QUIC Thread Assist Core

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20348)

1 files changed, 97 insertions, 0 deletions

diff --git a/include/internal/quic_thread_assist.h b/include/internal/quic_thread_assist.h
new file mode 100644
index 0000000000..94fcaec004
--- /dev/null
+++ b/include/internal/quic_thread_assist.h
@@ -0,0 +1,97 @@
+/*
+ * Copyright 2023 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_THREAD_ASSIST_H
+# define OSSL_QUIC_THREAD_ASSIST_H
+
+# include <openssl/ssl.h>
+# include "internal/thread.h"
+
+# if defined(OPENSSL_NO_QUIC) || defined(OPENSSL_NO_THREAD_POOL)
+#  define OPENSSL_NO_QUIC_THREAD_ASSIST
+# endif
+
+# ifndef OPENSSL_NO_QUIC_THREAD_ASSIST
+
+/*
+ * QUIC Thread Assisted Functionality
+ * ==================================
+ *
+ * Where OS threading support is available, QUIC can optionally support a thread
+ * assisted mode of operation. The purpose of this mode of operation is to
+ * ensure that assorted timeout events which QUIC expects to be handled in a
+ * timely manner can be handled without the application needing to ensure that
+ * SSL_tick() is called  on  time. This is not needed if the application always
+ * has a call blocking to SSL_read() or SSL_write() (or another I/O function) on
+ * a QUIC SSL object, but if the application goes for long periods of time
+ * without makingany such call to a QUIC SSL object, libssl cannot ordinarily
+ * guarantee that QUIC timeout events will be serviced in a timely fashion.
+ * Thread assisted  mode is therefore of use to applications which do not always
+ * have an ongoing call to an I/O function on a QUIC SSL object but also do not
+ * want to have to arrange periodic ticking.
+ *
+ * A consequence of this is that the intrusiveness of thread assisted mode upon
+ * the general architecture of our QUIC engine is actually fairly limited and
+ * amounts to an automatic ticking of the QUIC engine when timeouts expire,
+ * synchronised correctly with an application's own threads using locking.
+ */
+typedef struct quic_thread_assist_st {
+    QUIC_CHANNEL *ch;
+    CRYPTO_CONDVAR *cv;
+    CRYPTO_THREAD *t;
+    int teardown, joined;
+} QUIC_THREAD_ASSIST;
+
+/*
+ * Initialise the thread assist object. The channel must have a valid mutex
+ * configured on it which will be retrieved automatically. It is assumed that
+ * the mutex is currently held when this function is called. This function does
+ * not affect the state of the mutex.
+ */
+int ossl_quic_thread_assist_init_start(QUIC_THREAD_ASSIST *qta,
+                                       QUIC_CHANNEL *ch);
+
+/*
+ * Request the thread assist helper to begin stopping the assist thread. This
+ * returns before the teardown is complete. Idempotent; multiple calls to this
+ * function are inconsequential.
+ *
+ * Precondition: channel mutex must be held (unchecked)
+ */
+int ossl_quic_thread_assist_stop_async(QUIC_THREAD_ASSIST *qta);
+
+/*
+ * Wait until the thread assist helper is torn down. This automatically implies
+ * the effects of ossl_quic_thread_assist_stop_async(). Returns immediately
+ * if the teardown has already completed.
+ *
+ * Precondition: channel mutex must be held (unchecked)
+ */
+int ossl_quic_thread_assist_wait_stopped(QUIC_THREAD_ASSIST *qta);
+
+/*
+ * Deallocates state associated with the thread assist helper.
+ * ossl_quic_thread_assist_wait_stopped() must have returned successfully before
+ * calling this. It does not matter whether the channel mutex is held or not.
+ *
+ * Precondition: ossl_quic_thread_assist_wait_stopped() has returned 1
+ *               (asserted)
+ */
+int ossl_quic_thread_assist_cleanup(QUIC_THREAD_ASSIST *qta);
+
+/*
+ * Must be called to notify the assist thread if the channel deadline changes.
+ *
+ * Precondition: channel mutex must be held (unchecked)
+ */
+int ossl_quic_thread_assist_notify_deadline_changed(QUIC_THREAD_ASSIST *qta);
+
+# endif
+
+#endif