PowerShell/native/getfullyqualifiedname.cpp

//! @file getfullyqualifiedname.cpp
//! @author George Fleming <v-geflem@microsoft.com>
//! @brief Implements GetFullyQualifiedName on Linux

#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include "getcomputername.h"
#include "getfullyqualifiedname.h"

//! @brief GetFullyQualifiedName retrieves the fully qualifed dns name of the host
//!
//! @exception errno Passes these errors via errno to GetLastError:
//! - ERROR_BAD_ENVIRONMENT: locale is not UTF-8 (from GetComputerName)
//! - ERROR_INVALID_FUNCTION: getlogin_r() returned an unrecognized error code (from GetComputerName)
//! - ERROR_INVALID_ADDRESS:  buffer is an invalid address (from GetComputerName)
//! - ERROR_GEN_FAILURE: buffer not large enough (from GetComputerName)
//! - ERROR_BAD_NET_NAME: Cannot determine network short name
//!
//! @retval username as UTF-8 string, or null if unsuccessful
//!

char* GetFullyQualifiedName()
{
    errno = 0;
    
    char *computerName = GetComputerName();
    if (NULL == computerName)
    {
	return NULL;
    }

    if (strchr(computerName, '.') != NULL)
    {
	return computerName;
    }

    struct addrinfo hints, *info;
    int gai_result;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC; /*either IPV4 or IPV6*/
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_CANONNAME;

    /* There are several ways to get the domain name:
     * uname(2), gethostbyname(3), resolver(3), getdomainname(2), 
     * and getaddrinfo(3).  Some of these are not portable, some aren't 
     * POSIX compliant, and some are being deprecated.  Getaddrinfo seems
     * to be the best choice right now.
     */
    if ((gai_result = getaddrinfo(computerName, "http", &hints, &info)) != 0) 
    {
        errno = ERROR_BAD_NET_NAME;
	return NULL;
    }

    // info is actually a link-list.  We'll just return the first full name

    char *fullName = strdup(info->ai_canonname);

    freeaddrinfo(info);
    free(computerName);
    return fullName;
}