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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*/
#include "ratelimiter.h"
#include <linux/siphash.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <net/ip.h>
static struct kmem_cache *entry_cache;
static hsiphash_key_t key;
static spinlock_t table_lock = __SPIN_LOCK_UNLOCKED("ratelimiter_table_lock");
static DEFINE_MUTEX(init_lock);
static u64 init_refcnt; /* Protected by init_lock, hence not atomic. */
static atomic_t total_entries = ATOMIC_INIT(0);
static unsigned int max_entries, table_size;
static void wg_ratelimiter_gc_entries(struct work_struct *);
static DECLARE_DEFERRABLE_WORK(gc_work, wg_ratelimiter_gc_entries);
static struct hlist_head *table_v4;
#if IS_ENABLED(CONFIG_IPV6)
static struct hlist_head *table_v6;
#endif
struct ratelimiter_entry {
u64 last_time_ns, tokens, ip;
void *net;
spinlock_t lock;
struct hlist_node hash;
struct rcu_head rcu;
};
enum {
PACKETS_PER_SECOND = 20,
PACKETS_BURSTABLE = 5,
PACKET_COST = NSEC_PER_SEC / PACKETS_PER_SECOND,
TOKEN_MAX = PACKET_COST * PACKETS_BURSTABLE
};
static void entry_free(struct rcu_head *rcu)
{
kmem_cache_free(entry_cache,
container_of(rcu, struct ratelimiter_entry, rcu));
atomic_dec(&total_entries);
}
static void entry_uninit(struct ratelimiter_entry *entry)
{
hlist_del_rcu(&entry->hash);
call_rcu(&entry->rcu, entry_free);
}
/* Calling this function with a NULL work uninits all entries. */
static void wg_ratelimiter_gc_entries(struct work_struct *work)
{
const u64 now = ktime_get_boot_fast_ns();
struct ratelimiter_entry *entry;
struct hlist_node *temp;
unsigned int i;
for (i = 0; i < table_size; ++i) {
spin_lock(&table_lock);
hlist_for_each_entry_safe(entry, temp, &table_v4[i], hash) {
if (unlikely(!work) ||
now - entry->last_time_ns > NSEC_PER_SEC)
entry_uninit(entry);
}
#if IS_ENABLED(CONFIG_IPV6)
hlist_for_each_entry_safe(entry, temp, &table_v6[i], hash) {
if (unlikely(!work) ||
now - entry->last_time_ns > NSEC_PER_SEC)
entry_uninit(entry);
}
#endif
spin_unlock(&table_lock);
if (likely(work))
cond_resched();
}
if (likely(work))
queue_delayed_work(system_power_efficient_wq, &gc_work, HZ);
}
bool wg_ratelimiter_allow(struct sk_buff *skb, struct net *net)
{
/* We only take the bottom half of the net pointer, so that we can hash
* 3 words in the end. This way, siphash's len param fits into the final
* u32, and we don't incur an extra round.
*/
const u32 net_word = (unsigned long)net;
struct ratelimiter_entry *entry;
struct hlist_head *bucket;
u64 ip;
if (skb->protocol == htons(ETH_P_IP)) {
ip = (u64 __force)ip_hdr(skb)->saddr;
bucket = &table_v4[hsiphash_2u32(net_word, ip, &key) &
(table_size - 1)];
}
#if IS_ENABLED(CONFIG_IPV6)
else if (skb->protocol == htons(ETH_P_IPV6)) {
/* Only use 64 bits, so as to ratelimit the whole /64. */
memcpy(&ip, &ipv6_hdr(skb)->saddr, sizeof(ip));
bucket = &table_v6[hsiphash_3u32(net_word, ip >> 32, ip, &key) &
(table_size - 1)];
}
#endif
else
return false;
rcu_read_lock();
hlist_for_each_entry_rcu(entry, bucket, hash) {
if (entry->net == net && entry->ip == ip) {
u64 now, tokens;
bool ret;
/* Quasi-inspired by nft_limit.c, but this is actually a
* slightly different algorithm. Namely, we incorporate
* the burst as part of the maximum tokens, rather than
* as part of the rate.
*/
spin_lock(&entry->lock);
now = ktime_get_boot_fast_ns();
tokens = min_t(u64, TOKEN_MAX,
entry->tokens + now -
entry->last_time_ns);
entry->last_time_ns = now;
ret = tokens >= PACKET_COST;
entry->tokens = ret ? tokens - PACKET_COST : tokens;
spin_unlock(&entry->lock);
rcu_read_unlock();
return ret;
}
}
rcu_read_unlock();
if (atomic_inc_return(&total_entries) > max_entries)
goto err_oom;
entry = kmem_cache_alloc(entry_cache, GFP_KERNEL);
if (unlikely(!entry))
goto err_oom;
entry->net = net;
entry->ip = ip;
INIT_HLIST_NODE(&entry->hash);
spin_lock_init(&entry->lock);
entry->last_time_ns = ktime_get_boot_fast_ns();
entry->tokens = TOKEN_MAX - PACKET_COST;
spin_lock(&table_lock);
hlist_add_head_rcu(&entry->hash, bucket);
spin_unlock(&table_lock);
return true;
err_oom:
atomic_dec(&total_entries);
return false;
}
int wg_ratelimiter_init(void)
{
mutex_lock(&init_lock);
if (++init_refcnt != 1)
goto out;
entry_cache = KMEM_CACHE(ratelimiter_entry, 0);
if (!entry_cache)
goto err;
/* xt_hashlimit.c uses a slightly different algorithm for ratelimiting,
* but what it shares in common is that it uses a massive hashtable. So,
* we borrow their wisdom about good table sizes on different systems
* dependent on RAM. This calculation here comes from there.
*/
table_size = (totalram_pages > (1U << 30) / PAGE_SIZE) ? 8192 :
max_t(unsigned long, 16, roundup_pow_of_two(
(totalram_pages << PAGE_SHIFT) /
(1U << 14) / sizeof(struct hlist_head)));
max_entries = table_size * 8;
table_v4 = kvzalloc(table_size * sizeof(*table_v4), GFP_KERNEL);
if (unlikely(!table_v4))
goto err_kmemcache;
#if IS_ENABLED(CONFIG_IPV6)
table_v6 = kvzalloc(table_size * sizeof(*table_v6), GFP_KERNEL);
if (unlikely(!table_v6)) {
kvfree(table_v4);
goto err_kmemcache;
}
#endif
queue_delayed_work(system_power_efficient_wq, &gc_work, HZ);
get_random_bytes(&key, sizeof(key));
out:
mutex_unlock(&init_lock);
return 0;
err_kmemcache:
kmem_cache_destroy(entry_cache);
err:
--init_refcnt;
mutex_unlock(&init_lock);
return -ENOMEM;
}
void wg_ratelimiter_uninit(void)
{
mutex_lock(&init_lock);
if (!init_refcnt || --init_refcnt)
goto out;
cancel_delayed_work_sync(&gc_work);
wg_ratelimiter_gc_entries(NULL);
rcu_barrier();
kvfree(table_v4);
#if IS_ENABLED(CONFIG_IPV6)
kvfree(table_v6);
#endif
kmem_cache_destroy(entry_cache);
out:
mutex_unlock(&init_lock);
}
#include "selftest/ratelimiter.c"
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