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(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 */ 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 * @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(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(&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 ssk, 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 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 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(sock_net(sk), sk->sk_prot, 1); 199 bucket = token_bucket(req->token); 200 spin_lock_bh(&bucket->lock); 201 202 /* pedantic lookup check for the moved token */ 203 pos = __token_lookup_req(bucket, req->token); 204 if (!WARN_ON_ONCE(pos != req)) 205 hlist_nulls_del_init_rcu(&req->token_node); 206 __sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain); 207 spin_unlock_bh(&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(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(sock_net(sk), net)) 261 continue; 262 263 if (!refcount_inc_not_zero(&sk->sk_refcnt)) 264 goto not_found; 265 266 if (READ_ONCE(msk->token) != token || 267 !net_eq(sock_net(sk), net)) { 268 sock_put(sk); 269 goto again; 270 } 271 goto found; 272 } 273 if (get_nulls_value(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(&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(sock_net(sk), net)) 317 continue; 318 319 if (num <= *s_num) 320 continue; 321 322 if (!refcount_inc_not_zero(&sk->sk_refcnt)) 323 continue; 324 325 if (!net_eq(sock_net(sk), 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(req); 353 struct mptcp_subflow_request_sock *pos; 354 struct token_bucket *bucket; 355 356 if (hlist_nulls_unhashed(&subflow_req->token_node)) 357 return; 358 359 bucket = token_bucket(subflow_req->token); 360 spin_lock_bh(&bucket->lock); 361 pos = __token_lookup_req(bucket, subflow_req->token); 362 if (!WARN_ON_ONCE(pos != subflow_req)) { 363 hlist_nulls_del_init_rcu(&pos->token_node); 364 bucket->chain_len--; 365 } 366 spin_unlock_bh(&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((struct sock *)msk)) 382 return; 383 384 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 385 bucket = token_bucket(msk->token); 386 spin_lock_bh(&bucket->lock); 387 pos = __token_lookup_msk(bucket, msk->token); 388 if (!WARN_ON_ONCE(pos != msk)) { 389 __sk_nulls_del_node_init_rcu((struct sock *)pos); 390 bucket->chain_len--; 391 } 392 spin_unlock_bh(&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("MPTCP token", 401 sizeof(struct token_bucket), 402 0, 403 20,/* one slot per 1MB of memory */ 404 HASH_ZERO, 405 NULL, 406 &token_mask, 407 0, 408 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