// SPDX-License-Identifier: GPL-2.0
/* Multipath TCP token management
* Copyright (c) 2017 - 2019, Intel Corporation.
*
* Note: This code is based on mptcp_ctrl.c from multipath-tcp.org,
* authored by:
*
* Sébastien Barré <[email protected]>
* Christoph Paasch <[email protected]>
* Jaakko Korkeaniemi <[email protected]>
* Gregory Detal <[email protected]>
* Fabien Duchêne <[email protected]>
* Andreas Seelinger <[email protected]>
* Lavkesh Lahngir <[email protected]>
* Andreas Ripke <[email protected]>
* Vlad Dogaru <[email protected]>
* Octavian Purdila <[email protected]>
* John Ronan <[email protected]>
* Catalin Nicutar <[email protected]>
* Brandon Heller <[email protected]>
*/
#define pr_fmt(fmt) "MPTCP: " fmt
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/memblock.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <net/sock.h>
#include <net/inet_common.h>
#include <net/protocol.h>
#include <net/mptcp.h>
#include "protocol.h"
#define TOKEN_MAX_CHAIN_LEN 4
struct token_bucket {
spinlock_t lock;
int chain_len;
struct hlist_nulls_head req_chain;
struct hlist_nulls_head msk_chain;
};
static struct token_bucket *token_hash __read_mostly;
static unsigned int token_mask __read_mostly;
static struct token_bucket *token_bucket(u32 token)
{
return &token_hash[token & token_mask];
}
/* called with bucket lock held */
static struct mptcp_subflow_request_sock *
__token_lookup_req(struct token_bucket *t, u32 token)
{
struct mptcp_subflow_request_sock *req;
struct hlist_nulls_node *pos;
hlist_nulls_for_each_entry_rcu(req, pos, &t->req_chain, token_node)
if (req->token == token)
return req;
return NULL;
}
/* called with bucket lock held */
static struct mptcp_sock *
__token_lookup_msk(struct token_bucket *t, u32 token)
{
struct hlist_nulls_node *pos;
struct sock *sk;
sk_nulls_for_each_rcu(sk, pos, &t->msk_chain)
if (mptcp_sk(sk)->token == token)
return mptcp_sk(sk);
return NULL;
}
static bool __token_bucket_busy(struct token_bucket *t, u32 token)
{
return !token || t->chain_len >= TOKEN_MAX_CHAIN_LEN ||
__token_lookup_req(t, token) || __token_lookup_msk(t, token);
}
static void mptcp_crypto_key_gen_sha(u64 *key, u32 *token, u64 *idsn)
{
/* we might consider a faster version that computes the key as a
* hash of some information available in the MPTCP socket. Use
* random data at the moment, as it's probably the safest option
* in case multiple sockets are opened in different namespaces at
* the same time.
*/
get_random_bytes(key, sizeof(u64));
mptcp_crypto_key_sha(*key, token, idsn);
}
/**
* mptcp_token_new_request - create new key/idsn/token for subflow_request
* @req: the request socket
*
* This function is called when a new mptcp connection is coming in.
*
* It creates a unique token to identify the new mptcp connection,
* a secret local key and the initial data sequence number (idsn).
*
* Returns 0 on success.
*/
int mptcp_token_new_request(struct request_sock *req)
{
struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
struct token_bucket *bucket;
u32 token;
mptcp_crypto_key_sha(subflow_req->local_key,
&subflow_req->token,
&subflow_req->idsn);
pr_debug("req=%p local_key=%llu, token=%u, idsn=%llu\n",
req, subflow_req->local_key, subflow_req->token,
subflow_req->idsn);
token = subflow_req->token;
bucket = token_bucket(token);
spin_lock_bh(&bucket->lock);
if (__token_bucket_busy(bucket, token)) {
spin_unlock_bh(&bucket->lock);
return -EBUSY;
}
hlist_nulls_add_head_rcu(&subflow_req->token_node, &bucket->req_chain);
bucket->chain_len++;
spin_unlock_bh(&bucket->lock);
return 0;
}
/**
* mptcp_token_new_connect - create new key/idsn/token for subflow
* @ssk: the socket that will initiate a connection
*
* This function is called when a new outgoing mptcp connection is
* initiated.
*
* It creates a unique token to identify the new mptcp connection,
* a secret local key and the initial data sequence number (idsn).
*
* On success, the mptcp connection can be found again using
* the computed token at a later time, this is needed to process
* join requests.
*
* returns 0 on success.
*/
int mptcp_token_new_connect(struct sock *ssk)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
struct mptcp_sock *msk = mptcp_sk(subflow->conn);
int retries = MPTCP_TOKEN_MAX_RETRIES;
struct sock *sk = subflow->conn;
struct token_bucket *bucket;
again:
mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token,
&subflow->idsn);
bucket = token_bucket(subflow->token);
spin_lock_bh(&bucket->lock);
if (__token_bucket_busy(bucket, subflow->token)) {
spin_unlock_bh(&bucket->lock);
if (!--retries)
return -EBUSY;
goto again;
}
pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n",
ssk, subflow->local_key, subflow->token, subflow->idsn);
WRITE_ONCE(msk->token, subflow->token);
__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
bucket->chain_len++;
spin_unlock_bh(&bucket->lock);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
return 0;
}
/**
* mptcp_token_accept - replace a req sk with full sock in token hash
* @req: the request socket to be removed
* @msk: the just cloned socket linked to the new connection
*
* Called when a SYN packet creates a new logical connection, i.e.
* is not a join request.
*/
void mptcp_token_accept(struct mptcp_subflow_request_sock *req,
struct mptcp_sock *msk)
{
struct mptcp_subflow_request_sock *pos;
struct sock *sk = (struct sock *)msk;
struct token_bucket *bucket;
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
bucket = token_bucket(req->token);
spin_lock_bh(&bucket->lock);
/* pedantic lookup check for the moved token */
pos = __token_lookup_req(bucket, req->token);
if (!WARN_ON_ONCE(pos != req))
hlist_nulls_del_init_rcu(&req->token_node);
__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
spin_unlock_bh(&bucket->lock);
}
bool mptcp_token_exists(u32 token)
{
struct hlist_nulls_node *pos;
struct token_bucket *bucket;
struct mptcp_sock *msk;
struct sock *sk;
rcu_read_lock();
bucket = token_bucket(token);
again:
sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
msk = mptcp_sk(sk);
if (READ_ONCE(msk->token) == token)
goto found;
}
if (get_nulls_value(pos) != (token & token_mask))
goto again;
rcu_read_unlock();
return false;
found:
rcu_read_unlock();
return true;
}
/**
* mptcp_token_get_sock - retrieve mptcp connection sock using its token
* @net: restrict to this namespace
* @token: token of the mptcp connection to retrieve
*
* This function returns the mptcp connection structure with the given token.
* A reference count on the mptcp socket returned is taken.
*
* returns NULL if no connection with the given token value exists.
*/
struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token)
{
struct hlist_nulls_node *pos;
struct token_bucket *bucket;
struct mptcp_sock *msk;
struct sock *sk;
rcu_read_lock();
bucket = token_bucket(token);
again:
sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
msk = mptcp_sk(sk);
if (READ_ONCE(msk->token) != token ||
!net_eq(sock_net(sk), net))
continue;
if (!refcount_inc_not_zero(&sk->sk_refcnt))
goto not_found;
if (READ_ONCE(msk->token) != token ||
!net_eq(sock_net(sk), net)) {
sock_put(sk);
goto again;
}
goto found;
}
if (get_nulls_value(pos) != (token & token_mask))
goto again;
not_found:
msk = NULL;
found:
rcu_read_unlock();
return msk;
}
EXPORT_SYMBOL_GPL(mptcp_token_get_sock);
/**
* mptcp_token_iter_next - iterate over the token container from given pos
* @net: namespace to be iterated
* @s_slot: start slot number
* @s_num: start number inside the given lock
*
* This function returns the first mptcp connection structure found inside the
* token container starting from the specified position, or NULL.
*
* On successful iteration, the iterator is moved to the next position and
* a reference to the returned socket is acquired.
*/
struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
long *s_num)
{
struct mptcp_sock *ret = NULL;
struct hlist_nulls_node *pos;
int slot, num = 0;
for (slot = *s_slot; slot <= token_mask; *s_num = 0, slot++) {
struct token_bucket *bucket = &token_hash[slot];
struct sock *sk;
num = 0;
if (hlist_nulls_empty(&bucket->msk_chain))
continue;
rcu_read_lock();
sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
++num;
if (!net_eq(sock_net(sk), net))
continue;
if (num <= *s_num)
continue;
if (!refcount_inc_not_zero(&sk->sk_refcnt))
continue;
if (!net_eq(sock_net(sk), net)) {
sock_put(sk);
continue;
}
ret = mptcp_sk(sk);
rcu_read_unlock();
goto out;
}
rcu_read_unlock();
}
out:
*s_slot = slot;
*s_num = num;
return ret;
}
EXPORT_SYMBOL_GPL(mptcp_token_iter_next);
/**
* mptcp_token_destroy_request - remove mptcp connection/token
* @req: mptcp request socket dropping the token
*
* Remove the token associated to @req.
*/
void mptcp_token_destroy_request(struct request_sock *req)
{
struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
struct mptcp_subflow_request_sock *pos;
struct token_bucket *bucket;
if (hlist_nulls_unhashed(&subflow_req->token_node))
return;
bucket = token_bucket(subflow_req->token);
spin_lock_bh(&bucket->lock);
pos = __token_lookup_req(bucket, subflow_req->token);
if (!WARN_ON_ONCE(pos != subflow_req)) {
hlist_nulls_del_init_rcu(&pos->token_node);
bucket->chain_len--;
}
spin_unlock_bh(&bucket->lock);
}
/**
* mptcp_token_destroy - remove mptcp connection/token
* @msk: mptcp connection dropping the token
*
* Remove the token associated to @msk
*/
void mptcp_token_destroy(struct mptcp_sock *msk)
{
struct sock *sk = (struct sock *)msk;
struct token_bucket *bucket;
struct mptcp_sock *pos;
if (sk_unhashed((struct sock *)msk))
return;
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
bucket = token_bucket(msk->token);
spin_lock_bh(&bucket->lock);
pos = __token_lookup_msk(bucket, msk->token);
if (!WARN_ON_ONCE(pos != msk)) {
__sk_nulls_del_node_init_rcu((struct sock *)pos);
bucket->chain_len--;
}
spin_unlock_bh(&bucket->lock);
WRITE_ONCE(msk->token, 0);
}
void __init mptcp_token_init(void)
{
int i;
token_hash = alloc_large_system_hash("MPTCP token",
sizeof(struct token_bucket),
0,
20,/* one slot per 1MB of memory */
HASH_ZERO,
NULL,
&token_mask,
0,
64 * 1024);
for (i = 0; i < token_mask + 1; ++i) {
INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i);
INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i);
spin_lock_init(&token_hash[i].lock);
}
}
#if IS_MODULE(CONFIG_MPTCP_KUNIT_TEST)
EXPORT_SYMBOL_GPL(mptcp_token_new_request);
EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
EXPORT_SYMBOL_GPL(mptcp_token_accept);
EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
EXPORT_SYMBOL_GPL(mptcp_token_destroy);
#endif
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