1// SPDX-License-Identifier: GPL-2.0
2/* Multipath TCP token management
3 * Copyright (c) 2017 - 2019, Intel Corporation.
4 *
5 * Note: This code is based on mptcp_ctrl.c from multipath-tcp.org,
6 *       authored by:
7 *
8 *       S��bastien Barr�� <sebastien.barre@uclouvain.be>
9 *       Christoph Paasch <christoph.paasch@uclouvain.be>
10 *       Jaakko Korkeaniemi <jaakko.korkeaniemi@aalto.fi>
11 *       Gregory Detal <gregory.detal@uclouvain.be>
12 *       Fabien Duch��ne <fabien.duchene@uclouvain.be>
13 *       Andreas Seelinger <Andreas.Seelinger@rwth-aachen.de>
14 *       Lavkesh Lahngir <lavkesh51@gmail.com>
15 *       Andreas Ripke <ripke@neclab.eu>
16 *       Vlad Dogaru <vlad.dogaru@intel.com>
17 *       Octavian Purdila <octavian.purdila@intel.com>
18 *       John Ronan <jronan@tssg.org>
19 *       Catalin Nicutar <catalin.nicutar@gmail.com>
20 *       Brandon Heller <brandonh@stanford.edu>
21 */
22
23#define pr_fmt(fmt) "MPTCP: " fmt
24
25#include <linux/kernel.h>
26#include <linux/module.h>
27#include <linux/memblock.h>
28#include <linux/ip.h>
29#include <linux/tcp.h>
30#include <net/sock.h>
31#include <net/inet_common.h>
32#include <net/protocol.h>
33#include <net/mptcp.h>
34#include "protocol.h"
35
36#define TOKEN_MAX_CHAIN_LEN	4
37
38struct token_bucket {
39	spinlock_t		lock;
40	int			chain_len;
41	struct hlist_nulls_head	req_chain;
42	struct hlist_nulls_head	msk_chain;
43};
44
45static struct token_bucket *token_hash __read_mostly;
46static unsigned int token_mask __read_mostly;
47
48static struct token_bucket *token_bucket(u32 token)
49{
50	return &token_hash[token & token_mask];
51}
52
53/* called with bucket lock held */
54static struct mptcp_subflow_request_sock *
55__token_lookup_req(struct token_bucket *t, u32 token)
56{
57	struct mptcp_subflow_request_sock *req;
58	struct hlist_nulls_node *pos;
59
60	hlist_nulls_for_each_entry_rcu(req, pos, &t->req_chain, token_node)
61		if (req->token == token)
62			return req;
63	return NULL;
64}
65
66/* called with bucket lock held */
67static struct mptcp_sock *
68__token_lookup_msk(struct token_bucket *t, u32 token)
69{
70	struct hlist_nulls_node *pos;
71	struct sock *sk;
72
73	sk_nulls_for_each_rcu(sk, pos, &t->msk_chain)
74		if (mptcp_sk(sk)->token == token)
75			return mptcp_sk(sk);
76	return NULL;
77}
78
79static bool __token_bucket_busy(struct token_bucket *t, u32 token)
80{
81	return !token || t->chain_len >= TOKEN_MAX_CHAIN_LEN ||
82	       __token_lookup_req(t, token) || __token_lookup_msk(t, token);
83}
84
85static void mptcp_crypto_key_gen_sha(u64 *key, u32 *token, u64 *idsn)
86{
87	/* we might consider a faster version that computes the key as a
88	 * hash of some information available in the MPTCP socket. Use
89	 * random data at the moment, as it's probably the safest option
90	 * in case multiple sockets are opened in different namespaces at
91	 * the same time.
92	 */
93	get_random_bytes(key, sizeof(u64));
94	mptcp_crypto_key_sha(*key, token, idsn);
95}
96
97/**
98 * mptcp_token_new_request - create new key/idsn/token for subflow_request
99 * @req: the request socket
100 *
101 * This function is called when a new mptcp connection is coming in.
102 *
103 * It creates a unique token to identify the new mptcp connection,
104 * a secret local key and the initial data sequence number (idsn).
105 *
106 * Returns 0 on success.
107 */
108int mptcp_token_new_request(struct request_sock *req)
109{
110	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
111	struct token_bucket *bucket;
112	u32 token;
113
114	mptcp_crypto_key_sha(subflow_req->local_key,
115			     &subflow_req->token,
116			     &subflow_req->idsn);
117	pr_debug("req=%p local_key=%llu, token=%u, idsn=%llu\n",
118		 req, subflow_req->local_key, subflow_req->token,
119		 subflow_req->idsn);
120
121	token = subflow_req->token;
122	bucket = token_bucket(token);
123	spin_lock_bh(&bucket->lock);
124	if (__token_bucket_busy(bucket, token)) {
125		spin_unlock_bh(&bucket->lock);
126		return -EBUSY;
127	}
128
129	hlist_nulls_add_head_rcu(&subflow_req->token_node, &bucket->req_chain);
130	bucket->chain_len++;
131	spin_unlock_bh(&bucket->lock);
132	return 0;
133}
134
135/**
136 * mptcp_token_new_connect - create new key/idsn/token for subflow
137 * @ssk: the socket that will initiate a connection
138 *
139 * This function is called when a new outgoing mptcp connection is
140 * initiated.
141 *
142 * It creates a unique token to identify the new mptcp connection,
143 * a secret local key and the initial data sequence number (idsn).
144 *
145 * On success, the mptcp connection can be found again using
146 * the computed token at a later time, this is needed to process
147 * join requests.
148 *
149 * returns 0 on success.
150 */
151int mptcp_token_new_connect(struct sock *ssk)
152{
153	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
154	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
155	int retries = MPTCP_TOKEN_MAX_RETRIES;
156	struct sock *sk = subflow->conn;
157	struct token_bucket *bucket;
158
159again:
160	mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token,
161				 &subflow->idsn);
162
163	bucket = token_bucket(subflow->token);
164	spin_lock_bh(&bucket->lock);
165	if (__token_bucket_busy(bucket, subflow->token)) {
166		spin_unlock_bh(&bucket->lock);
167		if (!--retries)
168			return -EBUSY;
169		goto again;
170	}
171
172	pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n",
173		 ssk, subflow->local_key, subflow->token, subflow->idsn);
174
175	WRITE_ONCE(msk->token, subflow->token);
176	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
177	bucket->chain_len++;
178	spin_unlock_bh(&bucket->lock);
179	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
180	return 0;
181}
182
183/**
184 * mptcp_token_accept - replace a req sk with full sock in token hash
185 * @req: the request socket to be removed
186 * @msk: the just cloned socket linked to the new connection
187 *
188 * Called when a SYN packet creates a new logical connection, i.e.
189 * is not a join request.
190 */
191void mptcp_token_accept(struct mptcp_subflow_request_sock *req,
192			struct mptcp_sock *msk)
193{
194	struct mptcp_subflow_request_sock *pos;
195	struct sock *sk = (struct sock *)msk;
196	struct token_bucket *bucket;
197
198	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
199	bucket = token_bucket(req->token);
200	spin_lock_bh(&bucket->lock);
201
202	/* pedantic lookup check for the moved token */
203	pos = __token_lookup_req(bucket, req->token);
204	if (!WARN_ON_ONCE(pos != req))
205		hlist_nulls_del_init_rcu(&req->token_node);
206	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
207	spin_unlock_bh(&bucket->lock);
208}
209
210bool mptcp_token_exists(u32 token)
211{
212	struct hlist_nulls_node *pos;
213	struct token_bucket *bucket;
214	struct mptcp_sock *msk;
215	struct sock *sk;
216
217	rcu_read_lock();
218	bucket = token_bucket(token);
219
220again:
221	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
222		msk = mptcp_sk(sk);
223		if (READ_ONCE(msk->token) == token)
224			goto found;
225	}
226	if (get_nulls_value(pos) != (token & token_mask))
227		goto again;
228
229	rcu_read_unlock();
230	return false;
231found:
232	rcu_read_unlock();
233	return true;
234}
235
236/**
237 * mptcp_token_get_sock - retrieve mptcp connection sock using its token
238 * @net: restrict to this namespace
239 * @token: token of the mptcp connection to retrieve
240 *
241 * This function returns the mptcp connection structure with the given token.
242 * A reference count on the mptcp socket returned is taken.
243 *
244 * returns NULL if no connection with the given token value exists.
245 */
246struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token)
247{
248	struct hlist_nulls_node *pos;
249	struct token_bucket *bucket;
250	struct mptcp_sock *msk;
251	struct sock *sk;
252
253	rcu_read_lock();
254	bucket = token_bucket(token);
255
256again:
257	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
258		msk = mptcp_sk(sk);
259		if (READ_ONCE(msk->token) != token ||
260		    !net_eq(sock_net(sk), net))
261			continue;
262
263		if (!refcount_inc_not_zero(&sk->sk_refcnt))
264			goto not_found;
265
266		if (READ_ONCE(msk->token) != token ||
267		    !net_eq(sock_net(sk), net)) {
268			sock_put(sk);
269			goto again;
270		}
271		goto found;
272	}
273	if (get_nulls_value(pos) != (token & token_mask))
274		goto again;
275
276not_found:
277	msk = NULL;
278
279found:
280	rcu_read_unlock();
281	return msk;
282}
283EXPORT_SYMBOL_GPL(mptcp_token_get_sock);
284
285/**
286 * mptcp_token_iter_next - iterate over the token container from given pos
287 * @net: namespace to be iterated
288 * @s_slot: start slot number
289 * @s_num: start number inside the given lock
290 *
291 * This function returns the first mptcp connection structure found inside the
292 * token container starting from the specified position, or NULL.
293 *
294 * On successful iteration, the iterator is moved to the next position and
295 * a reference to the returned socket is acquired.
296 */
297struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
298					 long *s_num)
299{
300	struct mptcp_sock *ret = NULL;
301	struct hlist_nulls_node *pos;
302	int slot, num = 0;
303
304	for (slot = *s_slot; slot <= token_mask; *s_num = 0, slot++) {
305		struct token_bucket *bucket = &token_hash[slot];
306		struct sock *sk;
307
308		num = 0;
309
310		if (hlist_nulls_empty(&bucket->msk_chain))
311			continue;
312
313		rcu_read_lock();
314		sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
315			++num;
316			if (!net_eq(sock_net(sk), net))
317				continue;
318
319			if (num <= *s_num)
320				continue;
321
322			if (!refcount_inc_not_zero(&sk->sk_refcnt))
323				continue;
324
325			if (!net_eq(sock_net(sk), net)) {
326				sock_put(sk);
327				continue;
328			}
329
330			ret = mptcp_sk(sk);
331			rcu_read_unlock();
332			goto out;
333		}
334		rcu_read_unlock();
335	}
336
337out:
338	*s_slot = slot;
339	*s_num = num;
340	return ret;
341}
342EXPORT_SYMBOL_GPL(mptcp_token_iter_next);
343
344/**
345 * mptcp_token_destroy_request - remove mptcp connection/token
346 * @req: mptcp request socket dropping the token
347 *
348 * Remove the token associated to @req.
349 */
350void mptcp_token_destroy_request(struct request_sock *req)
351{
352	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
353	struct mptcp_subflow_request_sock *pos;
354	struct token_bucket *bucket;
355
356	if (hlist_nulls_unhashed(&subflow_req->token_node))
357		return;
358
359	bucket = token_bucket(subflow_req->token);
360	spin_lock_bh(&bucket->lock);
361	pos = __token_lookup_req(bucket, subflow_req->token);
362	if (!WARN_ON_ONCE(pos != subflow_req)) {
363		hlist_nulls_del_init_rcu(&pos->token_node);
364		bucket->chain_len--;
365	}
366	spin_unlock_bh(&bucket->lock);
367}
368
369/**
370 * mptcp_token_destroy - remove mptcp connection/token
371 * @msk: mptcp connection dropping the token
372 *
373 * Remove the token associated to @msk
374 */
375void mptcp_token_destroy(struct mptcp_sock *msk)
376{
377	struct sock *sk = (struct sock *)msk;
378	struct token_bucket *bucket;
379	struct mptcp_sock *pos;
380
381	if (sk_unhashed((struct sock *)msk))
382		return;
383
384	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
385	bucket = token_bucket(msk->token);
386	spin_lock_bh(&bucket->lock);
387	pos = __token_lookup_msk(bucket, msk->token);
388	if (!WARN_ON_ONCE(pos != msk)) {
389		__sk_nulls_del_node_init_rcu((struct sock *)pos);
390		bucket->chain_len--;
391	}
392	spin_unlock_bh(&bucket->lock);
393	WRITE_ONCE(msk->token, 0);
394}
395
396void __init mptcp_token_init(void)
397{
398	int i;
399
400	token_hash = alloc_large_system_hash("MPTCP token",
401					     sizeof(struct token_bucket),
402					     0,
403					     20,/* one slot per 1MB of memory */
404					     HASH_ZERO,
405					     NULL,
406					     &token_mask,
407					     0,
408					     64 * 1024);
409	for (i = 0; i < token_mask + 1; ++i) {
410		INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i);
411		INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i);
412		spin_lock_init(&token_hash[i].lock);
413	}
414}
415
416#if IS_MODULE(CONFIG_MPTCP_KUNIT_TEST)
417EXPORT_SYMBOL_GPL(mptcp_token_new_request);
418EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
419EXPORT_SYMBOL_GPL(mptcp_token_accept);
420EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
421EXPORT_SYMBOL_GPL(mptcp_token_destroy);
422#endif
423