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_CHAIN_LEN 4
37
38 struct 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
45 static struct token_bucket *token_hash __read_mostly;
46 static unsigned int token_mask __read_mostly;
47
token_bucket(u32 token)48 static struct token_bucket *token_bucket(u32 token)
49 {
50 return &token_hash[token & token_mask];
51 }
52
53 /* called with bucket lock held */
54 static struct mptcp_subflow_request_sock *
__token_lookup_req(struct token_bucket * t,u32 token)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 */
67 static struct mptcp_sock *
__token_lookup_msk(struct token_bucket * t,u32 token)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
__token_bucket_busy(struct token_bucket * t,u32 token)79 static 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
mptcp_crypto_key_gen_sha(u64 * key,u32 * token,u64 * idsn)85 static 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 */
mptcp_token_new_request(struct request_sock * req)108 int 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 * @sk: 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 */
mptcp_token_new_connect(struct sock * sk)151 int mptcp_token_new_connect(struct sock *sk)
152 {
153 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
154 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
155 int retries = MPTCP_TOKEN_MAX_RETRIES;
156 struct token_bucket *bucket;
157
158 again:
159 mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token,
160 &subflow->idsn);
161
162 bucket = token_bucket(subflow->token);
163 spin_lock_bh(&bucket->lock);
164 if (__token_bucket_busy(bucket, subflow->token)) {
165 spin_unlock_bh(&bucket->lock);
166 if (!--retries)
167 return -EBUSY;
168 goto again;
169 }
170
171 pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n",
172 sk, subflow->local_key, subflow->token, subflow->idsn);
173
174 WRITE_ONCE(msk->token, subflow->token);
175 __sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
176 bucket->chain_len++;
177 spin_unlock_bh(&bucket->lock);
178 return 0;
179 }
180
181 /**
182 * mptcp_token_accept - replace a req sk with full sock in token hash
183 * @req: the request socket to be removed
184 * @msk: the just cloned socket linked to the new connection
185 *
186 * Called when a SYN packet creates a new logical connection, i.e.
187 * is not a join request.
188 */
mptcp_token_accept(struct mptcp_subflow_request_sock * req,struct mptcp_sock * msk)189 void mptcp_token_accept(struct mptcp_subflow_request_sock *req,
190 struct mptcp_sock *msk)
191 {
192 struct mptcp_subflow_request_sock *pos;
193 struct token_bucket *bucket;
194
195 bucket = token_bucket(req->token);
196 spin_lock_bh(&bucket->lock);
197
198 /* pedantic lookup check for the moved token */
199 pos = __token_lookup_req(bucket, req->token);
200 if (!WARN_ON_ONCE(pos != req))
201 hlist_nulls_del_init_rcu(&req->token_node);
202 __sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
203 spin_unlock_bh(&bucket->lock);
204 }
205
mptcp_token_exists(u32 token)206 bool mptcp_token_exists(u32 token)
207 {
208 struct hlist_nulls_node *pos;
209 struct token_bucket *bucket;
210 struct mptcp_sock *msk;
211 struct sock *sk;
212
213 rcu_read_lock();
214 bucket = token_bucket(token);
215
216 again:
217 sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
218 msk = mptcp_sk(sk);
219 if (READ_ONCE(msk->token) == token)
220 goto found;
221 }
222 if (get_nulls_value(pos) != (token & token_mask))
223 goto again;
224
225 rcu_read_unlock();
226 return false;
227 found:
228 rcu_read_unlock();
229 return true;
230 }
231
232 /**
233 * mptcp_token_get_sock - retrieve mptcp connection sock using its token
234 * @net: restrict to this namespace
235 * @token: token of the mptcp connection to retrieve
236 *
237 * This function returns the mptcp connection structure with the given token.
238 * A reference count on the mptcp socket returned is taken.
239 *
240 * returns NULL if no connection with the given token value exists.
241 */
mptcp_token_get_sock(struct net * net,u32 token)242 struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token)
243 {
244 struct hlist_nulls_node *pos;
245 struct token_bucket *bucket;
246 struct mptcp_sock *msk;
247 struct sock *sk;
248
249 rcu_read_lock();
250 bucket = token_bucket(token);
251
252 again:
253 sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
254 msk = mptcp_sk(sk);
255 if (READ_ONCE(msk->token) != token ||
256 !net_eq(sock_net(sk), net))
257 continue;
258
259 if (!refcount_inc_not_zero(&sk->sk_refcnt))
260 goto not_found;
261
262 if (READ_ONCE(msk->token) != token ||
263 !net_eq(sock_net(sk), net)) {
264 sock_put(sk);
265 goto again;
266 }
267 goto found;
268 }
269 if (get_nulls_value(pos) != (token & token_mask))
270 goto again;
271
272 not_found:
273 msk = NULL;
274
275 found:
276 rcu_read_unlock();
277 return msk;
278 }
279 EXPORT_SYMBOL_GPL(mptcp_token_get_sock);
280
281 /**
282 * mptcp_token_iter_next - iterate over the token container from given pos
283 * @net: namespace to be iterated
284 * @s_slot: start slot number
285 * @s_num: start number inside the given lock
286 *
287 * This function returns the first mptcp connection structure found inside the
288 * token container starting from the specified position, or NULL.
289 *
290 * On successful iteration, the iterator is move to the next position and the
291 * the acquires a reference to the returned socket.
292 */
mptcp_token_iter_next(const struct net * net,long * s_slot,long * s_num)293 struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
294 long *s_num)
295 {
296 struct mptcp_sock *ret = NULL;
297 struct hlist_nulls_node *pos;
298 int slot, num = 0;
299
300 for (slot = *s_slot; slot <= token_mask; *s_num = 0, slot++) {
301 struct token_bucket *bucket = &token_hash[slot];
302 struct sock *sk;
303
304 num = 0;
305
306 if (hlist_nulls_empty(&bucket->msk_chain))
307 continue;
308
309 rcu_read_lock();
310 sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
311 ++num;
312 if (!net_eq(sock_net(sk), net))
313 continue;
314
315 if (num <= *s_num)
316 continue;
317
318 if (!refcount_inc_not_zero(&sk->sk_refcnt))
319 continue;
320
321 if (!net_eq(sock_net(sk), net)) {
322 sock_put(sk);
323 continue;
324 }
325
326 ret = mptcp_sk(sk);
327 rcu_read_unlock();
328 goto out;
329 }
330 rcu_read_unlock();
331 }
332
333 out:
334 *s_slot = slot;
335 *s_num = num;
336 return ret;
337 }
338 EXPORT_SYMBOL_GPL(mptcp_token_iter_next);
339
340 /**
341 * mptcp_token_destroy_request - remove mptcp connection/token
342 * @req: mptcp request socket dropping the token
343 *
344 * Remove the token associated to @req.
345 */
mptcp_token_destroy_request(struct request_sock * req)346 void mptcp_token_destroy_request(struct request_sock *req)
347 {
348 struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
349 struct mptcp_subflow_request_sock *pos;
350 struct token_bucket *bucket;
351
352 if (hlist_nulls_unhashed(&subflow_req->token_node))
353 return;
354
355 bucket = token_bucket(subflow_req->token);
356 spin_lock_bh(&bucket->lock);
357 pos = __token_lookup_req(bucket, subflow_req->token);
358 if (!WARN_ON_ONCE(pos != subflow_req)) {
359 hlist_nulls_del_init_rcu(&pos->token_node);
360 bucket->chain_len--;
361 }
362 spin_unlock_bh(&bucket->lock);
363 }
364
365 /**
366 * mptcp_token_destroy - remove mptcp connection/token
367 * @msk: mptcp connection dropping the token
368 *
369 * Remove the token associated to @msk
370 */
mptcp_token_destroy(struct mptcp_sock * msk)371 void mptcp_token_destroy(struct mptcp_sock *msk)
372 {
373 struct token_bucket *bucket;
374 struct mptcp_sock *pos;
375
376 if (sk_unhashed((struct sock *)msk))
377 return;
378
379 bucket = token_bucket(msk->token);
380 spin_lock_bh(&bucket->lock);
381 pos = __token_lookup_msk(bucket, msk->token);
382 if (!WARN_ON_ONCE(pos != msk)) {
383 __sk_nulls_del_node_init_rcu((struct sock *)pos);
384 bucket->chain_len--;
385 }
386 spin_unlock_bh(&bucket->lock);
387 }
388
mptcp_token_init(void)389 void __init mptcp_token_init(void)
390 {
391 int i;
392
393 token_hash = alloc_large_system_hash("MPTCP token",
394 sizeof(struct token_bucket),
395 0,
396 20,/* one slot per 1MB of memory */
397 HASH_ZERO,
398 NULL,
399 &token_mask,
400 0,
401 64 * 1024);
402 for (i = 0; i < token_mask + 1; ++i) {
403 INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i);
404 INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i);
405 spin_lock_init(&token_hash[i].lock);
406 }
407 }
408
409 #if IS_MODULE(CONFIG_MPTCP_KUNIT_TEST)
410 EXPORT_SYMBOL_GPL(mptcp_token_new_request);
411 EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
412 EXPORT_SYMBOL_GPL(mptcp_token_accept);
413 EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
414 EXPORT_SYMBOL_GPL(mptcp_token_destroy);
415 #endif
416