struct seq_file *seq,
-					struct rtable *r)
-{
-	struct rt_cache_iter_state *st = seq->private;
-	while ((r = __rt_cache_get_next(seq, r)) != NULL) {
-		if (dev_net(r->dst.dev) != seq_file_net(seq))
-			continue;
-		if (r->rt_genid == st->genid)
-			break;
-	}
-	return r;
-}
-
-static struct rtable *rt_cache_get_idx(struct seq_file *seq, loff_t pos)
-{
-	struct rtable *r = rt_cache_get_first(seq);
-
-	if (r)
-		while (pos && (r = rt_cache_get_next(seq, r)))
-			--pos;
-	return pos ? NULL : r;
-}
-
 static void *rt_cache_seq_start(struct seq_file *seq, loff_t *pos)
 {
-	struct rt_cache_iter_state *st = seq->private;
 	if (*pos)
-		return rt_cache_get_idx(seq, *pos - 1);
-	st->genid = rt_genid(seq_file_net(seq));
+		return NULL;
 	return SEQ_START_TOKEN;
 }
 
 static void *rt_cache_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
-	struct rtable *r;
-
-	if (v == SEQ_START_TOKEN)
-		r = rt_cache_get_first(seq);
-	else
-		r = rt_cache_get_next(seq, v);
 	++*pos;
-	return r;
+	return NULL;
 }
 
 static void rt_cache_seq_stop(struct seq_file *seq, void *v)
 {
-	if (v && v != SEQ_START_TOKEN)
-		rcu_read_unlock_bh();
 }
 
 static int rt_cache_seq_show(struct seq_file *seq, void *v)
@@ -396,24 +236,6 @@ static int rt_cache_seq_show(struct seq_file *seq, void *v)
 			   "Iface\tDestination\tGateway \tFlags\t\tRefCnt\tUse\t"
 			   "Metric\tSource\t\tMTU\tWindow\tIRTT\tTOS\tHHRef\t"
 			   "HHUptod\tSpecDst");
-	else {
-		struct rtable *r = v;
-		int len;
-
-		seq_printf(seq, "%s\t%08X\t%08X\t%8X\t%d\t%u\t%d\t"
-			   "%08X\t%d\t%u\t%u\t%02X\t%d\t%1d\t%08X%n",
-			   r->dst.dev ? r->dst.dev->name : "*",
-			   (__force u32)r->rt_dst,
-			   (__force u32)r->rt_gateway,
-			   r->rt_flags, atomic_read(&r->dst.__refcnt),
-			   r->dst.__use, 0, (__force u32)r->rt_src,
-			   dst_metric_advmss(&r->dst) + 40,
-			   dst_metric(&r->dst, RTAX_WINDOW), 0,
-			   r->rt_key_tos,
-			   -1, 0, 0, &len);
-
-		seq_printf(seq, "%*s\n", 127 - len, "");
-	}
 	return 0;
 }
 
@@ -426,8 +248,7 @@ static const struct seq_operations rt_cache_seq_ops = {
 
 static int rt_cache_seq_open(struct inode *inode, struct file *file)
 {
-	return seq_open_net(inode, file, &rt_cache_seq_ops,
-			sizeof(struct rt_cache_iter_state));
+	return seq_open(file, &rt_cache_seq_ops);
 }
 
 static const struct file_operations rt_cache_seq_fops = {
@@ -435,7 +256,7 @@ static const struct file_operations rt_cache_seq_fops = {
 	.open	 = rt_cache_seq_open,
 	.read	 = seq_read,
 	.llseek	 = seq_lseek,
-	.release = seq_release_net,
+	.release = seq_release,
 };
 
 
@@ -625,263 +446,12 @@ static inline int ip_rt_proc_init(void)
 }
 #endif /* CONFIG_PROC_FS */
 
-static inline void rt_free(struct rtable *rt)
-{
-	call_rcu_bh(&rt->dst.rcu_head, dst_rcu_free);
-}
-
-static inline void rt_drop(struct rtable *rt)
-{
-	ip_rt_put(rt);
-	call_rcu_bh(&rt->dst.rcu_head, dst_rcu_free);
-}
-
-static inline int rt_fast_clean(struct rtable *rth)
-{
-	/* Kill broadcast/multicast entries very aggresively, if they
-	   collide in hash table with more useful entries */
-	return (rth->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) &&
-		rt_is_input_route(rth) && rth->dst.rt_next;
-}
-
-static inline int rt_valuable(struct rtable *rth)
-{
-	return (rth->rt_flags & (RTCF_REDIRECTED | RTCF_NOTIFY)) ||
-		rth->dst.expires;
-}
-
-static int rt_may_expire(struct rtable *rth, unsigned long tmo1, unsigned long tmo2)
-{
-	unsigned long age;
-	int ret = 0;
-
-	if (atomic_read(&rth->dst.__refcnt))
-		goto out;
-
-	age = jiffies - rth->dst.lastuse;
-	if ((age <= tmo1 && !rt_fast_clean(rth)) ||
-	    (age <= tmo2 && rt_valuable(rth)))
-		goto out;
-	ret = 1;
-out:	return ret;
-}
-
-/* Bits of score are:
- * 31: very valuable
- * 30: not quite useless
- * 29..0: usage counter
- */
-static inline u32 rt_score(struct rtable *rt)
-{
-	u32 score = jiffies - rt->dst.lastuse;
-
-	score = ~score & ~(3<<30);
-
-	if (rt_valuable(rt))
-		score |= (1<<31);
-
-	if (rt_is_output_route(rt) ||
-	    !(rt->rt_flags & (RTCF_BROADCAST|RTCF_MULTICAST|RTCF_LOCAL)))
-		score |= (1<<30);
-
-	return score;
-}
-
-static inline bool rt_caching(const struct net *net)
-{
-	return net->ipv4.current_rt_cache_rebuild_count <=
-		net->ipv4.sysctl_rt_cache_rebuild_count;
-}
-
-static inline bool compare_hash_inputs(const struct rtable *rt1,
-				       const struct rtable *rt2)
-{
-	return ((((__force u32)rt1->rt_key_dst ^ (__force u32)rt2->rt_key_dst) |
-		((__force u32)rt1->rt_key_src ^ (__force u32)rt2->rt_key_src) |
-		(rt1->rt_route_iif ^ rt2->rt_route_iif)) == 0);
-}
-
-static inline int compare_keys(struct rtable *rt1, struct rtable *rt2)
-{
-	return (((__force u32)rt1->rt_key_dst ^ (__force u32)rt2->rt_key_dst) |
-		((__force u32)rt1->rt_key_src ^ (__force u32)rt2->rt_key_src) |
-		(rt1->rt_mark ^ rt2->rt_mark) |
-		(rt1->rt_key_tos ^ rt2->rt_key_tos) |
-		(rt1->rt_route_iif ^ rt2->rt_route_iif) |
-		(rt1->rt_oif ^ rt2->rt_oif)) == 0;
-}
-
-static inline int compare_netns(struct rtable *rt1, struct rtable *rt2)
-{
-	return net_eq(dev_net(rt1->dst.dev), dev_net(rt2->dst.dev));
-}
-
 static inline int rt_is_expired(struct rtable *rth)
 {
 	return rth->rt_genid != rt_genid(dev_net(rth->dst.dev));
 }
 
 /*
- * Perform a full scan of hash table and free all entries.
- * Can be called by a softirq or a process.
- * In the later case, we want to be reschedule if necessary
- */
-static void rt_do_flush(struct net *net, int process_context)
-{
-	unsigned int i;
-	struct rtable *rth, *next;
-
-	for (i = 0; i <= rt_hash_mask; i++) {
-		struct rtable __rcu **pprev;
-		struct rtable *list;
-
-		if (process_context && need_resched())
-			cond_resched();
-		rth = rcu_access_pointer(rt_hash_table[i].chain);
-		if (!rth)
-			continue;
-
-		spin_lock_bh(rt_hash_lock_addr(i));
-
-		list = NULL;
-		pprev = &rt_hash_table[i].chain;
-		rth = rcu_dereference_protected(*pprev,
-			lockdep_is_held(rt_hash_lock_addr(i)));
-
-		while (rth) {
-			next = rcu_dereference_protected(rth->dst.rt_next,
-				lockdep_is_held(rt_hash_lock_addr(i)));
-
-			if (!net ||
-			    net_eq(dev_net(rth->dst.dev), net)) {
-				rcu_assign_pointer(*pprev, next);
-				rcu_assign_pointer(rth->dst.rt_next, list);
-				list = rth;
-			} else {
-				pprev = &rth->dst.rt_next;
-			}
-			rth = next;
-		}
-
-		spin_unlock_bh(rt_hash_lock_addr(i));
-
-		for (; list; list = next) {
-			next = rcu_dereference_protected(list->dst.rt_next, 1);
-			rt_free(list);
-		}
-	}
-}
-
-/*
- * While freeing expired entries, we compute average chain length
- * and standard deviation, using fixed-point arithmetic.
- * This to have an estimation of rt_chain_length_max
- *  rt_chain_length_max = max(elasticity, AVG + 4*SD)
- * We use 3 bits for frational part, and 29 (or 61) for magnitude.
- */
-
-#define FRACT_BITS 3
-#define ONE (1UL << FRACT_BITS)
-
-/*
- * Given a hash chain and an item in this hash chain,
- * find if a previous entry has the same hash_inputs
- * (but differs on tos, mark or oif)
- * Returns 0 if an alias is found.
- * Returns ONE if rth has no alias before itself.
- */
-static int has_noalias(const struct rtable *head, const struct rtable *rth)
-{
-	const struct rtable *aux = head;
-
-	while (aux != rth) {
-		if (compare_hash_inputs(aux, rth))
-			return 0;
-		aux = rcu_dereference_protected(aux->dst.rt_next, 1);
-	}
-	return ONE;
-}
-
-static void rt_check_expire(void)
-{
-	static unsigned int rover;
-	unsigned int i = rover, goal;
-	struct rtable *rth;
-	struct rtable __rcu **rthp;
-	unsigned long samples = 0;
-	unsigned long sum = 0, sum2 = 0;
-	unsigned long delta;
-	u64 mult;
-
-	delta = jiffies - expires_ljiffies;
-	expires_ljiffies = jiffies;
-	mult = ((u64)delta) << rt_hash_log;
-	if (ip_rt_gc_timeout > 1)
-		do_div(mult, ip_rt_gc_timeout);
-	goal = (unsigned int)mult;
-	if (goal > rt_hash_mask)
-		goal = rt_hash_mask + 1;
-	for (; goal > 0; goal--) {
-		unsigned long tmo = ip_rt_gc_timeout;
-		unsigned long length;
-
-		i = (i + 1) & rt_hash_mask;
-		rthp = &rt_hash_table[i].chain;
-
-		if (need_resched())
-			cond_resched();
-
-		samples++;
-
-		if (rcu_dereference_raw(*rthp) == NULL)
-			continue;
-		length = 0;
-		spin_lock_bh(rt_hash_lock_addr(i));
-		while ((rth = rcu_dereference_protected(*rthp,
-					lockdep_is_held(rt_hash_lock_addr(i)))) != NULL) {
-			prefetch(rth->dst.rt_next);
-			if (rt_is_expired(rth) ||
-			    rt_may_expire(rth, tmo, ip_rt_gc_timeout)) {
-				*rthp = rth->dst.rt_next;
-				rt_free(rth);
-				continue;
-			}
-
-			/* We only count entries on a chain with equal
-			 * hash inputs once so that entries for
-			 * different QOS levels, and other non-hash
-			 * input attributes don't unfairly skew the
-			 * length computation
-			 */
-			tmo >>= 1;
-			rthp = &rth->dst.rt_next;
-			length += has_noalias(rt_hash_table[i].chain, rth);
-		}
-		spin_unlock_bh(rt_hash_lock_addr(i));
-		sum += length;
-		sum2 += length*length;
-	}
-	if (samples) {
-		unsigned long avg = sum / samples;
-		unsigned long sd = int_sqrt(sum2 / samples - avg*avg);
-		rt_chain_length_max = max_t(unsigned long,
-					ip_rt_gc_elasticity,
-					(avg + 4*sd) >> FRACT_BITS);
-	}
-	rover = i;
-}
-
-/*
- * rt_worker_func() is run in process context.
- * we call rt_check_expire() to scan part of the hash table
- */
-static void rt_worker_func(struct work_struct *work)
-{
-	rt_check_expire();
-	schedule_delayed_work(&expires_work, ip_rt_gc_interval);
-}
-
-/*
  * Perturbation of rt_genid by a small quantity [1..256]
  * Using 8 bits of shuffling ensure we can call rt_cache_invalidate()
  * many times (2^24) without giving recent rt_genid.
@@ -902,167 +472,6 @@ static void rt_cache_invalidate(struct net *net)
 void rt_cache_flush(struct net *net, int delay)
 {
 	rt_cache_invalidate(net);
-	if (delay >= 0)
-		rt_do_flush(net, !in_softirq());
-}
-
-/* Flush previous cache invalidated entries from the cache */
-void rt_cache_flush_batch(struct net *net)
-{
-	rt_do_flush(net, !in_softirq());
-}
-
-static void rt_emergency_hash_rebuild(struct net *net)
-{
-	net_warn_ratelimited("Route hash chain too long!\n");
-	rt_cache_invalidate(net);
-}
-
-/*
-   Short description of GC goals.
-
-   We want to build algorithm, which will keep routing cache
-   at some equilibrium point, when number of aged off entries
-   is kept approximately equal to newly generated ones.
-
-   Current expiration strength is variable "expire".
-   We try to adjust it dynamically, so that if networking
-   is idle expires is large enough to keep enough of warm entries,
-   and when load increases it reduces to limit cache size.
- */
-
-static int rt_garbage_collect(struct dst_ops *ops)
-{
-	static unsigned long expire = RT_GC_TIMEOUT;
-	static unsigned long last_gc;
-	static int rover;
-	static int equilibrium;
-	struct rtable *rth;
-	struct rtable __rcu **rthp;
-	unsigned long now = jiffies;
-	int goal;
-	int entries = dst_entries_get_fast(&ipv4_dst_ops);
-
-	/*
-	 * Garbage collection is pretty expensive,
-	 * do not make it too frequently.
-	 */
-
-	RT_CACHE_STAT_INC(gc_total);
-
-	if (now - last_gc < ip_rt_gc_min_interval &&
-	    entries < ip_rt_max_size) {
-		RT_CACHE_STAT_INC(gc_ignored);
-		goto out;
-	}
-
-	entries = dst_entries_get_slow(&ipv4_dst_ops);
-	/* Calculate number of entries, which we want to expire now. */
-	goal = entries - (ip_rt_gc_elasticity << rt_hash_log);
-	if (goal <= 0) {
-		if (equilibrium < ipv4_dst_ops.gc_thresh)
-			equilibrium = ipv4_dst_ops.gc_thresh;
-		goal = entries - equilibrium;
-		if (goal > 0) {
-			equilibrium += min_t(unsigned int, goal >> 1, rt_hash_mask + 1);
-			goal = entries - equilibrium;
-		}
-	} else {
-		/* We are in dangerous area. Try to reduce cache really
-		 * aggressively.
-		 */
-		goal = max_t(unsigned int, goal >> 1, rt_hash_mask + 1);
-		equilibrium = entries - goal;
-	}
-
-	if (now - last_gc >= ip_rt_gc_min_interval)
-		last_gc = now;
-
-	if (goal <= 0) {
-		equilibrium += goal;
-		goto work_done;
-	}
-
-	do {
-		int i, k;
-
-		for (i = rt_hash_mask, k = rover; i >= 0; i--) {
-			unsigned long tmo = expire;
-
-			k = (k + 1) & rt_hash_mask;
-			rthp = &rt_hash_table[k].chain;
-			spin_lock_bh(rt_hash_lock_addr(k));
-			while ((rth = rcu_dereference_protected(*rthp,
-					lockdep_is_held(rt_hash_lock_addr(k)))) != NULL) {
-				if (!rt_is_expired(rth) &&
-					!rt_may_expire(rth, tmo, expire)) {
-					tmo >>= 1;
-					rthp = &rth->dst.rt_next;
-					continue;
-				}
-				*rthp = rth->dst.rt_next;
-				rt_free(rth);
-				goal--;
-			}
-			spin_unlock_bh(rt_hash_lock_addr(k));
-			if (goal <= 0)
-				break;
-		}
-		rover = k;
-
-		if (goal <= 0)
-			goto work_done;
-
-		/* Goal is not achieved. We stop process if:
-
-		   - if expire reduced to zero. Otherwise, expire is halfed.
-		   - if table is not full.
-		   - if we are called from interrupt.
-		   - jiffies check is just fallback/debug loop breaker.
-		     We will not spin here for long time in any case.
-		 */
-
-		RT_CACHE_STAT_INC(gc_goal_miss);
-
-		if (expire == 0)
-			break;
-
-		expire >>= 1;
-
-		if (dst_entries_get_fast(&ipv4_dst_ops) < ip_rt_max_size)
-			goto out;
-	} while (!in_softirq() && time_before_eq(jiffies, now));
-
-	if (dst_entries_get_fast(&ipv4_dst_ops) < ip_rt_max_size)
-		goto out;
-	if (dst_entries_get_slow(&ipv4_dst_ops) < ip_rt_max_size)
-		goto out;
-	net_warn_ratelimited("dst cache overflow\n");
-	RT_CACHE_STAT_INC(gc_dst_overflow);
-	return 1;
-
-work_done:
-	expire += ip_rt_gc_min_interval;
-	if (expire > ip_rt_gc_timeout ||
-	    dst_entries_get_fast(&ipv4_dst_ops) < ipv4_dst_ops.gc_thresh ||
-	    dst_entries_get_slow(&ipv4_dst_ops) < ipv4_dst_ops.gc_thresh)
-		expire = ip_rt_gc_timeout;
-out:	return 0;
-}
-
-/*
- * Returns number of entries in a hash chain that have different hash_inputs
- */
-static int slow_chain_length(const struct rtable *head)
-{
-	int length = 0;
-	const struct rtable *rth = head;
-
-	while (rth) {
-		length += has_noalias(head, rth);
-		rth = rcu_dereference_protected(rth->dst.rt_next, 1);
-	}
-	return length >> FRACT_BITS;
 }
 
 static struct neighbour *ipv4_neigh_lookup(const struct dst_entry *dst,
@@ -1086,139 +495,6 @@ static struct neighbour *ipv4_neigh_lookup(const struct dst_entry *dst,
 	return neigh_create(&arp_tbl, pkey, dev);
 }
 
-static struct rtable *rt_intern_hash(unsigned int hash, struct rtable *rt,
-				     struct sk_buff *skb, int ifindex)
-{
-	struct rtable	*rth, *cand;
-	struct rtable __rcu **rthp, **candp;
-	unsigned long	now;
-	u32 		min_score;
-	int		chain_length;
-
-restart:
-	chain_length = 0;
-	min_score = ~(u32)0;
-	cand = NULL;
-	candp = NULL;
-	now = jiffies;
-
-	if (!rt_caching(dev_net(rt->dst.dev)) || (rt->dst.flags & DST_NOCACHE)) {
-		/*
-		 * If we're not caching, just tell the caller we
-		 * were successful and don't touch the route.  The
-		 * caller hold the sole reference to the cache entry, and
-		 * it will be released when the caller is done with it.
-		 * If we drop it here, the callers have no way to resolve routes
-		 * when we're not caching.  Instead, just point *rp at rt, so
-		 * the caller gets a single use out of the route
-		 * Note that we do rt_free on this new route entry, so that
-		 * once its refcount hits zero, we are still able to reap it
-		 * (Thanks Alexey)
-		 * Note: To avoid expensive rcu stuff for this uncached dst,
-		 * we set DST_NOCACHE so that dst_release() can free dst without
-		 * waiting a grace period.
-		 */
-
-		rt->dst.flags |= DST_NOCACHE;
-		goto skip_hashing;
-	}
-
-	rthp = &rt_hash_table[hash].chain;
-
-	spin_lock_bh(rt_hash_lock_addr(hash));
-	while ((rth = rcu_dereference_protected(*rthp,
-			lockdep_is_held(rt_hash_lock_addr(hash)))) != NULL) {
-		if (rt_is_expired(rth)) {
-			*rthp = rth->dst.rt_next;
-			rt_free(rth);
-			continue;
-		}
-		if (compare_keys(rth, rt) && compare_netns(rth, rt)) {
-			/* Put it first */
-			*rthp = rth->dst.rt_next;
-			/*
-			 * Since lookup is lockfree, the deletion
-			 * must be visible to another weakly ordered CPU before
-			 * the insertion at the start of the hash chain.
-			 */
-			rcu_assign_pointer(rth->dst.rt_next,
-					   rt_hash_table[hash].chain);
-			/*
-			 * Since lookup is lockfree, the update writes
-			 * must be ordered for consistency on SMP.
-			 */
-			rcu_assign_pointer(rt_hash_table[hash].chain, rth);
-
-			dst_use(&rth->dst, now);
-			spin_unlock_bh(rt_hash_lock_addr(hash));
-
-			rt_drop(rt);
-			if (skb)
-				skb_dst_set(skb, &rth->dst);
-			return rth;
-		}
-
-		if (!atomic_read(&rth->dst.__refcnt)) {
-			u32 score = rt_score(rth);
-
-			if (score <= min_score) {
-				cand = rth;
-				candp = rthp;
-				min_score = score;
-			}
-		}
-
-		chain_length++;
-
-		rthp = &rth->dst.rt_next;
-	}
-
-	if (cand) {
-		/* ip_rt_gc_elasticity used to be average length of chain
-		 * length, when exceeded gc becomes really aggressive.
-		 *
-		 * The second limit is less certain. At the moment it allows
-		 * only 2 entries per bucket. We will see.
-		 */
-		if (chain_length > ip_rt_gc_elasticity) {
-			*candp = cand->dst.rt_next;
-			rt_free(cand);
-		}
-	} else {
-		if (chain_length > rt_chain_length_max &&
-		    slow_chain_length(rt_hash_table[hash].chain) > rt_chain_length_max) {
-			struct net *net = dev_net(rt->dst.dev);
-			int num = ++net->ipv4.current_rt_cache_rebuild_count;
-			if (!rt_caching(net)) {
-				pr_warn("%s: %d rebuilds is over limit, route caching disabled\n",
-					rt->dst.dev->name, num);
-			}
-			rt_emergency_hash_rebuild(net);
-			spin_unlock_bh(rt_hash_lock_addr(hash));
-
-			hash = rt_hash(rt->rt_key_dst, rt->rt_key_src,
-					ifindex, rt_genid(net));
-			goto restart;
-		}
-	}
-
-	rt->dst.rt_next = rt_hash_table[hash].chain;
-
-	/*
-	 * Since lookup is lockfree, we must make sure
-	 * previous writes to rt are committed to memory
-	 * before making rt visible to other CPUS.
-	 */
-	rcu_assign_pointer(rt_hash_table[hash].chain, rt);
-
-	spin_unlock_bh(rt_hash_lock_addr(hash));
-
-skip_hashing:
-	if (skb)
-		skb_dst_set(skb, &rt->dst);
-	return rt;
-}
-
 /*
  * Peer allocation may fail only in serious out-of-memory conditions.  However
  * we still can generate some output.
@@ -1255,26 +531,6 @@ void __ip_select_ident(struct iphdr *iph, struct dst_entry *dst, int more)
 }
 EXPORT_SYMBOL(__ip_select_ident);
 
-static void rt_del(unsigned int hash, struct rtable *rt)
-{
-	struct rtable __rcu **rthp;
-	struct rtable *aux;
-
-	rthp = &rt_hash_table[hash].chain;
-	spin_lock_bh(rt_hash_lock_addr(hash));
-	ip_rt_put(rt);
-	while ((aux = rcu_dereference_protected(*rthp,
-			lockdep_is_held(rt_hash_lock_addr(hash)))) != NULL) {
-		if (aux == rt || rt_is_expired(aux)) {
-			*rthp = aux->dst.rt_next;
-			rt_free(aux);
-			continue;
-		}
-		rthp = &aux->dst.rt_next;
-	}
-	spin_unlock_bh(rt_hash_lock_addr(hash));
-}
-
 static void __build_flow_key(struct flowi4 *fl4, const struct sock *sk,
 			     const struct iphdr *iph,
 			     int oif, u8 tos,
@@ -1518,10 +774,7 @@ static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst)
 			ret = NULL;
 		} else if ((rt->rt_flags & RTCF_REDIRECTED) ||
 			   rt->dst.expires) {
-			unsigned int hash = rt_hash(rt->rt_key_dst, rt->rt_key_src,
-						rt->rt_oif,
-						rt_genid(dev_net(dst->dev)));
-			rt_del(hash, rt);
+			ip_rt_put(rt);
 			ret = NULL;
 		}
 	}
@@ -1969,7 +1222,7 @@ static struct rtable *rt_dst_alloc(struct net_device *dev,
 				   bool nopolicy, bool noxfrm)
 {
 	return dst_alloc(&ipv4_dst_ops, dev, 1, -1,
-			 DST_HOST |
+			 DST_HOST | DST_NOCACHE |
 			 (nopolicy ? DST_NOPOLICY : 0) |
 			 (noxfrm ? DST_NOXFRM : 0));
 }
@@ -1978,7 +1231,6 @@ static struct rtable *rt_dst_alloc(struct net_device *dev,
 static int ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 				u8 tos, struct net_device *dev, int our)
 {
-	unsigned int hash;
 	struct rtable *rth;
 	struct in_device *in_dev = __in_dev_get_rcu(dev);
 	u32 itag = 0;
@@ -2042,9 +1294,8 @@ static int ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 #endif
 	RT_CACHE_STAT_INC(in_slow_mc);
 
-	hash = rt_hash(daddr, saddr, dev->ifindex, rt_genid(dev_net(dev)));
-	rth = rt_intern_hash(hash, rth, skb, dev->ifindex);
-	return IS_ERR(rth) ? PTR_ERR(rth) : 0;
+	skb_dst_set(skb, &rth->dst);
+	return 0;
 
 e_nobufs:
 	return -ENOBUFS;
@@ -2176,7 +1427,6 @@ static int ip_mkroute_input(struct sk_buff *skb,
 {
 	struct rtable *rth = NULL;
 	int err;
-	unsigned int hash;
 
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 	if (res->fi && res->fi->fib_nhs > 1)
@@ -2188,12 +1438,7 @@ static int ip_mkroute_input(struct sk_buff *skb,
 	if (err)
 		return err;
 
-	/* put it into the cache */
-	hash = rt_hash(daddr, saddr, fl4->flowi4_iif,
-		       rt_genid(dev_net(rth->dst.dev)));
-	rth = rt_intern_hash(hash, rth, skb, fl4->flowi4_iif);
-	if (IS_ERR(rth))
-		return PTR_ERR(rth);
+	skb_dst_set(skb, &rth->dst);
 	return 0;
 }
 
@@ -2217,7 +1462,6 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	unsigned int	flags = 0;
 	u32		itag = 0;
 	struct rtable	*rth;
-	unsigned int	hash;
 	int		err = -EINVAL;
 	struct net    *net = dev_net(dev);
 
@@ -2339,11 +1583,8 @@ local_input:
 		rth->dst.error= -err;
 		rth->rt_flags 	&= ~RTCF_LOCAL;
 	}
-	hash = rt_hash(daddr, saddr, fl4.flowi4_iif, rt_genid(net));
-	rth = rt_intern_hash(hash, rth, skb, fl4.flowi4_iif);
+	skb_dst_set(skb, &rth->dst);
 	err = 0;
-	if (IS_ERR(rth))
-		err = PTR_ERR(rth);
 	goto out;
 
 no_route:
@@ -2382,46 +1623,10 @@ martian_source_keep_err:
 int ip_route_input_common(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 			   u8 tos, struct net_device *dev, bool noref)
 {
-	struct rtable	*rth;
-	unsigned int	hash;
-	int iif = dev->ifindex;
-	struct net *net;
 	int res;
 
-	net = dev_net(dev);
-
 	rcu_read_lock();
 
-	if (!rt_caching(net))
-		goto skip_cache;
-
-	tos &= IPTOS_RT_MASK;
-	hash = rt_hash(daddr, saddr, iif, rt_genid(net));
-
-	for (rth = rcu_dereference(rt_hash_table[hash].chain); rth;
-	     rth = rcu_dereference(rth->dst.rt_next)) {
-		if ((((__force u32)rth->rt_key_dst ^ (__force u32)daddr) |
-		     ((__force u32)rth->rt_key_src ^ (__force u32)saddr) |
-		     (rth->rt_route_iif ^ iif) |
-		     (rth->rt_key_tos ^ tos)) == 0 &&
-		    rth->rt_mark == skb->mark &&
-		    net_eq(dev_net(rth->dst.dev), net) &&
-		    !rt_is_expired(rth)) {
-			if (noref) {
-				dst_use_noref(&rth->dst, jiffies);
-				skb_dst_set_noref(skb, &rth->dst);
-			} else {
-				dst_use(&rth->dst, jiffies);
-				skb_dst_set(skb, &rth->dst);
-			}
-			RT_CACHE_STAT_INC(in_hit);
-			rcu_read_unlock();
-			return 0;
-		}
-		RT_CACHE_STAT_INC(in_hlist_search);
-	}
-
-skip_cache:
 	/* Multicast recognition logic is moved from route cache to here.
 	   The problem was that too many Ethernet cards have broken/missing
 	   hardware multicast filters :-( As result the host on multicasting
@@ -2563,10 +1768,9 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
 
 /*
  * Major route resolver routine.
- * called with rcu_read_lock();
  */
 
-static struct rtable *ip_route_output_slow(struct net *net, struct flowi4 *fl4)
+struct rtable *__ip_route_output_key(struct net *net, struct flowi4 *fl4)
 {
 	struct net_device *dev_out = NULL;
 	__u8 tos = RT_FL_TOS(fl4);
@@ -2746,57 +1950,11 @@ static struct rtable *ip_route_output_slow(struct net *net, struct flowi4 *fl4)
 make_route:
 	rth = __mkroute_output(&res, fl4, orig_daddr, orig_saddr, orig_oif,
 			       tos, dev_out, flags);
-	if (!IS_ERR(rth)) {
-		unsigned int hash;
-
-		hash = rt_hash(orig_daddr, orig_saddr, orig_oif,
-			       rt_genid(dev_net(dev_out)));
-		rth = rt_intern_hash(hash, rth, NULL, orig_oif);
-	}
 
 out:
 	rcu_read_unlock();
 	return rth;
 }
-
-struct rtable *__ip_route_output_key(struct net *net, struct flowi4 *flp4)
-{
-	struct rtable *rth;
-	unsigned int hash;
-
-	if (!rt_caching(net))
-		goto slow_output;
-
-	hash = rt_hash(flp4->daddr, flp4->saddr, flp4->flowi4_oif, rt_genid(net));
-
-	rcu_read_lock_bh();
-	for (rth = rcu_dereference_bh(rt_hash_table[hash].chain); rth;
-		rth = rcu_dereference_bh(rth->dst.rt_next)) {
-		if (rth->rt_key_dst == flp4->daddr &&
-		    rth->rt_key_src == flp4->saddr &&
-		    rt_is_output_route(rth) &&
-		    rth->rt_oif == flp4->flowi4_oif &&
-		    rth->rt_mark == flp4->flowi4_mark &&
-		    !((rth->rt_key_tos ^ flp4->flowi4_tos) &
-			    (IPTOS_RT_MASK | RTO_ONLINK)) &&
-		    net_eq(dev_net(rth->dst.dev), net) &&
-		    !rt_is_expired(rth)) {
-			dst_use(&rth->dst, jiffies);
-			RT_CACHE_STAT_INC(out_hit);
-			rcu_read_unlock_bh();
-			if (!flp4->saddr)
-				flp4->saddr = rth->rt_src;
-			if (!flp4->daddr)
-				flp4->daddr = rth->rt_dst;
-			return rth;
-		}
-		RT_CACHE_STAT_INC(out_hlist_search);
-	}
-	rcu_read_unlock_bh();
-
-slow_output:
-	return ip_route_output_slow(net, flp4);
-}
 EXPORT_SYMBOL_GPL(__ip_route_output_key);
 
 static struct dst_entry *ipv4_blackhole_dst_check(struct dst_entry *dst, u32 cookie)
@@ -3106,43 +2264,6 @@ errout_free:
 
 int ip_rt_dump(struct sk_buff *skb,  struct netlink_callback *cb)
 {
-	struct rtable *rt;
-	int h, s_h;
-	int idx, s_idx;
-	struct net *net;
-
-	net = sock_net(skb->sk);
-
-	s_h = cb->args[0];
-	if (s_h < 0)
-		s_h = 0;
-	s_idx = idx = cb->args[1];
-	for (h = s_h; h <= rt_hash_mask; h++, s_idx = 0) {
-		if (!rt_hash_table[h].chain)
-			continue;
-		rcu_read_lock_bh();
-		for (rt = rcu_dereference_bh(rt_hash_table[h].chain), idx = 0; rt;
-		     rt = rcu_dereference_bh(rt->dst.rt_next), idx++) {
-			if (!net_eq(dev_net(rt->dst.dev), net) || idx < s_idx)
-				continue;
-			if (rt_is_expired(rt))
-				continue;
-			skb_dst_set_noref(skb, &rt->dst);
-			if (rt_fill_info(net, skb, NETLINK_CB(cb->skb).pid,
-					 cb->nlh->nlmsg_seq, RTM_NEWROUTE,
-					 1, NLM_F_MULTI) <= 0) {
-				skb_dst_drop(skb);
-				rcu_read_unlock_bh();
-				goto done;
-			}
-			skb_dst_drop(skb);
-		}
-		rcu_read_unlock_bh();
-	}
-
-done:
-	cb->args[0] = h;
-	cb->args[1] = idx;
 	return skb->len;
 }
 
@@ -3376,22 +2497,6 @@ static __net_initdata struct pernet_operations ipv4_inetpeer_ops = {
 struct ip_rt_acct __percpu *ip_rt_acct __read_mostly;
 #endif /* CONFIG_IP_ROUTE_CLASSID */
 
-static __initdata unsigned long rhash_entries;
-static int __init set_rhash_entries(char *str)
-{
-	ssize_t ret;
-
-	if (!str)
-		return 0;
-
-	ret = kstrtoul(str, 0, &rhash_entries);
-	if (ret)
-		return 0;
-
-	return 1;
-}
-__setup("rhash_entries=", set_rhash_entries);
-
 int __init ip_rt_init(void)
 {
 	int rc = 0;
@@ -3414,31 +2519,12 @@ int __init ip_rt_init(void)
 	if (dst_entries_init(&ipv4_dst_blackhole_ops) < 0)
 		panic("IP: failed to allocate ipv4_dst_blackhole_ops counter\n");
 
-	rt_hash_table = (struct rt_hash_bucket *)
-		alloc_large_system_hash("IP route cache",
-					sizeof(struct rt_hash_bucket),
-					rhash_entries,
-					(totalram_pages >= 128 * 1024) ?
-					15 : 17,
-					0,
-					&rt_hash_log,
-					&rt_hash_mask,
-					0,
-					rhash_entries ? 0 : 512 * 1024);
-	memset(rt_hash_table, 0, (rt_hash_mask + 1) * sizeof(struct rt_hash_bucket));
-	rt_hash_lock_init();
-
-	ipv4_dst_ops.gc_thresh = (rt_hash_mask + 1);
-	ip_rt_max_size = (rt_hash_mask + 1) * 16;
+	ipv4_dst_ops.gc_thresh = ~0;
+	ip_rt_max_size = INT_MAX;
 
 	devinet_init();
 	ip_fib_init();
 
-	INIT_DELAYED_WORK_DEFERRABLE(&expires_work, rt_worker_func);
-	expires_ljiffies = jiffies;
-	schedule_delayed_work(&expires_work,
-		net_random() % ip_rt_gc_interval + ip_rt_gc_interval);
-
 	if (ip_rt_proc_init())
 		pr_err("Unable to create route proc files\n");
 #ifdef CONFIG_XFRM