include/internal/quic_fc.h

   1 /*
   2  * Copyright 2022-2023 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   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
   8  */
   9
  10 #ifndef OSSL_QUIC_FC_H
  11 # define OSSL_QUIC_FC_H
  12
  13 # include <openssl/ssl.h>
  14 # include "internal/time.h"
  15
  16 # ifndef OPENSSL_NO_QUIC
  17
  18 /*
  19  * TX Flow Controller (TXFC)
  20  * =========================
  21  *
  22  * For discussion, see doc/designs/quic-design/quic-fc.md.
  23  */
  24 typedef struct quic_txfc_st QUIC_TXFC;
  25
  26 struct quic_txfc_st {
  27     QUIC_TXFC   *parent; /* stream-level iff non-NULL */
  28     uint64_t    swm, cwm;
  29     char        has_become_blocked;
  30 };
  31
  32 /*
  33  * Initialises a TX flow controller. conn_txfc should be non-NULL and point to
  34  * the connection-level flow controller if the TXFC is for stream-level flow
  35  * control, and NULL otherwise.
  36  */
  37 int ossl_quic_txfc_init(QUIC_TXFC *txfc, QUIC_TXFC *conn_txfc);
  38
  39 /*
  40  * Gets the parent (i.e., connection-level) TX flow controller. Returns NULL if
  41  * called on a connection-level TX flow controller.
  42  */
  43 QUIC_TXFC *ossl_quic_txfc_get_parent(QUIC_TXFC *txfc);
  44
  45 /*
  46  * Bump the credit watermark (CWM) value. This is the 'On TX Window Updated'
  47  * operation. This function is a no-op if it has already been called with an
  48  * equal or higher CWM value.
  49  *
  50  * It returns 1 iff the call resulted in the CWM being bumped and 0 if it was
  51  * not increased because it has already been called with an equal or higher CWM
  52  * value. This is not an error per se but may indicate a local programming error
  53  * or a protocol error in a remote peer.
  54  */
  55 int ossl_quic_txfc_bump_cwm(QUIC_TXFC *txfc, uint64_t cwm);
  56
  57 /*
  58  * Get the number of bytes by which we are in credit. This is the number of
  59  * controlled bytes we are allowed to send. (Thus if this function returns 0, we
  60  * are currently blocked.)
  61  *
  62  * If called on a stream-level TXFC, ossl_quic_txfc_get_credit is called on
  63  * the connection-level TXFC as well, and the lesser of the two values is
  64  * returned.
  65  */
  66 uint64_t ossl_quic_txfc_get_credit(QUIC_TXFC *txfc);
  67
  68 /*
  69  * Like ossl_quic_txfc_get_credit(), but when called on a stream-level TXFC,
  70  * retrieves only the stream-level credit value and does not clamp it based on
  71  * connection-level flow control.
  72  */
  73 uint64_t ossl_quic_txfc_get_credit_local(QUIC_TXFC *txfc);
  74
  75 /*
  76  * Consume num_bytes of credit. This is the 'On TX' operation. This should be
  77  * called when we transmit any controlled bytes. Calling this with an argument
  78  * of 0 is a no-op.
  79  *
  80  * We must never transmit more controlled bytes than we are in credit for (see
  81  * the return value of ossl_quic_txfc_get_credit()). If you call this function
  82  * with num_bytes greater than our current credit, this function consumes the
  83  * remainder of the credit and returns 0. This indicates a serious programming
  84  * error on the caller's part. Otherwise, the function returns 1.
  85  *
  86  * If called on a stream-level TXFC, ossl_quic_txfc_consume_credit() is called
  87  * on the connection-level TXFC also. If the call to that function on the
  88  * connection-level TXFC returns zero, this function will also return zero.
  89  */
  90 int ossl_quic_txfc_consume_credit(QUIC_TXFC *txfc, uint64_t num_bytes);
  91
  92 /*
  93  * Like ossl_quic_txfc_consume_credit(), but when called on a stream-level TXFC,
  94  * consumes only from the stream-level credit and does not inform the
  95  * connection-level TXFC.
  96  */
  97 int ossl_quic_txfc_consume_credit_local(QUIC_TXFC *txfc, uint64_t num_bytes);
  98
  99 /*
 100  * This flag is provided for convenience. A caller is not required to use it. It
 101  * is a boolean flag set whenever our credit drops to zero. If clear is 1, the
 102  * flag is cleared. The old value of the flag is returned. Callers may use this
 103  * to determine if they need to send a DATA_BLOCKED or STREAM_DATA_BLOCKED
 104  * frame, which should contain the value returned by ossl_quic_txfc_get_cwm().
 105  */
 106 int ossl_quic_txfc_has_become_blocked(QUIC_TXFC *txfc, int clear);
 107
 108 /*
 109  * Get the current CWM value. This is mainly only needed when generating a
 110  * DATA_BLOCKED or STREAM_DATA_BLOCKED frame, or for diagnostic purposes.
 111  */
 112 uint64_t ossl_quic_txfc_get_cwm(QUIC_TXFC *txfc);
 113
 114 /*
 115  * Get the current spent watermark (SWM) value. This is purely for diagnostic
 116  * use and should not be needed in normal circumstances.
 117  */
 118 uint64_t ossl_quic_txfc_get_swm(QUIC_TXFC *txfc);
 119
 120 /*
 121  * RX Flow Controller (RXFC)
 122  * =========================
 123  */
 124 typedef struct quic_rxfc_st QUIC_RXFC;
 125
 126 struct quic_rxfc_st {
 127     /*
 128      * swm is the sent/received watermark, which tracks how much we have
 129      * received from the peer. rwm is the retired watermark, which tracks how
 130      * much has been passed to the application. esrwm is the rwm value at which
 131      * the current auto-tuning epoch started. hwm is the highest stream length
 132      * (STREAM frame offset + payload length) we have seen from a STREAM frame
 133      * yet.
 134      */
 135     uint64_t        cwm, swm, rwm, esrwm, hwm, cur_window_size, max_window_size;
 136     OSSL_TIME       epoch_start;
 137     OSSL_TIME       (*now)(void *arg);
 138     void            *now_arg;
 139     QUIC_RXFC       *parent;
 140     unsigned char   error_code, has_cwm_changed, is_fin, standalone;
 141 };
 142
 143 /*
 144  * Initialises an RX flow controller. conn_rxfc should be non-NULL and point to
 145  * a connection-level RXFC if the RXFC is for stream-level flow control, and
 146  * NULL otherwise. initial_window_size and max_window_size specify the initial
 147  * and absolute maximum window sizes, respectively. Window size values are
 148  * expressed in bytes and determine how much credit the RXFC extends to the peer
 149  * to transmit more data at a time.
 150  */
 151 int ossl_quic_rxfc_init(QUIC_RXFC *rxfc, QUIC_RXFC *conn_rxfc,
 152                         uint64_t initial_window_size,
 153                         uint64_t max_window_size,
 154                         OSSL_TIME (*now)(void *arg),
 155                         void *now_arg);
 156
 157 /*
 158  * Initialises an RX flow controller which is used by itself and not under a
 159  * connection-level RX flow controller. This can be used for stream count
 160  * enforcement as well as CRYPTO buffer enforcement.
 161  */
 162 int ossl_quic_rxfc_init_standalone(QUIC_RXFC *rxfc,
 163                                    uint64_t initial_window_size,
 164                                    OSSL_TIME (*now)(void *arg),
 165                                    void *now_arg);
 166
 167 /*
 168  * Gets the parent (i.e., connection-level) RXFC. Returns NULL if called on a
 169  * connection-level RXFC.
 170  */
 171 QUIC_RXFC *ossl_quic_rxfc_get_parent(QUIC_RXFC *rxfc);
 172
 173 /*
 174  * Changes the current maximum window size value.
 175  */
 176 void ossl_quic_rxfc_set_max_window_size(QUIC_RXFC *rxfc,
 177                                         size_t max_window_size);
 178
 179 /*
 180  * To be called whenever a STREAM frame is received.
 181  *
 182  * end is the value (offset + len), where offset is the offset field of the
 183  * STREAM frame and len is the length of the STREAM frame's payload in bytes.
 184  *
 185  * is_fin should be 1 if the STREAM frame had the FIN flag set and 0 otherwise.
 186  *
 187  * This function may be used on a stream-level RXFC only. The connection-level
 188  * RXFC will have its state updated by the stream-level RXFC.
 189  *
 190  * You should check ossl_quic_rxfc_has_error() on both connection-level and
 191  * stream-level RXFCs after calling this function, as an incoming STREAM frame
 192  * may cause flow control limits to be exceeded by an errant peer. This
 193  * function still returns 1 in this case, as this is not a caller error.
 194  *
 195  * Returns 1 on success or 0 on failure.
 196  */
 197 int ossl_quic_rxfc_on_rx_stream_frame(QUIC_RXFC *rxfc,
 198                                       uint64_t end, int is_fin);
 199
 200 /*
 201  * To be called whenever controlled bytes are retired, i.e. when bytes are
 202  * dequeued from a QUIC stream and passed to the application. num_bytes
 203  * is the number of bytes which were passed to the application.
 204  *
 205  * You should call this only on a stream-level RXFC. This function will update
 206  * the connection-level RXFC automatically.
 207  *
 208  * rtt should be the current best understanding of the RTT to the peer, as
 209  * offered by the Statistics Manager.
 210  *
 211  * You should check ossl_quic_rxfc_has_cwm_changed() after calling this
 212  * function, as it may have caused the RXFC to decide to grant more flow control
 213  * credit to the peer.
 214  *
 215  * Returns 1 on success and 0 on failure.
 216  */
 217 int ossl_quic_rxfc_on_retire(QUIC_RXFC *rxfc,
 218                              uint64_t num_bytes,
 219                              OSSL_TIME rtt);
 220
 221 /*
 222  * Returns the current CWM which the RXFC thinks the peer should have.
 223  *
 224  * Note that the RXFC will increase this value in response to events, at which
 225  * time a MAX_DATA or MAX_STREAM_DATA frame must be generated. Use
 226  * ossl_quic_rxfc_has_cwm_changed() to detect this condition.
 227  *
 228  * This value increases monotonically.
 229  */
 230 uint64_t ossl_quic_rxfc_get_cwm(QUIC_RXFC *rxfc);
 231
 232 /*
 233  * Returns the current SWM. This is the total number of bytes the peer has
 234  * transmitted to us. This is intended for diagnostic use only; you should
 235  * not need it.
 236  */
 237 uint64_t ossl_quic_rxfc_get_swm(QUIC_RXFC *rxfc);
 238
 239 /*
 240  * Returns the current RWM. This is the total number of bytes that has been
 241  * retired. This is intended for diagnostic use only; you should not need it.
 242  */
 243 uint64_t ossl_quic_rxfc_get_rwm(QUIC_RXFC *rxfc);
 244
 245 /*
 246  * Returns the CWM changed flag. If clear is 1, the flag is cleared and the old
 247  * value is returned.
 248  */
 249 int ossl_quic_rxfc_has_cwm_changed(QUIC_RXFC *rxfc, int clear);
 250
 251 /*
 252  * Returns a QUIC_ERR_* error code if a flow control error has been detected.
 253  * Otherwise, returns QUIC_ERR_NO_ERROR. If clear is 1, the error is cleared
 254  * and the old value is returned.
 255  *
 256  * May return one of the following values:
 257  *
 258  * QUIC_ERR_FLOW_CONTROL_ERROR:
 259  *   This indicates a flow control protocol violation by the remote peer; the
 260  *   connection should be terminated in this event.
 261  * QUIC_ERR_FINAL_SIZE:
 262  *   The peer attempted to change the stream length after ending the stream.
 263  */
 264 int ossl_quic_rxfc_get_error(QUIC_RXFC *rxfc, int clear);
 265
 266 /*
 267  * Returns 1 if the RXFC is a stream-level RXFC and the RXFC knows the final
 268  * size for the stream in bytes. If this is the case and final_size is non-NULL,
 269  * writes the final size to *final_size. Otherwise, returns 0.
 270  */
 271 int ossl_quic_rxfc_get_final_size(const QUIC_RXFC *rxfc, uint64_t *final_size);
 272
 273 # endif
 274
 275 #endif