include/internal/ring_buf.h

   1 /*
   2  * Copyright 2022 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_INTERNAL_RING_BUF_H
  11 # define OSSL_INTERNAL_RING_BUF_H
  12 # pragma once
  13
  14 # include <openssl/e_os2.h>              /* For 'ossl_inline' */
  15
  16 /*
  17  * ==================================================================
  18  * Byte-wise ring buffer which supports pushing and popping blocks of multiple
  19  * bytes at a time. The logical offset of each byte for the purposes of a QUIC
  20  * stream is tracked. Bytes can be popped from the ring buffer in two stages;
  21  * first they are popped, and then they are culled. Bytes which have been popped
  22  * but not yet culled will not be overwritten, and can be restored.
  23  */
  24 struct ring_buf {
  25     void       *start;
  26     size_t      alloc;        /* size of buffer allocation in bytes */
  27
  28     /*
  29      * Logical offset of the head (where we append to). This is the current size
  30      * of the QUIC stream. This increases monotonically.
  31      */
  32     uint64_t    head_offset;
  33
  34     /*
  35      * Logical offset of the cull tail. Data is no longer needed and is
  36      * deallocated as the cull tail advances, which occurs as data is
  37      * acknowledged. This increases monotonically.
  38      */
  39     uint64_t    ctail_offset;
  40 };
  41
  42 static ossl_inline int ring_buf_init(struct ring_buf *r)
  43 {
  44     r->start = NULL;
  45     r->alloc = 0;
  46     r->head_offset = r->ctail_offset = 0;
  47     return 1;
  48 }
  49
  50 static ossl_inline void ring_buf_destroy(struct ring_buf *r)
  51 {
  52     OPENSSL_free(r->start);
  53     r->start = NULL;
  54     r->alloc = 0;
  55 }
  56
  57 static ossl_inline size_t ring_buf_used(struct ring_buf *r)
  58 {
  59     return (size_t)(r->head_offset - r->ctail_offset);
  60 }
  61
  62 static ossl_inline size_t ring_buf_avail(struct ring_buf *r)
  63 {
  64     return r->alloc - ring_buf_used(r);
  65 }
  66
  67 static ossl_inline int ring_buf_write_at(struct ring_buf *r,
  68                                          uint64_t logical_offset,
  69                                          const unsigned char *buf,
  70                                          size_t buf_len)
  71 {
  72     size_t avail, idx, l;
  73     unsigned char *start = r->start;
  74     int i;
  75
  76     avail = ring_buf_avail(r);
  77     if (logical_offset < r->ctail_offset
  78         || logical_offset + buf_len > r->head_offset + avail)
  79         return 0;
  80
  81     for (i = 0; buf_len > 0 && i < 2; ++i) {
  82         idx = logical_offset % r->alloc;
  83         l = r->alloc - idx;
  84         if (buf_len < l)
  85             l = buf_len;
  86
  87         memcpy(start + idx, buf, l);
  88         if (r->head_offset < logical_offset + l)
  89             r->head_offset = logical_offset + l;
  90
  91         logical_offset += l;
  92         buf += l;
  93         buf_len -= l;
  94     }
  95
  96     assert(buf_len == 0);
  97
  98     return 1;
  99 }
 100
 101 static ossl_inline size_t ring_buf_push(struct ring_buf *r,
 102                                         const unsigned char *buf,
 103                                         size_t buf_len)
 104 {
 105     size_t pushed = 0, avail, idx, l;
 106     unsigned char *start = r->start;
 107
 108     for (;;) {
 109         avail = ring_buf_avail(r);
 110         if (buf_len > avail)
 111             buf_len = avail;
 112
 113         if (buf_len == 0)
 114             break;
 115
 116         idx = r->head_offset % r->alloc;
 117         l = r->alloc - idx;
 118         if (buf_len < l)
 119             l = buf_len;
 120
 121         memcpy(start + idx, buf, l);
 122         r->head_offset  += l;
 123         buf             += l;
 124         buf_len         -= l;
 125         pushed          += l;
 126     }
 127
 128     return pushed;
 129 }
 130
 131 static ossl_inline const unsigned char *ring_buf_get_ptr(const struct ring_buf *r,
 132                                                          uint64_t logical_offset,
 133                                                          size_t *max_len)
 134 {
 135     unsigned char *start = r->start;
 136     size_t idx;
 137
 138     if (logical_offset >= r->head_offset || logical_offset < r->ctail_offset)
 139         return NULL;
 140     idx = logical_offset % r->alloc;
 141     *max_len = r->alloc - idx;
 142     return start + idx;
 143 }
 144
 145 /*
 146  * Retrieves data out of the read side of the ring buffer starting at the given
 147  * logical offset. *buf is set to point to a contiguous span of bytes and
 148  * *buf_len is set to the number of contiguous bytes. After this function
 149  * returns, there may or may not be more bytes available at the logical offset
 150  * of (logical_offset + *buf_len) by calling this function again. If the logical
 151  * offset is out of the range retained by the ring buffer, returns 0, else
 152  * returns 1. A logical offset at the end of the range retained by the ring
 153  * buffer is not considered an error and is returned with a *buf_len of 0.
 154  *
 155  * The ring buffer state is not changed.
 156  */
 157 static ossl_inline int ring_buf_get_buf_at(const struct ring_buf *r,
 158                                            uint64_t logical_offset,
 159                                            const unsigned char **buf,
 160                                            size_t *buf_len)
 161 {
 162     const unsigned char *start = r->start;
 163     size_t idx, l;
 164
 165     if (logical_offset > r->head_offset || logical_offset < r->ctail_offset)
 166         return 0;
 167
 168     if (r->alloc == 0) {
 169         *buf        = NULL;
 170         *buf_len    = 0;
 171         return 1;
 172     }
 173
 174     idx = logical_offset % r->alloc;
 175     l   = (size_t)(r->head_offset - logical_offset);
 176     if (l > r->alloc - idx)
 177         l = r->alloc - idx;
 178
 179     *buf        = start + idx;
 180     *buf_len    = l;
 181     return 1;
 182 }
 183
 184 static ossl_inline void ring_buf_cpop_range(struct ring_buf *r,
 185                                             uint64_t start, uint64_t end,
 186                                             int cleanse)
 187 {
 188     assert(end >= start);
 189
 190     if (start > r->ctail_offset)
 191         return;
 192
 193     if (cleanse && r->alloc > 0 && end > r->ctail_offset) {
 194         size_t idx = r->ctail_offset % r->alloc;
 195         uint64_t cleanse_end = end + 1;
 196         size_t l;
 197
 198         if (cleanse_end > r->head_offset)
 199             cleanse_end = r->head_offset;
 200         l = (size_t)(cleanse_end - r->ctail_offset);
 201         if (l > r->alloc - idx) {
 202             OPENSSL_cleanse((unsigned char *)r->start + idx, r->alloc - idx);
 203             l -= r->alloc - idx;
 204             idx = 0;
 205         }
 206         if (l > 0)
 207             OPENSSL_cleanse((unsigned char *)r->start + idx, l);
 208     }
 209
 210     r->ctail_offset = end + 1;
 211     /* Allow culling unpushed data */
 212     if (r->head_offset < r->ctail_offset)
 213         r->head_offset = r->ctail_offset;
 214 }
 215
 216 static ossl_inline int ring_buf_resize(struct ring_buf *r, size_t num_bytes)
 217 {
 218     struct ring_buf rnew = {0};
 219     const unsigned char *src = NULL;
 220     size_t src_len = 0, copied = 0;
 221
 222     if (num_bytes == r->alloc)
 223         return 1;
 224
 225     if (num_bytes < ring_buf_used(r))
 226         return 0;
 227
 228     rnew.start = OPENSSL_malloc(num_bytes);
 229     if (rnew.start == NULL)
 230         return 0;
 231
 232     rnew.alloc          = num_bytes;
 233     rnew.head_offset    = r->head_offset - ring_buf_used(r);
 234     rnew.ctail_offset   = rnew.head_offset;
 235
 236     for (;;) {
 237         if (!ring_buf_get_buf_at(r, r->ctail_offset + copied, &src, &src_len)) {
 238             OPENSSL_free(rnew.start);
 239             return 0;
 240         }
 241
 242         if (src_len == 0)
 243             break;
 244
 245         if (ring_buf_push(&rnew, src, src_len) != src_len) {
 246             OPENSSL_free(rnew.start);
 247             return 0;
 248         }
 249
 250         copied += src_len;
 251     }
 252
 253     assert(rnew.head_offset == r->head_offset);
 254     rnew.ctail_offset   = r->ctail_offset;
 255
 256     OPENSSL_free(r->start);
 257     memcpy(r, &rnew, sizeof(*r));
 258     return 1;
 259 }
 260
 261 #endif                          /* OSSL_INTERNAL_RING_BUF_H */