linux/net/mptcp/token.c
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   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 *       S\xC3\xA9bastien Barr\xC3\xA9 <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 Duch\xC3\xAAne <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(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 */
 108int 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 * @sk: 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 *sk)
 152{
 153        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 154        struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 155        int retries = MPTCP_TOKEN_MAX_RETRIES;
 156        struct token_bucket *bucket;
 157
 158again:
 159        mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token,
 160                                 &subflow->idsn);
 161
 162        bucket = token_bucket(subflow->token);
 163        spin_lock_bh(&bucket->lock);
 164        if (__token_bucket_busy(bucket, subflow->token)) {
 165                spin_unlock_bh(&bucket->lock);
 166                if (!--retries)
 167                        return -EBUSY;
 168                goto again;
 169        }
 170
 171        pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n",
 172                 sk, subflow->local_key, subflow->token, subflow->idsn);
 173
 174        WRITE_ONCE(msk->token, subflow->token);
 175        __sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
 176        bucket->chain_len++;
 177        spin_unlock_bh(&bucket->lock);
 178        return 0;
 179}
 180
 181/**
 182 * mptcp_token_accept - replace a req sk with full sock in token hash
 183 * @req: the request socket to be removed
 184 * @msk: the just cloned socket linked to the new connection
 185 *
 186 * Called when a SYN packet creates a new logical connection, i.e.
 187 * is not a join request.
 188 */
 189void mptcp_token_accept(struct mptcp_subflow_request_sock *req,
 190                        struct mptcp_sock *msk)
 191{
 192        struct mptcp_subflow_request_sock *pos;
 193        struct token_bucket *bucket;
 194
 195        bucket = token_bucket(req->token);
 196        spin_lock_bh(&bucket->lock);
 197
 198        /* pedantic lookup check for the moved token */
 199        pos = __token_lookup_req(bucket, req->token);
 200        if (!WARN_ON_ONCE(pos != req))
 201                hlist_nulls_del_init_rcu(&req->token_node);
 202        __sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
 203        spin_unlock_bh(&bucket->lock);
 204}
 205
 206bool mptcp_token_exists(u32 token)
 207{
 208        struct hlist_nulls_node *pos;
 209        struct token_bucket *bucket;
 210        struct mptcp_sock *msk;
 211        struct sock *sk;
 212
 213        rcu_read_lock();
 214        bucket = token_bucket(token);
 215
 216again:
 217        sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
 218                msk = mptcp_sk(sk);
 219                if (READ_ONCE(msk->token) == token)
 220                        goto found;
 221        }
 222        if (get_nulls_value(pos) != (token & token_mask))
 223                goto again;
 224
 225        rcu_read_unlock();
 226        return false;
 227found:
 228        rcu_read_unlock();
 229        return true;
 230}
 231
 232/**
 233 * mptcp_token_get_sock - retrieve mptcp connection sock using its token
 234 * @token: token of the mptcp connection to retrieve
 235 *
 236 * This function returns the mptcp connection structure with the given token.
 237 * A reference count on the mptcp socket returned is taken.
 238 *
 239 * returns NULL if no connection with the given token value exists.
 240 */
 241struct mptcp_sock *mptcp_token_get_sock(u32 token)
 242{
 243        struct hlist_nulls_node *pos;
 244        struct token_bucket *bucket;
 245        struct mptcp_sock *msk;
 246        struct sock *sk;
 247
 248        rcu_read_lock();
 249        bucket = token_bucket(token);
 250
 251again:
 252        sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
 253                msk = mptcp_sk(sk);
 254                if (READ_ONCE(msk->token) != token)
 255                        continue;
 256                if (!refcount_inc_not_zero(&sk->sk_refcnt))
 257                        goto not_found;
 258                if (READ_ONCE(msk->token) != token) {
 259                        sock_put(sk);
 260                        goto again;
 261                }
 262                goto found;
 263        }
 264        if (get_nulls_value(pos) != (token & token_mask))
 265                goto again;
 266
 267not_found:
 268        msk = NULL;
 269
 270found:
 271        rcu_read_unlock();
 272        return msk;
 273}
 274EXPORT_SYMBOL_GPL(mptcp_token_get_sock);
 275
 276/**
 277 * mptcp_token_iter_next - iterate over the token container from given pos
 278 * @net: namespace to be iterated
 279 * @s_slot: start slot number
 280 * @s_num: start number inside the given lock
 281 *
 282 * This function returns the first mptcp connection structure found inside the
 283 * token container starting from the specified position, or NULL.
 284 *
 285 * On successful iteration, the iterator is move to the next position and the
 286 * the acquires a reference to the returned socket.
 287 */
 288struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
 289                                         long *s_num)
 290{
 291        struct mptcp_sock *ret = NULL;
 292        struct hlist_nulls_node *pos;
 293        int slot, num = 0;
 294
 295        for (slot = *s_slot; slot <= token_mask; *s_num = 0, slot++) {
 296                struct token_bucket *bucket = &token_hash[slot];
 297                struct sock *sk;
 298
 299                num = 0;
 300
 301                if (hlist_nulls_empty(&bucket->msk_chain))
 302                        continue;
 303
 304                rcu_read_lock();
 305                sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
 306                        ++num;
 307                        if (!net_eq(sock_net(sk), net))
 308                                continue;
 309
 310                        if (num <= *s_num)
 311                                continue;
 312
 313                        if (!refcount_inc_not_zero(&sk->sk_refcnt))
 314                                continue;
 315
 316                        if (!net_eq(sock_net(sk), net)) {
 317                                sock_put(sk);
 318                                continue;
 319                        }
 320
 321                        ret = mptcp_sk(sk);
 322                        rcu_read_unlock();
 323                        goto out;
 324                }
 325                rcu_read_unlock();
 326        }
 327
 328out:
 329        *s_slot = slot;
 330        *s_num = num;
 331        return ret;
 332}
 333EXPORT_SYMBOL_GPL(mptcp_token_iter_next);
 334
 335/**
 336 * mptcp_token_destroy_request - remove mptcp connection/token
 337 * @req: mptcp request socket dropping the token
 338 *
 339 * Remove the token associated to @req.
 340 */
 341void mptcp_token_destroy_request(struct request_sock *req)
 342{
 343        struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 344        struct mptcp_subflow_request_sock *pos;
 345        struct token_bucket *bucket;
 346
 347        if (hlist_nulls_unhashed(&subflow_req->token_node))
 348                return;
 349
 350        bucket = token_bucket(subflow_req->token);
 351        spin_lock_bh(&bucket->lock);
 352        pos = __token_lookup_req(bucket, subflow_req->token);
 353        if (!WARN_ON_ONCE(pos != subflow_req)) {
 354                hlist_nulls_del_init_rcu(&pos->token_node);
 355                bucket->chain_len--;
 356        }
 357        spin_unlock_bh(&bucket->lock);
 358}
 359
 360/**
 361 * mptcp_token_destroy - remove mptcp connection/token
 362 * @msk: mptcp connection dropping the token
 363 *
 364 * Remove the token associated to @msk
 365 */
 366void mptcp_token_destroy(struct mptcp_sock *msk)
 367{
 368        struct token_bucket *bucket;
 369        struct mptcp_sock *pos;
 370
 371        if (sk_unhashed((struct sock *)msk))
 372                return;
 373
 374        bucket = token_bucket(msk->token);
 375        spin_lock_bh(&bucket->lock);
 376        pos = __token_lookup_msk(bucket, msk->token);
 377        if (!WARN_ON_ONCE(pos != msk)) {
 378                __sk_nulls_del_node_init_rcu((struct sock *)pos);
 379                bucket->chain_len--;
 380        }
 381        spin_unlock_bh(&bucket->lock);
 382}
 383
 384void __init mptcp_token_init(void)
 385{
 386        int i;
 387
 388        token_hash = alloc_large_system_hash("MPTCP token",
 389                                             sizeof(struct token_bucket),
 390                                             0,
 391                                             20,/* one slot per 1MB of memory */
 392                                             HASH_ZERO,
 393                                             NULL,
 394                                             &token_mask,
 395                                             0,
 396                                             64 * 1024);
 397        for (i = 0; i < token_mask + 1; ++i) {
 398                INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i);
 399                INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i);
 400                spin_lock_init(&token_hash[i].lock);
 401        }
 402}
 403
 404#if IS_MODULE(CONFIG_MPTCP_KUNIT_TEST)
 405EXPORT_SYMBOL_GPL(mptcp_token_new_request);
 406EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
 407EXPORT_SYMBOL_GPL(mptcp_token_accept);
 408EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
 409EXPORT_SYMBOL_GPL(mptcp_token_destroy);
 410#endif
 411