Ubuntu Manpage: getipnodebyname, getipnodebyaddr, freehostent

NAME

       getipnodebyname, getipnodebyaddr, freehostent - get network hostnames and addresses

SYNOPSIS

       #include <sys/types.h>
       #include <sys/socket.h>
       #include <netdb.h>

       struct hostent *getipnodebyname(const char *name, int af,
                                       int flags, int *error_num);

       struct hostent *getipnodebyaddr(const void *addr, size_t len,
                                       int af, int *error_num);

       void freehostent(struct hostent *ip);

DESCRIPTION

       These  functions  are  deprecated  (and  unavailable  in  glibc).   Use getaddrinfo(3) and getnameinfo(3)
       instead.

       The getipnodebyname() and getipnodebyaddr() functions return the names and addresses of a  network  host.
       These functions return a pointer to the following structure:

           struct hostent {
               char  *h_name;
               char **h_aliases;
               int    h_addrtype;
               int    h_length;
               char **h_addr_list;
           };

       These  functions replace the gethostbyname(3) and gethostbyaddr(3) functions, which could access only the
       IPv4 network address family.  The getipnodebyname() and getipnodebyaddr() functions can  access  multiple
       network address families.

       Unlike  the  gethostby  functions,  these functions return pointers to dynamically allocated memory.  The
       freehostent() function is used to release the dynamically allocated memory after  the  caller  no  longer
       needs the hostent structure.

   getipnodebyname() arguments
       The  getipnodebyname()  function  looks up network addresses for the host specified by the name argument.
       The af argument specifies one of the following values:

       AF_INET
              The name argument points to a dotted-quad IPv4 address or a name of an IPv4 network host.

       AF_INET6
              The name argument points to a hexadecimal IPv6 address or a name of an IPv6 network host.

       The flags argument specifies additional options.  More than one option can be specified by bitwise OR-ing
       them together.  flags should be set to 0 if no options are desired.

       AI_V4MAPPED
              This  flag  is used with AF_INET6 to request a query for IPv4 addresses instead of IPv6 addresses;
              the IPv4 addresses will be mapped to IPv6 addresses.

       AI_ALL This flag is used with AI_V4MAPPED to request a query for both IPv4 and IPv6 addresses.  Any  IPv4
              address found will be mapped to an IPv6 address.

       AI_ADDRCONFIG
              This  flag  is used with AF_INET6 to further request that queries for IPv6 addresses should not be
              made unless the system has at least one IPv6 address assigned to a  network  interface,  and  that
              queries  for  IPv4  addresses  should  not be made unless the system has at least one IPv4 address
              assigned to a network interface.  This flag may be used by itself or with the AI_V4MAPPED flag.

       AI_DEFAULT
              This flag is equivalent to (AI_ADDRCONFIG | AI_V4MAPPED).

   getipnodebyaddr() arguments
       The getipnodebyaddr() function looks up the name of the host whose network address is  specified  by  the
       addr argument.  The af argument specifies one of the following values:

       AF_INET
              The addr argument points to a struct in_addr and len must be set to sizeof(struct in_addr).

       AF_INET6
              The addr argument points to a struct in6_addr and len must be set to sizeof(struct in6_addr).

RETURN VALUE

NULL is returned if an error occurred, and error_num will contain an error code from the following list:

HOST_NOT_FOUND
The hostname or network address was not found.

NO_ADDRESS
The domain name server recognized the network address or name, but no answer was returned. This
can happen if the network host has only IPv4 addresses and a request has been made for IPv6
information only, or vice versa.

NO_RECOVERY
The domain name server returned a permanent failure response.

TRY_AGAIN
The domain name server returned a temporary failure response. You might have better luck next
time.

A successful query returns a pointer to a hostent structure that contains the following fields:

h_name This is the official name of this network host.

h_aliases
This is an array of pointers to unofficial aliases for the same host. The array is terminated by
a null pointer.

h_addrtype
This is a copy of the af argument to getipnodebyname() or getipnodebyaddr(). h_addrtype will
always be AF_INET if the af argument was AF_INET. h_addrtype will always be AF_INET6 if the af
argument was AF_INET6.

h_length
This field will be set to sizeof(struct in_addr) if h_addrtype is AF_INET, and to sizeof(struct
in6_addr) if h_addrtype is AF_INET6.

h_addr_list
This is an array of one or more pointers to network address structures for the network host. The
array is terminated by a null pointer.

CONFORMING TO

       RFC 2553.

NOTES

       These  functions  were  present  in  glibc  2.1.91-95, but were removed again.  Several UNIX-like systems
       support them, but all call them deprecated.

COLOPHON

       This page is part of release 4.15 of  the  Linux  man-pages  project.   A  description  of  the  project,
       information   about   reporting   bugs,   and   the  latest  version  of  this  page,  can  be  found  at
       https://www.kernel.org/doc/man-pages/.