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