apr_status_t bind_to_addr(apr_socket_t *newsock, apr_sockaddr_t *laddr,

        const char *proxy_function, proxy_server_conf *conf, server_rec *s)

{

    int i;

    const int idx = conf->bind_idx;

    const int range = conf->bind_range;

    const int start = conf->bind_port;

    for(i = 0; i < range; ++i) { /* loop until we can bind correctly*/

        int port = start + ((idx + i) % range);

        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, "proxy: %s: trying to bind to %s:%u",

                proxy_function, laddr,port, NULL);

        laddr->sa.sin.sin_port = htons(port);

        laddr->port = port;

        if (apr_socket_bind(newsock, laddr) == APR_SUCCESS) {

            ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, "proxy: %s: bound to %s:%u",

                    proxy_function, laddr, laddr->port, NULL);

            conf->bind_idx = i + 1;

            return APR_SUCCESS;

        }

    }

    return APR_EINVAL;

}

        if (conf->bindopt_set) {

            rv = APR_EINVAL;

            apr_sockaddr_t *addr;

            for(*addr = conf->bind_addr; addr; addr = addr->next) {

                if (addr->family != backend_addr->family) continue;

                rv = bind_to_addr(newsock, addr, proxy_function, conf, s);

                if (rv == APR_SUCCESS) break;

            }

            if (rv != APR_SUCCESS) {

                ap_log_error(APLOG_MARK, APLOG_ERR, 0, s, "proxy: %s: could not bind to %s:%u+%u",

                        proxy_function,conf->bind_addr, conf->bind_port, conf->bind_range, NULL);

                return DECLINED;

            }

        }

/* Value from /usr/sys/port_kernel.h is it exposed in any portable header? */

#define PORT_MAX_PORTS 0x10000

/* a sane value for RANGE of bind */

#define MIN_RANGE_HINT 8

    ps->bindopt_set = 0;

    ps->bind_idx = 0;

    ps->bind_addr = 0;

    ps->bindopt_set = overrides->bindopt_set || base->bindopt_set;

static const char*

    set_proxy_bindaddr(cmd_parms *parms, void *dummy, const char *addr)

{

    char *range, *host, *scope_id;

    apr_port_t port;

    int r = 0;

    proxy_server_conf *psf =

    ap_get_module_config(parms->server->module_config, &proxy_module);

    range = ap_strrchr((char*)addr, '+');

    if (range) {

        *range++ = 0;

        r = atoi(range);

        if (r < MIN_RANGE_HINT)

            ap_log_error(APLOG_MARK, APLOG_WARNING, 0, NULL,

                    "range %u is too low, consider increasing the bind range.", r, NULL);

    }

    /* We dont accept a single port with out a range as it would be same

     * as a single threaded single process http-client

     *

     * We do not allow ip:0+0 or ip:0 as it can be specified more clearly

     * as just ip.

     *

     * we dont accept a range with out a port either.

     */

    if((apr_parse_addr_port(&host, &scope_id, &port, addr, parms->pool)

                != APR_SUCCESS)

            || scope_id               /* we dont know how to use scope_id */

            || (!port && range)       /* only a combo [port+range] is valid */

            || (port && (!range || r < 0)) /* Let admin specify r=0 if he wants to */

            || ((port + r) >= PORT_MAX_PORTS)

      )

        return "ProxyBindAddress:  Invalid address -"

               " format is <addr>[:<port>+<range>]";

    /* Preparse the address */

    if((apr_sockaddr_info_get(&(psf->bind_addr), host, APR_UNSPEC, port, 0, parms->pool)

            != APR_SUCCESS) || !psf->bind_addr)

        return "ProxyBindAddress: Hostname did not resolve.";

    psf->bind_port = port;

    /* If there didn't exist a port then there was no range either. so we have the

     * starting value 0 for r when no port was specified.*/

    psf->bind_range = r + 1;

    psf->bind_idx = 0;

    psf->bindopt_set = 1;

    return NULL;

}

    AP_INIT_TAKE1("ProxyBindAddress", set_proxy_bindaddr, NULL, RSRC_CONF,

     "Set the source address for a proxied connection. "),

    /*bind to local ports*/

    apr_sockaddr_t *bind_addr;

    apr_port_t bind_port;

    apr_port_t bind_range;             /* restrict the source ports used by mod_proxy */

    int bind_idx;

    char bindopt_set;