HP-UX Reference (11i v2 03/08) - 3 Library Functions A-M (vol 6)

g
getaddrinfo(3N) getaddrinfo(3N)
If the flag bit NI_NAMEREQD is
set, an error is returned if the host’s name cannot be located in the
DNS.
If the flag bit
NI_NUMERICSERV
is set, the numeric form of the service address is returned (e.g., its
port number) instead of its name. The two
NI_NUMERICxxx flags are required to support the -n flag
that many commands provide.
A fifth flag bit,
NI_DGRAM
, specifies that the service is a datagram service, and causes get-
servbyport() to be called with a second argument of "udp" instead of its default of "tcp". This is
required for the few ports (512-514) that have different services for UDP and TCP.
These
NI_xxx flags are defined in
<netdb.h> along with the AI_xxx flags already defined for getad-
drinfo().
Name Service Switch-Based Operation
The
getnameinfo()
and getaddrinfo()
library routines internally call the name service switch to
access the
ipnodes database lookup policy configured in the
/etc/nsswitch.conf
file (see
nsswitch.conf(4)) for the name/address resolution, and
services database lookup policy for the
service/port resolution. The lookup policy defines the order and criteria of the supported name services
that can be used for resolution. If addresses are not gathered after contacting all the
ipnodes direc-
tives, and if the caller has set the
ai_family to AF_INET or set ai_flags to AI_V4MAPPED with an
ai_family of AF_INET6, getaddrinfo()
/getnameinfo() uses the hosts directive in the
/etc/nsswitch.conf
file to resolve the hostname/address. In this case, when the hosts directive
hostname/address resolution fails, the error number returned will be that of the error returned by the
hosts directive lookup. The operations of these name services, Domain Name Server and Nonserver
Modes, are described below:
Domain Name Server Operation
If the local system is configured to use the BIND name server,
named (see named(1M) and resolver (4))
for name/address resolution, the function
getnameinfo()
/getaddrinfo() retrieves the host infor-
mation from the name server. The host names are matched irrespective of upper or lower case alphatets.
For example, the domain names
berkeley.edu, Berkeley.EDU, and BERKELEY.EDU match the
same entry berkeley.edu in the name server database. When hosts directive is used for
hostname/address resolution, a delay may be observed due to an additional lookup using the sources
specified for hosts directive.
Nonserver Operation
During a name/address resolution, if the database is configured for files resolution,
getnameinfo()
and getaddrinfo() use the
/etc/hosts file for resolution. Similarly, if the services database is
configured for files resolution, the
/etc/services
file is used for resolution. If the /etc/hosts file
is used for name/address resolution, the method used by the functions
getnameinfo() and getad-
drinfo() to search an address is listed below:
getnameinfo() Sequentially searches the /etc/hosts file until an address matching the src
parameter is found or till the end of file is encountered.
getaddrinfo() Sequentially searches the /etc/hosts file until a host name (official name
or an alias name) matching the name parameter is found or until the end of
file is encountered. The host names are matched irrespective of upper or lower
case alphabets.
WARNINGS
Obsolescent Interfaces
The following interfaces are included to support existing applications and may be removed in future
releases.
struct hostent *getipnodebyname(const char *name,
int af,
int flags,
int *error_num);
int getipnodebyaddr(const void *src,
size_t len,
int af,
int *error_num);
Section 3−−342 Hewlett-Packard Company − 4 − HP-UX 11i Version 2: August 2003