path: root/modules/proxy/mod_proxy.c

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2000-2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 * Portions of this software are based upon public domain software
 * originally written at the National Center for Supercomputing Applications,
 * University of Illinois, Urbana-Champaign.
 */

#define CORE_PRIVATE

#include "mod_proxy.h"

extern module AP_MODULE_DECLARE_DATA proxy_module;


/*
 * A Web proxy module. Stages:
 *
 *  translate_name: set filename to proxy:<URL>
 *  type_checker:   set type to PROXY_MAGIC_TYPE if filename begins proxy:
 *  fix_ups:        convert the URL stored in the filename to the
 *                  canonical form.
 *  handler:        handle proxy requests
 */

/* -------------------------------------------------------------- */
/* Translate the URL into a 'filename' */

static int alias_match(const char *uri, const char *alias_fakename)
{
    const char *end_fakename = alias_fakename + strlen(alias_fakename);
    const char *aliasp = alias_fakename, *urip = uri;

    while (aliasp < end_fakename) {
	if (*aliasp == '/') {
	    /* any number of '/' in the alias matches any number in
	     * the supplied URI, but there must be at least one...
	     */
	    if (*urip != '/')
		return 0;

	    while (*aliasp == '/')
		++aliasp;
	    while (*urip == '/')
		++urip;
	}
	else {
	    /* Other characters are compared literally */
	    if (*urip++ != *aliasp++)
		return 0;
	}
    }

    /* Check last alias path component matched all the way */

    if (aliasp[-1] != '/' && *urip != '\0' && *urip != '/')
	return 0;

    /* Return number of characters from URI which matched (may be
     * greater than length of alias, since we may have matched
     * doubled slashes)
     */

    return urip - uri;
}

/* Detect if an absoluteURI should be proxied or not.  Note that we
 * have to do this during this phase because later phases are
 * "short-circuiting"... i.e. translate_names will end when the first
 * module returns OK.  So for example, if the request is something like:
 *
 * GET http://othervhost/cgi-bin/printenv HTTP/1.0
 *
 * mod_alias will notice the /cgi-bin part and ScriptAlias it and
 * short-circuit the proxy... just because of the ordering in the
 * configuration file.
 */
static int proxy_detect(request_rec *r)
{
    void *sconf = r->server->module_config;
    proxy_server_conf *conf;

    conf = (proxy_server_conf *) ap_get_module_config(sconf, &proxy_module);

    if (conf->req && r->parsed_uri.scheme) {
	/* but it might be something vhosted */
       if (!(r->parsed_uri.hostname
	    && !strcasecmp(r->parsed_uri.scheme, ap_http_method(r))
	    && ap_matches_request_vhost(r, r->parsed_uri.hostname,
               r->parsed_uri.port_str ? r->parsed_uri.port : ap_default_port(r)))) {
	    r->proxyreq = PROXYREQ_PROXY;
	    r->uri = r->unparsed_uri;
	    r->filename = apr_pstrcat(r->pool, "proxy:", r->uri, NULL);
	    r->handler = "proxy-server";
        }
    }
    /* We need special treatment for CONNECT proxying: it has no scheme part */
    else if (conf->req && r->method_number == M_CONNECT
	     && r->parsed_uri.hostname
	     && r->parsed_uri.port_str) {
	    r->proxyreq = PROXYREQ_PROXY;
	    r->uri = r->unparsed_uri;
	    r->filename = apr_pstrcat(r->pool, "proxy:", r->uri, NULL);
	    r->handler = "proxy-server";
    }
    return DECLINED;
}

static int proxy_trans(request_rec *r)
{
    void *sconf = r->server->module_config;
    proxy_server_conf *conf =
    (proxy_server_conf *) ap_get_module_config(sconf, &proxy_module);
    int i, len;
    struct proxy_alias *ent = (struct proxy_alias *) conf->aliases->elts;

    if (r->proxyreq) {
	/* someone has already set up the proxy, it was possibly ourselves
	 * in proxy_detect
	 */
	return OK;
    }

    /* XXX: since r->uri has been manipulated already we're not really
     * compliant with RFC1945 at this point.  But this probably isn't
     * an issue because this is a hybrid proxy/origin server.
     */

    for (i = 0; i < conf->aliases->nelts; i++) {
        len = alias_match(r->uri, ent[i].fake);
	    
       if (len > 0) {
           r->filename = apr_pstrcat(r->pool, "proxy:", ent[i].real,
                                 r->uri + len, NULL);
           r->handler = "proxy-server";
           r->proxyreq = PROXYREQ_REVERSE;
           return OK;
	}
    }
    return DECLINED;
}

/* -------------------------------------------------------------- */
/* Fixup the filename */

/*
 * Canonicalise the URL
 */
static int proxy_fixup(request_rec *r)
{
    char *url, *p;
    int access_status;

    if (!r->proxyreq || strncmp(r->filename, "proxy:", 6) != 0)
	return DECLINED;

    url = &r->filename[6];

    /* canonicalise each specific scheme */
    if ((access_status = proxy_run_canon_handler(r, url))) {
	return access_status;
    }

    p = strchr(url, ':');
    if (p == NULL || p == url)
	return HTTP_BAD_REQUEST;

    return OK;		/* otherwise; we've done the best we can */
}

/* Send a redirection if the request contains a hostname which is not */
/* fully qualified, i.e. doesn't have a domain name appended. Some proxy */
/* servers like Netscape's allow this and access hosts from the local */
/* domain in this case. I think it is better to redirect to a FQDN, since */
/* these will later be found in the bookmarks files. */
/* The "ProxyDomain" directive determines what domain will be appended */
static int proxy_needsdomain(request_rec *r, const char *url, const char *domain)
{
    char *nuri;
    const char *ref;

    /* We only want to worry about GETs */
    if (!r->proxyreq || r->method_number != M_GET || !r->parsed_uri.hostname)
	return DECLINED;

    /* If host does contain a dot already, or it is "localhost", decline */
    if (strchr(r->parsed_uri.hostname, '.') != NULL
     || strcasecmp(r->parsed_uri.hostname, "localhost") == 0)
	return DECLINED;	/* host name has a dot already */

    ref = apr_table_get(r->headers_in, "Referer");

    /* Reassemble the request, but insert the domain after the host name */
    /* Note that the domain name always starts with a dot */
    r->parsed_uri.hostname = apr_pstrcat(r->pool, r->parsed_uri.hostname,
				     domain, NULL);
    nuri = ap_unparse_uri_components(r->pool,
				  &r->parsed_uri,
				  UNP_REVEALPASSWORD);

    apr_table_set(r->headers_out, "Location", nuri);
    ap_log_rerror(APLOG_MARK, APLOG_INFO|APLOG_NOERRNO, 0, r,
		"Domain missing: %s sent to %s%s%s", r->uri,
		ap_unparse_uri_components(r->pool, &r->parsed_uri,
		      UNP_OMITUSERINFO),
		ref ? " from " : "", ref ? ref : "");

    return HTTP_MOVED_PERMANENTLY;
}

/* -------------------------------------------------------------- */
/* Invoke handler */

static int proxy_handler(request_rec *r)
{
    char *url, *scheme, *p;
    const char *p2;
    void *sconf = r->server->module_config;
    proxy_server_conf *conf = (proxy_server_conf *)
        ap_get_module_config(sconf, &proxy_module);
    apr_array_header_t *proxies = conf->proxies;
    struct proxy_remote *ents = (struct proxy_remote *) proxies->elts;
    int i, rc, access_status;
    int direct_connect = 0;
    const char *str;
    long maxfwd;

    /* is this for us? */
    if (!r->proxyreq || strncmp(r->filename, "proxy:", 6) != 0)
	return DECLINED;

    /* handle max-forwards / OPTIONS / TRACE */
    if ((str = apr_table_get(r->headers_in, "Max-Forwards"))) {
	maxfwd = strtol(str, NULL, 10);
	if (maxfwd < 1) {
            switch (r->method_number) {
            case M_TRACE: {
	        int access_status;
	        r->proxyreq = PROXYREQ_NONE;
	        if ((access_status = ap_send_http_trace(r)))
		    ap_die(access_status, r);
	        else
		    ap_finalize_request_protocol(r);
	        return OK;
            }
            case M_OPTIONS: {
	        int access_status;
	        r->proxyreq = PROXYREQ_NONE;
	        if ((access_status = ap_send_http_options(r)))
		    ap_die(access_status, r);
	        else
		    ap_finalize_request_protocol(r);
	        return OK;
            }
	    default: {
		return ap_proxyerror(r, HTTP_BAD_GATEWAY,
		                     "Max-Forwards has reached zero - proxy loop?");
	    }
            }
	}
	maxfwd = (maxfwd > 0) ? maxfwd - 1 : 0;
    }
    else {
	/* set configured max-forwards */
	maxfwd = conf->maxfwd;
    }
    apr_table_setn(r->headers_in, "Max-Forwards", 
		   apr_psprintf(r->pool, "%ld", (maxfwd > 0) ? maxfwd : 0));

    if ((rc = ap_setup_client_block(r, REQUEST_CHUNKED_ERROR)))
	return rc;

    url = r->filename + 6;
    p = strchr(url, ':');
    if (p == NULL)
	return HTTP_BAD_REQUEST;

    /* If the host doesn't have a domain name, add one and redirect. */
    if (conf->domain != NULL) {
	rc = proxy_needsdomain(r, url, conf->domain);
	if (ap_is_HTTP_REDIRECT(rc))
	    return HTTP_MOVED_PERMANENTLY;
    }

    *p = '\0';
    scheme = apr_pstrdup(r->pool, url);
    *p = ':';

    /* Check URI's destination host against NoProxy hosts */
    /* Bypass ProxyRemote server lookup if configured as NoProxy */
    /* we only know how to handle communication to a proxy via http */
    /*if (strcasecmp(scheme, "http") == 0) */
    {
	int ii;
	struct dirconn_entry *list = (struct dirconn_entry *) conf->dirconn->elts;

	for (direct_connect = ii = 0; ii < conf->dirconn->nelts && !direct_connect; ii++) {
	    direct_connect = list[ii].matcher(&list[ii], r);
	}
#if DEBUGGING
	ap_log_rerror(APLOG_MARK, APLOG_DEBUG|APLOG_NOERRNO, r,
		     (direct_connect) ? "NoProxy for %s" : "UseProxy for %s",
		     r->uri);
#endif
    }

    /* firstly, try a proxy, unless a NoProxy directive is active */
    if (!direct_connect) {
	for (i = 0; i < proxies->nelts; i++) {
            p2 = ap_strchr_c(ents[i].scheme, ':');  /* is it a partial URL? */
	    if (strcmp(ents[i].scheme, "*") == 0 ||
		(p2 == NULL && strcasecmp(scheme, ents[i].scheme) == 0) ||
		(p2 != NULL &&
	        strncasecmp(url, ents[i].scheme, strlen(ents[i].scheme)) == 0)) {

		/* handle the scheme */
		ap_log_error(APLOG_MARK, APLOG_DEBUG | APLOG_NOERRNO, 0, r->server,
			     "Trying to run scheme_handler against proxy");
		access_status = proxy_run_scheme_handler(r, conf, url, ents[i].hostname, ents[i].port);

		/* an error or success */
		if (access_status != DECLINED && access_status != HTTP_BAD_GATEWAY) {
		    return access_status;
		}
		/* we failed to talk to the upstream proxy */
	    }
	}
    }

    /* otherwise, try it direct */
    /* N.B. what if we're behind a firewall, where we must use a proxy or
     * give up??
     */

    /* handle the scheme */
    ap_log_error(APLOG_MARK, APLOG_DEBUG | APLOG_NOERRNO, 0, r->server,
		 "Trying to run scheme_handler");
    access_status = proxy_run_scheme_handler(r, conf, url, NULL, 0);
    if (DECLINED == access_status) {
        ap_log_error(APLOG_MARK, APLOG_DEBUG | APLOG_NOERRNO, 0, r->server,
		     "Neither CONNECT, HTTP or FTP for %s",
		     r->uri);
	return HTTP_FORBIDDEN;
    }
    return access_status;
}

/* -------------------------------------------------------------- */
/* Setup configurable data */

static void * create_proxy_config(apr_pool_t *p, server_rec *s)
{
    proxy_server_conf *ps = ap_pcalloc(p, sizeof(proxy_server_conf));

    ps->proxies = ap_make_array(p, 10, sizeof(struct proxy_remote));
    ps->aliases = ap_make_array(p, 10, sizeof(struct proxy_alias));
    ps->raliases = ap_make_array(p, 10, sizeof(struct proxy_alias));
    ps->noproxies = ap_make_array(p, 10, sizeof(struct noproxy_entry));
    ps->dirconn = ap_make_array(p, 10, sizeof(struct dirconn_entry));
    ps->allowed_connect_ports = ap_make_array(p, 10, sizeof(int));
    ps->domain = NULL;
    ps->viaopt = via_off; /* initially backward compatible with 1.3.1 */
    ps->viaopt_set = 0; /* 0 means default */
    ps->req = 0;
    ps->req_set = 0;
    ps->recv_buffer_size = 0; /* this default was left unset for some reason */
    ps->recv_buffer_size_set = 0;
    ps->maxfwd = DEFAULT_MAX_FORWARDS;
    ps->maxfwd_set = 0;

    return ps;
}

static void * merge_proxy_config(apr_pool_t *p, void *basev, void *overridesv)
{
    proxy_server_conf *ps = ap_pcalloc(p, sizeof(proxy_server_conf));
    proxy_server_conf *base = (proxy_server_conf *) basev;
    proxy_server_conf *overrides = (proxy_server_conf *) overridesv;

    ps->proxies = ap_append_arrays(p, base->proxies, overrides->proxies);
    ps->aliases = ap_append_arrays(p, base->aliases, overrides->aliases);
    ps->raliases = ap_append_arrays(p, base->raliases, overrides->raliases);
    ps->noproxies = ap_append_arrays(p, base->noproxies, overrides->noproxies);
    ps->dirconn = ap_append_arrays(p, base->dirconn, overrides->dirconn);
    ps->allowed_connect_ports = ap_append_arrays(p, base->allowed_connect_ports, overrides->allowed_connect_ports);

    ps->domain = (overrides->domain == NULL) ? base->domain : overrides->domain;
    ps->viaopt = (overrides->viaopt_set == 0) ? base->viaopt : overrides->viaopt;
    ps->req = (overrides->req_set == 0) ? base->req : overrides->req;
    ps->recv_buffer_size = (overrides->recv_buffer_size_set == 0) ? base->recv_buffer_size : overrides->recv_buffer_size;
    ps->maxfwd = (overrides->maxfwd_set == 0) ? base->maxfwd : overrides->maxfwd;

    return ps;
}

static const char *
    add_proxy(cmd_parms *cmd, void *dummy, const char *f1, const char *r1)
{
    server_rec *s = cmd->server;
    proxy_server_conf *conf =
    (proxy_server_conf *) ap_get_module_config(s->module_config, &proxy_module);
    struct proxy_remote *new;
    char *p, *q;
    char *r, *f, *scheme;
    int port;

    r = apr_pstrdup(cmd->pool, r1);
    scheme = apr_pstrdup(cmd->pool, r1);
    f = apr_pstrdup(cmd->pool, f1);
    p = strchr(r, ':');
    if (p == NULL || p[1] != '/' || p[2] != '/' || p[3] == '\0') {
	return "ProxyRemote: Bad syntax for a remote proxy server";
    }
    else {
	scheme[p-r] = 0;
    }
    q = strchr(p + 3, ':');
    if (q != NULL) {
	if (sscanf(q + 1, "%u", &port) != 1 || port > 65535)
	    return "ProxyRemote: Bad syntax for a remote proxy server (bad port number)";
	*q = '\0';
    }
    else
	port = -1;
    *p = '\0';
    if (strchr(f, ':') == NULL)
	ap_str_tolower(f);		/* lowercase scheme */
    ap_str_tolower(p + 3);		/* lowercase hostname */

    if (port == -1) {
	port = ap_default_port_for_scheme(scheme);
    }

    new = apr_array_push(conf->proxies);
    new->scheme = f;
    new->protocol = r;
    new->hostname = p + 3;
    new->port = port;
    return NULL;
}

static const char *
    add_pass(cmd_parms *cmd, void *dummy, const char *f, const char *r)
{
    server_rec *s = cmd->server;
    proxy_server_conf *conf =
    (proxy_server_conf *) ap_get_module_config(s->module_config, &proxy_module);
    struct proxy_alias *new;

    new = apr_array_push(conf->aliases);
    new->fake = f;
    new->real = r;
    return NULL;
}

static const char *
    add_pass_reverse(cmd_parms *cmd, void *dummy, const char *f, const char *r)
{
    server_rec *s = cmd->server;
    proxy_server_conf *conf;
    struct proxy_alias *new;

    conf = (proxy_server_conf *)ap_get_module_config(s->module_config, 
                                                  &proxy_module);
    new = apr_array_push(conf->raliases);
    new->fake = f;
    new->real = r;
    return NULL;
}

static const char *
    set_proxy_exclude(cmd_parms *parms, void *dummy, const char *arg)
{
    server_rec *s = parms->server;
    proxy_server_conf *conf =
    ap_get_module_config(s->module_config, &proxy_module);
    struct noproxy_entry *new;
    struct noproxy_entry *list = (struct noproxy_entry *) conf->noproxies->elts;
    struct apr_sockaddr_t *addr;
    int found = 0;
    int i;

    /* Don't duplicate entries */
    for (i = 0; i < conf->noproxies->nelts; i++) {
	if (apr_strnatcasecmp(arg, list[i].name) == 0) { /* ignore case for host names */
	    found = 1;
	}
    }

    if (!found) {
	new = apr_array_push(conf->noproxies);
	new->name = arg;
	if (APR_SUCCESS == apr_sockaddr_info_get(&addr, new->name, APR_UNSPEC, 0, 0, parms->pool)) {
	    new->addr = addr;
	}
	else {
	    new->addr = NULL;
	}
    }
    return NULL;
}

/*
 * Set the ports CONNECT can use
 */
static const char *
    set_allowed_ports(cmd_parms *parms, void *dummy, const char *arg)
{
    server_rec *s = parms->server;
    proxy_server_conf *conf =
      ap_get_module_config(s->module_config, &proxy_module);
    int *New;

    if (!apr_isdigit(arg[0]))
	return "AllowCONNECT: port number must be numeric";

    New = apr_array_push(conf->allowed_connect_ports);
    *New = atoi(arg);
    return NULL;
}

/* Similar to set_proxy_exclude(), but defining directly connected hosts,
 * which should never be accessed via the configured ProxyRemote servers
 */
static const char *
    set_proxy_dirconn(cmd_parms *parms, void *dummy, const char *arg)
{
    server_rec *s = parms->server;
    proxy_server_conf *conf =
    ap_get_module_config(s->module_config, &proxy_module);
    struct dirconn_entry *New;
    struct dirconn_entry *list = (struct dirconn_entry *) conf->dirconn->elts;
    int found = 0;
    int i;

    /* Don't duplicate entries */
    for (i = 0; i < conf->dirconn->nelts; i++) {
	if (strcasecmp(arg, list[i].name) == 0)
	    found = 1;
    }

    if (!found) {
	New = apr_array_push(conf->dirconn);
        New->name = apr_pstrdup(parms->pool, arg);
	New->hostentry = NULL;

	if (ap_proxy_is_ipaddr(New, parms->pool)) {
#if DEBUGGING
        ap_log_error(APLOG_MARK, APLOG_STARTUP | APLOG_NOERRNO, 0, NULL,
                         "Parsed addr %s", inet_ntoa(New->addr));
        ap_log_error(APLOG_MARK, APLOG_STARTUP | APLOG_NOERRNO, 0, NULL,
                         "Parsed mask %s", inet_ntoa(New->mask));
#endif
	}
	else if (ap_proxy_is_domainname(New, parms->pool)) {
	    ap_str_tolower(New->name);
#if DEBUGGING
        ap_log_error(APLOG_MARK, APLOG_STARTUP | APLOG_NOERRNO, 0, NULL,
                         "Parsed domain %s", New->name);
#endif
	}
	else if (ap_proxy_is_hostname(New, parms->pool)) {
	    ap_str_tolower(New->name);
#if DEBUGGING
        ap_log_error(APLOG_MARK, APLOG_STARTUP | APLOG_NOERRNO, 0, NULL,
                         "Parsed host %s", New->name);
#endif
	}
	else {
	    ap_proxy_is_word(New, parms->pool);
#if DEBUGGING
	    fprintf(stderr, "Parsed word %s\n", New->name);
#endif
	}
    }
    return NULL;
}

static const char *
    set_proxy_domain(cmd_parms *parms, void *dummy, const char *arg)
{
    proxy_server_conf *psf =
    ap_get_module_config(parms->server->module_config, &proxy_module);

    if (arg[0] != '.')
	return "ProxyDomain: domain name must start with a dot.";

    psf->domain = arg;
    return NULL;
}

static const char *
    set_proxy_req(cmd_parms *parms, void *dummy, int flag)
{
    proxy_server_conf *psf =
    ap_get_module_config(parms->server->module_config, &proxy_module);

    psf->req = flag;
    psf->req_set = 1;
    return NULL;
}

static const char *
    set_recv_buffer_size(cmd_parms *parms, void *dummy, const char *arg)
{
    proxy_server_conf *psf =
    ap_get_module_config(parms->server->module_config, &proxy_module);
    int s = atoi(arg);
    if (s < 512 && s != 0) {
	return "ProxyReceiveBufferSize must be >= 512 bytes, or 0 for system default.";
    }

    psf->recv_buffer_size = s;
    psf->recv_buffer_size_set = 1;
    return NULL;
}

static const char *
    set_max_forwards(cmd_parms *parms, void *dummy, const char *arg)
{
    proxy_server_conf *psf =
    ap_get_module_config(parms->server->module_config, &proxy_module);
    long s = atol(arg);
    if (s < 0) {
	return "ProxyMaxForwards must be greater or equal to zero..";
    }

    psf->maxfwd = s;
    psf->maxfwd_set = 1;
    return NULL;
}

static const char*
    set_via_opt(cmd_parms *parms, void *dummy, const char *arg)
{
    proxy_server_conf *psf =
    ap_get_module_config(parms->server->module_config, &proxy_module);

    if (strcasecmp(arg, "Off") == 0)
        psf->viaopt = via_off;
    else if (strcasecmp(arg, "On") == 0)
        psf->viaopt = via_on;
    else if (strcasecmp(arg, "Block") == 0)
        psf->viaopt = via_block;
    else if (strcasecmp(arg, "Full") == 0)
        psf->viaopt = via_full;
    else {
	return "ProxyVia must be one of: "
               "off | on | full | block";
    }

    psf->viaopt_set = 1;
    return NULL;    
}

static const command_rec proxy_cmds[] =
{
    AP_INIT_FLAG("ProxyRequests", set_proxy_req, NULL, RSRC_CONF,
     "on if the true proxy requests should be accepted"),
    AP_INIT_TAKE2("ProxyRemote", add_proxy, NULL, RSRC_CONF,
     "a scheme, partial URL or '*' and a proxy server"),
    AP_INIT_TAKE2("ProxyPass", add_pass, NULL, RSRC_CONF,
     "a virtual path and a URL"),
    AP_INIT_TAKE2("ProxyPassReverse", add_pass_reverse, NULL, RSRC_CONF,
     "a virtual path and a URL for reverse proxy behaviour"),
    AP_INIT_ITERATE("ProxyBlock", set_proxy_exclude, NULL, RSRC_CONF,
     "A list of names, hosts or domains to which the proxy will not connect"),
    AP_INIT_TAKE1("ProxyReceiveBufferSize", set_recv_buffer_size, NULL, RSRC_CONF,
     "Receive buffer size for outgoing HTTP and FTP connections in bytes"),
    AP_INIT_TAKE1("ProxyMaxForwards", set_max_forwards, NULL, RSRC_CONF,
     "The maximum number of proxies a request may be forwarded through."),
    AP_INIT_ITERATE("NoProxy", set_proxy_dirconn, NULL, RSRC_CONF,
     "A list of domains, hosts, or subnets to which the proxy will connect directly"),
    AP_INIT_TAKE1("ProxyDomain", set_proxy_domain, NULL, RSRC_CONF,
     "The default intranet domain name (in absence of a domain in the URL)"),
    AP_INIT_ITERATE("AllowCONNECT", set_allowed_ports, NULL, RSRC_CONF,
     "A list of ports which CONNECT may connect to"),
    AP_INIT_TAKE1("ProxyVia", set_via_opt, NULL, RSRC_CONF,
     "Configure Via: proxy header header to one of: on | off | block | full"),
    {NULL}
};

static void register_hooks(apr_pool_t *p)
{
    /* handler */
    ap_hook_handler(proxy_handler, NULL, NULL, APR_HOOK_FIRST);
    /* filename-to-URI translation */
    ap_hook_translate_name(proxy_trans, NULL, NULL, APR_HOOK_FIRST);
    /* fixups */
    ap_hook_fixups(proxy_fixup, NULL, NULL, APR_HOOK_FIRST);
    /* post read_request handling */
    ap_hook_post_read_request(proxy_detect, NULL, NULL, APR_HOOK_FIRST);
}

module AP_MODULE_DECLARE_DATA proxy_module =
{
    STANDARD20_MODULE_STUFF,
    NULL,			/* create per-directory config structure */
    NULL,			/* merge per-directory config structures */
    create_proxy_config,	/* create per-server config structure */
    merge_proxy_config,		/* merge per-server config structures */
    proxy_cmds,			/* command table */
    register_hooks
};

APR_HOOK_STRUCT(
	APR_HOOK_LINK(scheme_handler)
	APR_HOOK_LINK(canon_handler)
)

APR_IMPLEMENT_EXTERNAL_HOOK_RUN_FIRST(proxy, PROXY, int, scheme_handler, 
                                     (request_rec *r, proxy_server_conf *conf, 
                                     char *url, const char *proxyhost, 
                                     apr_port_t proxyport),(r,conf,url,
                                     proxyhost,proxyport),DECLINED)
APR_IMPLEMENT_EXTERNAL_HOOK_RUN_FIRST(proxy, PROXY, int, canon_handler, 
                                     (request_rec *r, char *url),(r,
                                     url),DECLINED)