/* 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 #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 * * 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: * ******************************************************************************/ /* * The push diary is based on the abandoned draft * * 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__) */