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
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(buf: key, len: sizeof(u64));
94 mptcp_crypto_key_sha(key: *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(rsk: req);
111 struct token_bucket *bucket;
112 u32 token;
113
114 mptcp_crypto_key_sha(key: subflow_req->local_key,
115 token: &subflow_req->token,
116 idsn: &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(lock: &bucket->lock);
124 if (__token_bucket_busy(t: bucket, token)) {
125 spin_unlock_bh(lock: &bucket->lock);
126 return -EBUSY;
127 }
128
129 hlist_nulls_add_head_rcu(n: &subflow_req->token_node, h: &bucket->req_chain);
130 bucket->chain_len++;
131 spin_unlock_bh(lock: &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(sk: 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(key: &subflow->local_key, token: &subflow->token,
161 idsn: &subflow->idsn);
162
163 bucket = token_bucket(token: subflow->token);
164 spin_lock_bh(lock: &bucket->lock);
165 if (__token_bucket_busy(t: bucket, token: subflow->token)) {
166 spin_unlock_bh(lock: &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(sk: (struct sock *)msk, list: &bucket->msk_chain);
177 bucket->chain_len++;
178 spin_unlock_bh(lock: &bucket->lock);
179 sock_prot_inuse_add(net: sock_net(sk), prot: sk->sk_prot, val: 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(net: sock_net(sk), prot: sk->sk_prot, val: 1);
199 bucket = token_bucket(token: req->token);
200 spin_lock_bh(lock: &bucket->lock);
201
202 /* pedantic lookup check for the moved token */
203 pos = __token_lookup_req(t: bucket, token: req->token);
204 if (!WARN_ON_ONCE(pos != req))
205 hlist_nulls_del_init_rcu(n: &req->token_node);
206 __sk_nulls_add_node_rcu(sk: (struct sock *)msk, list: &bucket->msk_chain);
207 spin_unlock_bh(lock: &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(ptr: 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(net1: sock_net(sk), net2: net))
261 continue;
262
263 if (!refcount_inc_not_zero(r: &sk->sk_refcnt))
264 goto not_found;
265
266 if (READ_ONCE(msk->token) != token ||
267 !net_eq(net1: sock_net(sk), net2: net)) {
268 sock_put(sk);
269 goto again;
270 }
271 goto found;
272 }
273 if (get_nulls_value(ptr: 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(h: &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(net1: sock_net(sk), net2: net))
317 continue;
318
319 if (num <= *s_num)
320 continue;
321
322 if (!refcount_inc_not_zero(r: &sk->sk_refcnt))
323 continue;
324
325 if (!net_eq(net1: sock_net(sk), net2: 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(rsk: req);
353 struct mptcp_subflow_request_sock *pos;
354 struct token_bucket *bucket;
355
356 if (hlist_nulls_unhashed(h: &subflow_req->token_node))
357 return;
358
359 bucket = token_bucket(token: subflow_req->token);
360 spin_lock_bh(lock: &bucket->lock);
361 pos = __token_lookup_req(t: bucket, token: subflow_req->token);
362 if (!WARN_ON_ONCE(pos != subflow_req)) {
363 hlist_nulls_del_init_rcu(n: &pos->token_node);
364 bucket->chain_len--;
365 }
366 spin_unlock_bh(lock: &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(sk: (struct sock *)msk))
382 return;
383
384 sock_prot_inuse_add(net: sock_net(sk), prot: sk->sk_prot, val: -1);
385 bucket = token_bucket(token: msk->token);
386 spin_lock_bh(lock: &bucket->lock);
387 pos = __token_lookup_msk(t: bucket, token: msk->token);
388 if (!WARN_ON_ONCE(pos != msk)) {
389 __sk_nulls_del_node_init_rcu(sk: (struct sock *)pos);
390 bucket->chain_len--;
391 }
392 spin_unlock_bh(lock: &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(tablename: "MPTCP token",
401 bucketsize: sizeof(struct token_bucket),
402 numentries: 0,
403 scale: 20,/* one slot per 1MB of memory */
404 HASH_ZERO,
405 NULL,
406 hash_mask: &token_mask,
407 low_limit: 0,
408 high_limit: 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

source code of linux/net/mptcp/token.c