Adding upstream version 2.4.56.upstream/2.4.56

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 158 insertions, 0 deletions

diff --git a/modules/http2/h2_push.h b/modules/http2/h2_push.h
new file mode 100644
index 0000000..947b73b
--- /dev/null
+++ b/modules/http2/h2_push.h
@@ -0,0 +1,158 @@
+/* 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__) */