1 files changed, 130 insertions, 2 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 2ea6dcc3e2c..21ce7e1b228 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -129,6 +129,7 @@ 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 ip_rt_secret_interval __read_mostly	= 10 * 60 * HZ;
+static int rt_chain_length_max __read_mostly	= 20;
 
 static void rt_worker_func(struct work_struct *work);
 static DECLARE_DELAYED_WORK(expires_work, rt_worker_func);
@@ -145,6 +146,7 @@ static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst);
 static void		 ipv4_link_failure(struct sk_buff *skb);
 static void		 ip_rt_update_pmtu(struct dst_entry *dst, u32 mtu);
 static int rt_garbage_collect(struct dst_ops *ops);
+static void rt_emergency_hash_rebuild(struct net *net);
 
 
 static struct dst_ops ipv4_dst_ops = {
@@ -201,6 +203,7 @@ const __u8 ip_tos2prio[16] = {
 struct rt_hash_bucket {
 	struct rtable	*chain;
 };
+
 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) || \
 	defined(CONFIG_PROVE_LOCKING)
 /*
@@ -674,6 +677,20 @@ static inline u32 rt_score(struct rtable *rt)
 	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 flowi *fl1,
+					const struct flowi *fl2)
+{
+	return (__force u32)(((fl1->nl_u.ip4_u.daddr ^ fl2->nl_u.ip4_u.daddr) |
+		(fl1->nl_u.ip4_u.saddr ^ fl2->nl_u.ip4_u.saddr) |
+		(fl1->iif ^ fl2->iif)) == 0);
+}
+
 static inline int compare_keys(struct flowi *fl1, struct flowi *fl2)
 {
 	return ((__force u32)((fl1->nl_u.ip4_u.daddr ^ fl2->nl_u.ip4_u.daddr) |
@@ -753,11 +770,24 @@ static void rt_do_flush(int process_context)
 	}
 }
 
+/*
+ * 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)
+
 static void rt_check_expire(void)
 {
 	static unsigned int rover;
 	unsigned int i = rover, goal;
 	struct rtable *rth, **rthp;
+	unsigned long length = 0, samples = 0;
+	unsigned long sum = 0, sum2 = 0;
 	u64 mult;
 
 	mult = ((u64)ip_rt_gc_interval) << rt_hash_log;
@@ -766,6 +796,7 @@ static void rt_check_expire(void)
 	goal = (unsigned int)mult;
 	if (goal > rt_hash_mask)
 		goal = rt_hash_mask + 1;
+	length = 0;
 	for (; goal > 0; goal--) {
 		unsigned long tmo = ip_rt_gc_timeout;
 
@@ -775,6 +806,8 @@ static void rt_check_expire(void)
 		if (need_resched())
 			cond_resched();
 
+		samples++;
+
 		if (*rthp == NULL)
 			continue;
 		spin_lock_bh(rt_hash_lock_addr(i));
@@ -789,11 +822,29 @@ static void rt_check_expire(void)
 				if (time_before_eq(jiffies, rth->u.dst.expires)) {
 					tmo >>= 1;
 					rthp = &rth->u.dst.rt_next;
+					/*
+					 * Only bump our length if the hash
+					 * inputs on entries n and n+1 are not
+					 * the same, 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
+					 */
+					if ((*rthp == NULL) ||
+					    !compare_hash_inputs(&(*rthp)->fl,
+								 &rth->fl))
+						length += ONE;
 					continue;
 				}
 			} else if (!rt_may_expire(rth, tmo, ip_rt_gc_timeout)) {
 				tmo >>= 1;
 				rthp = &rth->u.dst.rt_next;
+				if ((*rthp == NULL) ||
+				    !compare_hash_inputs(&(*rthp)->fl,
+							 &rth->fl))
+					length += ONE;
 				continue;
 			}
 
@@ -802,6 +853,15 @@ static void rt_check_expire(void)
 			rt_free(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;
 }
@@ -851,6 +911,26 @@ static void rt_secret_rebuild(unsigned long __net)
 	mod_timer(&net->ipv4.rt_secret_timer, jiffies + ip_rt_secret_interval);
 }
 
+static void rt_secret_rebuild_oneshot(struct net *net)
+{
+	del_timer_sync(&net->ipv4.rt_secret_timer);
+	rt_cache_invalidate(net);
+	if (ip_rt_secret_interval) {
+		net->ipv4.rt_secret_timer.expires += ip_rt_secret_interval;
+		add_timer(&net->ipv4.rt_secret_timer);
+	}
+}
+
+static void rt_emergency_hash_rebuild(struct net *net)
+{
+	if (net_ratelimit()) {
+		printk(KERN_WARNING "Route hash chain too long!\n");
+		printk(KERN_WARNING "Adjust your secret_interval!\n");
+	}
+
+	rt_secret_rebuild_oneshot(net);
+}
+
 /*
    Short description of GC goals.
 
@@ -989,6 +1069,7 @@ out:	return 0;
 static int rt_intern_hash(unsigned hash, struct rtable *rt, struct rtable **rp)
 {
 	struct rtable	*rth, **rthp;
+	struct rtable	*rthi;
 	unsigned long	now;
 	struct rtable *cand, **candp;
 	u32 		min_score;
@@ -1002,7 +1083,13 @@ restart:
 	candp = NULL;
 	now = jiffies;
 
+	if (!rt_caching(dev_net(rt->u.dst.dev))) {
+		rt_drop(rt);
+		return 0;
+	}
+
 	rthp = &rt_hash_table[hash].chain;
+	rthi = NULL;
 
 	spin_lock_bh(rt_hash_lock_addr(hash));
 	while ((rth = *rthp) != NULL) {
@@ -1048,6 +1135,17 @@ restart:
 		chain_length++;
 
 		rthp = &rth->u.dst.rt_next;
+
+		/*
+		 * check to see if the next entry in the chain
+		 * contains the same hash input values as rt.  If it does
+		 * This is where we will insert into the list, instead of
+		 * at the head.  This groups entries that differ by aspects not
+		 * relvant to the hash function together, which we use to adjust
+		 * our chain length
+		 */
+		if (*rthp && compare_hash_inputs(&(*rthp)->fl, &rt->fl))
+			rthi = rth;
 	}
 
 	if (cand) {
@@ -1061,6 +1159,16 @@ restart:
 			*candp = cand->u.dst.rt_next;
 			rt_free(cand);
 		}
+	} else {
+		if (chain_length > rt_chain_length_max) {
+			struct net *net = dev_net(rt->u.dst.dev);
+			int num = ++net->ipv4.current_rt_cache_rebuild_count;
+			if (!rt_caching(dev_net(rt->u.dst.dev))) {
+				printk(KERN_WARNING "%s: %d rebuilds is over limit, route caching disabled\n",
+					rt->u.dst.dev->name, num);
+			}
+			rt_emergency_hash_rebuild(dev_net(rt->u.dst.dev));
+		}
 	}
 
 	/* Try to bind route to arp only if it is output
@@ -1098,7 +1206,11 @@ restart:
 		}
 	}
 
-	rt->u.dst.rt_next = rt_hash_table[hash].chain;
+	if (rthi)
+		rt->u.dst.rt_next = rthi->u.dst.rt_next;
+	else
+		rt->u.dst.rt_next = rt_hash_table[hash].chain;
+
 #if RT_CACHE_DEBUG >= 2
 	if (rt->u.dst.rt_next) {
 		struct rtable *trt;
@@ -1114,7 +1226,11 @@ restart:
 	 * previous writes to rt are comitted to memory
 	 * before making rt visible to other CPUS.
 	 */
-	rcu_assign_pointer(rt_hash_table[hash].chain, rt);
+	if (rthi)
+		rcu_assign_pointer(rthi->u.dst.rt_next, rt);
+	else
+		rcu_assign_pointer(rt_hash_table[hash].chain, rt);
+
 	spin_unlock_bh(rt_hash_lock_addr(hash));
 	*rp = rt;
 	return 0;
@@ -1217,6 +1333,9 @@ void ip_rt_redirect(__be32 old_gw, __be32 daddr, __be32 new_gw,
 	    || ipv4_is_zeronet(new_gw))
 		goto reject_redirect;
 
+	if (!rt_caching(net))
+		goto reject_redirect;
+
 	if (!IN_DEV_SHARED_MEDIA(in_dev)) {
 		if (!inet_addr_onlink(in_dev, new_gw, old_gw))
 			goto reject_redirect;
@@ -2130,6 +2249,10 @@ int ip_route_input(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	struct net *net;
 
 	net = dev_net(dev);
+
+	if (!rt_caching(net))
+		goto skip_cache;
+
 	tos &= IPTOS_RT_MASK;
 	hash = rt_hash(daddr, saddr, iif, rt_genid(net));
 
@@ -2154,6 +2277,7 @@ int ip_route_input(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	}
 	rcu_read_unlock();
 
+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
@@ -2539,6 +2663,9 @@ int __ip_route_output_key(struct net *net, struct rtable **rp,
 	unsigned hash;
 	struct rtable *rth;
 
+	if (!rt_caching(net))
+		goto slow_output;
+
 	hash = rt_hash(flp->fl4_dst, flp->fl4_src, flp->oif, rt_genid(net));
 
 	rcu_read_lock_bh();
@@ -2563,6 +2690,7 @@ int __ip_route_output_key(struct net *net, struct rtable **rp,
 	}
 	rcu_read_unlock_bh();
 
+slow_output:
 	return ip_route_output_slow(net, rp, flp);
 }