getnameinfo Subroutine

AIX Version 4.3 Base Operating System and Extensions Technical Reference, Volume 1

getnameinfo Subroutine

Purpose

Hostname-to-service name translation [given the binary address and port].

Note: This is the reverse functionality of getaddrinfo: hostname-to-address translation.

Attention: This is not a POSIX (1003.1g) specified function.

Library

Library (libc.a)

Syntax

#include <sys/socket.h>
#include <netdb.h>
int
getnameinfo (sa, salen, host, hostlen, 
serv, servlen, flags)
const struct sockaddr *sa;
char *host;
size_t hostlen;
char *serv;
size_t servlen;
int flags;

Description

The first argument, sa, points to either a sockaddr_in structure (for IPv4) or a sockaddr_in6 structure (for IPv6) that holds the IP address and port number. The argument, salen, gives the length of the sockaddr_in or sockaddr_in6 structure.

Note: A reverse lookup is performed on the IP address and port number provided in sa.

The argument, host, copies the hostname associated with the IP address into a buffer. The argument, hostlen, provides the length of this buffer. The service name associated with the port number is copied into the buffer pointed to by the argument serv. The argument, servlen, provides the length of this buffer.

The final argument defines flags that may be used to modify the default actions of this function. By default, the fully-qualified domain name (FQDN) for the host is looked up in the DNS and returned.

NI_NOFQDN	If set, return only the hostname portion of the FQDN. If clear, return the FQDN.
NI_NUMERICHOST	If set, return the numeric form of the host address. If clear, return the name.
NI_NAMEREQD	If set, return an error if the host's name cannot be determined. If clear, return the numeric form of the host's address (as if NI_NUMERICHOST had been set).
NI_NUMERICSERV	If set, return the numeric form of the desired service. If clear, return the service name.
NI_DGRAM	If set, consider the desired service to be a datagram service, (i.e., call getservbyport with an agrument of udp). If clear, consider the desired service to be a stream service (i.e., call getserbyport with an argument of tcp).

Return Values

If successful, the strings for hostname and service are copied into host and serv, respectively. If unsuccessful, zero values for either hostlen or servlen will suppress the associated lookup; in this case no data is copied into the applicable buffer.

Related Information

The getaddrinfo subroutine, freeaddrinfo subroutine, and gai_strerror subroutine.

Subroutines Overview in AIX Version 4 General Programming Concepts: Writing and Debugging Programs.