diff options
Diffstat (limited to 'kernel/net/ipv4/inetpeer.c')
| -rw-r--r-- | kernel/net/ipv4/inetpeer.c | 558 |
1 files changed, 558 insertions, 0 deletions
diff --git a/kernel/net/ipv4/inetpeer.c b/kernel/net/ipv4/inetpeer.c new file mode 100644 index 000000000..241afd743 --- /dev/null +++ b/kernel/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); |