xref: /kernel/linux/linux-5.10/net/mptcp/token.c (revision 8c2ecf20) 
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 *       Sébastien Barré <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 Duchêne <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_RETRIES	4
37#define TOKEN_MAX_CHAIN_LEN	4
38
39struct token_bucket {
40	spinlock_t		lock;
41	int			chain_len;
42	struct hlist_nulls_head	req_chain;
43	struct hlist_nulls_head	msk_chain;
44};
45
46static struct token_bucket *token_hash __read_mostly;
47static unsigned int token_mask __read_mostly;
48
49static struct token_bucket *token_bucket(u32 token)
50{
51	return &token_hash[token & token_mask];
52}
53
54/* called with bucket lock held */
55static struct mptcp_subflow_request_sock *
56__token_lookup_req(struct token_bucket *t, u32 token)
57{
58	struct mptcp_subflow_request_sock *req;
59	struct hlist_nulls_node *pos;
60
61	hlist_nulls_for_each_entry_rcu(req, pos, &t->req_chain, token_node)
62		if (req->token == token)
63			return req;
64	return NULL;
65}
66
67/* called with bucket lock held */
68static struct mptcp_sock *
69__token_lookup_msk(struct token_bucket *t, u32 token)
70{
71	struct hlist_nulls_node *pos;
72	struct sock *sk;
73
74	sk_nulls_for_each_rcu(sk, pos, &t->msk_chain)
75		if (mptcp_sk(sk)->token == token)
76			return mptcp_sk(sk);
77	return NULL;
78}
79
80static bool __token_bucket_busy(struct token_bucket *t, u32 token)
81{
82	return !token || t->chain_len >= TOKEN_MAX_CHAIN_LEN ||
83	       __token_lookup_req(t, token) || __token_lookup_msk(t, token);
84}
85
86static void mptcp_crypto_key_gen_sha(u64 *key, u32 *token, u64 *idsn)
87{
88	/* we might consider a faster version that computes the key as a
89	 * hash of some information available in the MPTCP socket. Use
90	 * random data at the moment, as it's probably the safest option
91	 * in case multiple sockets are opened in different namespaces at
92	 * the same time.
93	 */
94	get_random_bytes(key, sizeof(u64));
95	mptcp_crypto_key_sha(*key, token, idsn);
96}
97
98/**
99 * mptcp_token_new_request - create new key/idsn/token for subflow_request
100 * @req: the request socket
101 *
102 * This function is called when a new mptcp connection is coming in.
103 *
104 * It creates a unique token to identify the new mptcp connection,
105 * a secret local key and the initial data sequence number (idsn).
106 *
107 * Returns 0 on success.
108 */
109int mptcp_token_new_request(struct request_sock *req)
110{
111	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
112	struct token_bucket *bucket;
113	u32 token;
114
115	mptcp_crypto_key_sha(subflow_req->local_key,
116			     &subflow_req->token,
117			     &subflow_req->idsn);
118	pr_debug("req=%p local_key=%llu, token=%u, idsn=%llu\n",
119		 req, subflow_req->local_key, subflow_req->token,
120		 subflow_req->idsn);
121
122	token = subflow_req->token;
123	bucket = token_bucket(token);
124	spin_lock_bh(&bucket->lock);
125	if (__token_bucket_busy(bucket, token)) {
126		spin_unlock_bh(&bucket->lock);
127		return -EBUSY;
128	}
129
130	hlist_nulls_add_head_rcu(&subflow_req->token_node, &bucket->req_chain);
131	bucket->chain_len++;
132	spin_unlock_bh(&bucket->lock);
133	return 0;
134}
135
136/**
137 * mptcp_token_new_connect - create new key/idsn/token for subflow
138 * @sk: the socket that will initiate a connection
139 *
140 * This function is called when a new outgoing mptcp connection is
141 * initiated.
142 *
143 * It creates a unique token to identify the new mptcp connection,
144 * a secret local key and the initial data sequence number (idsn).
145 *
146 * On success, the mptcp connection can be found again using
147 * the computed token at a later time, this is needed to process
148 * join requests.
149 *
150 * returns 0 on success.
151 */
152int mptcp_token_new_connect(struct sock *sk)
153{
154	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
155	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
156	int retries = TOKEN_MAX_RETRIES;
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		 sk, 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	return 0;
180}
181
182/**
183 * mptcp_token_accept - replace a req sk with full sock in token hash
184 * @req: the request socket to be removed
185 * @msk: the just cloned socket linked to the new connection
186 *
187 * Called when a SYN packet creates a new logical connection, i.e.
188 * is not a join request.
189 */
190void mptcp_token_accept(struct mptcp_subflow_request_sock *req,
191			struct mptcp_sock *msk)
192{
193	struct mptcp_subflow_request_sock *pos;
194	struct token_bucket *bucket;
195
196	bucket = token_bucket(req->token);
197	spin_lock_bh(&bucket->lock);
198
199	/* pedantic lookup check for the moved token */
200	pos = __token_lookup_req(bucket, req->token);
201	if (!WARN_ON_ONCE(pos != req))
202		hlist_nulls_del_init_rcu(&req->token_node);
203	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
204	spin_unlock_bh(&bucket->lock);
205}
206
207bool mptcp_token_exists(u32 token)
208{
209	struct hlist_nulls_node *pos;
210	struct token_bucket *bucket;
211	struct mptcp_sock *msk;
212	struct sock *sk;
213
214	rcu_read_lock();
215	bucket = token_bucket(token);
216
217again:
218	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
219		msk = mptcp_sk(sk);
220		if (READ_ONCE(msk->token) == token)
221			goto found;
222	}
223	if (get_nulls_value(pos) != (token & token_mask))
224		goto again;
225
226	rcu_read_unlock();
227	return false;
228found:
229	rcu_read_unlock();
230	return true;
231}
232
233/**
234 * mptcp_token_get_sock - retrieve mptcp connection sock using its token
235 * @net: restrict to this namespace
236 * @token: token of the mptcp connection to retrieve
237 *
238 * This function returns the mptcp connection structure with the given token.
239 * A reference count on the mptcp socket returned is taken.
240 *
241 * returns NULL if no connection with the given token value exists.
242 */
243struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token)
244{
245	struct hlist_nulls_node *pos;
246	struct token_bucket *bucket;
247	struct mptcp_sock *msk;
248	struct sock *sk;
249
250	rcu_read_lock();
251	bucket = token_bucket(token);
252
253again:
254	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
255		msk = mptcp_sk(sk);
256		if (READ_ONCE(msk->token) != token ||
257		    !net_eq(sock_net(sk), net))
258			continue;
259
260		if (!refcount_inc_not_zero(&sk->sk_refcnt))
261			goto not_found;
262
263		if (READ_ONCE(msk->token) != token ||
264		    !net_eq(sock_net(sk), net)) {
265			sock_put(sk);
266			goto again;
267		}
268		goto found;
269	}
270	if (get_nulls_value(pos) != (token & token_mask))
271		goto again;
272
273not_found:
274	msk = NULL;
275
276found:
277	rcu_read_unlock();
278	return msk;
279}
280EXPORT_SYMBOL_GPL(mptcp_token_get_sock);
281
282/**
283 * mptcp_token_iter_next - iterate over the token container from given pos
284 * @net: namespace to be iterated
285 * @s_slot: start slot number
286 * @s_num: start number inside the given lock
287 *
288 * This function returns the first mptcp connection structure found inside the
289 * token container starting from the specified position, or NULL.
290 *
291 * On successful iteration, the iterator is move to the next position and the
292 * the acquires a reference to the returned socket.
293 */
294struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
295					 long *s_num)
296{
297	struct mptcp_sock *ret = NULL;
298	struct hlist_nulls_node *pos;
299	int slot, num = 0;
300
301	for (slot = *s_slot; slot <= token_mask; *s_num = 0, slot++) {
302		struct token_bucket *bucket = &token_hash[slot];
303		struct sock *sk;
304
305		num = 0;
306
307		if (hlist_nulls_empty(&bucket->msk_chain))
308			continue;
309
310		rcu_read_lock();
311		sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
312			++num;
313			if (!net_eq(sock_net(sk), net))
314				continue;
315
316			if (num <= *s_num)
317				continue;
318
319			if (!refcount_inc_not_zero(&sk->sk_refcnt))
320				continue;
321
322			if (!net_eq(sock_net(sk), net)) {
323				sock_put(sk);
324				continue;
325			}
326
327			ret = mptcp_sk(sk);
328			rcu_read_unlock();
329			goto out;
330		}
331		rcu_read_unlock();
332	}
333
334out:
335	*s_slot = slot;
336	*s_num = num;
337	return ret;
338}
339EXPORT_SYMBOL_GPL(mptcp_token_iter_next);
340
341/**
342 * mptcp_token_destroy_request - remove mptcp connection/token
343 * @req: mptcp request socket dropping the token
344 *
345 * Remove the token associated to @req.
346 */
347void mptcp_token_destroy_request(struct request_sock *req)
348{
349	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
350	struct mptcp_subflow_request_sock *pos;
351	struct token_bucket *bucket;
352
353	if (hlist_nulls_unhashed(&subflow_req->token_node))
354		return;
355
356	bucket = token_bucket(subflow_req->token);
357	spin_lock_bh(&bucket->lock);
358	pos = __token_lookup_req(bucket, subflow_req->token);
359	if (!WARN_ON_ONCE(pos != subflow_req)) {
360		hlist_nulls_del_init_rcu(&pos->token_node);
361		bucket->chain_len--;
362	}
363	spin_unlock_bh(&bucket->lock);
364}
365
366/**
367 * mptcp_token_destroy - remove mptcp connection/token
368 * @msk: mptcp connection dropping the token
369 *
370 * Remove the token associated to @msk
371 */
372void mptcp_token_destroy(struct mptcp_sock *msk)
373{
374	struct token_bucket *bucket;
375	struct mptcp_sock *pos;
376
377	if (sk_unhashed((struct sock *)msk))
378		return;
379
380	bucket = token_bucket(msk->token);
381	spin_lock_bh(&bucket->lock);
382	pos = __token_lookup_msk(bucket, msk->token);
383	if (!WARN_ON_ONCE(pos != msk)) {
384		__sk_nulls_del_node_init_rcu((struct sock *)pos);
385		bucket->chain_len--;
386	}
387	spin_unlock_bh(&bucket->lock);
388}
389
390void __init mptcp_token_init(void)
391{
392	int i;
393
394	token_hash = alloc_large_system_hash("MPTCP token",
395					     sizeof(struct token_bucket),
396					     0,
397					     20,/* one slot per 1MB of memory */
398					     HASH_ZERO,
399					     NULL,
400					     &token_mask,
401					     0,
402					     64 * 1024);
403	for (i = 0; i < token_mask + 1; ++i) {
404		INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i);
405		INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i);
406		spin_lock_init(&token_hash[i].lock);
407	}
408}
409
410#if IS_MODULE(CONFIG_MPTCP_KUNIT_TESTS)
411EXPORT_SYMBOL_GPL(mptcp_token_new_request);
412EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
413EXPORT_SYMBOL_GPL(mptcp_token_accept);
414EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
415EXPORT_SYMBOL_GPL(mptcp_token_destroy);
416#endif
417