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/* SPDX-License-Identifier: GPL-2.0
*
* Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*/
#include "hashtables.h"
#include "peer.h"
#include "noise.h"
static u32 pubkey_hashfn(const void *data, u32 len, u32 seed)
{
/* The rhashtable API only allows 32 bits of seed, while siphash expects 128 bits. */
siphash_key_t key = { .key = { seed } };
return siphash(data, len, &key);
}
static const struct rhashtable_params pubkey_params = {
.key_offset = offsetof(struct wireguard_peer, handshake.remote_static),
.key_len = FIELD_SIZEOF(struct wireguard_peer, handshake.remote_static),
.head_offset = offsetof(struct wireguard_peer, pubkey_hash),
.hashfn = pubkey_hashfn,
.automatic_shrinking = true,
};
int pubkey_hashtable_init(struct pubkey_hashtable *table)
{
return rhashtable_init(&table->hashtable, &pubkey_params);
}
void pubkey_hashtable_cleanup(struct pubkey_hashtable *table)
{
rhashtable_destroy(&table->hashtable);
}
void pubkey_hashtable_add(struct pubkey_hashtable *table, struct wireguard_peer *peer)
{
/* TODO: does this really work with hash collisions? */
rhashtable_insert_fast(&table->hashtable, &peer->pubkey_hash, pubkey_params);
}
void pubkey_hashtable_remove(struct pubkey_hashtable *table, struct wireguard_peer *peer)
{
rhashtable_remove_fast(&table->hashtable, &peer->pubkey_hash, pubkey_params);
}
/* Returns a strong reference to a peer */
struct wireguard_peer *pubkey_hashtable_lookup(struct pubkey_hashtable *table, const u8 pubkey[NOISE_PUBLIC_KEY_LEN])
{
struct wireguard_peer *peer;
rcu_read_lock_bh();
peer = peer_get(rhashtable_lookup_fast(&table->hashtable, pubkey, pubkey_params));
rcu_read_unlock_bh();
return peer;
}
static u32 index_hashfn(const void *data, u32 len, u32 seed)
{
BUG_ON(len != 4);
return *(u32 *)data;
}
static const struct rhashtable_params index_params = {
.key_offset = offsetof(struct index_hashtable_entry, index),
.key_len = FIELD_SIZEOF(struct index_hashtable_entry, index),
.head_offset = offsetof(struct index_hashtable_entry, index_hash),
.hashfn = index_hashfn,
.automatic_shrinking = true,
};
int index_hashtable_init(struct index_hashtable *table)
{
int ret;
ret = rhashtable_init(&table->hashtable, &index_params);
spin_lock_init(&table->lock);
return ret;
}
void index_hashtable_cleanup(struct index_hashtable *table)
{
rhashtable_destroy(&table->hashtable);
}
/* At the moment, we limit ourselves to 2^20 total peers, which generally might amount to 2^20*3
* items in this hashtable. The algorithm below works by picking a random number and testing it.
* We can see that these limits mean we usually succeed pretty quickly:
*
* >>> def calculation(tries, size):
* ... return (size / 2**32)**(tries - 1) * (1 - (size / 2**32))
* ...
* >>> calculation(1, 2**20 * 3)
* 0.999267578125
* >>> calculation(2, 2**20 * 3)
* 0.0007318854331970215
* >>> calculation(3, 2**20 * 3)
* 5.360489012673497e-07
* >>> calculation(4, 2**20 * 3)
* 3.9261394135792216e-10
*
* At the moment, we don't do any masking, so this algorithm isn't exactly constant time in
* either the random guessing or in the hash list lookup. We could require a minimum of 3
* tries, which would successfully mask the guessing. TODO: this would not, however, help
* with the growing hash lengths.
*/
__le32 index_hashtable_insert(struct index_hashtable *table, struct index_hashtable_entry *entry)
{
struct index_hashtable_entry *existing_entry;
rcu_read_lock_bh();
search_unused_slot:
/* First we try to find an unused slot, randomly, while unlocked. */
entry->index = (__force __le32)get_random_u32();
existing_entry = rhashtable_lookup_fast(&table->hashtable, &entry->index, index_params);
if (existing_entry && 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_bh(&table->lock);
existing_entry = rhashtable_lookup_fast(&table->hashtable, &entry->index, index_params);
if (existing_entry && existing_entry->index == entry->index) {
spin_unlock_bh(&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. */
rhashtable_insert_fast(&table->hashtable, &entry->index_hash, index_params);
spin_unlock_bh(&table->lock);
rcu_read_unlock_bh();
return entry->index;
}
bool index_hashtable_replace(struct index_hashtable *table, struct index_hashtable_entry *old, struct index_hashtable_entry *new)
{
int ret;
if (unlikely(rhashtable_lookup_fast(&table->hashtable, old, index_params)))
return false;
spin_lock_bh(&table->lock);
new->index = old->index;
ret = rhashtable_replace_fast(&table->hashtable, &old->index_hash, &new->index_hash, index_params);
WARN_ON_ONCE(ret != 0);
spin_unlock_bh(&table->lock);
return true;
}
void index_hashtable_remove(struct index_hashtable *table, struct index_hashtable_entry *entry)
{
spin_lock_bh(&table->lock);
rhashtable_remove_fast(&table->hashtable, &entry->index_hash, index_params);
spin_unlock_bh(&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 *entry = NULL;
rcu_read_lock_bh();
entry = rhashtable_lookup_fast(&table->hashtable, &index, index_params);
if (likely(entry && entry->type & type_mask)) {
entry->peer = peer_get(entry->peer);
if (unlikely(!entry->peer))
entry = NULL;
}
rcu_read_unlock_bh();
return entry;
}
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