mod_proxy_http.c

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/* 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.
 */
 
/* HTTP routines for Apache proxy */
 
#include "mod_proxy.h"
#include "ap_regex.h"
 
module AP_MODULE_DECLARE_DATA proxy_http_module;
 
static int (*ap_proxy_clear_connection_fn)(request_rec *r, apr_table_t *headers) =
        NULL;
 
static apr_status_t ap_proxy_http_cleanup(const char *scheme,
                                          request_rec *r,
                                          proxy_conn_rec *backend);
 
static apr_status_t ap_proxygetline(apr_bucket_brigade *bb, char *s, int n,
                                    request_rec *r, int flags, int *read);
 
static const char *get_url_scheme(const char **url, int *is_ssl)
{
    const char *u = *url;
 
    switch (u[0]) {
    case 'h':
    case 'H':
        if (strncasecmp(u + 1, "ttp", 3) == 0) {
            if (u[4] == ':') {
                *is_ssl = 0;
                *url = u + 5;
                return "http";
            }
            if (apr_tolower(u[4]) == 's' && u[5] == ':') {
                *is_ssl = 1;
                *url = u + 6;
                return "https";
            }
        }
        break;
 
    case 'w':
    case 'W':
        if (apr_tolower(u[1]) == 's') {
            if (u[2] == ':') {
                *is_ssl = 0;
                *url = u + 3;
                return "ws";
            }
            if (apr_tolower(u[2]) == 's' && u[3] == ':') {
                *is_ssl = 1;
                *url = u + 4;
                return "wss";
            }
        }
        break;
    }
 
    *is_ssl = 0;
    return NULL;
}
 
/*
 * Canonicalise http-like URLs.
 *  scheme is the scheme for the URL
 *  url    is the URL starting with the first '/'
 */
static int proxy_http_canon(request_rec *r, char *url)
{
    const char *base_url = url;
    char *host, *path, sport[7];
    char *search = NULL;
    const char *err;
    const char *scheme;
    apr_port_t port, def_port;
    int is_ssl = 0;
 
    scheme = get_url_scheme((const char **)&url, &is_ssl);
    if (!scheme) {
        return DECLINED;
    }
    port = def_port = (is_ssl) ? DEFAULT_HTTPS_PORT : DEFAULT_HTTP_PORT;
 
    ap_log_rerror(APLOG_MARK, APLOG_TRACE1, 0, r,
                  "HTTP: canonicalising URL %s", base_url);
 
    /* do syntatic check.
     * We break the URL into host, port, path, search
     */
    err = ap_proxy_canon_netloc(r->pool, &url, NULL, NULL, &host, &port);
    if (err) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01083)
                      "error parsing URL %s: %s", base_url, err);
        return HTTP_BAD_REQUEST;
    }
 
    /*
     * now parse path/search args, according to rfc1738:
     * process the path.
     *
     * In a reverse proxy, our URL has been processed, so canonicalise
     * unless proxy-nocanon is set to say it's raw
     * In a forward proxy, we have and MUST NOT MANGLE the original.
     */
    switch (r->proxyreq) {
    default: /* wtf are we doing here? */
    case PROXYREQ_REVERSE:
        if (apr_table_get(r->notes, "proxy-nocanon")) {
            path = url;   /* this is the raw path */
        }
        else if (apr_table_get(r->notes, "proxy-noencode")) {
            path = url;   /* this is the encoded path already */
            search = r->args;
        }
        else {
            core_dir_config *d = ap_get_core_module_config(r->per_dir_config);
            int flags = d->allow_encoded_slashes && !d->decode_encoded_slashes ? PROXY_CANONENC_NOENCODEDSLASHENCODING : 0;
 
            path = ap_proxy_canonenc_ex(r->pool, url, strlen(url), enc_path,
                                        flags, r->proxyreq);
            if (!path) {
                return HTTP_BAD_REQUEST;
            }
            search = r->args;
        }
        break;
    case PROXYREQ_PROXY:
        path = url;
        break;
    }
    /*
     * If we have a raw control character or a ' ' in nocanon path or
     * r->args, correct encoding was missed.
     */
    if (path == url && *ap_scan_vchar_obstext(path)) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(10415)
                      "To be forwarded path contains control "
                      "characters or spaces");
        return HTTP_FORBIDDEN;
    }
    if (search && *ap_scan_vchar_obstext(search)) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(10408)
                      "To be forwarded query string contains control "
                      "characters or spaces");
        return HTTP_FORBIDDEN;
    }
 
    if (port != def_port)
        apr_snprintf(sport, sizeof(sport), ":%d", port);
    else
        sport[0] = '\0';
 
    if (ap_strchr_c(host, ':')) { /* if literal IPv6 address */
        host = apr_pstrcat(r->pool, "[", host, "]", NULL);
    }
 
    r->filename = apr_pstrcat(r->pool, "proxy:", scheme, "://", host, sport,
                              "/", path, (search) ? "?" : "", search, NULL);
    return OK;
}
 
/* Clear all connection-based headers from the incoming headers table */
typedef struct header_dptr {
    apr_pool_t *pool;
    apr_table_t *table;
    apr_time_t time;
} header_dptr;
static ap_regex_t *warn_rx;
static int clean_warning_headers(void *data, const char *key, const char *val)
{
    apr_table_t *headers = ((header_dptr*)data)->table;
    apr_pool_t *pool = ((header_dptr*)data)->pool;
    char *warning;
    char *date;
    apr_time_t warn_time;
    const int nmatch = 3;
    ap_regmatch_t pmatch[3];
 
    if (headers == NULL) {
        ((header_dptr*)data)->table = headers = apr_table_make(pool, 2);
    }
/*
 * Parse this, suckers!
 *
 *    Warning    = "Warning" ":" 1#warning-value
 *
 *    warning-value = warn-code SP warn-agent SP warn-text
 *                                             [SP warn-date]
 *
 *    warn-code  = 3DIGIT
 *    warn-agent = ( host [ ":" port ] ) | pseudonym
 *                    ; the name or pseudonym of the server adding
 *                    ; the Warning header, for use in debugging
 *    warn-text  = quoted-string
 *    warn-date  = <"> HTTP-date <">
 *
 * Buggrit, use a bloomin' regexp!
 * (\d{3}\s+\S+\s+\".*?\"(\s+\"(.*?)\")?)  --> whole in $1, date in $3
 */
    while (!ap_regexec(warn_rx, val, nmatch, pmatch, 0)) {
        warning = apr_pstrndup(pool, val+pmatch[0].rm_so,
                               pmatch[0].rm_eo - pmatch[0].rm_so);
        warn_time = 0;
        if (pmatch[2].rm_eo > pmatch[2].rm_so) {
            /* OK, we have a date here */
            date = apr_pstrndup(pool, val+pmatch[2].rm_so,
                                pmatch[2].rm_eo - pmatch[2].rm_so);
            warn_time = apr_date_parse_http(date);
        }
        if (!warn_time || (warn_time == ((header_dptr*)data)->time)) {
            apr_table_addn(headers, key, warning);
        }
        val += pmatch[0].rm_eo;
    }
    return 1;
}
static apr_table_t *ap_proxy_clean_warnings(apr_pool_t *p, apr_table_t *headers)
{
   header_dptr x;
   x.pool = p;
   x.table = NULL;
   x.time = apr_date_parse_http(apr_table_get(headers, "Date"));
   apr_table_do(clean_warning_headers, &x, headers, "Warning", NULL);
   if (x.table != NULL) {
       apr_table_unset(headers, "Warning");
       return apr_table_overlay(p, headers, x.table);
   }
   else {
        return headers;
   }
}
 
static void add_te_chunked(apr_pool_t *p,
                           apr_bucket_alloc_t *bucket_alloc,
                           apr_bucket_brigade *header_brigade)
{
    apr_bucket *e;
    char *buf;
    const char te_hdr[] = "Transfer-Encoding: chunked" CRLF;
 
    buf = apr_pmemdup(p, te_hdr, sizeof(te_hdr)-1);
    ap_xlate_proto_to_ascii(buf, sizeof(te_hdr)-1);
 
    e = apr_bucket_pool_create(buf, sizeof(te_hdr)-1, p, bucket_alloc);
    APR_BRIGADE_INSERT_TAIL(header_brigade, e);
}
 
static void add_cl(apr_pool_t *p,
                   apr_bucket_alloc_t *bucket_alloc,
                   apr_bucket_brigade *header_brigade,
                   const char *cl_val)
{
    apr_bucket *e;
    char *buf;
 
    buf = apr_pstrcat(p, "Content-Length: ",
                      cl_val,
                      CRLF,
                      NULL);
    ap_xlate_proto_to_ascii(buf, strlen(buf));
    e = apr_bucket_pool_create(buf, strlen(buf), p, bucket_alloc);
    APR_BRIGADE_INSERT_TAIL(header_brigade, e);
}
 
#ifndef CRLF_ASCII
#define CRLF_ASCII  "\015\012"
#endif
#ifndef ZERO_ASCII
#define ZERO_ASCII  "\060"
#endif
 
#define MAX_MEM_SPOOL 16384
 
typedef enum {
    RB_INIT = 0,
    RB_STREAM_CL,
    RB_STREAM_CHUNKED,
    RB_SPOOL_CL
} rb_methods;
 
typedef struct {
    apr_pool_t *p;
    request_rec *r;
    const char *proto;
    proxy_worker *worker;
    proxy_server_conf *sconf;
 
    char server_portstr[32];
    proxy_conn_rec *backend;
    conn_rec *origin;
 
    apr_bucket_alloc_t *bucket_alloc;
    apr_bucket_brigade *header_brigade;
    apr_bucket_brigade *input_brigade;
    char *old_cl_val, *old_te_val;
    apr_off_t cl_val;
 
    rb_methods rb_method;
 
    const char *upgrade;
 
    unsigned int do_100_continue        :1,
                 prefetch_nonblocking   :1,
                 force10                :1;
} proxy_http_req_t;
 
static int stream_reqbody(proxy_http_req_t *req)
{
    request_rec *r = req->r;
    int seen_eos = 0, rv = OK;
    apr_size_t hdr_len;
    char chunk_hdr[20];  /* must be here due to transient bucket. */
    conn_rec *origin = req->origin;
    proxy_conn_rec *p_conn = req->backend;
    apr_bucket_alloc_t *bucket_alloc = req->bucket_alloc;
    apr_bucket_brigade *header_brigade = req->header_brigade;
    apr_bucket_brigade *input_brigade = req->input_brigade;
    rb_methods rb_method = req->rb_method;
    apr_off_t bytes, bytes_streamed = 0;
    apr_bucket *e;
 
    do {
        if (APR_BRIGADE_EMPTY(input_brigade)
                && APR_BRIGADE_EMPTY(header_brigade)) {
            rv = ap_proxy_read_input(r, p_conn, input_brigade,
                                     HUGE_STRING_LEN);
            if (rv != OK) {
                return rv;
            }
        }
 
        if (!APR_BRIGADE_EMPTY(input_brigade)) {
            /* If this brigade contains EOS, remove it and be done. */
            if (APR_BUCKET_IS_EOS(APR_BRIGADE_LAST(input_brigade))) {
                seen_eos = 1;
 
                /* We can't pass this EOS to the output_filters. */
                e = APR_BRIGADE_LAST(input_brigade);
                apr_bucket_delete(e);
            }
 
            apr_brigade_length(input_brigade, 1, &bytes);
            bytes_streamed += bytes;
 
            if (rb_method == RB_STREAM_CHUNKED) {
                if (bytes) {
                    /*
                     * Prepend the size of the chunk
                     */
                    hdr_len = apr_snprintf(chunk_hdr, sizeof(chunk_hdr),
                                           "%" APR_UINT64_T_HEX_FMT CRLF,
                                           (apr_uint64_t)bytes);
                    ap_xlate_proto_to_ascii(chunk_hdr, hdr_len);
                    e = apr_bucket_transient_create(chunk_hdr, hdr_len,
                                                    bucket_alloc);
                    APR_BRIGADE_INSERT_HEAD(input_brigade, e);
 
                    /*
                     * Append the end-of-chunk CRLF
                     */
                    e = apr_bucket_immortal_create(CRLF_ASCII, 2, bucket_alloc);
                    APR_BRIGADE_INSERT_TAIL(input_brigade, e);
                }
                if (seen_eos) {
                    /*
                     * Append the tailing 0-size chunk
                     */
                    e = apr_bucket_immortal_create(ZERO_ASCII CRLF_ASCII
                                                   /* <trailers> */
                                                   CRLF_ASCII,
                                                   5, bucket_alloc);
                    APR_BRIGADE_INSERT_TAIL(input_brigade, e);
                }
            }
            else if (rb_method == RB_STREAM_CL
                     && (bytes_streamed > req->cl_val
                         || (seen_eos && bytes_streamed < req->cl_val))) {
                /* C-L != bytes streamed?!?
                 *
                 * Prevent HTTP Request/Response Splitting.
                 *
                 * We can't stream more (or less) bytes at the back end since
                 * they could be interpreted in separate requests (more bytes
                 * now would start a new request, less bytes would make the
                 * first bytes of the next request be part of the current one).
                 *
                 * It can't happen from the client connection here thanks to
                 * ap_http_filter(), but some module's filter may be playing
                 * bad games, hence the HTTP_INTERNAL_SERVER_ERROR.
                 */
                ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01086)
                              "read %s bytes of request body than expected "
                              "(got %" APR_OFF_T_FMT ", expected "
                              "%" APR_OFF_T_FMT ")",
                              bytes_streamed > req->cl_val ? "more" : "less",
                              bytes_streamed, req->cl_val);
                return HTTP_INTERNAL_SERVER_ERROR;
            }
 
            if (seen_eos && apr_table_get(r->subprocess_env,
                                          "proxy-sendextracrlf")) {
                e = apr_bucket_immortal_create(CRLF_ASCII, 2, bucket_alloc);
                APR_BRIGADE_INSERT_TAIL(input_brigade, e);
            }
        }
 
        /* If we never sent the header brigade, go ahead and take care of
         * that now by prepending it (once only since header_brigade will be
         * empty afterward).
         */
        APR_BRIGADE_PREPEND(input_brigade, header_brigade);
 
        /* Flush here on EOS because we won't ap_proxy_read_input() again. */
        rv = ap_proxy_pass_brigade(bucket_alloc, r, p_conn, origin,
                                   input_brigade, seen_eos);
        if (rv != OK) {
            return rv;
        }
    } while (!seen_eos);
 
    return OK;
}
 
static void terminate_headers(proxy_http_req_t *req)
{
    apr_bucket_alloc_t *bucket_alloc = req->bucket_alloc;
    apr_bucket *e;
    char *buf;
 
    /*
     * Handle Connection: header if we do HTTP/1.1 request:
     * If we plan to close the backend connection sent Connection: close
     * otherwise sent Connection: Keep-Alive.
     */
    if (!req->force10) {
        if (req->upgrade) {
            buf = apr_pstrdup(req->p, "Connection: Upgrade" CRLF);
            ap_xlate_proto_to_ascii(buf, strlen(buf));
            e = apr_bucket_pool_create(buf, strlen(buf), req->p, bucket_alloc);
            APR_BRIGADE_INSERT_TAIL(req->header_brigade, e);
 
            /* Tell the backend that it can upgrade the connection. */
            buf = apr_pstrcat(req->p, "Upgrade: ", req->upgrade, CRLF, NULL);
        }
        else if (ap_proxy_connection_reusable(req->backend)) {
            buf = apr_pstrdup(req->p, "Connection: Keep-Alive" CRLF);
        }
        else {
            buf = apr_pstrdup(req->p, "Connection: close" CRLF);
        }
        ap_xlate_proto_to_ascii(buf, strlen(buf));
        e = apr_bucket_pool_create(buf, strlen(buf), req->p, bucket_alloc);
        APR_BRIGADE_INSERT_TAIL(req->header_brigade, e);
    }
 
    /* add empty line at the end of the headers */
    e = apr_bucket_immortal_create(CRLF_ASCII, 2, bucket_alloc);
    APR_BRIGADE_INSERT_TAIL(req->header_brigade, e);
}
 
static int ap_proxy_http_prefetch(proxy_http_req_t *req,
                                  apr_uri_t *uri, char *url)
{
    apr_pool_t *p = req->p;
    request_rec *r = req->r;
    conn_rec *c = r->connection;
    proxy_conn_rec *p_conn = req->backend;
    apr_bucket_alloc_t *bucket_alloc = req->bucket_alloc;
    apr_bucket_brigade *header_brigade = req->header_brigade;
    apr_bucket_brigade *input_brigade = req->input_brigade;
    apr_bucket *e;
    apr_off_t bytes_read = 0;
    apr_off_t bytes;
    int rv;
 
    rv = ap_proxy_create_hdrbrgd(p, header_brigade, r, p_conn,
                                 req->worker, req->sconf,
                                 uri, url, req->server_portstr,
                                 &req->old_cl_val, &req->old_te_val);
    if (rv != OK) {
        return rv;
    }
 
    /* sub-requests never use keepalives, and mustn't pass request bodies.
     * Because the new logic looks at input_brigade, we will self-terminate
     * input_brigade and jump past all of the request body logic...
     * Reading anything with ap_get_brigade is likely to consume the
     * main request's body or read beyond EOS - which would be unpleasant.
     *
     * An exception: when a kept_body is present, then subrequest CAN use
     * pass request bodies, and we DONT skip the body.
     */
    if (!r->kept_body && r->main) {
        /* XXX: Why DON'T sub-requests use keepalives? */
        p_conn->close = 1;
        req->old_te_val = NULL;
        req->old_cl_val = NULL;
        req->rb_method = RB_STREAM_CL;
        e = apr_bucket_eos_create(input_brigade->bucket_alloc);
        APR_BRIGADE_INSERT_TAIL(input_brigade, e);
        goto skip_body;
    }
 
    /* WE only understand chunked.  Other modules might inject
     * (and therefore, decode) other flavors but we don't know
     * that the can and have done so unless they remove
     * their decoding from the headers_in T-E list.
     * XXX: Make this extensible, but in doing so, presume the
     * encoding has been done by the extensions' handler, and
     * do not modify add_te_chunked's logic
     */
    if (req->old_te_val && ap_cstr_casecmp(req->old_te_val, "chunked") != 0) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01093)
                      "%s Transfer-Encoding is not supported",
                      req->old_te_val);
        return HTTP_INTERNAL_SERVER_ERROR;
    }
 
    if (req->old_cl_val && req->old_te_val) {
        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01094)
                      "client %s (%s) requested Transfer-Encoding "
                      "chunked body with Content-Length (C-L ignored)",
                      c->client_ip, c->remote_host ? c->remote_host: "");
        req->old_cl_val = NULL;
        p_conn->close = 1;
    }
 
    rv = ap_proxy_prefetch_input(r, req->backend, input_brigade,
                                 req->prefetch_nonblocking ? APR_NONBLOCK_READ
                                                           : APR_BLOCK_READ,
                                 &bytes_read, MAX_MEM_SPOOL);
    if (rv != OK) {
        return rv;
    }
 
    /* Use chunked request body encoding or send a content-length body?
     *
     * Prefer C-L when:
     *
     *   We have no request body (handled by RB_STREAM_CL)
     *
     *   We have a request body length <= MAX_MEM_SPOOL
     *
     *   The administrator has setenv force-proxy-request-1.0
     *
     *   The client sent a C-L body, and the administrator has
     *   not setenv proxy-sendchunked or has set setenv proxy-sendcl
     *
     *   The client sent a T-E body, and the administrator has
     *   setenv proxy-sendcl, and not setenv proxy-sendchunked
     *
     * If both proxy-sendcl and proxy-sendchunked are set, the
     * behavior is the same as if neither were set, large bodies
     * that can't be read will be forwarded in their original
     * form of C-L, or T-E.
     *
     * To ensure maximum compatibility, setenv proxy-sendcl
     * To reduce server resource use,   setenv proxy-sendchunked
     *
     * Then address specific servers with conditional setenv
     * options to restore the default behavior where desirable.
     *
     * We have to compute content length by reading the entire request
     * body; if request body is not small, we'll spool the remaining
     * input to a temporary file.  Chunked is always preferable.
     *
     * We can only trust the client-provided C-L if the T-E header
     * is absent, and the filters are unchanged (the body won't
     * be resized by another content filter).
     */
    if (!APR_BRIGADE_EMPTY(input_brigade)
        && APR_BUCKET_IS_EOS(APR_BRIGADE_LAST(input_brigade))) {
        /* The whole thing fit, so our decision is trivial, use
         * the filtered bytes read from the client for the request
         * body Content-Length.
         *
         * If we expected no body, and read no body, do not set
         * the Content-Length.
         */
        if (req->old_cl_val || req->old_te_val || bytes_read) {
            req->old_cl_val = apr_off_t_toa(r->pool, bytes_read);
            req->cl_val = bytes_read;
        }
        req->rb_method = RB_STREAM_CL;
    }
    else if (req->old_te_val) {
        if (req->force10
             || (apr_table_get(r->subprocess_env, "proxy-sendcl")
                  && !apr_table_get(r->subprocess_env, "proxy-sendchunks")
                  && !apr_table_get(r->subprocess_env, "proxy-sendchunked"))) {
            req->rb_method = RB_SPOOL_CL;
        }
        else {
            req->rb_method = RB_STREAM_CHUNKED;
        }
    }
    else if (req->old_cl_val) {
        if (r->input_filters == r->proto_input_filters) {
            if (!ap_parse_strict_length(&req->cl_val, req->old_cl_val)) {
                ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01085)
                              "could not parse request Content-Length (%s)",
                              req->old_cl_val);
                return HTTP_BAD_REQUEST;
            }
            req->rb_method = RB_STREAM_CL;
        }
        else if (!req->force10
                  && (apr_table_get(r->subprocess_env, "proxy-sendchunks")
                      || apr_table_get(r->subprocess_env, "proxy-sendchunked"))
                  && !apr_table_get(r->subprocess_env, "proxy-sendcl")) {
            req->rb_method = RB_STREAM_CHUNKED;
        }
        else {
            req->rb_method = RB_SPOOL_CL;
        }
    }
    else {
        /* This is an appropriate default; very efficient for no-body
         * requests, and has the behavior that it will not add any C-L
         * when the old_cl_val is NULL.
         */
        req->rb_method = RB_SPOOL_CL;
    }
 
    switch (req->rb_method) {
    case RB_STREAM_CHUNKED:
        add_te_chunked(req->p, bucket_alloc, header_brigade);
        break;
 
    case RB_STREAM_CL:
        if (req->old_cl_val) {
            add_cl(req->p, bucket_alloc, header_brigade, req->old_cl_val);
        }
        break;
 
    default: /* => RB_SPOOL_CL */
        /* If we have to spool the body, do it now, before connecting or
         * reusing the backend connection.
         */
        rv = ap_proxy_spool_input(r, p_conn, input_brigade,
                                  &bytes, MAX_MEM_SPOOL);
        if (rv != OK) {
            return rv;
        }
        if (bytes || req->old_te_val || req->old_cl_val) {
            add_cl(p, bucket_alloc, header_brigade, apr_off_t_toa(p, bytes));
        }
    }
 
/* Yes I hate gotos.  This is the subrequest shortcut */
skip_body:
    terminate_headers(req);
 
    return OK;
}
 
static int ap_proxy_http_request(proxy_http_req_t *req)
{
    int rv;
    request_rec *r = req->r;
 
    /* send the request header/body, if any. */
    switch (req->rb_method) {
    case RB_SPOOL_CL:
    case RB_STREAM_CL:
    case RB_STREAM_CHUNKED:
        if (req->do_100_continue) {
            rv = ap_proxy_pass_brigade(req->bucket_alloc, r, req->backend,
                                       req->origin, req->header_brigade, 1);
        }
        else {
            rv = stream_reqbody(req);
        }
        break;
 
    default:
        /* shouldn't be possible */
        rv = HTTP_INTERNAL_SERVER_ERROR;
        break;
    }
 
    if (rv != OK) {
        conn_rec *c = r->connection;
        /* apr_status_t value has been logged in lower level method */
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01097)
                      "pass request body failed to %pI (%s) from %s (%s)",
                      req->backend->addr,
                      req->backend->hostname ? req->backend->hostname: "",
                      c->client_ip, c->remote_host ? c->remote_host: "");
        return rv;
    }
 
    return OK;
}
 
/*
 * If the date is a valid RFC 850 date or asctime() date, then it
 * is converted to the RFC 1123 format.
 */
static const char *date_canon(apr_pool_t *p, const char *date)
{
    apr_status_t rv;
    char* ndate;
 
    apr_time_t time = apr_date_parse_http(date);
    if (!time) {
        return date;
    }
 
    ndate = apr_palloc(p, APR_RFC822_DATE_LEN);
    rv = apr_rfc822_date(ndate, time);
    if (rv != APR_SUCCESS) {
        return date;
    }
 
    return ndate;
}
 
static request_rec *make_fake_req(conn_rec *c, request_rec *r)
{
    apr_pool_t *pool;
    request_rec *rp;
 
    apr_pool_create(&pool, c->pool);
    apr_pool_tag(pool, "proxy_http_rp");
 
    rp = apr_pcalloc(pool, sizeof(*r));
 
    rp->pool            = pool;
    rp->status          = HTTP_OK;
 
    rp->headers_in      = apr_table_make(pool, 50);
    rp->trailers_in     = apr_table_make(pool, 5);
 
    rp->subprocess_env  = apr_table_make(pool, 50);
    rp->headers_out     = apr_table_make(pool, 12);
    rp->trailers_out    = apr_table_make(pool, 5);
    rp->err_headers_out = apr_table_make(pool, 5);
    rp->notes           = apr_table_make(pool, 5);
 
    rp->server = r->server;
    rp->log = r->log;
    rp->proxyreq = r->proxyreq;
    rp->request_time = r->request_time;
    rp->connection      = c;
    rp->output_filters  = c->output_filters;
    rp->input_filters   = c->input_filters;
    rp->proto_output_filters  = c->output_filters;
    rp->proto_input_filters   = c->input_filters;
    rp->useragent_ip = c->client_ip;
    rp->useragent_addr = c->client_addr;
 
    rp->request_config  = ap_create_request_config(pool);
    proxy_run_create_req(r, rp);
 
    return rp;
}
 
static void process_proxy_header(request_rec *r, proxy_dir_conf *c,
                                 const char *key, const char *value)
{
    static const char *date_hdrs[]
        = { "Date", "Expires", "Last-Modified", NULL };
    static const struct {
        const char *name;
        ap_proxy_header_reverse_map_fn func;
    } transform_hdrs[] = {
        { "Location", ap_proxy_location_reverse_map },
        { "Content-Location", ap_proxy_location_reverse_map },
        { "URI", ap_proxy_location_reverse_map },
        { "Destination", ap_proxy_location_reverse_map },
        { "Set-Cookie", ap_proxy_cookie_reverse_map },
        { NULL, NULL }
    };
    int i;
    for (i = 0; date_hdrs[i]; ++i) {
        if (!ap_cstr_casecmp(date_hdrs[i], key)) {
            apr_table_add(r->headers_out, key,
                          date_canon(r->pool, value));
            return;
        }
    }
    for (i = 0; transform_hdrs[i].name; ++i) {
        if (!ap_cstr_casecmp(transform_hdrs[i].name, key)) {
            apr_table_add(r->headers_out, key,
                          (*transform_hdrs[i].func)(r, c, value));
            return;
       }
    }
    apr_table_add(r->headers_out, key, value);
}
 
/*
 * Note: pread_len is the length of the response that we've  mistakenly
 * read (assuming that we don't consider that an  error via
 * ProxyBadHeader StartBody). This depends on buffer actually being
 * local storage to the calling code in order for pread_len to make
 * any sense at all, since we depend on buffer still containing
 * what was read by ap_getline() upon return.
 */
static apr_status_t ap_proxy_read_headers(request_rec *r, request_rec *rr,
                                  char *buffer, int size,
                                  conn_rec *c, int *pread_len)
{
    int len;
    char *value, *end;
    int saw_headers = 0;
    void *sconf = r->server->module_config;
    proxy_server_conf *psc;
    proxy_dir_conf *dconf;
    apr_status_t rc;
    apr_bucket_brigade *tmp_bb;
 
    dconf = ap_get_module_config(r->per_dir_config, &proxy_module);
    psc = (proxy_server_conf *) ap_get_module_config(sconf, &proxy_module);
 
    r->headers_out = apr_table_make(r->pool, 20);
    r->trailers_out = apr_table_make(r->pool, 5);
    *pread_len = 0;
 
    /*
     * Read header lines until we get the empty separator line, a read error,
     * the connection closes (EOF), or we timeout.
     */
    ap_log_rerror(APLOG_MARK, APLOG_TRACE4, 0, r,
                  "Headers received from backend:");
 
    tmp_bb = apr_brigade_create(r->pool, c->bucket_alloc);
    while (1) {
        rc = ap_proxygetline(tmp_bb, buffer, size, rr,
                             AP_GETLINE_FOLD | AP_GETLINE_NOSPC_EOL, &len);
 
 
        if (rc != APR_SUCCESS) {
            if (APR_STATUS_IS_ENOSPC(rc)) {
                int trunc = (len > 128 ? 128 : len) / 2;
                ap_log_rerror(APLOG_MARK, APLOG_WARNING, rc, r, APLOGNO(10124)
                        "header size is over the limit allowed by "
                        "ResponseFieldSize (%d bytes). "
                        "Bad response header: '%.*s[...]%s'",
                        size, trunc, buffer, buffer + len - trunc);
            }
            else {
                ap_log_rerror(APLOG_MARK, APLOG_WARNING, rc, r, APLOGNO(10404) 
                              "Error reading headers from backend");
            }
            r->headers_out = NULL;
            return rc;
        }
 
        if (len <= 0) {
            break;
        }
        else {
            ap_log_rerror(APLOG_MARK, APLOG_TRACE4, 0, r, "%s", buffer);
        }
 
        if (!(value = strchr(buffer, ':'))) {     /* Find the colon separator */
 
            /* We may encounter invalid headers, usually from buggy
             * MS IIS servers, so we need to determine just how to handle
             * them. We can either ignore them, assume that they mark the
             * start-of-body (eg: a missing CRLF) or (the default) mark
             * the headers as totally bogus and return a 500. The sole
             * exception is an extra "HTTP/1.0 200, OK" line sprinkled
             * in between the usual MIME headers, which is a favorite
             * IIS bug.
             */
             /* XXX: The mask check is buggy if we ever see an HTTP/1.10 */
 
            if (!apr_date_checkmask(buffer, "HTTP/#.# ###*")) {
                if (psc->badopt == bad_error) {
                    /* Nope, it wasn't even an extra HTTP header. Give up. */
                    r->headers_out = NULL;
                    return APR_EINVAL;
                }
                else if (psc->badopt == bad_body) {
                    /* if we've already started loading headers_out, then
                     * return what we've accumulated so far, in the hopes
                     * that they are useful; also note that we likely pre-read
                     * the first line of the response.
                     */
                    if (saw_headers) {
                        ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, r, APLOGNO(01098)
                                      "Starting body due to bogus non-header "
                                      "in headers returned by %s (%s)",
                                      r->uri, r->method);
                        *pread_len = len;
                        return APR_SUCCESS;
                    }
                    else {
                        ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, r, APLOGNO(01099)
                                      "No HTTP headers returned by %s (%s)",
                                      r->uri, r->method);
                        return APR_SUCCESS;
                    }
                }
            }
            /* this is the psc->badopt == bad_ignore case */
            ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, r, APLOGNO(01100)
                          "Ignoring bogus HTTP header returned by %s (%s)",
                          r->uri, r->method);
            continue;
        }
 
        *value = '\0';
        ++value;
        /* XXX: RFC2068 defines only SP and HT as whitespace, this test is
         * wrong... and so are many others probably.
         */
        while (apr_isspace(*value))
            ++value;            /* Skip to start of value   */
 
        /* should strip trailing whitespace as well */
        for (end = &value[strlen(value)-1]; end > value && apr_isspace(*end); --end)
            *end = '\0';
 
        /* make sure we add so as not to destroy duplicated headers
         * Modify headers requiring canonicalisation and/or affected
         * by ProxyPassReverse and family with process_proxy_header
         */
        process_proxy_header(r, dconf, buffer, value);
        saw_headers = 1;
    }
    return APR_SUCCESS;
}
 
 
 
static int addit_dammit(void *v, const char *key, const char *val)
{
    apr_table_addn(v, key, val);
    return 1;
}
 
static apr_status_t ap_proxygetline(apr_bucket_brigade *bb, char *s, int n,
                                    request_rec *r, int flags, int *read)
{
    apr_status_t rv;
    apr_size_t len;
 
    rv = ap_rgetline(&s, n, &len, r, flags, bb);
    apr_brigade_cleanup(bb);
 
    if (rv == APR_SUCCESS || APR_STATUS_IS_ENOSPC(rv)) {
        *read = (int)len;
    } else {
        *read = -1;
    }
 
    return rv;
}
 
/*
 * Limit the number of interim responses we sent back to the client. Otherwise
 * we suffer from a memory build up. Besides there is NO sense in sending back
 * an unlimited number of interim responses to the client. Thus if we cross
 * this limit send back a 502 (Bad Gateway).
 */
#ifndef AP_MAX_INTERIM_RESPONSES
#define AP_MAX_INTERIM_RESPONSES 10
#endif
 
static int add_trailers(void *data, const char *key, const char *val)
{
    if (val) {
        apr_table_add((apr_table_t*)data, key, val);
    }
    return 1;
}
 
static int send_continue_body(proxy_http_req_t *req)
{
    int status;
 
    /* Send the request body (fully). */
    switch(req->rb_method) {
    case RB_SPOOL_CL:
    case RB_STREAM_CL:
    case RB_STREAM_CHUNKED:
        status = stream_reqbody(req);
        break;
    default:
        /* Shouldn't happen */
        status = HTTP_INTERNAL_SERVER_ERROR;
        break;
    }
    if (status != OK) {
        conn_rec *c = req->r->connection;
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, req->r,
                APLOGNO(10154) "pass request body failed "
                "to %pI (%s) from %s (%s) with status %i",
                req->backend->addr,
                req->backend->hostname ? req->backend->hostname : "",
                c->client_ip, c->remote_host ? c->remote_host : "",
                status);
        req->backend->close = 1;
    }
    return status;
}
 
static
int ap_proxy_http_process_response(proxy_http_req_t *req)
{
    apr_pool_t *p = req->p;
    request_rec *r = req->r;
    conn_rec *c = r->connection;
    proxy_worker *worker = req->worker;
    proxy_conn_rec *backend = req->backend;
    conn_rec *origin = req->origin;
    int do_100_continue = req->do_100_continue;
    int status;
 
    char *buffer;
    char fixed_buffer[HUGE_STRING_LEN];
    const char *buf;
    char keepchar;
    apr_bucket *e;
    apr_bucket_brigade *bb;
    apr_bucket_brigade *pass_bb;
    int len, backasswards;
    int interim_response = 0; /* non-zero whilst interim 1xx responses
                               * are being read. */
    apr_size_t response_field_size = 0;
    int pread_len = 0;
    apr_table_t *save_table;
    int backend_broke = 0;
    static const char *hop_by_hop_hdrs[] =
        {"Keep-Alive", "Proxy-Authenticate", "TE", "Trailer", "Upgrade", NULL};
    int i;
    const char *te = NULL;
    int original_status = r->status;
    int proxy_status = OK;
    const char *original_status_line = r->status_line;
    const char *proxy_status_line = NULL;
    apr_interval_time_t old_timeout = 0;
    proxy_dir_conf *dconf;
 
    dconf = ap_get_module_config(r->per_dir_config, &proxy_module);
 
    bb = apr_brigade_create(p, c->bucket_alloc);
    pass_bb = apr_brigade_create(p, c->bucket_alloc);
 
    /* Only use dynamically sized buffer if user specifies ResponseFieldSize */
    if(backend->worker->s->response_field_size_set) {
        response_field_size = backend->worker->s->response_field_size;
 
        if (response_field_size != HUGE_STRING_LEN)
            buffer = apr_pcalloc(p, response_field_size);
        else
            buffer = fixed_buffer;
    }
    else {
        response_field_size = HUGE_STRING_LEN;
        buffer = fixed_buffer;
    }
 
    /* Setup for 100-Continue timeout if appropriate */
    if (do_100_continue && worker->s->ping_timeout_set) {
        apr_socket_timeout_get(backend->sock, &old_timeout);
        if (worker->s->ping_timeout != old_timeout) {
            apr_status_t rc;
            rc = apr_socket_timeout_set(backend->sock, worker->s->ping_timeout);
            if (rc != APR_SUCCESS) {
                ap_log_rerror(APLOG_MARK, APLOG_ERR, rc, r, APLOGNO(01101)
                              "could not set 100-Continue timeout");
            }
        }
    }
 
    /* Get response from the remote server, and pass it up the
     * filter chain
     */
 
    backend->r = make_fake_req(origin, r);
    /* In case anyone needs to know, this is a fake request that is really a
     * response.
     */
    backend->r->proxyreq = PROXYREQ_RESPONSE;
    apr_table_setn(r->notes, "proxy-source-port", apr_psprintf(r->pool, "%hu",
                   origin->local_addr->port));
    do {
        apr_status_t rc;
        const char *upgrade = NULL;
        int major = 0, minor = 0;
        int toclose = 0;
 
        apr_brigade_cleanup(bb);
 
        rc = ap_proxygetline(backend->tmp_bb, buffer, response_field_size,
                             backend->r, 0, &len);
        if (len == 0) {
            /* handle one potential stray CRLF */
            rc = ap_proxygetline(backend->tmp_bb, buffer, response_field_size,
                                 backend->r, 0, &len);
        }
        if (len <= 0) {
            ap_log_rerror(APLOG_MARK, APLOG_ERR, rc, r, APLOGNO(01102)
                          "error reading status line from remote "
                          "server %s:%d", backend->hostname, backend->port);
            if (APR_STATUS_IS_TIMEUP(rc)) {
                apr_table_setn(r->notes, "proxy_timedout", "1");
                ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01103) "read timeout");
                if (do_100_continue) {
                    return ap_proxyerror(r, HTTP_SERVICE_UNAVAILABLE,
                                         "Timeout on 100-Continue");
                }
            }
            /*
             * If we are a reverse proxy request shutdown the connection
             * WITHOUT ANY response to trigger a retry by the client
             * if allowed (as for idempotent requests).
             * BUT currently we should not do this if the request is the
             * first request on a keepalive connection as browsers like
             * seamonkey only display an empty page in this case and do
             * not do a retry. We should also not do this on a
             * connection which times out; instead handle as
             * we normally would handle timeouts
             */
            if (r->proxyreq == PROXYREQ_REVERSE && c->keepalives &&
                !APR_STATUS_IS_TIMEUP(rc)) {
                apr_bucket *eos;
 
                ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01104)
                              "Closing connection to client because"
                              " reading from backend server %s:%d failed."
                              " Number of keepalives %i", backend->hostname,
                              backend->port, c->keepalives);
                ap_proxy_backend_broke(r, bb);
                /*
                 * Add an EOC bucket to signal the ap_http_header_filter
                 * that it should get out of our way, BUT ensure that the
                 * EOC bucket is inserted BEFORE an EOS bucket in bb as
                 * some resource filters like mod_deflate pass everything
                 * up to the EOS down the chain immediately and sent the
                 * remainder of the brigade later (or even never). But in
                 * this case the ap_http_header_filter does not get out of
                 * our way soon enough.
                 */
                e = ap_bucket_eoc_create(c->bucket_alloc);
                eos = APR_BRIGADE_LAST(bb);
                while ((APR_BRIGADE_SENTINEL(bb) != eos)
                       && !APR_BUCKET_IS_EOS(eos)) {
                    eos = APR_BUCKET_PREV(eos);
                }
                if (eos == APR_BRIGADE_SENTINEL(bb)) {
                    APR_BRIGADE_INSERT_TAIL(bb, e);
                }
                else {
                    APR_BUCKET_INSERT_BEFORE(eos, e);
                }
                ap_pass_brigade(r->output_filters, bb);
                /* Mark the backend connection for closing */
                backend->close = 1;
                if (origin->keepalives) {
                    /* We already had a request on this backend connection and
                     * might just have run into a keepalive race. Hence we
                     * think positive and assume that the backend is fine and
                     * we do not need to signal an error on backend side.
                     */
                    return OK;
                }
                /*
                 * This happened on our first request on this connection to the
                 * backend. This indicates something fishy with the backend.
                 * Return HTTP_INTERNAL_SERVER_ERROR to signal an unrecoverable
                 * server error. We do not worry about r->status code and a
                 * possible error response here as the ap_http_outerror_filter
                 * will fix all of this for us.
                 */
                return HTTP_INTERNAL_SERVER_ERROR;
            }
            if (!c->keepalives) {
                ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01105)
                              "NOT Closing connection to client"
                              " although reading from backend server %s:%d"
                              " failed.",
                              backend->hostname, backend->port);
            }
            return ap_proxyerror(r, HTTP_BAD_GATEWAY,
                                 "Error reading from remote server");
        }
        /* XXX: Is this a real headers length send from remote? */
        backend->worker->s->read += len;
 
        /* Is it an HTTP/1 response?
         * This is buggy if we ever see an HTTP/1.10
         */
        if (apr_date_checkmask(buffer, "HTTP/#.# ###*")) {
            major = buffer[5] - '0';
            minor = buffer[7] - '0';
 
            /* If not an HTTP/1 message or
             * if the status line was > 8192 bytes
             */
            if ((major != 1) || (len >= response_field_size - 1)) {
                return ap_proxyerror(r, HTTP_BAD_GATEWAY,
                            apr_pstrcat(p, "Corrupt status line returned "
                                        "by remote server: ", buffer, NULL));
            }
            backasswards = 0;
 
            keepchar = buffer[12];
            buffer[12] = '\0';
            proxy_status = atoi(&buffer[9]);
            apr_table_setn(r->notes, "proxy-status",
                           apr_pstrdup(r->pool, &buffer[9]));
 
            if (keepchar != '\0') {
                buffer[12] = keepchar;
            } else {
                /* 2616 requires the space in Status-Line; the origin
                 * server may have sent one but ap_rgetline_core will
                 * have stripped it. */
                buffer[12] = ' ';
                buffer[13] = '\0';
            }
            proxy_status_line = apr_pstrdup(p, &buffer[9]);
 
            /* The status out of the front is the same as the status coming in
             * from the back, until further notice.
             */
            r->status = proxy_status;
            r->status_line = proxy_status_line;
 
            ap_log_rerror(APLOG_MARK, APLOG_TRACE3, 0, r,
                          "Status from backend: %d", proxy_status);
 
            /* read the headers. */
            /* N.B. for HTTP/1.0 clients, we have to fold line-wrapped headers*/
            /* Also, take care with headers with multiple occurrences. */
 
            /* First, tuck away all already existing cookies */
            save_table = apr_table_make(r->pool, 2);
            apr_table_do(addit_dammit, save_table, r->headers_out,
                         "Set-Cookie", NULL);
 
            /* shove the headers direct into r->headers_out */
            rc = ap_proxy_read_headers(r, backend->r, buffer, response_field_size,
                                       origin, &pread_len);
 
            if (rc != APR_SUCCESS || r->headers_out == NULL) {
                ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, r, APLOGNO(01106)
                              "bad HTTP/%d.%d header returned by %s (%s)",
                              major, minor, r->uri, r->method);
                backend->close = 1;
                /*
                 * ap_send_error relies on a headers_out to be present. we
                 * are in a bad position here.. so force everything we send out
                 * to have nothing to do with the incoming packet
                 */
                r->headers_out = apr_table_make(r->pool,1);
                r->status = HTTP_BAD_GATEWAY;
                r->status_line = "bad gateway";
                return r->status;
            }
 
            /* Now, add in the just read cookies */
            apr_table_do(addit_dammit, save_table, r->headers_out,
                         "Set-Cookie", NULL);
 
            /* and now load 'em all in */
            if (!apr_is_empty_table(save_table)) {
                apr_table_unset(r->headers_out, "Set-Cookie");
                r->headers_out = apr_table_overlay(r->pool,
                                                   r->headers_out,
                                                   save_table);
            }
 
            /*
             * Save a possible Transfer-Encoding header as we need it later for
             * ap_http_filter to know where to end.
             */
            te = apr_table_get(r->headers_out, "Transfer-Encoding");
 
            /* can't have both Content-Length and Transfer-Encoding */
            if (te && apr_table_get(r->headers_out, "Content-Length")) {
                /*
                 * 2616 section 4.4, point 3: "if both Transfer-Encoding
                 * and Content-Length are received, the latter MUST be
                 * ignored";
                 *
                 * To help mitigate HTTP Splitting, unset Content-Length
                 * and shut down the backend server connection
                 * XXX: We aught to treat such a response as uncachable
                 */
                apr_table_unset(r->headers_out, "Content-Length");
                ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01107)
                              "server %s:%d returned Transfer-Encoding"
                              " and Content-Length",
                              backend->hostname, backend->port);
                backend->close = 1;
            }
 
            upgrade = apr_table_get(r->headers_out, "Upgrade");
            if (proxy_status == HTTP_SWITCHING_PROTOCOLS) {
                if (!upgrade || !req->upgrade || (strcasecmp(req->upgrade,
                                                             upgrade) != 0)) {
                    return ap_proxyerror(r, HTTP_BAD_GATEWAY,
                                         apr_pstrcat(p, "Unexpected Upgrade: ",
                                                     upgrade ? upgrade : "n/a",
                                                     " (expecting ",
                                                     req->upgrade ? req->upgrade
                                                                  : "n/a", ")",
                                                     NULL));
                }
                backend->close = 1;
            }
 
            /* strip connection listed hop-by-hop headers from response */
            toclose = ap_proxy_clear_connection_fn(r, r->headers_out);
            if (toclose) {
                backend->close = 1;
                if (toclose < 0) {
                    return ap_proxyerror(r, HTTP_BAD_GATEWAY,
                                         "Malformed connection header");
                }
            }
 
            if ((buf = apr_table_get(r->headers_out, "Content-Type"))) {
                ap_set_content_type(r, apr_pstrdup(p, buf));
            }
            if (!ap_is_HTTP_INFO(proxy_status)) {
                ap_proxy_pre_http_request(origin, backend->r);
            }
 
            /* Clear hop-by-hop headers */
            for (i=0; hop_by_hop_hdrs[i]; ++i) {
                apr_table_unset(r->headers_out, hop_by_hop_hdrs[i]);
            }
 
            /* Delete warnings with wrong date */
            r->headers_out = ap_proxy_clean_warnings(p, r->headers_out);
 
            /* handle Via header in response */
            if (req->sconf->viaopt != via_off
                    && req->sconf->viaopt != via_block) {
                const char *server_name = ap_get_server_name(r);
                /* If USE_CANONICAL_NAME_OFF was configured for the proxy virtual host,
                 * then the server name returned by ap_get_server_name() is the
                 * origin server name (which does make too much sense with Via: headers)
                 * so we use the proxy vhost's name instead.
                 */
                if (server_name == r->hostname)
                    server_name = r->server->server_hostname;
                /* create a "Via:" response header entry and merge it */
                apr_table_addn(r->headers_out, "Via",
                               (req->sconf->viaopt == via_full)
                                     ? apr_psprintf(p, "%d.%d %s%s (%s)",
                                           HTTP_VERSION_MAJOR(r->proto_num),
                                           HTTP_VERSION_MINOR(r->proto_num),
                                           server_name,
                                           req->server_portstr,
                                           AP_SERVER_BASEVERSION)
                                     : apr_psprintf(p, "%d.%d %s%s",
                                           HTTP_VERSION_MAJOR(r->proto_num),
                                           HTTP_VERSION_MINOR(r->proto_num),
                                           server_name,
                                           req->server_portstr)
                );
            }
 
            /* cancel keepalive if HTTP/1.0 or less */
            if ((major < 1) || (minor < 1)) {
                backend->close = 1;
                origin->keepalive = AP_CONN_CLOSE;
            }
            else {
                /*
                 * Keep track of the number of keepalives we processed on this
                 * connection.
                 */
                origin->keepalives++;
            }
 
        } else {
            /* an http/0.9 response */
            backasswards = 1;
            r->status = proxy_status = 200;
            r->status_line = "200 OK";
            backend->close = 1;
        }
 
        if (ap_is_HTTP_INFO(proxy_status)) {
            const char *policy = NULL;
 
            /* RFC2616 tells us to forward this.
             *
             * OTOH, an interim response here may mean the backend
             * is playing sillybuggers.  The Client didn't ask for
             * it within the defined HTTP/1.1 mechanisms, and if
             * it's an extension, it may also be unsupported by us.
             *
             * There's also the possibility that changing existing
             * behaviour here might break something.
             *
             * So let's make it configurable.
             *
             * We need to force "r->expecting_100 = 1" for RFC behaviour
             * otherwise ap_send_interim_response() does nothing when
             * the client did not ask for 100-continue.
             *
             * 101 Switching Protocol has its own configuration which
             * shouldn't be interfered by "proxy-interim-response".
             */
            if (proxy_status != HTTP_SWITCHING_PROTOCOLS) {
                policy = apr_table_get(r->subprocess_env,
                                       "proxy-interim-response");
            }
            ap_log_rerror(APLOG_MARK, APLOG_TRACE2, 0, r,
                          "HTTP: received interim %d response (policy: %s)",
                          r->status, policy ? policy : "n/a");
            if (!policy
                    || (!strcasecmp(policy, "RFC")
                        && (proxy_status != HTTP_CONTINUE
                            || (r->expecting_100 = 1)))) {
                switch (proxy_status) {
                case HTTP_SWITCHING_PROTOCOLS:
                    AP_DEBUG_ASSERT(upgrade != NULL);
                    apr_table_setn(r->headers_out, "Connection", "Upgrade");
                    apr_table_setn(r->headers_out, "Upgrade",
                                   apr_pstrdup(p, upgrade));
                    break;
                }
                ap_send_interim_response(r, 1);
            }
            /* FIXME: refine this to be able to specify per-response-status
             * policies and maybe also add option to bail out with 502
             */
            else if (strcasecmp(policy, "Suppress")) {
                ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, r, APLOGNO(01108)
                              "undefined proxy interim response policy");
            }
            interim_response++;
        }
        else {
            interim_response = 0;
        }
 
        /* If we still do 100-continue (end-to-end or ping), either the
         * current response is the expected "100 Continue" and we are done
         * with this mode, or this is another interim response and we'll wait
         * for the next one, or this is a final response and hence the backend
         * did not honor our expectation.
         */
        if (do_100_continue && (!interim_response
                                || proxy_status == HTTP_CONTINUE)) {
            /* RFC 7231 - Section 5.1.1 - Expect - Requirement for servers
             *   A server that responds with a final status code before
             *   reading the entire message body SHOULD indicate in that
             *   response whether it intends to close the connection or
             *   continue reading and discarding the request message.
             *
             * So, if this response is not an interim 100 Continue, we can
             * avoid sending the request body if the backend responded with
             * "Connection: close" or HTTP < 1.1, and either let the core
             * discard it or the caller try another balancer member with the
             * same body (given status 503, though not implemented yet).
             */
            int do_send_body = (proxy_status == HTTP_CONTINUE
                                || (!toclose && major > 0 && minor > 0));
 
            /* Reset to old timeout iff we've adjusted it. */
            if (worker->s->ping_timeout_set) {
                apr_socket_timeout_set(backend->sock, old_timeout);
            }
 
            ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(10153)
                          "HTTP: %s100 continue sent by %pI (%s): "
                          "%ssending body (response: HTTP/%i.%i %s)",
                          proxy_status != HTTP_CONTINUE ? "no " : "",
                          backend->addr,
                          backend->hostname ? backend->hostname : "",
                          do_send_body ? "" : "not ",
                          major, minor, proxy_status_line);
 
            if (do_send_body) {
                status = send_continue_body(req);
                if (status != OK) {
                    return status;
                }
            }
            else {
                /* If we don't read the client connection any further, since
                 * there are pending data it should be "Connection: close"d to
                 * prevent reuse. We don't exactly c->keepalive = AP_CONN_CLOSE
                 * here though, because error_override or a potential retry on
                 * another backend could finally read that data and finalize
                 * the request processing, making keep-alive possible. So what
                 * we do is leaving r->expecting_100 alone, ap_set_keepalive()
                 * will do the right thing according to the final response and
                 * any later update of r->expecting_100.
                 */
            }
 
            /* Once only! */
            do_100_continue = 0;
        }
 
        if (proxy_status == HTTP_SWITCHING_PROTOCOLS) {
            apr_status_t rv;
            proxy_tunnel_rec *tunnel;
            apr_interval_time_t client_timeout = -1,
                                backend_timeout = -1;
 
            /* If we didn't send the full body yet, do it now */
            if (do_100_continue) {
                r->expecting_100 = 0;
                status = send_continue_body(req);
                if (status != OK) {
                    return status;
                }
            }
 
            ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(10239)
                          "HTTP: tunneling protocol %s", upgrade);
 
            rv = ap_proxy_tunnel_create(&tunnel, r, origin, upgrade);
            if (rv != APR_SUCCESS) {
                ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(10240)
                              "can't create tunnel for %s", upgrade);
                return HTTP_INTERNAL_SERVER_ERROR;
            }
 
            /* Set timeout to the highest configured for client or backend */
            apr_socket_timeout_get(backend->sock, &backend_timeout);
            apr_socket_timeout_get(ap_get_conn_socket(c), &client_timeout);
            if (backend_timeout >= 0 && backend_timeout > client_timeout) {
                tunnel->timeout = backend_timeout;
            }
            else {
                tunnel->timeout = client_timeout;
            }
 
            /* Let proxy tunnel forward everything */
            status = ap_proxy_tunnel_run(tunnel);
 
            /* We are done with both connections */
            return DONE;
        }
 
        if (interim_response) {
            /* Already forwarded above, read next response */
            continue;
        }
 
        /* Moved the fixups of Date headers and those affected by
         * ProxyPassReverse/etc from here to ap_proxy_read_headers
         */
 
        /* PR 41646: get HEAD right with ProxyErrorOverride */
        if (ap_proxy_should_override(dconf, proxy_status)) {
            if (proxy_status == HTTP_UNAUTHORIZED) {
                const char *buf;
                const char *wa = "WWW-Authenticate";
                if ((buf = apr_table_get(r->headers_out, wa))) {
                    apr_table_set(r->err_headers_out, wa, buf);
                } else {
                    ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01109)
                                  "origin server sent 401 without "
                                  "WWW-Authenticate header");
                }
            }
 
            /* clear r->status for override error, otherwise ErrorDocument
             * thinks that this is a recursive error, and doesn't find the
             * custom error page
             */
            r->status = HTTP_OK;
            /* Discard body, if one is expected */
            if (!r->header_only && !AP_STATUS_IS_HEADER_ONLY(proxy_status)) {
                const char *tmp;
                /* Add minimal headers needed to allow http_in filter
                 * detecting end of body without waiting for a timeout. */
                if ((tmp = apr_table_get(r->headers_out, "Transfer-Encoding"))) {
                    apr_table_set(backend->r->headers_in, "Transfer-Encoding", tmp);
                }
                else if ((tmp = apr_table_get(r->headers_out, "Content-Length"))) {
                    apr_table_set(backend->r->headers_in, "Content-Length", tmp);
                }
                else if (te) {
                    apr_table_set(backend->r->headers_in, "Transfer-Encoding", te);
                }
                ap_discard_request_body(backend->r);
            }
            /*
             * prevent proxy_handler() from treating this as an
             * internal error.
             */
            apr_table_setn(r->notes, "proxy-error-override", "1");
            return proxy_status;
        }
 
        /* Forward back Upgrade header if it matches the configured one(s), it
         * may be an HTTP_UPGRADE_REQUIRED response or some other status where
         * Upgrade makes sense to negotiate the protocol by other means.
         */
        if (upgrade && ap_proxy_worker_can_upgrade(p, worker, upgrade,
                                                   (*req->proto == 'w')
                                                   ? "WebSocket" : NULL)) {
            apr_table_setn(r->headers_out, "Connection", "Upgrade");
            apr_table_setn(r->headers_out, "Upgrade", apr_pstrdup(p, upgrade));
        }
 
        r->sent_bodyct = 1;
        /*
         * Is it an HTTP/0.9 response or did we maybe preread the 1st line of
         * the response? If so, load the extra data. These are 2 mutually
         * exclusive possibilities, that just happen to require very
         * similar behavior.
         */
        if (backasswards || pread_len) {
            apr_ssize_t cntr = (apr_ssize_t)pread_len;
            if (backasswards) {
                /*@@@FIXME:
                 * At this point in response processing of a 0.9 response,
                 * we don't know yet whether data is binary or not.
                 * mod_charset_lite will get control later on, so it cannot
                 * decide on the conversion of this buffer full of data.
                 * However, chances are that we are not really talking to an
                 * HTTP/0.9 server, but to some different protocol, therefore
                 * the best guess IMHO is to always treat the buffer as "text/x":
                 */
                ap_xlate_proto_to_ascii(buffer, len);
                cntr = (apr_ssize_t)len;
            }
            e = apr_bucket_heap_create(buffer, cntr, NULL, c->bucket_alloc);
            APR_BRIGADE_INSERT_TAIL(bb, e);
        }
 
        /* send body - but only if a body is expected */
        if ((!r->header_only) &&                   /* not HEAD request */
            (proxy_status != HTTP_NO_CONTENT) &&      /* not 204 */
            (proxy_status != HTTP_NOT_MODIFIED)) {    /* not 304 */
            apr_read_type_e mode;
            int finish;
 
            /* We need to copy the output headers and treat them as input
             * headers as well.  BUT, we need to do this before we remove
             * TE, so that they are preserved accordingly for
             * ap_http_filter to know where to end.
             */
            backend->r->headers_in = apr_table_clone(backend->r->pool, r->headers_out);
            /*
             * Restore Transfer-Encoding header from response if we saved
             * one before and there is none left. We need it for the
             * ap_http_filter. See above.
             */
            if (te && !apr_table_get(backend->r->headers_in, "Transfer-Encoding")) {
                apr_table_add(backend->r->headers_in, "Transfer-Encoding", te);
            }
 
            apr_table_unset(r->headers_out,"Transfer-Encoding");
 
            ap_log_rerror(APLOG_MARK, APLOG_TRACE3, 0, r, "start body send");
 
            /* read the body, pass it to the output filters */
 
            /* Handle the case where the error document is itself reverse
             * proxied and was successful. We must maintain any previous
             * error status so that an underlying error (eg HTTP_NOT_FOUND)
             * doesn't become an HTTP_OK.
             */
            if (ap_proxy_should_override(dconf, original_status)) {
                r->status = original_status;
                r->status_line = original_status_line;
            }
 
            mode = APR_NONBLOCK_READ;
            finish = FALSE;
            do {
                apr_off_t readbytes;
                apr_status_t rv;
 
                rv = ap_get_brigade(backend->r->input_filters, bb,
                                    AP_MODE_READBYTES, mode,
                                    req->sconf->io_buffer_size);
 
                /* ap_get_brigade will return success with an empty brigade
                 * for a non-blocking read which would block: */
                if (mode == APR_NONBLOCK_READ
                    && (APR_STATUS_IS_EAGAIN(rv)
                        || (rv == APR_SUCCESS && APR_BRIGADE_EMPTY(bb)))) {
                    /* flush to the client and switch to blocking mode */
                    e = apr_bucket_flush_create(c->bucket_alloc);
                    APR_BRIGADE_INSERT_TAIL(bb, e);
                    if (ap_pass_brigade(r->output_filters, bb)
                        || c->aborted) {
                        backend->close = 1;
                        break;
                    }
                    apr_brigade_cleanup(bb);
                    mode = APR_BLOCK_READ;
                    continue;
                }
                else if (rv == APR_EOF) {
                    backend->close = 1;
                    break;
                }
                else if (rv != APR_SUCCESS) {
                    /* In this case, we are in real trouble because
                     * our backend bailed on us. Pass along a 502 error
                     * error bucket
                     */
                    ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(01110)
                                  "error reading response");
                    apr_brigade_cleanup(bb);
                    ap_proxy_backend_broke(r, bb);
                    ap_pass_brigade(r->output_filters, bb);
                    backend_broke = 1;
                    backend->close = 1;
                    break;
                }
                /* next time try a non-blocking read */
                mode = APR_NONBLOCK_READ;
 
                if (!apr_is_empty_table(backend->r->trailers_in)) {
                    apr_table_do(add_trailers, r->trailers_out,
                            backend->r->trailers_in, NULL);
                    apr_table_clear(backend->r->trailers_in);
                }
 
                apr_brigade_length(bb, 0, &readbytes);
                backend->worker->s->read += readbytes;
#if DEBUGGING
                {
                ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01111)
                              "readbytes: %#x", readbytes);
                }
#endif
                /* sanity check */
                if (APR_BRIGADE_EMPTY(bb)) {
                    break;
                }
 
                /* Switch the allocator lifetime of the buckets */
                ap_proxy_buckets_lifetime_transform(r, bb, pass_bb);
 
                /* found the last brigade? */
                if (APR_BUCKET_IS_EOS(APR_BRIGADE_LAST(pass_bb))) {
 
                    /* signal that we must leave */
                    finish = TRUE;
 
                    /* the brigade may contain transient buckets that contain
                     * data that lives only as long as the backend connection.
                     * Force a setaside so these transient buckets become heap
                     * buckets that live as long as the request.
                     */
                    for (e = APR_BRIGADE_FIRST(pass_bb); e
                            != APR_BRIGADE_SENTINEL(pass_bb); e
                            = APR_BUCKET_NEXT(e)) {
                        apr_bucket_setaside(e, r->pool);
                    }
 
                    /* finally it is safe to clean up the brigade from the
                     * connection pool, as we have forced a setaside on all
                     * buckets.
                     */
                    apr_brigade_cleanup(bb);
 
                    /* make sure we release the backend connection as soon
                     * as we know we are done, so that the backend isn't
                     * left waiting for a slow client to eventually
                     * acknowledge the data.
                     */
                    ap_proxy_release_connection(backend->worker->s->scheme,
                            backend, r->server);
                    /* Ensure that the backend is not reused */
                    req->backend = NULL;
 
                }
 
                /* try send what we read */
                if (ap_pass_brigade(r->output_filters, pass_bb) != APR_SUCCESS
                    || c->aborted) {
                    /* Ack! Phbtt! Die! User aborted! */
                    /* Only close backend if we haven't got all from the
                     * backend. Furthermore if req->backend is NULL it is no
                     * longer safe to fiddle around with backend as it might
                     * be already in use by another thread.
                     */
                    if (req->backend) {
                        /* this causes socket close below */
                        req->backend->close = 1;
                    }
                    finish = TRUE;
                }
 
                /* make sure we always clean up after ourselves */
                apr_brigade_cleanup(pass_bb);
                apr_brigade_cleanup(bb);
 
            } while (!finish);
 
            ap_log_rerror(APLOG_MARK, APLOG_TRACE2, 0, r, "end body send");
        }
        else {
            ap_log_rerror(APLOG_MARK, APLOG_TRACE2, 0, r, "header only");
 
            /* make sure we release the backend connection as soon
             * as we know we are done, so that the backend isn't
             * left waiting for a slow client to eventually
             * acknowledge the data.
             */
            ap_proxy_release_connection(backend->worker->s->scheme,
                    backend, r->server);
            /* Ensure that the backend is not reused */
            req->backend = NULL;
 
            /* Pass EOS bucket down the filter chain. */
            e = apr_bucket_eos_create(c->bucket_alloc);
            APR_BRIGADE_INSERT_TAIL(bb, e);
            ap_pass_brigade(r->output_filters, bb);
 
            apr_brigade_cleanup(bb);
        }
    } while (interim_response && (interim_response < AP_MAX_INTERIM_RESPONSES));
 
    /* We have to cleanup bb brigade, because buckets inserted to it could be
     * created from scpool and this pool can be freed before this brigade. */
    apr_brigade_cleanup(bb);
 
    /* See define of AP_MAX_INTERIM_RESPONSES for why */
    if (interim_response >= AP_MAX_INTERIM_RESPONSES) {
        return ap_proxyerror(r, HTTP_BAD_GATEWAY,
                             apr_psprintf(p,
                             "Too many (%d) interim responses from origin server",
                             interim_response));
    }
 
    /* If our connection with the client is to be aborted, return DONE. */
    if (c->aborted || backend_broke) {
        return DONE;
    }
 
    return OK;
}
 
static
apr_status_t ap_proxy_http_cleanup(const char *scheme, request_rec *r,
                                   proxy_conn_rec *backend)
{
    ap_proxy_release_connection(scheme, backend, r->server);
    return OK;
}
 
/*
 * This handles http:// URLs, and other URLs using a remote proxy over http
 * If proxyhost is NULL, then contact the server directly, otherwise
 * go via the proxy.
 * Note that if a proxy is used, then URLs other than http: can be accessed,
 * also, if we have trouble which is clearly specific to the proxy, then
 * we return DECLINED so that we can try another proxy. (Or the direct
 * route.)
 */
static int proxy_http_handler(request_rec *r, proxy_worker *worker,
                              proxy_server_conf *conf,
                              char *url, const char *proxyname,
                              apr_port_t proxyport)
{
    int status;
    const char *scheme;
    const char *u = url;
    proxy_http_req_t *req = NULL;
    proxy_conn_rec *backend = NULL;
    apr_bucket_brigade *input_brigade = NULL;
    int is_ssl = 0;
    conn_rec *c = r->connection;
    proxy_dir_conf *dconf;
    int retry = 0;
    char *locurl = url;
    int toclose = 0;
    /*
     * Use a shorter-lived pool to reduce memory usage
     * and avoid a memory leak
     */
    apr_pool_t *p = r->pool;
    apr_uri_t *uri;
 
    scheme = get_url_scheme(&u, &is_ssl);
    if (!scheme && proxyname && strncasecmp(url, "ftp:", 4) == 0) {
        u = url + 4;
        scheme = "ftp";
        is_ssl = 0;
    }
    if (!scheme || u[0] != '/' || u[1] != '/' || u[2] == '\0') {
        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01113)
                      "HTTP: declining URL %s", url);
        return DECLINED; /* only interested in HTTP, WS or FTP via proxy */
    }
    if (is_ssl && !ap_ssl_has_outgoing_handlers()) {
        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01112)
                      "HTTP: declining URL %s (mod_ssl not configured?)", url);
        return DECLINED;
    }
    ap_log_rerror(APLOG_MARK, APLOG_TRACE1, 0, r, "HTTP: serving URL %s", url);
 
    /* create space for state information */
    if ((status = ap_proxy_acquire_connection(scheme, &backend,
                                              worker, r->server)) != OK) {
        return status;
    }
 
    backend->is_ssl = is_ssl;
 
    req = apr_pcalloc(p, sizeof(*req));
    req->p = p;
    req->r = r;
    req->sconf = conf;
    req->worker = worker;
    req->backend = backend;
    req->proto = scheme;
    req->bucket_alloc = c->bucket_alloc;
    req->rb_method = RB_INIT;
 
    dconf = ap_get_module_config(r->per_dir_config, &proxy_module);
 
    if (apr_table_get(r->subprocess_env, "force-proxy-request-1.0")) {
        req->force10 = 1;
    }
    else if (*worker->s->upgrade || *req->proto == 'w') {
        /* Forward Upgrade header if it matches the configured one(s),
         * the default being "WebSocket" for ws[s] schemes.
         */
        const char *upgrade = apr_table_get(r->headers_in, "Upgrade");
        if (upgrade && ap_proxy_worker_can_upgrade(p, worker, upgrade,
                                                   (*req->proto == 'w')
                                                   ? "WebSocket" : NULL)) {
            req->upgrade = upgrade;
        }
    }
 
    /* We possibly reuse input data prefetched in previous call(s), e.g. for a
     * balancer fallback scenario, and in this case the 100 continue settings
     * should be consistent between balancer members. If not, we need to ignore
     * Proxy100Continue on=>off once we tried to prefetch already, otherwise
     * the HTTP_IN filter won't send 100 Continue for us anymore, and we might
     * deadlock with the client waiting for each other. Note that off=>on is
     * not an issue because in this case r->expecting_100 is false (the 100
     * Continue is out already), but we make sure that prefetch will be
     * nonblocking to avoid passing more time there. 
     */
    apr_pool_userdata_get((void **)&input_brigade, "proxy-req-input", p);
 
    /* Should we handle end-to-end or ping 100-continue? */
    if (!req->force10
        && ((r->expecting_100 && (dconf->forward_100_continue || input_brigade))
            || PROXY_SHOULD_PING_100_CONTINUE(worker, r))) {
        /* Tell ap_proxy_create_hdrbrgd() to preserve/add the Expect header */
        apr_table_setn(r->notes, "proxy-100-continue", "1");
        req->do_100_continue = 1;
    }
 
    /* Should we block while prefetching the body or try nonblocking and flush
     * data to the backend ASAP?
     */
    if (input_brigade
            || req->do_100_continue
            || apr_table_get(r->subprocess_env,
                             "proxy-prefetch-nonblocking")) {
        req->prefetch_nonblocking = 1;
    }
 
    /*
     * In the case that we are handling a reverse proxy connection and this
     * is not a request that is coming over an already kept alive connection
     * with the client, do NOT reuse the connection to the backend, because
     * we cannot forward a failure to the client in this case as the client
     * does NOT expect this in this situation.
     * Yes, this creates a performance penalty.
     */
    if ((r->proxyreq == PROXYREQ_REVERSE) && (!c->keepalives)
        && (apr_table_get(r->subprocess_env, "proxy-initial-not-pooled"))) {
        backend->close = 1;
    }
 
    /* Step One: Determine Who To Connect To */
    uri = apr_palloc(p, sizeof(*uri));
    if ((status = ap_proxy_determine_connection(p, r, conf, worker, backend,
                                            uri, &locurl, proxyname,
                                            proxyport, req->server_portstr,
                                            sizeof(req->server_portstr))))
        goto cleanup;
 
    /* The header is always (re-)built since it depends on worker settings,
     * but the body can be fetched only once (even partially), so it's saved
     * in between proxy_http_handler() calls should we come back here.
     */
    req->header_brigade = apr_brigade_create(p, req->bucket_alloc);
    if (input_brigade == NULL) {
        input_brigade = apr_brigade_create(p, req->bucket_alloc);
        apr_pool_userdata_setn(input_brigade, "proxy-req-input", NULL, p);
    }
    req->input_brigade = input_brigade;
 
    /* Prefetch (nonlocking) the request body so to increase the chance to get
     * the whole (or enough) body and determine Content-Length vs chunked or
     * spooled. By doing this before connecting or reusing the backend, we want
     * to minimize the delay between this connection is considered alive and
     * the first bytes sent (should the client's link be slow or some input
     * filter retain the data). This is a best effort to prevent the backend
     * from closing (from under us) what it thinks is an idle connection, hence
     * to reduce to the minimum the unavoidable local is_socket_connected() vs
     * remote keepalive race condition.
     */
    if ((status = ap_proxy_http_prefetch(req, uri, locurl)) != OK)
        goto cleanup;
 
    /* We need to reset backend->close now, since ap_proxy_http_prefetch() set
     * it to disable the reuse of the connection *after* this request (no keep-
     * alive), not to close any reusable connection before this request. However
     * assure what is expected later by using a local flag and do the right thing
     * when ap_proxy_connect_backend() below provides the connection to close.
     */
    toclose = backend->close;
    backend->close = 0;
 
    while (retry < 2) {
        if (retry) {
            char *newurl = url;
 
            /* Step One (again): (Re)Determine Who To Connect To */
            if ((status = ap_proxy_determine_connection(p, r, conf, worker,
                            backend, uri, &newurl, proxyname, proxyport,
                            req->server_portstr, sizeof(req->server_portstr))))
                break;
 
            /* The code assumes locurl is not changed during the loop, or
             * ap_proxy_http_prefetch() would have to be called every time,
             * and header_brigade be changed accordingly...
             */
            AP_DEBUG_ASSERT(strcmp(newurl, locurl) == 0);
        }
 
        /* Step Two: Make the Connection */
        if (ap_proxy_check_connection(scheme, backend, r->server, 1,
                                      PROXY_CHECK_CONN_EMPTY)
                && ap_proxy_connect_backend(scheme, backend, worker,
                                            r->server)) {
            ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01114)
                          "HTTP: failed to make connection to backend: %s",
                          backend->hostname);
            status = HTTP_SERVICE_UNAVAILABLE;
            break;
        }
 
        /* Step Three: Create conn_rec */
        if ((status = ap_proxy_connection_create_ex(scheme, backend, r)) != OK)
            break;
        req->origin = backend->connection;
 
        /* Don't recycle the connection if prefetch (above) told not to do so */
        if (toclose) {
            backend->close = 1;
            req->origin->keepalive = AP_CONN_CLOSE;
        }
 
        /* Step Four: Send the Request
         * On the off-chance that we forced a 100-Continue as a
         * kinda HTTP ping test, allow for retries
         */
        status = ap_proxy_http_request(req);
        if (status != OK) {
            if (req->do_100_continue && status == HTTP_SERVICE_UNAVAILABLE) {
                ap_log_rerror(APLOG_MARK, APLOG_INFO, status, r, APLOGNO(01115)
                              "HTTP: 100-Continue failed to %pI (%s:%d)",
                              backend->addr, backend->hostname, backend->port);
                backend->close = 1;
                retry++;
                continue;
            }
            break;
        }
 
        /* Step Five: Receive the Response... Fall thru to cleanup */
        status = ap_proxy_http_process_response(req);
 
        break;
    }
 
    /* Step Six: Clean Up */
cleanup:
    if (req->backend) {
        if (status != OK)
            req->backend->close = 1;
        ap_proxy_http_cleanup(scheme, r, req->backend);
    }
    return status;
}
 
/* post_config hook: */
static int proxy_http_post_config(apr_pool_t *pconf, apr_pool_t *plog,
        apr_pool_t *ptemp, server_rec *s)
{
 
    /* proxy_http_post_config() will be called twice during startup.  So, don't
     * set up the static data the 1st time through. */
    if (ap_state_query(AP_SQ_MAIN_STATE) == AP_SQ_MS_CREATE_PRE_CONFIG) {
        return OK;
    }
 
    ap_proxy_clear_connection_fn =
            APR_RETRIEVE_OPTIONAL_FN(ap_proxy_clear_connection);
    if (!ap_proxy_clear_connection_fn) {
        ap_log_error(APLOG_MARK, APLOG_EMERG, 0, s, APLOGNO(02477)
                     "mod_proxy must be loaded for mod_proxy_http");
        return !OK;
    }
 
    return OK;
}
 
static void ap_proxy_http_register_hook(apr_pool_t *p)
{
    ap_hook_post_config(proxy_http_post_config, NULL, NULL, APR_HOOK_MIDDLE);
    proxy_hook_scheme_handler(proxy_http_handler, NULL, NULL, APR_HOOK_FIRST);
    proxy_hook_canon_handler(proxy_http_canon, NULL, NULL, APR_HOOK_FIRST);
    warn_rx = ap_pregcomp(p, "[0-9]{3}[ \t]+[^ \t]+[ \t]+\"[^\"]*\"([ \t]+\"([^\"]+)\")?", 0);
}
 
AP_DECLARE_MODULE(proxy_http) = {
    STANDARD20_MODULE_STUFF,
    NULL,              /* create per-directory config structure */
    NULL,              /* merge per-directory config structures */
    NULL,              /* create per-server config structure */
    NULL,              /* merge per-server config structures */
    NULL,              /* command apr_table_t */
    ap_proxy_http_register_hook/* register hooks */
};