Loading...
Note: File does not exist in v3.15.
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
159 pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n",
160 sk, subflow->local_key, subflow->token, subflow->idsn);
161
162again:
163 mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token,
164 &subflow->idsn);
165
166 bucket = token_bucket(subflow->token);
167 spin_lock_bh(&bucket->lock);
168 if (__token_bucket_busy(bucket, subflow->token)) {
169 spin_unlock_bh(&bucket->lock);
170 if (!--retries)
171 return -EBUSY;
172 goto again;
173 }
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 * @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 */
242struct mptcp_sock *mptcp_token_get_sock(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
252again:
253 sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
254 msk = mptcp_sk(sk);
255 if (READ_ONCE(msk->token) != token)
256 continue;
257 if (!refcount_inc_not_zero(&sk->sk_refcnt))
258 goto not_found;
259 if (READ_ONCE(msk->token) != token) {
260 sock_put(sk);
261 goto again;
262 }
263 goto found;
264 }
265 if (get_nulls_value(pos) != (token & token_mask))
266 goto again;
267
268not_found:
269 msk = NULL;
270
271found:
272 rcu_read_unlock();
273 return msk;
274}
275EXPORT_SYMBOL_GPL(mptcp_token_get_sock);
276
277/**
278 * mptcp_token_iter_next - iterate over the token container from given pos
279 * @net: namespace to be iterated
280 * @s_slot: start slot number
281 * @s_num: start number inside the given lock
282 *
283 * This function returns the first mptcp connection structure found inside the
284 * token container starting from the specified position, or NULL.
285 *
286 * On successful iteration, the iterator is move to the next position and the
287 * the acquires a reference to the returned socket.
288 */
289struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
290 long *s_num)
291{
292 struct mptcp_sock *ret = NULL;
293 struct hlist_nulls_node *pos;
294 int slot, num;
295
296 for (slot = *s_slot; slot <= token_mask; *s_num = 0, slot++) {
297 struct token_bucket *bucket = &token_hash[slot];
298 struct sock *sk;
299
300 num = 0;
301
302 if (hlist_nulls_empty(&bucket->msk_chain))
303 continue;
304
305 rcu_read_lock();
306 sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
307 ++num;
308 if (!net_eq(sock_net(sk), net))
309 continue;
310
311 if (num <= *s_num)
312 continue;
313
314 if (!refcount_inc_not_zero(&sk->sk_refcnt))
315 continue;
316
317 if (!net_eq(sock_net(sk), net)) {
318 sock_put(sk);
319 continue;
320 }
321
322 ret = mptcp_sk(sk);
323 rcu_read_unlock();
324 goto out;
325 }
326 rcu_read_unlock();
327 }
328
329out:
330 *s_slot = slot;
331 *s_num = num;
332 return ret;
333}
334EXPORT_SYMBOL_GPL(mptcp_token_iter_next);
335
336/**
337 * mptcp_token_destroy_request - remove mptcp connection/token
338 * @req: mptcp request socket dropping the token
339 *
340 * Remove the token associated to @req.
341 */
342void mptcp_token_destroy_request(struct request_sock *req)
343{
344 struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
345 struct mptcp_subflow_request_sock *pos;
346 struct token_bucket *bucket;
347
348 if (hlist_nulls_unhashed(&subflow_req->token_node))
349 return;
350
351 bucket = token_bucket(subflow_req->token);
352 spin_lock_bh(&bucket->lock);
353 pos = __token_lookup_req(bucket, subflow_req->token);
354 if (!WARN_ON_ONCE(pos != subflow_req)) {
355 hlist_nulls_del_init_rcu(&pos->token_node);
356 bucket->chain_len--;
357 }
358 spin_unlock_bh(&bucket->lock);
359}
360
361/**
362 * mptcp_token_destroy - remove mptcp connection/token
363 * @msk: mptcp connection dropping the token
364 *
365 * Remove the token associated to @msk
366 */
367void mptcp_token_destroy(struct mptcp_sock *msk)
368{
369 struct token_bucket *bucket;
370 struct mptcp_sock *pos;
371
372 if (sk_unhashed((struct sock *)msk))
373 return;
374
375 bucket = token_bucket(msk->token);
376 spin_lock_bh(&bucket->lock);
377 pos = __token_lookup_msk(bucket, msk->token);
378 if (!WARN_ON_ONCE(pos != msk)) {
379 __sk_nulls_del_node_init_rcu((struct sock *)pos);
380 bucket->chain_len--;
381 }
382 spin_unlock_bh(&bucket->lock);
383}
384
385void __init mptcp_token_init(void)
386{
387 int i;
388
389 token_hash = alloc_large_system_hash("MPTCP token",
390 sizeof(struct token_bucket),
391 0,
392 20,/* one slot per 1MB of memory */
393 HASH_ZERO,
394 NULL,
395 &token_mask,
396 0,
397 64 * 1024);
398 for (i = 0; i < token_mask + 1; ++i) {
399 INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i);
400 INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i);
401 spin_lock_init(&token_hash[i].lock);
402 }
403}
404
405#if IS_MODULE(CONFIG_MPTCP_KUNIT_TESTS)
406EXPORT_SYMBOL_GPL(mptcp_token_new_request);
407EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
408EXPORT_SYMBOL_GPL(mptcp_token_accept);
409EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
410EXPORT_SYMBOL_GPL(mptcp_token_destroy);
411#endif