text: /****************************************************************************
   * libs/libc/unistd/lib_gethostname.c
   *
   *   Copyright (C) 2015 Stavros Polymenis. All rights reserved.
   *   Copyright (C) 2015, 2016 Gregory Nutt. All rights reserved.
   *   Author: Stavros Polymenis <sp@orbitalfox.com>
   *           Gregory Nutt <gnutt@nuttx.org>
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. 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.
   * 3. Neither the name NuttX 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 OWNER 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.
   *
   ****************************************************************************/
  
  /****************************************************************************
   * Included Files
   ****************************************************************************/
  
  #include <nuttx/config.h>
  
  #include <sys/utsname.h>
  #include <string.h>
  #include <unistd.h>
  
  #include <nuttx/irq.h>
  
  /* This file is only compiled if network support is enabled */
  
  #ifdef CONFIG_NET
  
  /****************************************************************************
   * Pre-processor Definitions
   ****************************************************************************/
  
  /* The default host name is a system configuration setting.  This may be
   * changed via sethostname(), however.
   */
  
  #ifndef CONFIG_NET_HOSTNAME
  #  define CONFIG_NET_HOSTNAME ""
  #endif
  
  /****************************************************************************
   * Public Data
   ****************************************************************************/
  
  /* This is the system hostname */
  
  char g_hostname[HOST_NAME_MAX + 1] = CONFIG_NET_HOSTNAME;
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: gethostname
   *
   * Description:
   *   The gethostname() function will return the standard host name for the
   *   current machine. The namelen argument will specify the size of the
   *   array pointed to by the name argument. The returned name will be null-
   *   terminated, except that if namelen is an insufficient length to hold the
   *   host name, then the returned name will be truncated and it is
   *   unspecified whether the returned name is null-terminated.
   *
   *   Host names are limited to {HOST_NAME_MAX} bytes.
   *
   * Input Parameters:
   *   name - The user-provided buffer to receive the host name.
   *   namelen - The size of the user provided buffer in bytes.
   *
   * Returned Value:
   *   Upon successful completion, 0 will be returned; otherwise, -1 will be
   *   returned.  No errors are defined;  errno variable is not set.
   *
   ****************************************************************************/
  
  int gethostname(FAR char *name, size_t namelen)
  {
  /* In the protected and kernel build modes where kernel and application code
   * are separated, the hostname is a common system property and must reside
   * only in the kernel.  In that case, we need to do things differently.
   *
   * uname() is implemented as a system call and can be called from user space.
   * So, in these configurations we will get the hostname via the uname
   * function.
   */
  
  #if (!defined(CONFIG_BUILD_PROTECTED) && !defined(CONFIG_BUILD_KERNEL)) || \
        defined(__KERNEL__)
  
    irqstate_t flags;
  
    /* Return the host name, truncating to fit into the user provided buffer.
     * The hostname is global resource.  There is a microscopic possibility
     * that it could change while we are copying it.
     */
  
    flags = enter_critical_section();
    strncpy(name, g_hostname, namelen);
    leave_critical_section(flags);
  
    return 0;
  
  #else
  
    struct utsname info;
    int ret;
  
    /* Get uname data */
  
    ret = uname(&info);
    if (ret < 0)
      {
        return ret;
      }
  
    /* Return the nodename from the uname data */
  
    strncpy(name, info.nodename, namelen);
    return 0;
  
  #endif
  }
  
  #endif /* CONFIG_NET */
  