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 | |
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 * |
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 * |
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 | |
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 | |
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(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 | */ |
108 | int 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 | */ |
151 | int 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 | |
159 | again: |
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 | */ |
191 | void 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 | |
210 | bool 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 | |
220 | again: |
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; |
231 | found: |
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 | */ |
246 | struct 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 | |
256 | again: |
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 | |
276 | not_found: |
277 | msk = NULL; |
278 | |
279 | found: |
280 | rcu_read_unlock(); |
281 | return msk; |
282 | } |
283 | EXPORT_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 | */ |
297 | struct 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 | |
337 | out: |
338 | *s_slot = slot; |
339 | *s_num = num; |
340 | return ret; |
341 | } |
342 | EXPORT_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 | */ |
350 | void 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 | */ |
375 | void 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 | |
396 | void __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) |
417 | EXPORT_SYMBOL_GPL(mptcp_token_new_request); |
418 | EXPORT_SYMBOL_GPL(mptcp_token_new_connect); |
419 | EXPORT_SYMBOL_GPL(mptcp_token_accept); |
420 | EXPORT_SYMBOL_GPL(mptcp_token_destroy_request); |
421 | EXPORT_SYMBOL_GPL(mptcp_token_destroy); |
422 | #endif |
423 | |