| /* Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef __mod_h2__h2_push__ |
| #define __mod_h2__h2_push__ |
| |
| #include <http_protocol.h> |
| |
| #include "h2.h" |
| #include "h2_headers.h" |
| |
| struct h2_request; |
| struct h2_ngheader; |
| struct h2_session; |
| struct h2_stream; |
| |
| typedef struct h2_push { |
| const struct h2_request *req; |
| h2_priority *priority; |
| } h2_push; |
| |
| typedef enum { |
| H2_PUSH_DIGEST_APR_HASH, |
| H2_PUSH_DIGEST_SHA256 |
| } h2_push_digest_type; |
| |
| /******************************************************************************* |
| * push diary |
| * |
| * - The push diary keeps track of resources already PUSHed via HTTP/2 on this |
| * connection. It records a hash value from the absolute URL of the resource |
| * pushed. |
| * - Lacking openssl, |
| * - with openssl, it uses SHA256 to calculate the hash value, otherwise it |
| * falls back to apr_hashfunc_default() |
| * - whatever the method to generate the hash, the diary keeps a maximum of 64 |
| * bits per hash, limiting the memory consumption to about |
| * H2PushDiarySize * 8 |
| * bytes. Entries are sorted by most recently used and oldest entries are |
| * forgotten first. |
| * - While useful by itself to avoid duplicated PUSHes on the same connection, |
| * the original idea was that clients provided a 'Cache-Digest' header with |
| * the values of *their own* cached resources. This was described in |
| * <https://datatracker.ietf.org/doc/draft-kazuho-h2-cache-digest/> |
| * and some subsequent revisions that tweaked values but kept the overall idea. |
| * - The draft was abandoned by the IETF http-wg, as support from major clients, |
| * e.g. browsers, was lacking for various reasons. |
| * - For these reasons, mod_h2 abandoned its support for client supplied values |
| * but keeps the diary. It seems to provide value for applications using PUSH, |
| * is configurable in size and defaults to a very moderate amount of memory |
| * used. |
| * - The cache digest header is a Golomb Coded Set of hash values, but it may |
| * limit the amount of bits per hash value even further. For a good description |
| * of GCS, read here: |
| * <http://giovanni.bajo.it/post/47119962313/golomb-coded-sets-smaller-than-bloom-filters> |
| ******************************************************************************/ |
| |
| |
| /* |
| * The push diary is based on the abandoned draft |
| * <https://datatracker.ietf.org/doc/draft-kazuho-h2-cache-digest/> |
| * that describes how to use golomb filters. |
| */ |
| |
| typedef struct h2_push_diary h2_push_diary; |
| |
| typedef void h2_push_digest_calc(h2_push_diary *diary, apr_uint64_t *phash, h2_push *push); |
| |
| struct h2_push_diary { |
| apr_array_header_t *entries; |
| int NMax; /* Maximum for N, should size change be necessary */ |
| int N; /* Current maximum number of entries, power of 2 */ |
| apr_uint64_t mask; /* mask for relevant bits */ |
| unsigned int mask_bits; /* number of relevant bits */ |
| const char *authority; |
| h2_push_digest_type dtype; |
| h2_push_digest_calc *dcalc; |
| }; |
| |
| /** |
| * Determine the list of h2_push'es to send to the client on behalf of |
| * the given request/response pair. |
| * |
| * @param p the pool to use |
| * @param req the requst from the client |
| * @param res the response from the server |
| * @return array of h2_push addresses or NULL |
| */ |
| #if AP_HAS_RESPONSE_BUCKETS |
| apr_array_header_t *h2_push_collect(apr_pool_t *p, |
| const struct h2_request *req, |
| apr_uint32_t push_policy, |
| const ap_bucket_response *res); |
| #else |
| apr_array_header_t *h2_push_collect(apr_pool_t *p, |
| const struct h2_request *req, |
| apr_uint32_t push_policy, |
| const struct h2_headers *res); |
| #endif |
| |
| /** |
| * Create a new push diary for the given maximum number of entries. |
| * |
| * @param p the pool to use |
| * @param N the max number of entries, rounded up to 2^x |
| * @return the created diary, might be NULL of max_entries is 0 |
| */ |
| h2_push_diary *h2_push_diary_create(apr_pool_t *p, int N); |
| |
| /** |
| * Filters the given pushes against the diary and returns only those pushes |
| * that were newly entered in the diary. |
| */ |
| apr_array_header_t *h2_push_diary_update(struct h2_session *session, apr_array_header_t *pushes); |
| |
| /** |
| * Collect pushes for the given request/response pair, enter them into the |
| * diary and return those pushes newly entered. |
| */ |
| #if AP_HAS_RESPONSE_BUCKETS |
| apr_array_header_t *h2_push_collect_update(struct h2_stream *stream, |
| const struct h2_request *req, |
| const ap_bucket_response *res); |
| #else |
| apr_array_header_t *h2_push_collect_update(struct h2_stream *stream, |
| const struct h2_request *req, |
| const struct h2_headers *res); |
| #endif |
| |
| /** |
| * Get a cache digest as described in |
| * https://datatracker.ietf.org/doc/draft-kazuho-h2-cache-digest/ |
| * from the contents of the push diary. |
| * |
| * @param diary the diary to calculdate the digest from |
| * @param p the pool to use |
| * @param authority the authority to get the data for, use NULL/"*" for all |
| * @param pdata on successful return, the binary cache digest |
| * @param plen on successful return, the length of the binary data |
| */ |
| apr_status_t h2_push_diary_digest_get(h2_push_diary *diary, apr_pool_t *p, |
| int maxP, const char *authority, |
| const char **pdata, apr_size_t *plen); |
| |
| #endif /* defined(__mod_h2__h2_push__) */ |