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-rw-r--r--net/ipv4/inetpeer.c558
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);
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-11-17 21:19:18 +0000