// SPDX-License-Identifier: GPL-2.0 /* Multipath TCP token management * Copyright (c) 2017 - 2019, Intel Corporation. * * Note: This code is based on mptcp_ctrl.c from multipath-tcp.org, * authored by: * * Sébastien Barré * Christoph Paasch * Jaakko Korkeaniemi * Gregory Detal * Fabien Duchêne * Andreas Seelinger * Lavkesh Lahngir * Andreas Ripke * Vlad Dogaru * Octavian Purdila * John Ronan * Catalin Nicutar * Brandon Heller */ #define pr_fmt(fmt) "MPTCP: " fmt #include #include #include #include #include #include #include #include #include #include "protocol.h" #define TOKEN_MAX_RETRIES 4 #define TOKEN_MAX_CHAIN_LEN 4 struct token_bucket { spinlock_t lock; int chain_len; struct hlist_nulls_head req_chain; struct hlist_nulls_head msk_chain; }; static struct token_bucket *token_hash __read_mostly; static unsigned int token_mask __read_mostly; static struct token_bucket *token_bucket(u32 token) { return &token_hash[token & token_mask]; } /* called with bucket lock held */ static struct mptcp_subflow_request_sock * __token_lookup_req(struct token_bucket *t, u32 token) { struct mptcp_subflow_request_sock *req; struct hlist_nulls_node *pos; hlist_nulls_for_each_entry_rcu(req, pos, &t->req_chain, token_node) if (req->token == token) return req; return NULL; } /* called with bucket lock held */ static struct mptcp_sock * __token_lookup_msk(struct token_bucket *t, u32 token) { struct hlist_nulls_node *pos; struct sock *sk; sk_nulls_for_each_rcu(sk, pos, &t->msk_chain) if (mptcp_sk(sk)->token == token) return mptcp_sk(sk); return NULL; } static bool __token_bucket_busy(struct token_bucket *t, u32 token) { return !token || t->chain_len >= TOKEN_MAX_CHAIN_LEN || __token_lookup_req(t, token) || __token_lookup_msk(t, token); } static void mptcp_crypto_key_gen_sha(u64 *key, u32 *token, u64 *idsn) { /* we might consider a faster version that computes the key as a * hash of some information available in the MPTCP socket. Use * random data at the moment, as it's probably the safest option * in case multiple sockets are opened in different namespaces at * the same time. */ get_random_bytes(key, sizeof(u64)); mptcp_crypto_key_sha(*key, token, idsn); } /** * mptcp_token_new_request - create new key/idsn/token for subflow_request * @req: the request socket * * This function is called when a new mptcp connection is coming in. * * It creates a unique token to identify the new mptcp connection, * a secret local key and the initial data sequence number (idsn). * * Returns 0 on success. */ int mptcp_token_new_request(struct request_sock *req) { struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req); struct token_bucket *bucket; u32 token; mptcp_crypto_key_sha(subflow_req->local_key, &subflow_req->token, &subflow_req->idsn); pr_debug("req=%p local_key=%llu, token=%u, idsn=%llu\n", req, subflow_req->local_key, subflow_req->token, subflow_req->idsn); token = subflow_req->token; bucket = token_bucket(token); spin_lock_bh(&bucket->lock); if (__token_bucket_busy(bucket, token)) { spin_unlock_bh(&bucket->lock); return -EBUSY; } hlist_nulls_add_head_rcu(&subflow_req->token_node, &bucket->req_chain); bucket->chain_len++; spin_unlock_bh(&bucket->lock); return 0; } /** * mptcp_token_new_connect - create new key/idsn/token for subflow * @sk: the socket that will initiate a connection * * This function is called when a new outgoing mptcp connection is * initiated. * * It creates a unique token to identify the new mptcp connection, * a secret local key and the initial data sequence number (idsn). * * On success, the mptcp connection can be found again using * the computed token at a later time, this is needed to process * join requests. * * returns 0 on success. */ int mptcp_token_new_connect(struct sock *sk) { struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); struct mptcp_sock *msk = mptcp_sk(subflow->conn); int retries = TOKEN_MAX_RETRIES; struct token_bucket *bucket; again: mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token, &subflow->idsn); bucket = token_bucket(subflow->token); spin_lock_bh(&bucket->lock); if (__token_bucket_busy(bucket, subflow->token)) { spin_unlock_bh(&bucket->lock); if (!--retries) return -EBUSY; goto again; } pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n", sk, subflow->local_key, subflow->token, subflow->idsn); WRITE_ONCE(msk->token, subflow->token); __sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain); bucket->chain_len++; spin_unlock_bh(&bucket->lock); return 0; } /** * mptcp_token_accept - replace a req sk with full sock in token hash * @req: the request socket to be removed * @msk: the just cloned socket linked to the new connection * * Called when a SYN packet creates a new logical connection, i.e. * is not a join request. */ void mptcp_token_accept(struct mptcp_subflow_request_sock *req, struct mptcp_sock *msk) { struct mptcp_subflow_request_sock *pos; struct token_bucket *bucket; bucket = token_bucket(req->token); spin_lock_bh(&bucket->lock); /* pedantic lookup check for the moved token */ pos = __token_lookup_req(bucket, req->token); if (!WARN_ON_ONCE(pos != req)) hlist_nulls_del_init_rcu(&req->token_node); __sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain); spin_unlock_bh(&bucket->lock); } bool mptcp_token_exists(u32 token) { struct hlist_nulls_node *pos; struct token_bucket *bucket; struct mptcp_sock *msk; struct sock *sk; rcu_read_lock(); bucket = token_bucket(token); again: sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) { msk = mptcp_sk(sk); if (READ_ONCE(msk->token) == token) goto found; } if (get_nulls_value(pos) != (token & token_mask)) goto again; rcu_read_unlock(); return false; found: rcu_read_unlock(); return true; } /** * mptcp_token_get_sock - retrieve mptcp connection sock using its token * @token: token of the mptcp connection to retrieve * * This function returns the mptcp connection structure with the given token. * A reference count on the mptcp socket returned is taken. * * returns NULL if no connection with the given token value exists. */ struct mptcp_sock *mptcp_token_get_sock(u32 token) { struct hlist_nulls_node *pos; struct token_bucket *bucket; struct mptcp_sock *msk; struct sock *sk; rcu_read_lock(); bucket = token_bucket(token); again: sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) { msk = mptcp_sk(sk); if (READ_ONCE(msk->token) != token) continue; if (!refcount_inc_not_zero(&sk->sk_refcnt)) goto not_found; if (READ_ONCE(msk->token) != token) { sock_put(sk); goto again; } goto found; } if (get_nulls_value(pos) != (token & token_mask)) goto again; not_found: msk = NULL; found: rcu_read_unlock(); return msk; } EXPORT_SYMBOL_GPL(mptcp_token_get_sock); /** * mptcp_token_iter_next - iterate over the token container from given pos * @net: namespace to be iterated * @s_slot: start slot number * @s_num: start number inside the given lock * * This function returns the first mptcp connection structure found inside the * token container starting from the specified position, or NULL. * * On successful iteration, the iterator is move to the next position and the * the acquires a reference to the returned socket. */ struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot, long *s_num) { struct mptcp_sock *ret = NULL; struct hlist_nulls_node *pos; int slot, num = 0; for (slot = *s_slot; slot <= token_mask; *s_num = 0, slot++) { struct token_bucket *bucket = &token_hash[slot]; struct sock *sk; num = 0; if (hlist_nulls_empty(&bucket->msk_chain)) continue; rcu_read_lock(); sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) { ++num; if (!net_eq(sock_net(sk), net)) continue; if (num <= *s_num) continue; if (!refcount_inc_not_zero(&sk->sk_refcnt)) continue; if (!net_eq(sock_net(sk), net)) { sock_put(sk); continue; } ret = mptcp_sk(sk); rcu_read_unlock(); goto out; } rcu_read_unlock(); } out: *s_slot = slot; *s_num = num; return ret; } EXPORT_SYMBOL_GPL(mptcp_token_iter_next); /** * mptcp_token_destroy_request - remove mptcp connection/token * @req: mptcp request socket dropping the token * * Remove the token associated to @req. */ void mptcp_token_destroy_request(struct request_sock *req) { struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req); struct mptcp_subflow_request_sock *pos; struct token_bucket *bucket; if (hlist_nulls_unhashed(&subflow_req->token_node)) return; bucket = token_bucket(subflow_req->token); spin_lock_bh(&bucket->lock); pos = __token_lookup_req(bucket, subflow_req->token); if (!WARN_ON_ONCE(pos != subflow_req)) { hlist_nulls_del_init_rcu(&pos->token_node); bucket->chain_len--; } spin_unlock_bh(&bucket->lock); } /** * mptcp_token_destroy - remove mptcp connection/token * @msk: mptcp connection dropping the token * * Remove the token associated to @msk */ void mptcp_token_destroy(struct mptcp_sock *msk) { struct token_bucket *bucket; struct mptcp_sock *pos; if (sk_unhashed((struct sock *)msk)) return; bucket = token_bucket(msk->token); spin_lock_bh(&bucket->lock); pos = __token_lookup_msk(bucket, msk->token); if (!WARN_ON_ONCE(pos != msk)) { __sk_nulls_del_node_init_rcu((struct sock *)pos); bucket->chain_len--; } spin_unlock_bh(&bucket->lock); } void __init mptcp_token_init(void) { int i; token_hash = alloc_large_system_hash("MPTCP token", sizeof(struct token_bucket), 0, 20,/* one slot per 1MB of memory */ HASH_ZERO, NULL, &token_mask, 0, 64 * 1024); for (i = 0; i < token_mask + 1; ++i) { INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i); INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i); spin_lock_init(&token_hash[i].lock); } } #if IS_MODULE(CONFIG_MPTCP_KUNIT_TESTS) EXPORT_SYMBOL_GPL(mptcp_token_new_request); EXPORT_SYMBOL_GPL(mptcp_token_new_connect); EXPORT_SYMBOL_GPL(mptcp_token_accept); EXPORT_SYMBOL_GPL(mptcp_token_destroy_request); EXPORT_SYMBOL_GPL(mptcp_token_destroy); #endif