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// 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 <sebastien.barre@uclouvain.be>
* Christoph Paasch <christoph.paasch@uclouvain.be>
* Jaakko Korkeaniemi <jaakko.korkeaniemi@aalto.fi>
* Gregory Detal <gregory.detal@uclouvain.be>
* Fabien Duchêne <fabien.duchene@uclouvain.be>
* Andreas Seelinger <Andreas.Seelinger@rwth-aachen.de>
* Lavkesh Lahngir <lavkesh51@gmail.com>
* Andreas Ripke <ripke@neclab.eu>
* Vlad Dogaru <vlad.dogaru@intel.com>
* Octavian Purdila <octavian.purdila@intel.com>
* John Ronan <jronan@tssg.org>
* Catalin Nicutar <catalin.nicutar@gmail.com>
* Brandon Heller <brandonh@stanford.edu>
*/
#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_RETRIES 4
#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
* @sk: 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 *sk)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
struct mptcp_sock *msk = mptcp_sk(subflow->conn);
int retries = TOKEN_MAX_RETRIES;
struct token_bucket *bucket;
pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n",
sk, subflow->local_key, subflow->token, subflow->idsn);
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;
}
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);
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 token_bucket *bucket;
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
* @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(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)
continue;
if (!refcount_inc_not_zero(&sk->sk_refcnt))
goto not_found;
if (READ_ONCE(msk->token) != token) {
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 move to the next position and the
* the acquires a reference to the returned socket.
*/
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
|