Initial import

1 files changed, 558 insertions, 0 deletions

diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
new file mode 100644
index 000000000..241afd743
--- /dev/null
+++ b/net/ipv4/inetpeer.c
@@ -0,0 +1,558 @@
+/*
+ *		INETPEER - A storage for permanent information about peers
+ *
+ *  This source is covered by the GNU GPL, the same as all kernel sources.
+ *
+ *  Authors:	Andrey V. Savochkin <saw@msu.ru>
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/random.h>
+#include <linux/timer.h>
+#include <linux/time.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/net.h>
+#include <linux/workqueue.h>
+#include <net/ip.h>
+#include <net/inetpeer.h>
+#include <net/secure_seq.h>
+
+/*
+ *  Theory of operations.
+ *  We keep one entry for each peer IP address.  The nodes contains long-living
+ *  information about the peer which doesn't depend on routes.
+ *
+ *  Nodes are removed only when reference counter goes to 0.
+ *  When it's happened the node may be removed when a sufficient amount of
+ *  time has been passed since its last use.  The less-recently-used entry can
+ *  also be removed if the pool is overloaded i.e. if the total amount of
+ *  entries is greater-or-equal than the threshold.
+ *
+ *  Node pool is organised as an AVL tree.
+ *  Such an implementation has been chosen not just for fun.  It's a way to
+ *  prevent easy and efficient DoS attacks by creating hash collisions.  A huge
+ *  amount of long living nodes in a single hash slot would significantly delay
+ *  lookups performed with disabled BHs.
+ *
+ *  Serialisation issues.
+ *  1.  Nodes may appear in the tree only with the pool lock held.
+ *  2.  Nodes may disappear from the tree only with the pool lock held
+ *      AND reference count being 0.
+ *  3.  Global variable peer_total is modified under the pool lock.
+ *  4.  struct inet_peer fields modification:
+ *		avl_left, avl_right, avl_parent, avl_height: pool lock
+ *		refcnt: atomically against modifications on other CPU;
+ *		   usually under some other lock to prevent node disappearing
+ *		daddr: unchangeable
+ */
+
+static struct kmem_cache *peer_cachep __read_mostly;
+
+static LIST_HEAD(gc_list);
+static const int gc_delay = 60 * HZ;
+static struct delayed_work gc_work;
+static DEFINE_SPINLOCK(gc_lock);
+
+#define node_height(x) x->avl_height
+
+#define peer_avl_empty ((struct inet_peer *)&peer_fake_node)
+#define peer_avl_empty_rcu ((struct inet_peer __rcu __force *)&peer_fake_node)
+static const struct inet_peer peer_fake_node = {
+	.avl_left	= peer_avl_empty_rcu,
+	.avl_right	= peer_avl_empty_rcu,
+	.avl_height	= 0
+};
+
+void inet_peer_base_init(struct inet_peer_base *bp)
+{
+	bp->root = peer_avl_empty_rcu;
+	seqlock_init(&bp->lock);
+	bp->total = 0;
+}
+EXPORT_SYMBOL_GPL(inet_peer_base_init);
+
+#define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */
+
+/* Exported for sysctl_net_ipv4.  */
+int inet_peer_threshold __read_mostly = 65536 + 128;	/* start to throw entries more
+					 * aggressively at this stage */
+int inet_peer_minttl __read_mostly = 120 * HZ;	/* TTL under high load: 120 sec */
+int inet_peer_maxttl __read_mostly = 10 * 60 * HZ;	/* usual time to live: 10 min */
+
+static void inetpeer_gc_worker(struct work_struct *work)
+{
+	struct inet_peer *p, *n, *c;
+	struct list_head list;
+
+	spin_lock_bh(&gc_lock);
+	list_replace_init(&gc_list, &list);
+	spin_unlock_bh(&gc_lock);
+
+	if (list_empty(&list))
+		return;
+
+	list_for_each_entry_safe(p, n, &list, gc_list) {
+
+		if (need_resched())
+			cond_resched();
+
+		c = rcu_dereference_protected(p->avl_left, 1);
+		if (c != peer_avl_empty) {
+			list_add_tail(&c->gc_list, &list);
+			p->avl_left = peer_avl_empty_rcu;
+		}
+
+		c = rcu_dereference_protected(p->avl_right, 1);
+		if (c != peer_avl_empty) {
+			list_add_tail(&c->gc_list, &list);
+			p->avl_right = peer_avl_empty_rcu;
+		}
+
+		n = list_entry(p->gc_list.next, struct inet_peer, gc_list);
+
+		if (!atomic_read(&p->refcnt)) {
+			list_del(&p->gc_list);
+			kmem_cache_free(peer_cachep, p);
+		}
+	}
+
+	if (list_empty(&list))
+		return;
+
+	spin_lock_bh(&gc_lock);
+	list_splice(&list, &gc_list);
+	spin_unlock_bh(&gc_lock);
+
+	schedule_delayed_work(&gc_work, gc_delay);
+}
+
+/* Called from ip_output.c:ip_init  */
+void __init inet_initpeers(void)
+{
+	struct sysinfo si;
+
+	/* Use the straight interface to information about memory. */
+	si_meminfo(&si);
+	/* The values below were suggested by Alexey Kuznetsov
+	 * <kuznet@ms2.inr.ac.ru>.  I don't have any opinion about the values
+	 * myself.  --SAW
+	 */
+	if (si.totalram <= (32768*1024)/PAGE_SIZE)
+		inet_peer_threshold >>= 1; /* max pool size about 1MB on IA32 */
+	if (si.totalram <= (16384*1024)/PAGE_SIZE)
+		inet_peer_threshold >>= 1; /* about 512KB */
+	if (si.totalram <= (8192*1024)/PAGE_SIZE)
+		inet_peer_threshold >>= 2; /* about 128KB */
+
+	peer_cachep = kmem_cache_create("inet_peer_cache",
+			sizeof(struct inet_peer),
+			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
+			NULL);
+
+	INIT_DEFERRABLE_WORK(&gc_work, inetpeer_gc_worker);
+}
+
+static int addr_compare(const struct inetpeer_addr *a,
+			const struct inetpeer_addr *b)
+{
+	int i, n = (a->family == AF_INET ? 1 : 4);
+
+	for (i = 0; i < n; i++) {
+		if (a->addr.a6[i] == b->addr.a6[i])
+			continue;
+		if ((__force u32)a->addr.a6[i] < (__force u32)b->addr.a6[i])
+			return -1;
+		return 1;
+	}
+
+	return 0;
+}
+
+#define rcu_deref_locked(X, BASE)				\
+	rcu_dereference_protected(X, lockdep_is_held(&(BASE)->lock.lock))
+
+/*
+ * Called with local BH disabled and the pool lock held.
+ */
+#define lookup(_daddr, _stack, _base)				\
+({								\
+	struct inet_peer *u;					\
+	struct inet_peer __rcu **v;				\
+								\
+	stackptr = _stack;					\
+	*stackptr++ = &_base->root;				\
+	for (u = rcu_deref_locked(_base->root, _base);		\
+	     u != peer_avl_empty;) {				\
+		int cmp = addr_compare(_daddr, &u->daddr);	\
+		if (cmp == 0)					\
+			break;					\
+		if (cmp == -1)					\
+			v = &u->avl_left;			\
+		else						\
+			v = &u->avl_right;			\
+		*stackptr++ = v;				\
+		u = rcu_deref_locked(*v, _base);		\
+	}							\
+	u;							\
+})
+
+/*
+ * Called with rcu_read_lock()
+ * Because we hold no lock against a writer, its quite possible we fall
+ * in an endless loop.
+ * But every pointer we follow is guaranteed to be valid thanks to RCU.
+ * We exit from this function if number of links exceeds PEER_MAXDEPTH
+ */
+static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
+				    struct inet_peer_base *base)
+{
+	struct inet_peer *u = rcu_dereference(base->root);
+	int count = 0;
+
+	while (u != peer_avl_empty) {
+		int cmp = addr_compare(daddr, &u->daddr);
+		if (cmp == 0) {
+			/* Before taking a reference, check if this entry was
+			 * deleted (refcnt=-1)
+			 */
+			if (!atomic_add_unless(&u->refcnt, 1, -1))
+				u = NULL;
+			return u;
+		}
+		if (cmp == -1)
+			u = rcu_dereference(u->avl_left);
+		else
+			u = rcu_dereference(u->avl_right);
+		if (unlikely(++count == PEER_MAXDEPTH))
+			break;
+	}
+	return NULL;
+}
+
+/* Called with local BH disabled and the pool lock held. */
+#define lookup_rightempty(start, base)				\
+({								\
+	struct inet_peer *u;					\
+	struct inet_peer __rcu **v;				\
+	*stackptr++ = &start->avl_left;				\
+	v = &start->avl_left;					\
+	for (u = rcu_deref_locked(*v, base);			\
+	     u->avl_right != peer_avl_empty_rcu;) {		\
+		v = &u->avl_right;				\
+		*stackptr++ = v;				\
+		u = rcu_deref_locked(*v, base);			\
+	}							\
+	u;							\
+})
+
+/* Called with local BH disabled and the pool lock held.
+ * Variable names are the proof of operation correctness.
+ * Look into mm/map_avl.c for more detail description of the ideas.
+ */
+static void peer_avl_rebalance(struct inet_peer __rcu **stack[],
+			       struct inet_peer __rcu ***stackend,
+			       struct inet_peer_base *base)
+{
+	struct inet_peer __rcu **nodep;
+	struct inet_peer *node, *l, *r;
+	int lh, rh;
+
+	while (stackend > stack) {
+		nodep = *--stackend;
+		node = rcu_deref_locked(*nodep, base);
+		l = rcu_deref_locked(node->avl_left, base);
+		r = rcu_deref_locked(node->avl_right, base);
+		lh = node_height(l);
+		rh = node_height(r);
+		if (lh > rh + 1) { /* l: RH+2 */
+			struct inet_peer *ll, *lr, *lrl, *lrr;
+			int lrh;
+			ll = rcu_deref_locked(l->avl_left, base);
+			lr = rcu_deref_locked(l->avl_right, base);
+			lrh = node_height(lr);
+			if (lrh <= node_height(ll)) {	/* ll: RH+1 */
+				RCU_INIT_POINTER(node->avl_left, lr);	/* lr: RH or RH+1 */
+				RCU_INIT_POINTER(node->avl_right, r);	/* r: RH */
+				node->avl_height = lrh + 1; /* RH+1 or RH+2 */
+				RCU_INIT_POINTER(l->avl_left, ll);       /* ll: RH+1 */
+				RCU_INIT_POINTER(l->avl_right, node);	/* node: RH+1 or RH+2 */
+				l->avl_height = node->avl_height + 1;
+				RCU_INIT_POINTER(*nodep, l);
+			} else { /* ll: RH, lr: RH+1 */
+				lrl = rcu_deref_locked(lr->avl_left, base);/* lrl: RH or RH-1 */
+				lrr = rcu_deref_locked(lr->avl_right, base);/* lrr: RH or RH-1 */
+				RCU_INIT_POINTER(node->avl_left, lrr);	/* lrr: RH or RH-1 */
+				RCU_INIT_POINTER(node->avl_right, r);	/* r: RH */
+				node->avl_height = rh + 1; /* node: RH+1 */
+				RCU_INIT_POINTER(l->avl_left, ll);	/* ll: RH */
+				RCU_INIT_POINTER(l->avl_right, lrl);	/* lrl: RH or RH-1 */
+				l->avl_height = rh + 1;	/* l: RH+1 */
+				RCU_INIT_POINTER(lr->avl_left, l);	/* l: RH+1 */
+				RCU_INIT_POINTER(lr->avl_right, node);	/* node: RH+1 */
+				lr->avl_height = rh + 2;
+				RCU_INIT_POINTER(*nodep, lr);
+			}
+		} else if (rh > lh + 1) { /* r: LH+2 */
+			struct inet_peer *rr, *rl, *rlr, *rll;
+			int rlh;
+			rr = rcu_deref_locked(r->avl_right, base);
+			rl = rcu_deref_locked(r->avl_left, base);
+			rlh = node_height(rl);
+			if (rlh <= node_height(rr)) {	/* rr: LH+1 */
+				RCU_INIT_POINTER(node->avl_right, rl);	/* rl: LH or LH+1 */
+				RCU_INIT_POINTER(node->avl_left, l);	/* l: LH */
+				node->avl_height = rlh + 1; /* LH+1 or LH+2 */
+				RCU_INIT_POINTER(r->avl_right, rr);	/* rr: LH+1 */
+				RCU_INIT_POINTER(r->avl_left, node);	/* node: LH+1 or LH+2 */
+				r->avl_height = node->avl_height + 1;
+				RCU_INIT_POINTER(*nodep, r);
+			} else { /* rr: RH, rl: RH+1 */
+				rlr = rcu_deref_locked(rl->avl_right, base);/* rlr: LH or LH-1 */
+				rll = rcu_deref_locked(rl->avl_left, base);/* rll: LH or LH-1 */
+				RCU_INIT_POINTER(node->avl_right, rll);	/* rll: LH or LH-1 */
+				RCU_INIT_POINTER(node->avl_left, l);	/* l: LH */
+				node->avl_height = lh + 1; /* node: LH+1 */
+				RCU_INIT_POINTER(r->avl_right, rr);	/* rr: LH */
+				RCU_INIT_POINTER(r->avl_left, rlr);	/* rlr: LH or LH-1 */
+				r->avl_height = lh + 1;	/* r: LH+1 */
+				RCU_INIT_POINTER(rl->avl_right, r);	/* r: LH+1 */
+				RCU_INIT_POINTER(rl->avl_left, node);	/* node: LH+1 */
+				rl->avl_height = lh + 2;
+				RCU_INIT_POINTER(*nodep, rl);
+			}
+		} else {
+			node->avl_height = (lh > rh ? lh : rh) + 1;
+		}
+	}
+}
+
+/* Called with local BH disabled and the pool lock held. */
+#define link_to_pool(n, base)					\
+do {								\
+	n->avl_height = 1;					\
+	n->avl_left = peer_avl_empty_rcu;			\
+	n->avl_right = peer_avl_empty_rcu;			\
+	/* lockless readers can catch us now */			\
+	rcu_assign_pointer(**--stackptr, n);			\
+	peer_avl_rebalance(stack, stackptr, base);		\
+} while (0)
+
+static void inetpeer_free_rcu(struct rcu_head *head)
+{
+	kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
+}
+
+static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base,
+			     struct inet_peer __rcu **stack[PEER_MAXDEPTH])
+{
+	struct inet_peer __rcu ***stackptr, ***delp;
+
+	if (lookup(&p->daddr, stack, base) != p)
+		BUG();
+	delp = stackptr - 1; /* *delp[0] == p */
+	if (p->avl_left == peer_avl_empty_rcu) {
+		*delp[0] = p->avl_right;
+		--stackptr;
+	} else {
+		/* look for a node to insert instead of p */
+		struct inet_peer *t;
+		t = lookup_rightempty(p, base);
+		BUG_ON(rcu_deref_locked(*stackptr[-1], base) != t);
+		**--stackptr = t->avl_left;
+		/* t is removed, t->daddr > x->daddr for any
+		 * x in p->avl_left subtree.
+		 * Put t in the old place of p. */
+		RCU_INIT_POINTER(*delp[0], t);
+		t->avl_left = p->avl_left;
+		t->avl_right = p->avl_right;
+		t->avl_height = p->avl_height;
+		BUG_ON(delp[1] != &p->avl_left);
+		delp[1] = &t->avl_left; /* was &p->avl_left */
+	}
+	peer_avl_rebalance(stack, stackptr, base);
+	base->total--;
+	call_rcu(&p->rcu, inetpeer_free_rcu);
+}
+
+/* perform garbage collect on all items stacked during a lookup */
+static int inet_peer_gc(struct inet_peer_base *base,
+			struct inet_peer __rcu **stack[PEER_MAXDEPTH],
+			struct inet_peer __rcu ***stackptr)
+{
+	struct inet_peer *p, *gchead = NULL;
+	__u32 delta, ttl;
+	int cnt = 0;
+
+	if (base->total >= inet_peer_threshold)
+		ttl = 0; /* be aggressive */
+	else
+		ttl = inet_peer_maxttl
+				- (inet_peer_maxttl - inet_peer_minttl) / HZ *
+					base->total / inet_peer_threshold * HZ;
+	stackptr--; /* last stack slot is peer_avl_empty */
+	while (stackptr > stack) {
+		stackptr--;
+		p = rcu_deref_locked(**stackptr, base);
+		if (atomic_read(&p->refcnt) == 0) {
+			smp_rmb();
+			delta = (__u32)jiffies - p->dtime;
+			if (delta >= ttl &&
+			    atomic_cmpxchg(&p->refcnt, 0, -1) == 0) {
+				p->gc_next = gchead;
+				gchead = p;
+			}
+		}
+	}
+	while ((p = gchead) != NULL) {
+		gchead = p->gc_next;
+		cnt++;
+		unlink_from_pool(p, base, stack);
+	}
+	return cnt;
+}
+
+struct inet_peer *inet_getpeer(struct inet_peer_base *base,
+			       const struct inetpeer_addr *daddr,
+			       int create)
+{
+	struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
+	struct inet_peer *p;
+	unsigned int sequence;
+	int invalidated, gccnt = 0;
+
+	/* Attempt a lockless lookup first.
+	 * Because of a concurrent writer, we might not find an existing entry.
+	 */
+	rcu_read_lock();
+	sequence = read_seqbegin(&base->lock);
+	p = lookup_rcu(daddr, base);
+	invalidated = read_seqretry(&base->lock, sequence);
+	rcu_read_unlock();
+
+	if (p)
+		return p;
+
+	/* If no writer did a change during our lookup, we can return early. */
+	if (!create && !invalidated)
+		return NULL;
+
+	/* retry an exact lookup, taking the lock before.
+	 * At least, nodes should be hot in our cache.
+	 */
+	write_seqlock_bh(&base->lock);
+relookup:
+	p = lookup(daddr, stack, base);
+	if (p != peer_avl_empty) {
+		atomic_inc(&p->refcnt);
+		write_sequnlock_bh(&base->lock);
+		return p;
+	}
+	if (!gccnt) {
+		gccnt = inet_peer_gc(base, stack, stackptr);
+		if (gccnt && create)
+			goto relookup;
+	}
+	p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;
+	if (p) {
+		p->daddr = *daddr;
+		atomic_set(&p->refcnt, 1);
+		atomic_set(&p->rid, 0);
+		p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
+		p->rate_tokens = 0;
+		/* 60*HZ is arbitrary, but chosen enough high so that the first
+		 * calculation of tokens is at its maximum.
+		 */
+		p->rate_last = jiffies - 60*HZ;
+		INIT_LIST_HEAD(&p->gc_list);
+
+		/* Link the node. */
+		link_to_pool(p, base);
+		base->total++;
+	}
+	write_sequnlock_bh(&base->lock);
+
+	return p;
+}
+EXPORT_SYMBOL_GPL(inet_getpeer);
+
+void inet_putpeer(struct inet_peer *p)
+{
+	p->dtime = (__u32)jiffies;
+	smp_mb__before_atomic();
+	atomic_dec(&p->refcnt);
+}
+EXPORT_SYMBOL_GPL(inet_putpeer);
+
+/*
+ *	Check transmit rate limitation for given message.
+ *	The rate information is held in the inet_peer entries now.
+ *	This function is generic and could be used for other purposes
+ *	too. It uses a Token bucket filter as suggested by Alexey Kuznetsov.
+ *
+ *	Note that the same inet_peer fields are modified by functions in
+ *	route.c too, but these work for packet destinations while xrlim_allow
+ *	works for icmp destinations. This means the rate limiting information
+ *	for one "ip object" is shared - and these ICMPs are twice limited:
+ *	by source and by destination.
+ *
+ *	RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate
+ *			  SHOULD allow setting of rate limits
+ *
+ * 	Shared between ICMPv4 and ICMPv6.
+ */
+#define XRLIM_BURST_FACTOR 6
+bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
+{
+	unsigned long now, token;
+	bool rc = false;
+
+	if (!peer)
+		return true;
+
+	token = peer->rate_tokens;
+	now = jiffies;
+	token += now - peer->rate_last;
+	peer->rate_last = now;
+	if (token > XRLIM_BURST_FACTOR * timeout)
+		token = XRLIM_BURST_FACTOR * timeout;
+	if (token >= timeout) {
+		token -= timeout;
+		rc = true;
+	}
+	peer->rate_tokens = token;
+	return rc;
+}
+EXPORT_SYMBOL(inet_peer_xrlim_allow);
+
+static void inetpeer_inval_rcu(struct rcu_head *head)
+{
+	struct inet_peer *p = container_of(head, struct inet_peer, gc_rcu);
+
+	spin_lock_bh(&gc_lock);
+	list_add_tail(&p->gc_list, &gc_list);
+	spin_unlock_bh(&gc_lock);
+
+	schedule_delayed_work(&gc_work, gc_delay);
+}
+
+void inetpeer_invalidate_tree(struct inet_peer_base *base)
+{
+	struct inet_peer *root;
+
+	write_seqlock_bh(&base->lock);
+
+	root = rcu_deref_locked(base->root, base);
+	if (root != peer_avl_empty) {
+		base->root = peer_avl_empty_rcu;
+		base->total = 0;
+		call_rcu(&root->gc_rcu, inetpeer_inval_rcu);
+	}
+
+	write_sequnlock_bh(&base->lock);
+}
+EXPORT_SYMBOL(inetpeer_invalidate_tree);