/* * Copyright 2022-2025 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the Apache License 2.0 (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy * in the file LICENSE in the source distribution or at * https://www.openssl.org/source/license.html */ #ifndef OSSL_QUIC_REACTOR_H #define OSSL_QUIC_REACTOR_H #include "internal/time.h" #include "internal/sockets.h" #include "internal/quic_predef.h" #include "internal/thread_arch.h" #include "internal/rio_notifier.h" #include <openssl/bio.h> #ifndef OPENSSL_NO_QUIC /* * Core I/O Reactor Framework * ========================== * * Manages use of async network I/O which the QUIC stack is built on. The core * mechanic looks like this: * * - There is a pollable FD for both the read and write side respectively. * Readability and writeability of these FDs respectively determines when * network I/O is available. * * - The reactor can export these FDs to the user, as well as flags indicating * whether the user should listen for readability, writeability, or neither. * * - The reactor can export a timeout indication to the user, indicating when * the reactor should be called (via libssl APIs) regardless of whether * the network socket has become ready. * * The reactor is based around a tick callback which is essentially the mutator * function. The mutator attempts to do whatever it can, attempting to perform * network I/O to the extent currently feasible. When done, the mutator returns * information to the reactor indicating when it should be woken up again: * * - Should it be woken up when network RX is possible? * - Should it be woken up when network TX is possible? * - Should it be woken up no later than some deadline X? * * The intention is that ALL I/O-related SSL_* functions with side effects (e.g. * SSL_read/SSL_write) consist of three phases: * * - Optionally mutate the QUIC machine's state. * - Optionally tick the QUIC reactor. * - Optionally mutate the QUIC machine's state. * * For example, SSL_write is a mutation (appending to a stream buffer) followed * by an optional tick (generally expected as we may want to send the data * immediately, though not strictly needed if transmission is being deferred due * to Nagle's algorithm, etc.). * * SSL_read is also a mutation and in principle does not need to tick the * reactor, but it generally will anyway to ensure that the reactor is regularly * ticked by an application which is only reading and not writing. * * If the SSL object is being used in blocking mode, SSL_read may need to block * if no data is available yet, and SSL_write may need to block if buffers * are full. * * The internals of the QUIC I/O engine always use asynchronous I/O. If the * application desires blocking semantics, we handle this by adding a blocking * adaptation layer on top of our internal asynchronous I/O API as exposed by * the reactor interface. */ struct quic_tick_result_st { OSSL_TIME tick_deadline; char net_read_desired; char net_write_desired; char notify_other_threads; }; static ossl_inline ossl_unused void ossl_quic_tick_result_merge_into(QUIC_TICK_RESULT *r, const QUIC_TICK_RESULT *src) { r->net_read_desired = r->net_read_desired || src->net_read_desired; r->net_write_desired = r->net_write_desired || src->net_write_desired; r->notify_other_threads = r->notify_other_threads || src->notify_other_threads; r->tick_deadline = ossl_time_min(r->tick_deadline, src->tick_deadline); } struct quic_reactor_st { /* * BIO poll descriptors which can be polled. poll_r is a poll descriptor * which becomes readable when the QUIC state machine can potentially do * work, and poll_w is a poll descriptor which becomes writable when the * QUIC state machine can potentially do work. Generally, either of these * conditions means that SSL_tick() should be called, or another SSL * function which implicitly calls SSL_tick() (e.g. SSL_read/SSL_write()). */ BIO_POLL_DESCRIPTOR poll_r, poll_w; OSSL_TIME tick_deadline; /* ossl_time_infinite() if none currently applicable */ void (*tick_cb)(QUIC_TICK_RESULT *res, void *arg, uint32_t flags); void *tick_cb_arg; /* The mutex used for ticking. Not owned by the reactor. */ CRYPTO_MUTEX *mutex; /* Used to notify other threads. Valid only if have_notifier is set. */ RIO_NOTIFIER notifier; /* * Condvar to assist synchronising use of the notifier. Valid only if * have_notifier is set. */ CRYPTO_CONDVAR *notifier_cv; /* * Count of the current number of blocking waiters. Like everything else, * this is protected by the caller's mutex (i.e., the engine mutex). */ size_t cur_blocking_waiters; /* * These are true if we would like to know when we can read or write from * the network respectively. */ unsigned int net_read_desired : 1; unsigned int net_write_desired : 1; /* * Are the read and write poll descriptors we are currently configured with * things we can actually poll? */ unsigned int can_poll_r : 1; unsigned int can_poll_w : 1; /* 1 if notifier is present and initialised. */ unsigned int have_notifier : 1; /* 1 if a block_until_pred call has put the notifier in the signalled state. */ unsigned int signalled_notifier : 1; }; /* Create an OS notifier? */ #define QUIC_REACTOR_FLAG_USE_NOTIFIER (1U << 0) int ossl_quic_reactor_init(QUIC_REACTOR *rtor, void (*tick_cb)(QUIC_TICK_RESULT *res, void *arg, uint32_t flags), void *tick_cb_arg, CRYPTO_MUTEX *mutex, OSSL_TIME initial_tick_deadline, uint64_t flags); void ossl_quic_reactor_cleanup(QUIC_REACTOR *rtor); void ossl_quic_reactor_set_poll_r(QUIC_REACTOR *rtor, const BIO_POLL_DESCRIPTOR *r); void ossl_quic_reactor_set_poll_w(QUIC_REACTOR *rtor, const BIO_POLL_DESCRIPTOR *w); const BIO_POLL_DESCRIPTOR *ossl_quic_reactor_get_poll_r(const QUIC_REACTOR *rtor); const BIO_POLL_DESCRIPTOR *ossl_quic_reactor_get_poll_w(const QUIC_REACTOR *rtor); int ossl_quic_reactor_can_poll_r(const QUIC_REACTOR *rtor); int ossl_quic_reactor_can_poll_w(const QUIC_REACTOR *rtor); int ossl_quic_reactor_can_support_poll_descriptor(const QUIC_REACTOR *rtor, const BIO_POLL_DESCRIPTOR *d); int ossl_quic_reactor_net_read_desired(QUIC_REACTOR *rtor); int ossl_quic_reactor_net_write_desired(QUIC_REACTOR *rtor); OSSL_TIME ossl_quic_reactor_get_tick_deadline(QUIC_REACTOR *rtor); /* * Do whatever work can be done, and as much work as can be done. This involves * e.g. seeing if we can read anything from the network (if we want to), seeing * if we can write anything to the network (if we want to), etc. * * If the CHANNEL_ONLY flag is set, this indicates that we should only * touch state which is synchronised by the channel mutex. */ #define QUIC_REACTOR_TICK_FLAG_CHANNEL_ONLY (1U << 0) int ossl_quic_reactor_tick(QUIC_REACTOR *rtor, uint32_t flags); RIO_NOTIFIER *ossl_quic_reactor_get0_notifier(QUIC_REACTOR *rtor); /* * Blocking I/O Adaptation Layer * ============================= * * The blocking I/O adaptation layer implements blocking I/O on top of our * asynchronous core. */ /* * ossl_quic_reactor_block_until_pred * ---------------------------------- * * The core mechanism of the Blocking I/O Adaption Layer is block_until_pred(), * which does not return until pred() returns a value other than 0. The blocker * uses OS I/O synchronisation primitives (e.g. poll(2)) and ticks the reactor * until the predicate is satisfied. The blocker is not required to call pred() * more than once between tick calls. * * When pred returns a non-zero value, that value is returned by this function. * This can be used to allow pred() to indicate error conditions and short * circuit the blocking process. * * A return value of -1 is reserved for network polling errors. Therefore this * return value should not be used by pred() if ambiguity is not desired. Note * that the predicate function can always arrange its own output mechanism, for * example by passing a structure of its own as the argument. * * If the SKIP_FIRST_TICK flag is set, the first call to reactor_tick() before * the first call to pred() is skipped. This is useful if it is known that * ticking the reactor again will not be useful (e.g. because it has already * been done). * * This function assumes a write lock is held for the entire QUIC_CHANNEL. If * mutex is non-NULL, it must be a lock currently held for write; it will be * unlocked during any sleep, and then relocked for write afterwards. * * This function must not be called by a thread currently using * ossl_quic_reactor_(enter/leave)_blocking_section() as this function also uses * those functions (see below); it is assumed if a caller is using those * functions it is implementing blocking semantics itself. There is no need to * use those functions if using this function. * * Precondition: If a reactor mutex is being used, it must be held (unchecked) * Postcondition: If a reactor mutex is being used, it is held * Invariant: The current thread does not have an outstanding * ossl_quic_reactor_enter_blocking_section() call (unchecked) */ #define SKIP_FIRST_TICK (1U << 0) int ossl_quic_reactor_block_until_pred(QUIC_REACTOR *rtor, int (*pred)(void *arg), void *pred_arg, uint32_t flags); /* * ossl_quic_reactor_(enter/leave)_blocking_section * ------------------------------------------------ * * This is used by blocking code outside of the reactor itself to inform the * reactor of when a thread begins or ends a blocking call. This is used by the * reactor so it knows if a tick means other threads might need to be woken up * via the notifier. The reactor mutex must be held while calling these * functions. * * The number of 'active' calls to these functions (i.e., the number of enter * calls which have yet to be matched with a subsequent leave call) must *at all * times* equal the number of threads blocking on the reactor. In other words, a * single thread is not permitted to use these functions "recursively". Failing * to adhere to this rule will result in deadlock. * * This means that if a caller has the concept of multiple concurrent blocking * calls on the same thread on the same reactor (which may occur in some * SSL_poll-related circumstances) it must do its own housekeeping to ensure it * only calls enter() once. See quic_reactor_wait_ctx.h for a utility which can * be used to accomplish this. * * ossl_quic_reactor_enter_blocking_section: * Precondition: The current thread does not have an outstanding * ossl_quic_reactor_enter_blocking_section() call (unchecked) * Postcondition: The current thread has an outstanding * ossl_quic_reactor_enter_blocking_section() call * * ossl_quic_reactor_leave_blocking_section: * Precondition: The current thread has an outstanding * ossl_quic_reactor_enter_blocking_section() call (unchecked) * Postcondition: The current thread does not have an outstanding * ossl_quic_reactor_enter_blocking_section() call * */ void ossl_quic_reactor_enter_blocking_section(QUIC_REACTOR *rtor); void ossl_quic_reactor_leave_blocking_section(QUIC_REACTOR *rtor); #endif #endif
