mod_proxy_fcgi.c

    ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01078) "serving URL %s", url);

    /* Create space for state information */
    status = ap_proxy_acquire_connection(FCGI_SCHEME, &backend, worker,
                                         r->server);
    if (status != OK) {
        if (backend) {
            backend->close = 1;
            ap_proxy_release_connection(FCGI_SCHEME, backend, r->server);
        }
        return status;
    }

    backend->is_ssl = 0;

    /* Step One: Determine Who To Connect To */
    uri = apr_palloc(p, sizeof(*uri));
    status = ap_proxy_determine_connection(p, r, conf, worker, backend,
                                           uri, &url, proxyname, proxyport,
                                           server_portstr,
                                           sizeof(server_portstr));
    if (status != OK) {
        goto cleanup;
    }

    /* This scheme handler does not reuse connections by default, to
     * avoid tying up a fastcgi that isn't expecting to work on
     * parallel requests.  But if the user went out of their way to
     * type the default value of disablereuse=off, we'll allow it.
     */
    backend->close = 1;
    if (worker->s->disablereuse_set && !worker->s->disablereuse) {
        backend->close = 0;
    }

    /* Step Two: Make the Connection */
    if (ap_proxy_check_connection(FCGI_SCHEME, backend, r->server, 0,
                                  PROXY_CHECK_CONN_EMPTY)
            && ap_proxy_connect_backend(FCGI_SCHEME, backend, worker,
                                        r->server)) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01079)
                      "failed to make connection to backend: %s",
                      backend->hostname);
        status = HTTP_SERVICE_UNAVAILABLE;
        goto cleanup;
    }

    /* Step Three: Process the Request */
    status = fcgi_do_request(p, r, backend, origin, dconf, uri, url,
                             server_portstr);

cleanup:
    ap_proxy_release_connection(FCGI_SCHEME, backend, r->server);
    return status;
}

static void *fcgi_create_dconf(apr_pool_t *p, char *path)
{
    fcgi_dirconf_t *a;

    a = (fcgi_dirconf_t *)apr_pcalloc(p, sizeof(fcgi_dirconf_t));
    a->backend_type = BACKEND_DEFAULT_UNKNOWN;
    a->env_fixups = apr_array_make(p, 20, sizeof(sei_entry));

    return a;
}

static void *fcgi_merge_dconf(apr_pool_t *p, void *basev, void *overridesv)
{
    fcgi_dirconf_t *a, *base, *over;

    a     = (fcgi_dirconf_t *)apr_pcalloc(p, sizeof(fcgi_dirconf_t));
    base  = (fcgi_dirconf_t *)basev;
    over  = (fcgi_dirconf_t *)overridesv;

    a->backend_type = (over->backend_type != BACKEND_DEFAULT_UNKNOWN)
                      ? over->backend_type
                      : base->backend_type;
    a->env_fixups = apr_array_append(p, base->env_fixups, over->env_fixups);
    return a;
}

static const char *cmd_servertype(cmd_parms *cmd, void *in_dconf,
                                   const char *val)
{
    fcgi_dirconf_t *dconf = in_dconf;

    if (!strcasecmp(val, "GENERIC")) {
       dconf->backend_type = BACKEND_GENERIC;
    }
    else if (!strcasecmp(val, "FPM")) {
       dconf->backend_type = BACKEND_FPM;
    }
    else {
        return "ProxyFCGIBackendType requires one of the following arguments: "
               "'GENERIC', 'FPM'";
    }

    return NULL;
}


static const char *cmd_setenv(cmd_parms *cmd, void *in_dconf,
                              const char *arg1, const char *arg2,
                              const char *arg3)
{
    fcgi_dirconf_t *dconf = in_dconf;
    const char *err;
    sei_entry *new;
    const char *envvar = arg2;

    new = apr_array_push(dconf->env_fixups);
    new->cond = ap_expr_parse_cmd(cmd, arg1, 0, &err, NULL);
    if (err) {
        return apr_psprintf(cmd->pool, "Could not parse expression \"%s\": %s",
                            arg1, err);
    }

    if (envvar[0] == '!') {
        /* Unset mode. */
        if (arg3) {
            return apr_psprintf(cmd->pool, "Third argument (\"%s\") is not "
                                "allowed when using ProxyFCGISetEnvIf's unset "
                                "mode (%s)", arg3, envvar);
        }
        else if (!envvar[1]) {
            /* i.e. someone tried to give us a name of just "!" */
            return "ProxyFCGISetEnvIf: \"!\" is not a valid variable name";
        }

        new->subst = NULL;
    }
    else {
        /* Set mode. */
        if (!arg3) {
            /* A missing expr-value should be treated as empty. */
            arg3 = "";
        }

        new->subst = ap_expr_parse_cmd(cmd, arg3, AP_EXPR_FLAG_STRING_RESULT, &err, NULL);
        if (err) {
            return apr_psprintf(cmd->pool, "Could not parse expression \"%s\": %s",
                                arg3, err);
        }
    }

    new->envname = envvar;

    return NULL;
}
static void register_hooks(apr_pool_t *p)
{
    proxy_hook_scheme_handler(proxy_fcgi_handler, NULL, NULL, APR_HOOK_FIRST);
    proxy_hook_canon_handler(proxy_fcgi_canon, NULL, NULL, APR_HOOK_FIRST);
}

static const command_rec command_table[] = {
    AP_INIT_TAKE1("ProxyFCGIBackendType", cmd_servertype, NULL, OR_FILEINFO,
                  "Specify the type of FastCGI server: 'Generic', 'FPM'"),
    AP_INIT_TAKE23("ProxyFCGISetEnvIf", cmd_setenv, NULL, OR_FILEINFO,
                  "expr-condition env-name expr-value"),
    { NULL }
};

AP_DECLARE_MODULE(proxy_fcgi) = {
    STANDARD20_MODULE_STUFF,
    fcgi_create_dconf,          /* create per-directory config structure */
    fcgi_merge_dconf,           /* merge per-directory config structures */
    NULL,                       /* create per-server config structure */
    NULL,                       /* merge per-server config structures */
    command_table,              /* command apr_table_t */
    register_hooks              /* register hooks */
};