net/mptcp/token.c

   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
  39 struct 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
  46 static struct token_bucket *token_hash __read_mostly;
  47 static unsigned int token_mask __read_mostly;
  48
  49 static struct token_bucket *token_bucket(u32 token)
  50 {
  51         return &token_hash[token & token_mask];
  52 }
  53
  54 /* called with bucket lock held */
  55 static 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 */
  68 static 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
  80 static 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
  86 static 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  */
 109 int 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  */
 152 int 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
 162 again:
 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  */
 190 void 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
 207 bool 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
 217 again:
 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;
 228 found:
 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  */
 242 struct 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
 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                         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
 268 not_found:
 269         msk = NULL;
 270
 271 found:
 272         rcu_read_unlock();
 273         return msk;
 274 }
 275 EXPORT_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  */
 289 struct 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 = 0;
 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
 329 out:
 330         *s_slot = slot;
 331         *s_num = num;
 332         return ret;
 333 }
 334 EXPORT_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  */
 342 void 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  */
 367 void 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
 385 void __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)
 406 EXPORT_SYMBOL_GPL(mptcp_token_new_request);
 407 EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
 408 EXPORT_SYMBOL_GPL(mptcp_token_accept);
 409 EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
 410 EXPORT_SYMBOL_GPL(mptcp_token_destroy);
 411 #endif