diff options
Diffstat (limited to 'drivers/net/wireguard/ratelimiter.c')
| -rw-r--r-- | drivers/net/wireguard/ratelimiter.c | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/drivers/net/wireguard/ratelimiter.c b/drivers/net/wireguard/ratelimiter.c new file mode 100644 index 000000000..dd55e5c26 --- /dev/null +++ b/drivers/net/wireguard/ratelimiter.c @@ -0,0 +1,223 @@ +// 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_coarse_boottime_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_coarse_boottime_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_coarse_boottime_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 = kvcalloc(table_size, sizeof(*table_v4), GFP_KERNEL); + if (unlikely(!table_v4)) + goto err_kmemcache; + +#if IS_ENABLED(CONFIG_IPV6) + table_v6 = kvcalloc(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" |