/* * 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 (refcount_read(&p->refcnt) == 1) { 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);} #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 = inetpeer_addr_cmp(_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 = inetpeer_addr_cmp(daddr, &u->daddr); if (cmp == 0) { /* Before taking a reference, check if this entry was * deleted (refcnt=0) */ if (!refcount_inc_not_zero(&u->refcnt)) { 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 (refcount_read(&p->refcnt) == 1) { smp_rmb(); delta = (__u32)jiffies - p->dtime; if (delta >= ttl && refcount_dec_if_one(&p->refcnt)) { 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) { refcount_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; refcount_set(&p->refcnt, 2); 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(); refcount_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 6bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout){ unsigned long now, token; bool rc = false; if (!peer) return true; Lines 1–500 of 542. Load more
/* * 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 (refcount_read(&p->refcnt) == 1) { 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); } #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 = inetpeer_addr_cmp(_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 = inetpeer_addr_cmp(daddr, &u->daddr); if (cmp == 0) { /* Before taking a reference, check if this entry was * deleted (refcnt=0) */ if (!refcount_inc_not_zero(&u->refcnt)) { 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 (refcount_read(&p->refcnt) == 1) { smp_rmb(); delta = (__u32)jiffies - p->dtime; if (delta >= ttl && refcount_dec_if_one(&p->refcnt)) { 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) { refcount_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; refcount_set(&p->refcnt, 2); 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(); refcount_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;