Lighttpd

#if defined(HAVE_IPV6) or similar flagging is missing in mod_proxy.c lines 757-769:

    switch(hctx->state) {
    case PROXY_STATE_INIT:
        if (strstr(host->host->ptr,":")) {
            if (-1 == (hctx->fd = socket(AF_INET6, SOCK_STREAM, 0))) {
            log_error_write(srv, __FILE__, __LINE__, "ss", "socket failed: ", strerror(errno));
            return HANDLER_ERROR;
            }
        } else {
            if (-1 == (hctx->fd = socket(AF_INET, SOCK_STREAM, 0))) {
            log_error_write(srv, __FILE__, __LINE__, "ss", "socket failed: ", strerror(errno));
            return HANDLER_ERROR;
            }
        }