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/* Copyright (C) 2015-2017 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. */
#include "ratelimiter.h"
#include <linux/siphash.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
#include <linux/hashtable.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 atomic64_t refcnt = ATOMIC64_INIT(0);
static atomic_t total_entries = ATOMIC_INIT(0);
static unsigned int max_entries, table_size;
static void gc_entries(struct work_struct *);
static DECLARE_DEFERRABLE_WORK(gc_work, gc_entries);
static struct hlist_head *table_v4;
#if IS_ENABLED(CONFIG_IPV6)
static struct hlist_head *table_v6;
#endif
struct entry {
u64 last_time_ns, tokens;
void *net;
__be32 ip[3];
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 entry, rcu));
atomic_dec(&total_entries);
}
static void entry_uninit(struct entry *entry)
{
hlist_del_rcu(&entry->hash);
call_rcu_bh(&entry->rcu, entry_free);
}
/* Calling this function with a NULL work uninits all entries. */
static void gc_entries(struct work_struct *work)
{
unsigned int i;
struct entry *entry;
struct hlist_node *temp;
const u64 now = ktime_get_ns();
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 ratelimiter_allow(struct sk_buff *skb, struct net *net)
{
struct entry *entry;
struct hlist_head *bucket;
struct { u32 net; __be32 ip[3]; } data = { .net = (unsigned long)net & 0xffffffff };
if (skb->len >= sizeof(struct iphdr) && ip_hdr(skb)->version == 4) {
data.ip[0] = ip_hdr(skb)->saddr;
bucket = &table_v4[hsiphash(&data, sizeof(u32) * 2, &key) & (table_size - 1)];
}
#if IS_ENABLED(CONFIG_IPV6)
else if (skb->len >= sizeof(struct ipv6hdr) && ip_hdr(skb)->version == 6) {
memcpy(data.ip, &ipv6_hdr(skb)->saddr, sizeof(u32) * 3); /* Only 96 bits */
bucket = &table_v6[hsiphash(&data, sizeof(u32) * 4, &key) & (table_size - 1)];
}
#endif
else
return false;
rcu_read_lock();
hlist_for_each_entry_rcu (entry, bucket, hash) {
if (entry->net == net && !memcmp(entry->ip, data.ip, sizeof(data.ip))) {
u64 now, tokens;
bool ret;
/* 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_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 (!entry)
goto err_oom;
entry->net = net;
memcpy(entry->ip, data.ip, sizeof(data.ip));
INIT_HLIST_NODE(&entry->hash);
spin_lock_init(&entry->lock);
entry->last_time_ns = ktime_get_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 ratelimiter_init(void)
{
if (atomic64_inc_return(&refcnt) != 1)
return 0;
entry_cache = kmem_cache_create("wireguard_ratelimiter", sizeof(struct entry), 0, 0, NULL);
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 > (1 << 30) / PAGE_SIZE) ? 8192 : max_t(unsigned long, 16, roundup_pow_of_two((totalram_pages << PAGE_SHIFT) / (1 << 14) / sizeof(struct hlist_head)));
max_entries = table_size * 8;
table_v4 = vmalloc(table_size * sizeof(struct hlist_head));
if (!table_v4)
goto err_kmemcache;
__hash_init(table_v4, table_size);
#if IS_ENABLED(CONFIG_IPV6)
table_v6 = vmalloc(table_size * sizeof(struct hlist_head));
if (!table_v6) {
vfree(table_v4);
goto err_kmemcache;
}
__hash_init(table_v6, table_size);
#endif
queue_delayed_work(system_power_efficient_wq, &gc_work, HZ);
get_random_bytes(&key, sizeof(key));
return 0;
err_kmemcache:
kmem_cache_destroy(entry_cache);
err:
atomic64_dec(&refcnt);
return -ENOMEM;
}
void ratelimiter_uninit(void)
{
if (atomic64_dec_return(&refcnt))
return;
cancel_delayed_work_sync(&gc_work);
gc_entries(NULL);
synchronize_rcu();
vfree(table_v4);
#if IS_ENABLED(CONFIG_IPV6)
vfree(table_v6);
#endif
kmem_cache_destroy(entry_cache);
}
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