libs/libc/netdb/lib_dnsbind.c

/****************************************************************************
 * libs/libc/netdb/lib_dnsbind.c
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * 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.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <sys/time.h>
#include <unistd.h>
#include <errno.h>
#include <debug.h>

#include <nuttx/net/dns.h>

#include "netdb/lib_dns.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

#ifndef CONFIG_NET_SOCKOPTS
#  error CONFIG_NET_SOCKOPTS required by this logic
#endif

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: dns_bind
 *
 * Description:
 *   Initialize the DNS resolver and return a socket bound to the DNS name
 *   server.  The name server was previously selected via dns_server().
 *
 * Input Parameters:
 *   retry_count - Current retry attempt (0 for first attempt)
 *   stream - Whether to use stream socket
 *
 * Returned Value:
 *   On success, the bound, non-negative socket descriptor is returned.  A
 *   negated errno value is returned on any failure.
 *
 ****************************************************************************/

int dns_bind(sa_family_t family, bool stream, int retry_count)
{
  int stype = stream ? SOCK_STREAM : SOCK_DGRAM;
  struct timeval tv;
  int sd;
  int ret;
  int timeout_sec;

  /* Calculate progressive timeout: (base timeout * 2^retry_count)
   * For retry_count 0: base timeout, 1: base*2, 2: base*4, etc.
   */

  timeout_sec = CONFIG_NETDB_DNSCLIENT_RECV_TIMEOUT;
  if (retry_count > 0)
    {
      /* Apply exponential backoff with configurable maximum */

      timeout_sec = timeout_sec << retry_count;
      if (CONFIG_NETDB_DNSCLIENT_MAX_TIMEOUT > 0 &&
          timeout_sec > CONFIG_NETDB_DNSCLIENT_MAX_TIMEOUT)
        {
          timeout_sec = CONFIG_NETDB_DNSCLIENT_MAX_TIMEOUT;
        }
    }

  /* Create a new socket */

  sd = socket(family, stype | SOCK_CLOEXEC, 0);
  if (sd < 0)
    {
      ret = -get_errno();
      nerr("ERROR: socket() failed: %d\n", ret);
      return ret;
    }

  /* Set up a receive timeout with progressive strategy */

  tv.tv_sec  = timeout_sec;
  tv.tv_usec = 0;

  ret = setsockopt(sd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(struct timeval));
  if (ret >= 0)
    {
      /* Set up a send timeout (same progressive strategy) */

      tv.tv_sec  = timeout_sec;
      tv.tv_usec = 0;

      ret = setsockopt(sd, SOL_SOCKET, SO_SNDTIMEO, &tv,
                       sizeof(struct timeval));
    }

  if (ret < 0)
    {
      ret = -get_errno();
      nerr("ERROR: setsockopt() failed: %d\n", ret);
      close(sd);
      return ret;
    }

  return sd;
}