aboutsummaryrefslogtreecommitdiffstatshomepage
path: root/src/hashtables.c
blob: f0d87690decb1fd3a4198bfb1de213f91026af06 (plain) (blame)
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
/* Copyright (C) 2015-2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. */

#include "hashtables.h"
#include "peer.h"
#include "noise.h"
#include "crypto/siphash24.h"

#include <linux/hashtable.h>

static inline struct hlist_head *pubkey_bucket(struct pubkey_hashtable *table, const uint8_t pubkey[NOISE_PUBLIC_KEY_LEN])
{
	/* siphash24 gives us a secure 64bit number based on a random key. Since the bits are
	 * uniformly distributed, we can then mask off to get the bits we need. */
	return &table->hashtable[siphash24(pubkey, NOISE_PUBLIC_KEY_LEN, table->key) & (HASH_SIZE(table->hashtable) - 1)];
}

void pubkey_hashtable_init(struct pubkey_hashtable *table)
{
	get_random_bytes(table->key, SIPHASH24_KEY_LEN);
	hash_init(table->hashtable);
	mutex_init(&table->lock);
}

void pubkey_hashtable_add(struct pubkey_hashtable *table, struct wireguard_peer *peer)
{
	mutex_lock(&table->lock);
	hlist_add_head_rcu(&peer->pubkey_hash, pubkey_bucket(table, peer->handshake.remote_static));
	mutex_unlock(&table->lock);
}

void pubkey_hashtable_remove(struct pubkey_hashtable *table, struct wireguard_peer *peer)
{
	mutex_lock(&table->lock);
	hlist_del_init_rcu(&peer->pubkey_hash);
	mutex_unlock(&table->lock);
}

/* Returns a strong reference to a peer */
struct wireguard_peer *pubkey_hashtable_lookup(struct pubkey_hashtable *table, const uint8_t pubkey[NOISE_PUBLIC_KEY_LEN])
{
	struct wireguard_peer *iter_peer, *peer = NULL;
	rcu_read_lock();
	hlist_for_each_entry_rcu(iter_peer, pubkey_bucket(table, pubkey), pubkey_hash) {
		if (!memcmp(pubkey, iter_peer->handshake.remote_static, NOISE_PUBLIC_KEY_LEN)) {
			peer = iter_peer;
			break;
		}
	}
	peer = peer_get(peer);
	rcu_read_unlock();
	return peer;
}

static inline struct hlist_head *index_bucket(struct index_hashtable *table, const __le32 index)
{
	/* Since the indices are random and thus all bits are uniformly distributed,
	 * we can find its bucket simply by masking. */
	return &table->hashtable[(__force u32)index & (HASH_SIZE(table->hashtable) - 1)];
}

void index_hashtable_init(struct index_hashtable *table)
{
	get_random_bytes(table->key, SIPHASH24_KEY_LEN);
	hash_init(table->hashtable);
	spin_lock_init(&table->lock);
}

__le32 index_hashtable_insert(struct index_hashtable *table, struct index_hashtable_entry *entry)
{
	struct index_hashtable_entry *existing_entry;
	unsigned long rand = get_random_long();

	spin_lock(&table->lock);
	hlist_del_init_rcu(&entry->index_hash);
	spin_unlock(&table->lock);

	rcu_read_lock();

search_unused_slot:
	/* First we try to find an unused slot, randomly, while unlocked. */
	++rand;
	entry->index = (__force __le32)siphash24((uint8_t *)&rand, sizeof(rand), table->key);
	hlist_for_each_entry_rcu(existing_entry, index_bucket(table, entry->index), index_hash) {
		if (existing_entry->index == entry->index)
			goto search_unused_slot; /* If it's already in use, we continue searching. */
	}

	/* Once we've found an unused slot, we lock it, and then double-check
	 * that nobody else stole it from us. */
	spin_lock(&table->lock);
	hlist_for_each_entry_rcu(existing_entry, index_bucket(table, entry->index), index_hash) {
		if (existing_entry->index == entry->index) {
			spin_unlock(&table->lock);
			goto search_unused_slot; /* If it was stolen, we start over. */
		}
	}
	/* Otherwise, we know we have it exclusively (since we're locked), so we insert. */
	hlist_add_head_rcu(&entry->index_hash, index_bucket(table, entry->index));
	spin_unlock(&table->lock);

	rcu_read_unlock();

	return entry->index;
}

void index_hashtable_replace(struct index_hashtable *table, struct index_hashtable_entry *old, struct index_hashtable_entry *new)
{
	spin_lock(&table->lock);
	new->index = old->index;
	hlist_replace_rcu(&old->index_hash, &new->index_hash);
	INIT_HLIST_NODE(&old->index_hash);
	spin_unlock(&table->lock);
}

void index_hashtable_remove(struct index_hashtable *table, struct index_hashtable_entry *entry)
{
	spin_lock(&table->lock);
	hlist_del_init_rcu(&entry->index_hash);
	spin_unlock(&table->lock);
}

/* Returns a strong reference to a entry->peer */
struct index_hashtable_entry *index_hashtable_lookup(struct index_hashtable *table, const enum index_hashtable_type type_mask, const __le32 index)
{
	struct index_hashtable_entry *iter_entry, *entry = NULL;
	rcu_read_lock();
	hlist_for_each_entry_rcu(iter_entry, index_bucket(table, index), index_hash) {
		if (iter_entry->index == index && (iter_entry->type & type_mask)) {
			entry = iter_entry;
			break;
		}
	}
	if (likely(entry)) {
		entry->peer = peer_get(entry->peer);
		if (unlikely(!entry->peer))
			entry = NULL;
	}
	rcu_read_unlock();
	return entry;
}