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_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