1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
|
/* SPDX-License-Identifier: GPL-2.0
*
* Copyright (C) 2015-2018 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 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 ratelimiter_entry {
u64 last_time_ns, tokens;
__be64 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 gc_entries(struct work_struct *work)
{
unsigned int i;
struct ratelimiter_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 ratelimiter_entry *entry;
struct hlist_head *bucket;
struct { __be64 ip; u32 net; } data = { .net = (unsigned long)net & 0xffffffff };
if (skb->protocol == htons(ETH_P_IP)) {
data.ip = (__force __be64)ip_hdr(skb)->saddr;
bucket = &table_v4[hsiphash(&data, sizeof(u32) * 3, &key) & (table_size - 1)];
}
#if IS_ENABLED(CONFIG_IPV6)
else if (skb->protocol == htons(ETH_P_IPV6)) {
memcpy(&data.ip, &ipv6_hdr(skb)->saddr, sizeof(__be64)); /* Only 64 bits */
bucket = &table_v6[hsiphash(&data, sizeof(u32) * 3, &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 == 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;
entry->ip = 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(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(struct hlist_head), GFP_KERNEL);
if (!table_v4)
goto err_kmemcache;
#if IS_ENABLED(CONFIG_IPV6)
table_v6 = kvzalloc(table_size * sizeof(struct hlist_head), GFP_KERNEL);
if (!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));
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);
rcu_barrier();
kvfree(table_v4);
#if IS_ENABLED(CONFIG_IPV6)
kvfree(table_v6);
#endif
kmem_cache_destroy(entry_cache);
}
#include "selftest/ratelimiter.h"
|
