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
39 struct 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
46 static struct token_bucket *token_hash __read_mostly;
47 static unsigned int token_mask __read_mostly;
48
token_bucket(u32 token)49 static struct token_bucket *token_bucket(u32 token)
50 {
51 return &token_hash[token & token_mask];
52 }
53
54 /* called with bucket lock held */
55 static struct mptcp_subflow_request_sock *
__token_lookup_req(struct token_bucket * t,u32 token)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 */
68 static struct mptcp_sock *
__token_lookup_msk(struct token_bucket * t,u32 token)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
__token_bucket_busy(struct token_bucket * t,u32 token)80 static 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
mptcp_crypto_key_gen_sha(u64 * key,u32 * token,u64 * idsn)86 static 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 */
mptcp_token_new_request(struct request_sock * req)109 int 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 */
mptcp_token_new_connect(struct sock * sk)152 int 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
159 again:
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 */
mptcp_token_accept(struct mptcp_subflow_request_sock * req,struct mptcp_sock * msk)190 void 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
mptcp_token_exists(u32 token)207 bool 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
217 again:
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;
228 found:
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 */
mptcp_token_get_sock(struct net * net,u32 token)243 struct 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
253 again:
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
273 not_found:
274 msk = NULL;
275
276 found:
277 rcu_read_unlock();
278 return msk;
279 }
280 EXPORT_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 */
mptcp_token_iter_next(const struct net * net,long * s_slot,long * s_num)294 struct 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
334 out:
335 *s_slot = slot;
336 *s_num = num;
337 return ret;
338 }
339 EXPORT_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 */
mptcp_token_destroy_request(struct request_sock * req)347 void 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 */
mptcp_token_destroy(struct mptcp_sock * msk)372 void 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
mptcp_token_init(void)390 void __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)
411 EXPORT_SYMBOL_GPL(mptcp_token_new_request);
412 EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
413 EXPORT_SYMBOL_GPL(mptcp_token_accept);
414 EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
415 EXPORT_SYMBOL_GPL(mptcp_token_destroy);
416 #endif
417