| /* |
| * 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. |
| * At this moment this information consists only of ID field for the next |
| * outgoing IP packet. This field is incremented with each packet as encoded |
| * in inet_getid() function (include/net/inetpeer.h). |
| * At the moment of writing this notes identifier of IP packets is generated |
| * to be unpredictable using this code only for packets subjected |
| * (actually or potentially) to defragmentation. I.e. DF packets less than |
| * PMTU in size when local fragmentation is disabled use a constant ID and do |
| * not use this code (see ip_select_ident() in include/net/ip.h). |
| * |
| * Route cache entries hold references to our nodes. |
| * New cache entries get references via lookup by destination IP address in |
| * the avl tree. The reference is grabbed only when it's needed i.e. only |
| * when we try to output IP packet which needs an unpredictable ID (see |
| * __ip_select_ident() in net/ipv4/route.c). |
| * 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 |
| * ip_id_count: atomic value (no lock needed) |
| */ |
| |
| 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->flush_seq = ~0U; |
| bp->total = 0; |
| } |
| EXPORT_SYMBOL_GPL(inet_peer_base_init); |
| |
| static atomic_t v4_seq = ATOMIC_INIT(0); |
| static atomic_t v6_seq = ATOMIC_INIT(0); |
| |
| static atomic_t *inetpeer_seq_ptr(int family) |
| { |
| return (family == AF_INET ? &v4_seq : &v6_seq); |
| } |
| |
| static inline void flush_check(struct inet_peer_base *base, int family) |
| { |
| atomic_t *fp = inetpeer_seq_ptr(family); |
| |
| if (unlikely(base->flush_seq != atomic_read(fp))) { |
| inetpeer_invalidate_tree(base); |
| base->flush_seq = atomic_read(fp); |
| } |
| } |
| |
| void inetpeer_invalidate_family(int family) |
| { |
| atomic_t *fp = inetpeer_seq_ptr(family); |
| |
| atomic_inc(fp); |
| } |
| |
| #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; |
| 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; |
| |
| flush_check(base, daddr->family); |
| |
| /* 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); |
| atomic_set(&p->ip_id_count, |
| (daddr->family == AF_INET) ? |
| secure_ip_id(daddr->addr.a4) : |
| secure_ipv6_id(daddr->addr.a6)); |
| 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); |