| /* |
| * 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/cache.h> |
| #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 RB 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: |
| * rb_node: 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 __ro_after_init; |
| |
| void inet_peer_base_init(struct inet_peer_base *bp) |
| { |
| bp->rb_root = RB_ROOT; |
| seqlock_init(&bp->lock); |
| bp->total = 0; |
| } |
| EXPORT_SYMBOL_GPL(inet_peer_base_init); |
| |
| #define PEER_MAX_GC 32 |
| |
| /* 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 */ |
| |
| /* 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); |
| } |
| |
| /* Called with rcu_read_lock() or base->lock held */ |
| static struct inet_peer *lookup(const struct inetpeer_addr *daddr, |
| struct inet_peer_base *base, |
| unsigned int seq, |
| struct inet_peer *gc_stack[], |
| unsigned int *gc_cnt, |
| struct rb_node **parent_p, |
| struct rb_node ***pp_p) |
| { |
| struct rb_node **pp, *parent, *next; |
| struct inet_peer *p; |
| |
| pp = &base->rb_root.rb_node; |
| parent = NULL; |
| while (1) { |
| int cmp; |
| |
| next = rcu_dereference_raw(*pp); |
| if (!next) |
| break; |
| parent = next; |
| p = rb_entry(parent, struct inet_peer, rb_node); |
| cmp = inetpeer_addr_cmp(daddr, &p->daddr); |
| if (cmp == 0) { |
| if (!refcount_inc_not_zero(&p->refcnt)) |
| break; |
| return p; |
| } |
| if (gc_stack) { |
| if (*gc_cnt < PEER_MAX_GC) |
| gc_stack[(*gc_cnt)++] = p; |
| } else if (unlikely(read_seqretry(&base->lock, seq))) { |
| break; |
| } |
| if (cmp == -1) |
| pp = &next->rb_left; |
| else |
| pp = &next->rb_right; |
| } |
| *parent_p = parent; |
| *pp_p = pp; |
| return NULL; |
| } |
| |
| static void inetpeer_free_rcu(struct rcu_head *head) |
| { |
| kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu)); |
| } |
| |
| /* perform garbage collect on all items stacked during a lookup */ |
| static void inet_peer_gc(struct inet_peer_base *base, |
| struct inet_peer *gc_stack[], |
| unsigned int gc_cnt) |
| { |
| struct inet_peer *p; |
| __u32 delta, ttl; |
| int i; |
| |
| 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; |
| for (i = 0; i < gc_cnt; i++) { |
| p = gc_stack[i]; |
| delta = (__u32)jiffies - p->dtime; |
| if (delta < ttl || !refcount_dec_if_one(&p->refcnt)) |
| gc_stack[i] = NULL; |
| } |
| for (i = 0; i < gc_cnt; i++) { |
| p = gc_stack[i]; |
| if (p) { |
| rb_erase(&p->rb_node, &base->rb_root); |
| base->total--; |
| call_rcu(&p->rcu, inetpeer_free_rcu); |
| } |
| } |
| } |
| |
| struct inet_peer *inet_getpeer(struct inet_peer_base *base, |
| const struct inetpeer_addr *daddr, |
| int create) |
| { |
| struct inet_peer *p, *gc_stack[PEER_MAX_GC]; |
| struct rb_node **pp, *parent; |
| unsigned int gc_cnt, seq; |
| int invalidated; |
| |
| /* Attempt a lockless lookup first. |
| * Because of a concurrent writer, we might not find an existing entry. |
| */ |
| rcu_read_lock(); |
| seq = read_seqbegin(&base->lock); |
| p = lookup(daddr, base, seq, NULL, &gc_cnt, &parent, &pp); |
| invalidated = read_seqretry(&base->lock, seq); |
| 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. |
| */ |
| parent = NULL; |
| write_seqlock_bh(&base->lock); |
| |
| gc_cnt = 0; |
| p = lookup(daddr, base, seq, gc_stack, &gc_cnt, &parent, &pp); |
| if (!p && create) { |
| p = kmem_cache_alloc(peer_cachep, GFP_ATOMIC); |
| 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; |
| |
| rb_link_node(&p->rb_node, parent, pp); |
| rb_insert_color(&p->rb_node, &base->rb_root); |
| base->total++; |
| } |
| } |
| if (gc_cnt) |
| inet_peer_gc(base, gc_stack, gc_cnt); |
| write_sequnlock_bh(&base->lock); |
| |
| return p; |
| } |
| EXPORT_SYMBOL_GPL(inet_getpeer); |
| |
| void inet_putpeer(struct inet_peer *p) |
| { |
| p->dtime = (__u32)jiffies; |
| |
| if (refcount_dec_and_test(&p->refcnt)) |
| call_rcu(&p->rcu, inetpeer_free_rcu); |
| } |
| 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); |
| |
| void inetpeer_invalidate_tree(struct inet_peer_base *base) |
| { |
| struct rb_node *p = rb_first(&base->rb_root); |
| |
| while (p) { |
| struct inet_peer *peer = rb_entry(p, struct inet_peer, rb_node); |
| |
| p = rb_next(p); |
| rb_erase(&peer->rb_node, &base->rb_root); |
| inet_putpeer(peer); |
| cond_resched(); |
| } |
| |
| base->total = 0; |
| } |
| EXPORT_SYMBOL(inetpeer_invalidate_tree); |