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/* 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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* http://www.apache.org/licenses/LICENSE-2.0
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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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#include "apr_strings.h"
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#include "apr_thread_proc.h" /* for RLIMIT stuff */
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#define APR_WANT_STRFUNC
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#include "http_config.h"
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#include "http_connection.h"
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#include "http_core.h"
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#include "http_protocol.h" /* For index_of_response(). Grump. */
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#include "http_request.h"
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/* Generate the human-readable hex representation of an unsigned long
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* (basically a faster version of 'sprintf("%lx")')
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#define HEX_DIGITS "0123456789abcdef"
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static char *etag_ulong_to_hex(char *next, unsigned long u)
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int shift = sizeof(unsigned long) * 8 - 4;
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unsigned long next_digit = ((u >> shift) & (unsigned long)0xf);
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*next++ = HEX_DIGITS[next_digit];
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*next++ = HEX_DIGITS[next_digit];
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*next++ = HEX_DIGITS[u & (unsigned long)0xf];
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#define ETAG_WEAK "W/"
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#define CHARS_PER_UNSIGNED_LONG (sizeof(unsigned long) * 2)
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* Construct an entity tag (ETag) from resource information. If it's a real
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* file, build in some of the file characteristics. If the modification time
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* is newer than (request-time minus 1 second), mark the ETag as weak - it
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* could be modified again in as short an interval. We rationalize the
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* modification time we're given to keep it from being in the future.
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AP_DECLARE(char *) ap_make_etag(request_rec *r, int force_weak)
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etag_components_t etag_bits;
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etag_components_t bits_added;
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cfg = (core_dir_config *)ap_get_module_config(r->per_dir_config,
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etag_bits = (cfg->etag_bits & (~ cfg->etag_remove)) | cfg->etag_add;
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* If it's a file (or we wouldn't be here) and no ETags
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* should be set for files, return an empty string and
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* note it for the header-sender to ignore.
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if (etag_bits & ETAG_NONE) {
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apr_table_setn(r->notes, "no-etag", "omit");
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if (etag_bits == ETAG_UNSET) {
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etag_bits = ETAG_BACKWARD;
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* Make an ETag header out of various pieces of information. We use
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* the last-modified date and, if we have a real file, the
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* length and inode number - note that this doesn't have to match
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* the content-length (i.e. includes), it just has to be unique
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* If the request was made within a second of the last-modified date,
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* we send a weak tag instead of a strong one, since it could
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* be modified again later in the second, and the validation
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* would be incorrect.
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if ((r->request_time - r->mtime > (1 * APR_USEC_PER_SEC)) &&
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weak_len = sizeof(ETAG_WEAK);
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if (r->finfo.filetype != 0) {
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* ETag gets set to [W/]"inode-size-mtime", modulo any
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etag = apr_palloc(r->pool, weak_len + sizeof("\"--\"") +
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3 * CHARS_PER_UNSIGNED_LONG + 1);
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if (etag_bits & ETAG_INODE) {
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next = etag_ulong_to_hex(next, (unsigned long)r->finfo.inode);
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bits_added |= ETAG_INODE;
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if (etag_bits & ETAG_SIZE) {
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if (bits_added != 0) {
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next = etag_ulong_to_hex(next, (unsigned long)r->finfo.size);
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bits_added |= ETAG_SIZE;
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if (etag_bits & ETAG_MTIME) {
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if (bits_added != 0) {
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next = etag_ulong_to_hex(next, (unsigned long)r->mtime);
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* Not a file document, so just use the mtime: [W/]"mtime"
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etag = apr_palloc(r->pool, weak_len + sizeof("\"\"") +
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CHARS_PER_UNSIGNED_LONG + 1);
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next = etag_ulong_to_hex(next, (unsigned long)r->mtime);
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AP_DECLARE(void) ap_set_etag(request_rec *r)
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char *variant_etag, *vlv;
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if (!r->vlist_validator) {
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etag = ap_make_etag(r, 0);
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/* If we get a blank etag back, don't set the header. */
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/* If we have a variant list validator (vlv) due to the
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* response being negotiated, then we create a structured
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* entity tag which merges the variant etag with the variant
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* list validator (vlv). This merging makes revalidation
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* somewhat safer, ensures that caches which can deal with
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* Vary will (eventually) be updated if the set of variants is
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* changed, and is also a protocol requirement for transparent
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* content negotiation.
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/* if the variant list validator is weak, we make the whole
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* structured etag weak. If we would not, then clients could
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* have problems merging range responses if we have different
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* variants with the same non-globally-unique strong etag.
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vlv = r->vlist_validator;
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vlv_weak = (vlv[0] == 'W');
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variant_etag = ap_make_etag(r, vlv_weak);
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/* If we get a blank etag back, don't append vlv and stop now. */
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if (!variant_etag[0]) {
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/* merge variant_etag and vlv into a structured etag */
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variant_etag[strlen(variant_etag) - 1] = '\0';
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etag = apr_pstrcat(r->pool, variant_etag, ";", vlv, NULL);
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apr_table_setn(r->headers_out, "ETag", etag);