mod_negotiation.c

Apache HTTP Server 是一个功能强大的灵活的与HTTP/1.1相兼容的web服务器.这里给出的是Apache HTTP服务器的源码。

/* Copyright 1999-2005 The Apache Software Foundation or its licensors, as
 * applicable.
 *
 * Licensed 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.
 */

/*
 * mod_negotiation.c: keeps track of MIME types the client is willing to
 * accept, and contains code to handle type arbitration.
 *
 * rst
 */

#include "apr.h"
#include "apr_strings.h"
#include "apr_file_io.h"
#include "apr_lib.h"

#define APR_WANT_STRFUNC
#include "apr_want.h"

#include "ap_config.h"
#include "httpd.h"
#include "http_config.h"
#include "http_request.h"
#include "http_protocol.h"
#include "http_core.h"
#include "http_log.h"
#include "util_script.h"


#define MAP_FILE_MAGIC_TYPE "application/x-type-map"

/* Commands --- configuring document caching on a per (virtual?)
 * server basis...
 */

typedef struct {
    int forcelangpriority;
    apr_array_header_t *language_priority;
} neg_dir_config;

/* forcelangpriority flags
 */
#define FLP_UNDEF    0    /* Same as FLP_DEFAULT, but base overrides */
#define FLP_NONE     1    /* Return 406, HTTP_NOT_ACCEPTABLE */
#define FLP_PREFER   2    /* Use language_priority rather than MC */
#define FLP_FALLBACK 4    /* Use language_priority rather than NA */

#define FLP_DEFAULT  FLP_PREFER

module AP_MODULE_DECLARE_DATA negotiation_module;

static void *create_neg_dir_config(apr_pool_t *p, char *dummy)
{
    neg_dir_config *new = (neg_dir_config *) apr_palloc(p,
                                                        sizeof(neg_dir_config));

    new->forcelangpriority = FLP_UNDEF;
    new->language_priority = NULL;
    return new;
}

static void *merge_neg_dir_configs(apr_pool_t *p, void *basev, void *addv)
{
    neg_dir_config *base = (neg_dir_config *) basev;
    neg_dir_config *add = (neg_dir_config *) addv;
    neg_dir_config *new = (neg_dir_config *) apr_palloc(p,
                                                        sizeof(neg_dir_config));

    /* give priority to the config in the subdirectory */
    new->forcelangpriority = (add->forcelangpriority != FLP_UNDEF)
                                ? add->forcelangpriority
                                : base->forcelangpriority;
    new->language_priority = add->language_priority
                                ? add->language_priority
                                : base->language_priority;
    return new;
}

static const char *set_language_priority(cmd_parms *cmd, void *n_,
                                         const char *lang)
{
    neg_dir_config *n = n_;
    const char **langp;

    if (!n->language_priority)
        n->language_priority = apr_array_make(cmd->pool, 4, sizeof(char *));

    langp = (const char **) apr_array_push(n->language_priority);
    *langp = lang;
    return NULL;
}

static const char *set_force_priority(cmd_parms *cmd, void *n_, const char *w)
{
    neg_dir_config *n = n_;

    if (!strcasecmp(w, "None")) {
        if (n->forcelangpriority & ~FLP_NONE) {
            return "Cannot combine ForceLanguagePriority options with None";
        }
        n->forcelangpriority = FLP_NONE;
    }
    else if (!strcasecmp(w, "Prefer")) {
        if (n->forcelangpriority & FLP_NONE) {
            return "Cannot combine ForceLanguagePriority options None and "
                   "Prefer";
        }
        n->forcelangpriority |= FLP_PREFER;
    }
    else if (!strcasecmp(w, "Fallback")) {
        if (n->forcelangpriority & FLP_NONE) {
            return "Cannot combine ForceLanguagePriority options None and "
                   "Fallback";
        }
        n->forcelangpriority |= FLP_FALLBACK;
    }
    else {
        return apr_pstrcat(cmd->pool, "Invalid ForceLanguagePriority option ",
                           w, NULL);
    }

    return NULL;
}

static const char *cache_negotiated_docs(cmd_parms *cmd, void *dummy,
                                         int arg)
{
    ap_set_module_config(cmd->server->module_config, &negotiation_module,
                         (arg ? "Cache" : NULL));
    return NULL;
}

static int do_cache_negotiated_docs(server_rec *s)
{
    return (ap_get_module_config(s->module_config,
                                 &negotiation_module) != NULL);
}

static const command_rec negotiation_cmds[] =
{
    AP_INIT_FLAG("CacheNegotiatedDocs", cache_negotiated_docs, NULL, RSRC_CONF,
                 "Either 'on' or 'off' (default)"),
    AP_INIT_ITERATE("LanguagePriority", set_language_priority, NULL,
                    OR_FILEINFO,
                    "space-delimited list of MIME language abbreviations"),
    AP_INIT_ITERATE("ForceLanguagePriority", set_force_priority, NULL,
                    OR_FILEINFO,
                    "Force LanguagePriority elections, either None, or "
                    "Fallback and/or Prefer"),
    {NULL}
};

/*
 * Record of available info on a media type specified by the client
 * (we also use 'em for encodings and languages)
 */

typedef struct accept_rec {
    char *name;                 /* MUST be lowercase */
    float quality;
    float level;
    char *charset;              /* for content-type only */
} accept_rec;

/*
 * Record of available info on a particular variant
 *
 * Note that a few of these fields are updated by the actual negotiation
 * code.  These are:
 *
 * level_matched --- initialized to zero.  Set to the value of level
 *             if the client actually accepts this media type at that
 *             level (and *not* if it got in on a wildcard).  See level_cmp
 *             below.
 * mime_stars -- initialized to zero.  Set to the number of stars
 *               present in the best matching Accept header element.
 *               1 for star/star, 2 for type/star and 3 for
 *               type/subtype.
 *
 * definite -- initialized to 1.  Set to 0 if there is a match which
 *             makes the variant non-definite according to the rules
 *             in rfc2296.
 */

typedef struct var_rec {
    request_rec *sub_req;       /* May be NULL (is, for map files) */
    const char *mime_type;      /* MUST be lowercase */
    const char *file_name;      /* Set to 'this' (for map file body content) */
    apr_off_t body;             /* Only for map file body content */
    const char *content_encoding;
    apr_array_header_t *content_languages; /* list of lang. for this variant */
    const char *content_charset;
    const char *description;

    /* The next five items give the quality values for the dimensions
     * of negotiation for this variant. They are obtained from the
     * appropriate header lines, except for source_quality, which
     * is obtained from the variant itself (the 'qs' parameter value
     * from the variant's mime-type). Apart from source_quality,
     * these values are set when we find the quality for each variant
     * (see best_match()). source_quality is set from the 'qs' parameter
     * of the variant description or mime type: see set_mime_fields().
     */
    float lang_quality;         /* quality of this variant's language */
    float encoding_quality;     /* ditto encoding */
    float charset_quality;      /* ditto charset */
    float mime_type_quality;    /* ditto media type */
    float source_quality;       /* source quality for this variant */

    /* Now some special values */
    float level;                /* Auxiliary to content-type... */
    apr_off_t bytes;            /* content length, if known */
    int lang_index;             /* Index into LanguagePriority list */
    int is_pseudo_html;         /* text/html, *or* the INCLUDES_MAGIC_TYPEs */

    /* Above are all written-once properties of the variant.  The
     * three fields below are changed during negotiation:
     */

    float level_matched;
    int mime_stars;
    int definite;
} var_rec;

/* Something to carry around the state of negotiation (and to keep
 * all of this thread-safe)...
 */

typedef struct {
    apr_pool_t *pool;
    request_rec *r;
    neg_dir_config *conf;
    char *dir_name;
    int accept_q;               /* 1 if an Accept item has a q= param */
    float default_lang_quality; /* fiddle lang q for variants with no lang */

    /* the array pointers below are NULL if the corresponding accept
     * headers are not present
     */
    apr_array_header_t *accepts;            /* accept_recs */
    apr_array_header_t *accept_encodings;   /* accept_recs */
    apr_array_header_t *accept_charsets;    /* accept_recs */
    apr_array_header_t *accept_langs;       /* accept_recs */

    apr_array_header_t *avail_vars;         /* available variants */

    int count_multiviews_variants;    /* number of variants found on disk */

    int is_transparent;       /* 1 if this resource is trans. negotiable */

    int dont_fiddle_headers;  /* 1 if we may not fiddle with accept hdrs */
    int ua_supports_trans;    /* 1 if ua supports trans negotiation */
    int send_alternates;      /* 1 if we want to send an Alternates header */
    int may_choose;           /* 1 if we may choose a variant for the client */
    int use_rvsa;             /* 1 if we must use RVSA/1.0 negotiation algo */
} negotiation_state;

/* A few functions to manipulate var_recs.
 * Cleaning out the fields...
 */

static void clean_var_rec(var_rec *mime_info)
{
    mime_info->sub_req = NULL;
    mime_info->mime_type = "";
    mime_info->file_name = "";
    mime_info->body = 0;
    mime_info->content_encoding = NULL;
    mime_info->content_languages = NULL;
    mime_info->content_charset = "";
    mime_info->description = "";

    mime_info->is_pseudo_html = 0;
    mime_info->level = 0.0f;
    mime_info->level_matched = 0.0f;
    mime_info->bytes = -1;
    mime_info->lang_index = -1;
    mime_info->mime_stars = 0;
    mime_info->definite = 1;

    mime_info->charset_quality = 1.0f;
    mime_info->encoding_quality = 1.0f;
    mime_info->lang_quality = 1.0f;
    mime_info->mime_type_quality = 1.0f;
    mime_info->source_quality = 0.0f;
}

/* Initializing the relevant fields of a variant record from the
 * accept_info read out of its content-type, one way or another.
 */

static void set_mime_fields(var_rec *var, accept_rec *mime_info)
{
    var->mime_type = mime_info->name;
    var->source_quality = mime_info->quality;
    var->level = mime_info->level;
    var->content_charset = mime_info->charset;

    var->is_pseudo_html = (!strcmp(var->mime_type, "text/html")
                           || !strcmp(var->mime_type, INCLUDES_MAGIC_TYPE)
                           || !strcmp(var->mime_type, INCLUDES_MAGIC_TYPE3));
}

/* Create a variant list validator in r using info from vlistr. */

static void set_vlist_validator(request_rec *r, request_rec *vlistr)
{
    /* Calculating the variant list validator is similar to
     * calculating an etag for the source of the variant list
     * information, so we use ap_make_etag().  Note that this
     * validator can be 'weak' in extreme case.
     */
    ap_update_mtime(vlistr, vlistr->finfo.mtime);
    r->vlist_validator = ap_make_etag(vlistr, 0);

    /* ap_set_etag will later take r->vlist_validator into account
     * when creating the etag header
     */
}


/*****************************************************************
 *
 * Parsing (lists of) media types and their parameters, as seen in
 * HTTPD header lines and elsewhere.
 */

/*
 * Get a single mime type entry --- one media type and parameters;
 * enter the values we recognize into the argument accept_rec
 */

static const char *get_entry(apr_pool_t *p, accept_rec *result,
                             const char *accept_line)
{
    result->quality = 1.0f;
    result->level = 0.0f;
    result->charset = "";

    /*
     * Note that this handles what I gather is the "old format",
     *
     *    Accept: text/html text/plain moo/zot
     *
     * without any compatibility kludges --- if the token after the
     * MIME type begins with a semicolon, we know we're looking at parms,
     * otherwise, we know we aren't.  (So why all the pissing and moaning
     * in the CERN server code?  I must be missing something).
     */

    result->name = ap_get_token(p, &accept_line, 0);
    ap_str_tolower(result->name);     /* You want case insensitive,
                                       * you'll *get* case insensitive.
                                       */

    /* KLUDGE!!! Default HTML to level 2.0 unless the browser
     * *explicitly* says something else.
     */

    if (!strcmp(result->name, "text/html") && (result->level == 0.0)) {
        result->level = 2.0f;
    }
    else if (!strcmp(result->name, INCLUDES_MAGIC_TYPE)) {
        result->level = 2.0f;
    }
    else if (!strcmp(result->name, INCLUDES_MAGIC_TYPE3)) {
        result->level = 3.0f;
    }

    while (*accept_line == ';') {
        /* Parameters ... */

        char *parm;
        char *cp;
        char *end;

        ++accept_line;
        parm = ap_get_token(p, &accept_line, 1);