text: /* 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_PROXY_H
  #define MOD_PROXY_H 
  
  /**
   * @file  mod_proxy.h
   * @brief Proxy Extension Module for Apache
   *
   * @defgroup MOD_PROXY mod_proxy
   * @ingroup  APACHE_MODS
   * @{
   */
  
  /*
  
     Also note numerous FIXMEs and CHECKMEs which should be eliminated.
  
     This code is once again experimental!
  
     Things to do:
  
     1. Make it completely work (for FTP too)
  
     2. HTTP/1.1
  
     Chuck Murcko <chuck@topsail.org> 02-06-01
  
   */
  
  #define CORE_PRIVATE
  
  #include "apr_hooks.h"
  #include "apr.h"
  #include "apr_lib.h"
  #include "apr_strings.h"
  #include "apr_buckets.h"
  #include "apr_md5.h"
  #include "apr_network_io.h"
  #include "apr_pools.h"
  #include "apr_strings.h"
  #include "apr_uri.h"
  #include "apr_date.h"
  #include "apr_strmatch.h"
  #include "apr_fnmatch.h"
  #include "apr_reslist.h"
  #define APR_WANT_STRFUNC
  #include "apr_want.h"
  
  #include "httpd.h"
  #include "http_config.h"
  #include "ap_config.h"
  #include "http_core.h"
  #include "http_protocol.h"
  #include "http_request.h"
  #include "http_vhost.h"
  #include "http_main.h"
  #include "http_log.h"
  #include "http_connection.h"
  #include "util_filter.h"
  #include "util_ebcdic.h"
  #include "ap_provider.h"
  
  #if APR_HAVE_NETINET_IN_H
  #include <netinet/in.h>
  #endif
  #if APR_HAVE_ARPA_INET_H
  #include <arpa/inet.h>
  #endif
  
  /* for proxy_canonenc() */
  enum enctype {
      enc_path, enc_search, enc_user, enc_fpath, enc_parm
  };
  
  #if APR_CHARSET_EBCDIC
  #define CRLF   "\r\n"
  #else /*APR_CHARSET_EBCDIC*/
  #define CRLF   "\015\012"
  #endif /*APR_CHARSET_EBCDIC*/
  
  /* default Max-Forwards header setting */
  /* Set this to -1, which complies with RFC2616 by not setting
   * max-forwards if the client didn't send it to us.
   */
  #define DEFAULT_MAX_FORWARDS    -1
  
  /* static information about a remote proxy */
  struct proxy_remote {
      const char *scheme;     /* the schemes handled by this proxy, or '*' */
      const char *protocol;   /* the scheme used to talk to this proxy */
      const char *hostname;   /* the hostname of this proxy */
      apr_port_t  port;       /* the port for this proxy */
      ap_regex_t *regexp;        /* compiled regex (if any) for the remote */
      int use_regex;          /* simple boolean. True if we have a regex pattern */
  };
  
  #define PROXYPASS_NOCANON 0x01
  #define PROXYPASS_INTERPOLATE 0x02
  struct proxy_alias {
      const char  *real;
      const char  *fake;
      ap_regex_t  *regex;
      unsigned int flags;
  };
  
  struct dirconn_entry {
      char *name;
      struct in_addr addr, mask;
      struct apr_sockaddr_t *hostaddr;
      int (*matcher) (struct dirconn_entry * This, request_rec *r);
  };
  
  struct noproxy_entry {
      const char *name;
      struct apr_sockaddr_t *addr;
  };
  
  typedef struct proxy_balancer  proxy_balancer;
  typedef struct proxy_worker    proxy_worker;
  typedef struct proxy_conn_pool proxy_conn_pool;
  typedef struct proxy_balancer_method proxy_balancer_method;
  
  typedef struct {
      apr_array_header_t *proxies;
      apr_array_header_t *sec_proxy;
      apr_array_header_t *aliases;
      apr_array_header_t *noproxies;
      apr_array_header_t *dirconn;
      apr_array_header_t *allowed_connect_ports;
      apr_array_header_t *workers;
      apr_array_header_t *balancers;
      proxy_worker       *forward;    /* forward proxy worker */
      proxy_worker       *reverse;    /* reverse "module-driven" proxy worker */
      const char *domain;     /* domain name to use in absence of a domain name in the request */
      int req;                /* true if proxy requests are enabled */
      char req_set;
      enum {
        via_off,
        via_on,
        via_block,
        via_full
      } viaopt;                   /* how to deal with proxy Via: headers */
      char viaopt_set;
      apr_size_t recv_buffer_size;
      char recv_buffer_size_set;
      apr_size_t io_buffer_size;
      char io_buffer_size_set;
      long maxfwd;
      char maxfwd_set;
      /** 
       * the following setting masks the error page
       * returned from the 'proxied server' and just 
       * forwards the status code upwards.
       * This allows the main server (us) to generate
       * the error page, (so it will look like a error
       * returned from the rest of the system 
       */
      int error_override;
      int error_override_set;
      int preserve_host;
      int preserve_host_set;
      apr_interval_time_t timeout;
      char timeout_set;
      enum {
        bad_error,
        bad_ignore,
        bad_body
      } badopt;                   /* how to deal with bad headers */
      char badopt_set;
  /* putting new stuff on the end maximises binary back-compatibility.
   * the strmatch_patterns are really a const just to have a
   * case-independent strstr.
   */
      enum {
          status_off,
          status_on,
          status_full
      } proxy_status;             /* Status display options */
      char proxy_status_set;
      apr_pool_t *pool;           /* Pool used for allocating this struct */
  } proxy_server_conf;
  
  
  typedef struct {
      const char *p;            /* The path */
      int         p_is_fnmatch; /* Is this path an fnmatch candidate? */
      ap_regex_t  *r;            /* Is this a regex? */
  
  /* ProxyPassReverse and friends are documented as working inside
   * <Location>.  But in fact they never have done in the case of
   * more than one <Location>, because the server_conf can't see it.
   * We need to move them to the per-dir config.
   * Discussed in February:
   * http://marc.theaimsgroup.com/?l=apache-httpd-dev&m=110726027118798&w=2
   */
      apr_array_header_t *raliases;
      apr_array_header_t* cookie_paths;
      apr_array_header_t* cookie_domains;
      const apr_strmatch_pattern* cookie_path_str;
      const apr_strmatch_pattern* cookie_domain_str;
      const char *ftp_directory_charset;
      int interpolate_env;
  } proxy_dir_conf;
  
  /* if we interpolate env vars per-request, we'll need a per-request
   * copy of the reverse proxy config
   */
  typedef struct {
      apr_array_header_t *raliases;
      apr_array_header_t* cookie_paths;
      apr_array_header_t* cookie_domains;
  } proxy_req_conf;
  
  typedef struct {
      conn_rec     *connection;
      const char   *hostname;
      apr_port_t   port;
      int          is_ssl;
      apr_pool_t   *pool;     /* Subpool for hostname and addr data */
      apr_socket_t *sock;     /* Connection socket */
      apr_sockaddr_t *addr;   /* Preparsed remote address info */
      apr_uint32_t flags;     /* Conection flags */
      int          close;     /* Close 'this' connection */
      int          close_on_recycle; /* Close the connection when returning to pool */
      proxy_worker *worker;   /* Connection pool this connection belongs to */
      void         *data;     /* per scheme connection data */
  #if APR_HAS_THREADS
      int          inreslist; /* connection in apr_reslist? */
  #endif
      apr_pool_t   *scpool;   /* Subpool used for socket and connection data */
      request_rec  *r;        /* Request record of the frontend request
                               * which the backend currently answers. */
      int          need_flush;/* Flag to decide whether we need to flush the
                               * filter chain or not */
      void         *forward;  /* opaque forward proxy data */
  } proxy_conn_rec;
  
  typedef struct {
          float cache_completion; /* completion percentage */
          int content_length; /* length of the content */
  } proxy_completion;
  
  /* Connection pool */
  struct proxy_conn_pool {
      apr_pool_t     *pool;   /* The pool used in constructor and destructor calls */
      apr_sockaddr_t *addr;   /* Preparsed remote address info */
  #if APR_HAS_THREADS
      apr_reslist_t  *res;    /* Connection resource list */
  #endif
      proxy_conn_rec *conn;   /* Single connection for prefork mpm's */
  };
  
  /* worker status flags */
  #define PROXY_WORKER_INITIALIZED    0x0001
  #define PROXY_WORKER_IGNORE_ERRORS  0x0002
  #define PROXY_WORKER_IN_SHUTDOWN    0x0010
  #define PROXY_WORKER_DISABLED       0x0020
  #define PROXY_WORKER_STOPPED        0x0040
  #define PROXY_WORKER_IN_ERROR       0x0080
  #define PROXY_WORKER_HOT_STANDBY    0x0100
  
  #define PROXY_WORKER_NOT_USABLE_BITMAP ( PROXY_WORKER_IN_SHUTDOWN | \
  PROXY_WORKER_DISABLED | PROXY_WORKER_STOPPED | PROXY_WORKER_IN_ERROR )
  
  /* NOTE: these check the shared status */
  #define PROXY_WORKER_IS_INITIALIZED(f)   ( (f)->s && \
    ( (f)->s->status &  PROXY_WORKER_INITIALIZED ) )
  
  #define PROXY_WORKER_IS_STANDBY(f)   ( (f)->s && \
    ( (f)->s->status &  PROXY_WORKER_HOT_STANDBY ) )
  
  #define PROXY_WORKER_IS_USABLE(f)   ( (f)->s && \
    ( !( (f)->s->status & PROXY_WORKER_NOT_USABLE_BITMAP) ) && \
    PROXY_WORKER_IS_INITIALIZED(f) )
  
  /* default worker retry timeout in seconds */
  #define PROXY_WORKER_DEFAULT_RETRY  60
  #define PROXY_WORKER_MAX_ROUTE_SIZ  63
  
  /* Runtime worker status informations. Shared in scoreboard */
  typedef struct {
      int             status;
      apr_time_t      error_time; /* time of the last error */
      int             retries;    /* number of retries on this worker */
      int             lbstatus;   /* Current lbstatus */
      int             lbfactor;   /* dynamic lbfactor */
      apr_off_t       transferred;/* Number of bytes transferred to remote */
      apr_off_t       read;       /* Number of bytes read from remote */
      apr_size_t      elected;    /* Number of times the worker was elected */
      char            route[PROXY_WORKER_MAX_ROUTE_SIZ+1];
      char            redirect[PROXY_WORKER_MAX_ROUTE_SIZ+1];
      void            *context;   /* general purpose storage */
      apr_size_t      busy;       /* busyness factor */
      int             lbset;      /* load balancer cluster set */
  } proxy_worker_stat;
  
  /* Worker configuration */
  struct proxy_worker {
      int             id;         /* scoreboard id */
      apr_interval_time_t retry;  /* retry interval */
      int             lbfactor;   /* initial load balancing factor */
      const char      *name;
      const char      *scheme;    /* scheme to use ajp|http|https */
      const char      *hostname;  /* remote backend address */
      const char      *route;     /* balancing route */
      const char      *redirect;  /* temporary balancing redirection route */
      int             status;     /* temporary worker status */
      apr_port_t      port;
      int             min;        /* Desired minimum number of available connections */
      int             smax;       /* Soft maximum on the total number of connections */
      int             hmax;       /* Hard maximum on the total number of connections */
      apr_interval_time_t ttl;    /* maximum amount of time in seconds a connection
                                   * may be available while exceeding the soft limit */
      apr_interval_time_t timeout; /* connection timeout */
      char            timeout_set;
      apr_interval_time_t acquire; /* acquire timeout when the maximum number of connections is exceeded */
      char            acquire_set;
      apr_size_t      recv_buffer_size;
      char            recv_buffer_size_set;
      apr_size_t      io_buffer_size;
      char            io_buffer_size_set;
      char            keepalive;
      char            keepalive_set;
      proxy_conn_pool     *cp;        /* Connection pool to use */
      proxy_worker_stat   *s;         /* Shared data */
      void            *opaque;    /* per scheme worker data */
      int             is_address_reusable;
  #if APR_HAS_THREADS
      apr_thread_mutex_t  *mutex;  /* Thread lock for updating address cache */
  #endif
      void            *context;   /* general purpose storage */
      enum {
           flush_off,
           flush_on,
           flush_auto
      } flush_packets;           /* control AJP flushing */
      int             flush_wait;  /* poll wait time in microseconds if flush_auto */
      int             lbset;      /* load balancer cluster set */
      apr_interval_time_t ping_timeout;
      char ping_timeout_set;
      char            retry_set;
      char            disablereuse;
      char            disablereuse_set;
      apr_interval_time_t conn_timeout;
      char            conn_timeout_set;
  };
  
  /*
   * Wait 10000 microseconds to find out if more data is currently
   * available at the backend. Just an arbitrary choose.
   */
  #define PROXY_FLUSH_WAIT 10000
  
  struct proxy_balancer {
      apr_array_header_t *workers; /* array of proxy_workers */
      const char *name;            /* name of the load balancer */
      const char *sticky;          /* sticky session identifier */
      int         sticky_force;    /* Disable failover for sticky sessions */
      apr_interval_time_t timeout; /* Timeout for waiting on free connection */
      int                 max_attempts; /* Number of attempts before failing */
      char                max_attempts_set;
      proxy_balancer_method *lbmethod;
  
      /* XXX: Perhaps we will need the proc mutex too.
       * Altrough we are only using arithmetic operations
       * it may lead to a incorrect calculations.
       * For now use only the thread mutex.
       */
  #if APR_HAS_THREADS
      apr_thread_mutex_t  *mutex;  /* Thread lock for updating lb params */
  #endif
      void            *context;   /* general purpose storage */
      int             scolonsep;  /* true if ';' seps sticky session paths */
  };
  
  struct proxy_balancer_method {
      const char *name;            /* name of the load balancer method*/
      proxy_worker *(*finder)(proxy_balancer *balancer,
                              request_rec *r);
      void            *context;   /* general purpose storage */
  };
  
  #if APR_HAS_THREADS
  #define PROXY_THREAD_LOCK(x)      apr_thread_mutex_lock((x)->mutex)
  #define PROXY_THREAD_UNLOCK(x)    apr_thread_mutex_unlock((x)->mutex)
  #else
  #define PROXY_THREAD_LOCK(x)      APR_SUCCESS
  #define PROXY_THREAD_UNLOCK(x)    APR_SUCCESS
  #endif
  
  /* hooks */
  
  /* Create a set of PROXY_DECLARE(type), PROXY_DECLARE_NONSTD(type) and 
   * PROXY_DECLARE_DATA with appropriate export and import tags for the platform
   */
  #if !defined(WIN32)
  #define PROXY_DECLARE(type)            type
  #define PROXY_DECLARE_NONSTD(type)     type
  #define PROXY_DECLARE_DATA
  #elif defined(PROXY_DECLARE_STATIC)
  #define PROXY_DECLARE(type)            type __stdcall
  #define PROXY_DECLARE_NONSTD(type)     type
  #define PROXY_DECLARE_DATA
  #elif defined(PROXY_DECLARE_EXPORT)
  #define PROXY_DECLARE(type)            __declspec(dllexport) type __stdcall
  #define PROXY_DECLARE_NONSTD(type)     __declspec(dllexport) type
  #define PROXY_DECLARE_DATA             __declspec(dllexport)
  #else
  #define PROXY_DECLARE(type)            __declspec(dllimport) type __stdcall
  #define PROXY_DECLARE_NONSTD(type)     __declspec(dllimport) type
  #define PROXY_DECLARE_DATA             __declspec(dllimport)
  #endif
  
  /**
   * Hook an optional proxy hook.  Unlike static hooks, this uses a macro
   * instead of a function.
   */
  #define PROXY_OPTIONAL_HOOK(name,fn,pre,succ,order) \
          APR_OPTIONAL_HOOK(proxy,name,fn,pre,succ,order)
  
  APR_DECLARE_EXTERNAL_HOOK(proxy, PROXY, int, scheme_handler, (request_rec *r, 
                            proxy_worker *worker, proxy_server_conf *conf, char *url, 
                            const char *proxyhost, apr_port_t proxyport))
  APR_DECLARE_EXTERNAL_HOOK(proxy, PROXY, int, canon_handler, (request_rec *r, 
                            char *url))
  
  APR_DECLARE_EXTERNAL_HOOK(proxy, PROXY, int, create_req, (request_rec *r, request_rec *pr))
  APR_DECLARE_EXTERNAL_HOOK(proxy, PROXY, int, fixups, (request_rec *r)) 
  
  /**
   * pre request hook.
   * It will return the most suitable worker at the moment
   * and coresponding balancer.
   * The url is rewritten from balancer://cluster/uri to scheme://host:port/uri
   * and then the scheme_handler is called.
   *
   */
  APR_DECLARE_EXTERNAL_HOOK(proxy, PROXY, int, pre_request, (proxy_worker **worker,
                            proxy_balancer **balancer,
                            request_rec *r,
                            proxy_server_conf *conf, char **url))                          
  /**
   * post request hook.
   * It is called after request for updating runtime balancer status.
   */
  APR_DECLARE_EXTERNAL_HOOK(proxy, PROXY, int, post_request, (proxy_worker *worker,
                            proxy_balancer *balancer, request_rec *r,
                            proxy_server_conf *conf))
  
  /**
   * request status hook
   * It is called after all proxy processing has been done.  This gives other
   * modules a chance to create default content on failure, for example
   */
  APR_DECLARE_EXTERNAL_HOOK(proxy, PROXY, int, request_status,
                            (int *status, request_rec *r))
  
  /* proxy_util.c */
  
  PROXY_DECLARE(request_rec *)ap_proxy_make_fake_req(conn_rec *c, request_rec *r);
  PROXY_DECLARE(int) ap_proxy_hex2c(const char *x);
  PROXY_DECLARE(void) ap_proxy_c2hex(int ch, char *x);
  PROXY_DECLARE(char *)ap_proxy_canonenc(apr_pool_t *p, const char *x, int len, enum enctype t,
                                         int forcedec, int proxyreq);
  PROXY_DECLARE(char *)ap_proxy_canon_netloc(apr_pool_t *p, char **const urlp, char **userp,
                                             char **passwordp, char **hostp, apr_port_t *port);
  PROXY_DECLARE(const char *)ap_proxy_date_canon(apr_pool_t *p, const char *x);
  PROXY_DECLARE(int) ap_proxy_liststr(const char *list, const char *val);
  PROXY_DECLARE(char *)ap_proxy_removestr(apr_pool_t *pool, const char *list, const char *val);
  PROXY_DECLARE(int) ap_proxy_hex2sec(const char *x);
  PROXY_DECLARE(void) ap_proxy_sec2hex(int t, char *y);
  PROXY_DECLARE(int) ap_proxyerror(request_rec *r, int statuscode, const char *message);
  PROXY_DECLARE(int) ap_proxy_is_ipaddr(struct dirconn_entry *This, apr_pool_t *p);
  PROXY_DECLARE(int) ap_proxy_is_domainname(struct dirconn_entry *This, apr_pool_t *p);
  PROXY_DECLARE(int) ap_proxy_is_hostname(struct dirconn_entry *This, apr_pool_t *p);
  PROXY_DECLARE(int) ap_proxy_is_word(struct dirconn_entry *This, apr_pool_t *p);
  PROXY_DECLARE(int) ap_proxy_checkproxyblock(request_rec *r, proxy_server_conf *conf, apr_sockaddr_t *uri_addr);
  PROXY_DECLARE(int) ap_proxy_pre_http_request(conn_rec *c, request_rec *r);
  PROXY_DECLARE(apr_status_t) ap_proxy_string_read(conn_rec *c, apr_bucket_brigade *bb, char *buff, size_t bufflen, int *eos);
  PROXY_DECLARE(void) ap_proxy_table_unmerge(apr_pool_t *p, apr_table_t *t, char *key);
  /* DEPRECATED (will be replaced with ap_proxy_connect_backend */
  PROXY_DECLARE(int) ap_proxy_connect_to_backend(apr_socket_t **, const char *, apr_sockaddr_t *, const char *, proxy_server_conf *, server_rec *, apr_pool_t *);
  PROXY_DECLARE(apr_status_t) ap_proxy_ssl_connection_cleanup(proxy_conn_rec *conn,
                                                              request_rec *r);
  PROXY_DECLARE(int) ap_proxy_ssl_enable(conn_rec *c);
  PROXY_DECLARE(int) ap_proxy_ssl_disable(conn_rec *c);
  PROXY_DECLARE(int) ap_proxy_conn_is_https(conn_rec *c);
  PROXY_DECLARE(const char *) ap_proxy_ssl_val(apr_pool_t *p, server_rec *s, conn_rec *c, request_rec *r, const char *var);
  
  /* Header mapping functions, and a typedef of their signature */
  PROXY_DECLARE(const char *) ap_proxy_location_reverse_map(request_rec *r, proxy_dir_conf *conf, const char *url);
  PROXY_DECLARE(const char *) ap_proxy_cookie_reverse_map(request_rec *r, proxy_dir_conf *conf, const char *str);
  
  #if !defined(WIN32)
  typedef const char *(*ap_proxy_header_reverse_map_fn)(request_rec *,
                         proxy_dir_conf *, const char *);
  #elif defined(PROXY_DECLARE_STATIC)
  typedef const char *(__stdcall *ap_proxy_header_reverse_map_fn)(request_rec *,
                                   proxy_dir_conf *, const char *);
  #elif defined(PROXY_DECLARE_EXPORT)
  typedef __declspec(dllexport) const char *
    (__stdcall *ap_proxy_header_reverse_map_fn)(request_rec *,
                 proxy_dir_conf *, const char *);
  #else
  typedef __declspec(dllimport) const char *
    (__stdcall *ap_proxy_header_reverse_map_fn)(request_rec *,
                 proxy_dir_conf *, const char *);
  #endif
  
  
  /* Connection pool API */
  /**
   * Get the worker from proxy configuration
   * @param p     memory pool used for finding worker
   * @param conf  current proxy server configuration
   * @param url   url to find the worker from
   * @return      proxy_worker or NULL if not found
   */
  PROXY_DECLARE(proxy_worker *) ap_proxy_get_worker(apr_pool_t *p,
                                                    proxy_server_conf *conf,
                                                    const char *url);
  /**
   * Add the worker to proxy configuration
   * @param worker the new worker
   * @param p      memory pool to allocate worker from 
   * @param conf   current proxy server configuration
   * @param url    url containing worker name
   * @return       error message or NULL if successfull
   */
  PROXY_DECLARE(const char *) ap_proxy_add_worker(proxy_worker **worker,
                                                  apr_pool_t *p,
                                                  proxy_server_conf *conf,
                                                  const char *url);
  
  /**
   * Create new worker
   * @param p      memory pool to allocate worker from 
   * @return       new worker
   */
  PROXY_DECLARE(proxy_worker *) ap_proxy_create_worker(apr_pool_t *p);
  
  /**
   * Initize the worker's shared data
   * @param conf   current proxy server configuration
   * @param worker worker to initialize
   * @param s      current server record
   * @param worker worker to initialize
   */
  PROXY_DECLARE(void) ap_proxy_initialize_worker_share(proxy_server_conf *conf,
                                                       proxy_worker *worker,
                                                       server_rec *s);
  
  
  /**
   * Initize the worker
   * @param worker worker to initialize
   * @param s      current server record
   * @return       APR_SUCCESS or error code
   */
  PROXY_DECLARE(apr_status_t) ap_proxy_initialize_worker(proxy_worker *worker,
                                                         server_rec *s);
  /**
   * Get the balancer from proxy configuration
   * @param p     memory pool used for finding balancer
   * @param conf  current proxy server configuration
   * @param url   url to find the worker from. Has to have balancer:// prefix
   * @return      proxy_balancer or NULL if not found
   */
  PROXY_DECLARE(proxy_balancer *) ap_proxy_get_balancer(apr_pool_t *p,
                                                        proxy_server_conf *conf,
                                                        const char *url);
  /**
   * Add the balancer to proxy configuration
   * @param balancer the new balancer
   * @param p      memory pool to allocate balancer from 
   * @param conf   current proxy server configuration
   * @param url    url containing balancer name
   * @return       error message or NULL if successfull
   */
  PROXY_DECLARE(const char *) ap_proxy_add_balancer(proxy_balancer **balancer,
                                                    apr_pool_t *p,
                                                    proxy_server_conf *conf,
                                                    const char *url);
  
  /**
   * Add the worker to the balancer
   * @param pool     memory pool for adding worker 
   * @param balancer balancer to add to
   * @param balancer worker to add
   * @note Single worker can be added to multiple balancers.
   */
  PROXY_DECLARE(void) ap_proxy_add_worker_to_balancer(apr_pool_t *pool,
                                                      proxy_balancer *balancer,
                                                      proxy_worker *worker);
  /**
   * Get the most suitable worker and(or) balancer for the request
   * @param worker   worker used for processing request
   * @param balancer balancer used for processing request
   * @param r        current request
   * @param conf     current proxy server configuration
   * @param url      request url that balancer can rewrite.
   * @return         OK or  HTTP_XXX error 
   * @note It calls balancer pre_request hook if the url starts with balancer://
   * The balancer then rewrites the url to particular worker, like http://host:port
   */
  PROXY_DECLARE(int) ap_proxy_pre_request(proxy_worker **worker,
                                          proxy_balancer **balancer,
                                          request_rec *r,
                                          proxy_server_conf *conf,
                                          char **url);
  /**
   * Post request worker and balancer cleanup
   * @param worker   worker used for processing request
   * @param balancer balancer used for processing request
   * @param r        current request
   * @param conf     current proxy server configuration
   * @return         OK or  HTTP_XXX error
   * @note When ever the pre_request is called, the post_request has to be
   * called too. 
   */
  PROXY_DECLARE(int) ap_proxy_post_request(proxy_worker *worker,
                                           proxy_balancer *balancer,
                                           request_rec *r,
                                           proxy_server_conf *conf);
  
  /**
   * Request status function
   * @param status   status of proxy request
   * @return         OK or DECLINED
   */
   PROXY_DECLARE(int) ap_proxy_request_status(int *status, request_rec *r);
  
  /**
   * Deternime backend hostname and port
   * @param p       memory pool used for processing
   * @param r       current request
   * @param conf    current proxy server configuration
   * @param worker  worker used for processing request
   * @param conn    proxy connection struct
   * @param uri     processed uri
   * @param url     request url
   * @param proxyname are we connecting directly or via s proxy
   * @param proxyport proxy host port
   * @param server_portstr Via headers server port
   * @param server_portstr_size size of the server_portstr buffer
   * @return         OK or HTTP_XXX error
   */                                         
  PROXY_DECLARE(int) ap_proxy_determine_connection(apr_pool_t *p, request_rec *r,
                                                   proxy_server_conf *conf,
                                                   proxy_worker *worker,
                                                   proxy_conn_rec *conn,
                                                   apr_uri_t *uri,
                                                   char **url,
                                                   const char *proxyname,
                                                   apr_port_t proxyport,
                                                   char *server_portstr,
                                                   int server_portstr_size);
  /**
   * Mark a worker for retry
   * @param proxy_function calling proxy scheme (http, ajp, ...)
   * @param conf    current proxy server configuration
   * @param worker  worker used for retrying
   * @param s       current server record
   * @return        OK if marked for retry, DECLINED otherwise
   * @note Worker will be marker for retry if the time of the last retry
   * has been ellapsed. In case there is no retry option set, defaults to
   * number_of_retries seconds.
   */                                         
  PROXY_DECLARE(int) ap_proxy_retry_worker(const char *proxy_function,
                                           proxy_worker *worker,
                                           server_rec *s);
  /**
   * Acquire a connection from workers connection pool
   * @param proxy_function calling proxy scheme (http, ajp, ...)
   * @param conn    acquired connection
   * @param worker  worker used for obtaining connection
   * @param s       current server record
   * @return        OK or HTTP_XXX error
   * @note If the number of connections is exhaused the function will
   * block untill the timeout is reached.
   */                                         
  PROXY_DECLARE(int) ap_proxy_acquire_connection(const char *proxy_function,
                                                 proxy_conn_rec **conn,
                                                 proxy_worker *worker,
                                                 server_rec *s);
  /**
   * Release a connection back to worker connection pool
   * @param proxy_function calling proxy scheme (http, ajp, ...)
   * @param conn    acquired connection
   * @param s       current server record
   * @return        OK or HTTP_XXX error
   * @note The connection will be closed if conn->close_on_release is set
   */                                         
  PROXY_DECLARE(int) ap_proxy_release_connection(const char *proxy_function,
                                                 proxy_conn_rec *conn,
                                                 server_rec *s);
  /**
   * Make a connection to the backend
   * @param proxy_function calling proxy scheme (http, ajp, ...)
   * @param conn    acquired connection
   * @param worker  connection worker
   * @param s       current server record
   * @return        OK or HTTP_XXX error
   * @note In case the socket already exists for conn, just check the link
   * status.
   */                                         
  PROXY_DECLARE(int) ap_proxy_connect_backend(const char *proxy_function,
                                              proxy_conn_rec *conn,
                                              proxy_worker *worker,
                                              server_rec *s);
  /**
   * Make a connection record for backend connection
   * @param proxy_function calling proxy scheme (http, ajp, ...)
   * @param conn    acquired connection
   * @param c       client connection record
   * @param s       current server record
   * @return        OK or HTTP_XXX error
   */                                         
  PROXY_DECLARE(int) ap_proxy_connection_create(const char *proxy_function,
                                                proxy_conn_rec *conn,
                                                conn_rec *c, server_rec *s);
  /**
   * Signal the upstream chain that the connection to the backend broke in the
   * middle of the response. This is done by sending an error bucket with
   * status HTTP_BAD_GATEWAY and an EOS bucket up the filter chain.
   * @param r       current request record of client request
   * @param brigade The brigade that is sent through the output filter chain
   */
  PROXY_DECLARE(void) ap_proxy_backend_broke(request_rec *r,
                                             apr_bucket_brigade *brigade);
  
  /* Scoreboard */
  #if MODULE_MAGIC_NUMBER_MAJOR > 20020903
  #define PROXY_HAS_SCOREBOARD 1
  #else
  #define PROXY_HAS_SCOREBOARD 0
  #endif
  
  /**
   * Transform buckets from one bucket allocator to another one by creating a
   * transient bucket for each data bucket and let it use the data read from
   * the old bucket. Metabuckets are transformed by just recreating them.
   * Attention: Currently only the following bucket types are handled:
   *
   * All data buckets
   * FLUSH
   * EOS
   *
   * If an other bucket type is found its type is logged as a debug message
   * and APR_EGENERAL is returned.
   * @param r    current request record of client request. Only used for logging
   *             purposes
   * @param from the brigade that contains the buckets to transform
   * @param to   the brigade that will receive the transformed buckets
   * @return     APR_SUCCESS if all buckets could be transformed APR_EGENERAL
   *             otherwise
   */
  PROXY_DECLARE(apr_status_t)
  ap_proxy_buckets_lifetime_transform(request_rec *r, apr_bucket_brigade *from,
                                          apr_bucket_brigade *to);
  
  #define PROXY_LBMETHOD "proxylbmethod"
  
  /* The number of dynamic workers that can be added when reconfiguring.
   * If this limit is reached you must stop and restart the server.
   */
  #define PROXY_DYNAMIC_BALANCER_LIMIT    16
  /**
   * Calculate number of maximum number of workers in scoreboard.
   * @return  number of workers to allocate in the scoreboard
   */
  int ap_proxy_lb_workers(void);
  
  /* For proxy_util */
  extern module PROXY_DECLARE_DATA proxy_module;
  
  extern int PROXY_DECLARE_DATA proxy_lb_workers;
  
  #endif /*MOD_PROXY_H*/
  /** @} */
  