text: /*
   * util/edns.c - handle base EDNS options.
   *
   * Copyright (c) 2018, NLnet Labs. All rights reserved.
   *
   * This software is open source.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * Redistributions of source code must retain the above copyright notice,
   * this list of conditions and the following disclaimer.
   *
   * Redistributions in binary form must reproduce the above copyright notice,
   * this list of conditions and the following disclaimer in the documentation
   * and/or other materials provided with the distribution.
   *
   * Neither the name of the NLNET LABS nor the names of its contributors may
   * be used to endorse or promote products derived from this software without
   * specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
   * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  /**
   * \file
   *
   * This file contains functions for base EDNS options.
   */
  
  #include "config.h"
  #include "util/edns.h"
  #include "util/config_file.h"
  #include "util/netevent.h"
  #include "util/regional.h"
  #include "util/data/msgparse.h"
  #include "util/data/msgreply.h"
  
  static int edns_keepalive(struct edns_data* edns_out, struct edns_data* edns_in,
  		struct comm_point* c, struct regional* region)
  {
  	if(c->type == comm_udp)
  		return 1;
  
  	/* To respond with a Keepalive option, the client connection
  	 * must have received one message with a TCP Keepalive EDNS option,
  	 * and that option must have 0 length data. Subsequent messages
  	 * sent on that connection will have a TCP Keepalive option.
  	 */
  	if(c->tcp_keepalive ||
  		edns_opt_list_find(edns_in->opt_list, LDNS_EDNS_KEEPALIVE)) {
  		int keepalive = c->tcp_timeout_msec / 100;
  		uint8_t data[2];
  		data[0] = (uint8_t)((keepalive >> 8) & 0xff);
  		data[1] = (uint8_t)(keepalive & 0xff);
  		if(!edns_opt_list_append(&edns_out->opt_list, LDNS_EDNS_KEEPALIVE,
  			sizeof(data), data, region))
  			return 0;
  		c->tcp_keepalive = 1;
  	}
  	return 1;
  }
  
  int apply_edns_options(struct edns_data* edns_out, struct edns_data* edns_in,
  	struct config_file* cfg, struct comm_point* c, struct regional* region)
  {
  	if(cfg->do_tcp_keepalive &&
  		!edns_keepalive(edns_out, edns_in, c, region))
  		return 0;
  
  	return 1;
  }
  