2 * Copyright 2022-2023 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
9 #ifndef OSSL_QUIC_REACTOR_H
10 # define OSSL_QUIC_REACTOR_H
12 # include "internal/time.h"
13 # include "internal/sockets.h"
14 # include "internal/quic_predef.h"
15 # include <openssl/bio.h>
17 # ifndef OPENSSL_NO_QUIC
20 * Core I/O Reactor Framework
21 * ==========================
23 * Manages use of async network I/O which the QUIC stack is built on. The core
24 * mechanic looks like this:
26 * - There is a pollable FD for both the read and write side respectively.
27 * Readability and writeability of these FDs respectively determines when
28 * network I/O is available.
30 * - The reactor can export these FDs to the user, as well as flags indicating
31 * whether the user should listen for readability, writeability, or neither.
33 * - The reactor can export a timeout indication to the user, indicating when
34 * the reactor should be called (via libssl APIs) regardless of whether
35 * the network socket has become ready.
37 * The reactor is based around a tick callback which is essentially the mutator
38 * function. The mutator attempts to do whatever it can, attempting to perform
39 * network I/O to the extent currently feasible. When done, the mutator returns
40 * information to the reactor indicating when it should be woken up again:
42 * - Should it be woken up when network RX is possible?
43 * - Should it be woken up when network TX is possible?
44 * - Should it be woken up no later than some deadline X?
46 * The intention is that ALL I/O-related SSL_* functions with side effects (e.g.
47 * SSL_read/SSL_write) consist of three phases:
49 * - Optionally mutate the QUIC machine's state.
50 * - Optionally tick the QUIC reactor.
51 * - Optionally mutate the QUIC machine's state.
53 * For example, SSL_write is a mutation (appending to a stream buffer) followed
54 * by an optional tick (generally expected as we may want to send the data
55 * immediately, though not strictly needed if transmission is being deferred due
56 * to Nagle's algorithm, etc.).
58 * SSL_read is also a mutation and in principle does not need to tick the
59 * reactor, but it generally will anyway to ensure that the reactor is regularly
60 * ticked by an application which is only reading and not writing.
62 * If the SSL object is being used in blocking mode, SSL_read may need to block
63 * if no data is available yet, and SSL_write may need to block if buffers
66 * The internals of the QUIC I/O engine always use asynchronous I/O. If the
67 * application desires blocking semantics, we handle this by adding a blocking
68 * adaptation layer on top of our internal asynchronous I/O API as exposed by
69 * the reactor interface.
71 struct quic_tick_result_st {
72 char net_read_desired;
73 char net_write_desired;
74 OSSL_TIME tick_deadline;
77 static ossl_inline ossl_unused void
78 ossl_quic_tick_result_merge_into(QUIC_TICK_RESULT *r,
79 const QUIC_TICK_RESULT *src)
81 r->net_read_desired = r->net_read_desired || src->net_read_desired;
82 r->net_write_desired = r->net_write_desired || src->net_write_desired;
83 r->tick_deadline = ossl_time_min(r->tick_deadline, src->tick_deadline);
86 struct quic_reactor_st {
88 * BIO poll descriptors which can be polled. poll_r is a poll descriptor
89 * which becomes readable when the QUIC state machine can potentially do
90 * work, and poll_w is a poll descriptor which becomes writable when the
91 * QUIC state machine can potentially do work. Generally, either of these
92 * conditions means that SSL_tick() should be called, or another SSL
93 * function which implicitly calls SSL_tick() (e.g. SSL_read/SSL_write()).
95 BIO_POLL_DESCRIPTOR poll_r, poll_w;
96 OSSL_TIME tick_deadline; /* ossl_time_infinite() if none currently applicable */
98 void (*tick_cb)(QUIC_TICK_RESULT *res, void *arg, uint32_t flags);
102 * These are true if we would like to know when we can read or write from
103 * the network respectively.
105 unsigned int net_read_desired : 1;
106 unsigned int net_write_desired : 1;
109 * Are the read and write poll descriptors we are currently configured with
110 * things we can actually poll?
112 unsigned int can_poll_r : 1;
113 unsigned int can_poll_w : 1;
116 void ossl_quic_reactor_init(QUIC_REACTOR *rtor,
117 void (*tick_cb)(QUIC_TICK_RESULT *res, void *arg,
120 OSSL_TIME initial_tick_deadline);
122 void ossl_quic_reactor_set_poll_r(QUIC_REACTOR *rtor,
123 const BIO_POLL_DESCRIPTOR *r);
125 void ossl_quic_reactor_set_poll_w(QUIC_REACTOR *rtor,
126 const BIO_POLL_DESCRIPTOR *w);
128 const BIO_POLL_DESCRIPTOR *ossl_quic_reactor_get_poll_r(const QUIC_REACTOR *rtor);
129 const BIO_POLL_DESCRIPTOR *ossl_quic_reactor_get_poll_w(const QUIC_REACTOR *rtor);
131 int ossl_quic_reactor_can_poll_r(const QUIC_REACTOR *rtor);
132 int ossl_quic_reactor_can_poll_w(const QUIC_REACTOR *rtor);
134 int ossl_quic_reactor_can_support_poll_descriptor(const QUIC_REACTOR *rtor,
135 const BIO_POLL_DESCRIPTOR *d);
137 int ossl_quic_reactor_net_read_desired(QUIC_REACTOR *rtor);
138 int ossl_quic_reactor_net_write_desired(QUIC_REACTOR *rtor);
140 OSSL_TIME ossl_quic_reactor_get_tick_deadline(QUIC_REACTOR *rtor);
143 * Do whatever work can be done, and as much work as can be done. This involves
144 * e.g. seeing if we can read anything from the network (if we want to), seeing
145 * if we can write anything to the network (if we want to), etc.
147 * If the CHANNEL_ONLY flag is set, this indicates that we should only
148 * touch state which is synchronised by the channel mutex.
150 #define QUIC_REACTOR_TICK_FLAG_CHANNEL_ONLY (1U << 0)
152 int ossl_quic_reactor_tick(QUIC_REACTOR *rtor, uint32_t flags);
155 * Blocking I/O Adaptation Layer
156 * =============================
158 * The blocking I/O adaptation layer implements blocking I/O on top of our
161 * The core mechanism is block_until_pred(), which does not return until pred()
162 * returns a value other than 0. The blocker uses OS I/O synchronisation
163 * primitives (e.g. poll(2)) and ticks the reactor until the predicate is
164 * satisfied. The blocker is not required to call pred() more than once between
167 * When pred returns a non-zero value, that value is returned by this function.
168 * This can be used to allow pred() to indicate error conditions and short
169 * circuit the blocking process.
171 * A return value of -1 is reserved for network polling errors. Therefore this
172 * return value should not be used by pred() if ambiguity is not desired. Note
173 * that the predicate function can always arrange its own output mechanism, for
174 * example by passing a structure of its own as the argument.
176 * If the SKIP_FIRST_TICK flag is set, the first call to reactor_tick() before
177 * the first call to pred() is skipped. This is useful if it is known that
178 * ticking the reactor again will not be useful (e.g. because it has already
181 * This function assumes a write lock is held for the entire QUIC_CHANNEL. If
182 * mutex is non-NULL, it must be a lock currently held for write; it will be
183 * unlocked during any sleep, and then relocked for write afterwards.
185 * Precondition: mutex is NULL or is held for write (unchecked)
186 * Postcondition: mutex is NULL or is held for write (unless
187 * CRYPTO_THREAD_write_lock fails)
189 #define SKIP_FIRST_TICK (1U << 0)
191 int ossl_quic_reactor_block_until_pred(QUIC_REACTOR *rtor,
192 int (*pred)(void *arg), void *pred_arg,
194 CRYPTO_RWLOCK *mutex);