netdir(3NSL) Networking Services Library Functions netdir(3NSL)NAME
netdir, netdir_getbyname, netdir_getbyaddr, netdir_free, net‐
dir_options, taddr2uaddr, uaddr2taddr, netdir_perror, netdir_sperror,
netdir_mergeaddr - generic transport name-to-address translation
SYNOPSIS
cc [ flag... ] file... -lnsl [ library...]
#include <netdir.h>
int netdir_getbyname(struct netconfig *config, struct nd_hostserv
*service, struct nd_addrlist **addrs);
int netdir_getbyaddr(struct netconfig *config, struct nd_hostservlist
**service, struct netbuf *netaddr);
void netdir_free(void *ptr, int struct_type);
int netdir_options(struct netconfig *config, int option, int fildes,
char *point_to_args);
char *taddr2uaddr(struct netconfig *config, struct netbuf *addr);
struct netbuf *uaddr2taddr(struct netconfig *config, char *uaddr);
void netdir_perror(char *s);
char *netdir_sperror(void);
DESCRIPTION
The netdir functions provide a generic interface for name-to-address
mapping that will work with all transport protocols. This interface
provides a generic way for programs to convert transport specific
addresses into common structures and back again. The netconfig struc‐
ture, described on the netconfig(4) manual page, identifies the trans‐
port.
The netdir_getbyname() function maps the machine name and service name
in the nd_hostserv structure to a collection of addresses of the type
understood by the transport identified in the netconfig structure. This
function returns all addresses that are valid for that transport in the
nd_addrlist structure. The nd_hostserv structure contains the follow‐
ing members:
char *h_host; /* host name */
char *h_serv; /* service name */
The nd_addrlist structure contains the following members:
int n_cnt; /* number of addresses */
struct netbuf *n_addrs;
The netdir_getbyname() function accepts some special-case host names.
The host names are defined in <netdir.h>. The currently defined host
names are:
HOST_SELF Represents the address to which local programs
will bind their endpoints. HOST_SELF differs
from the host name provided by gethostname(3C),
which represents the address to which remote
programs will bind their endpoints.
HOST_ANY Represents any host accessible by this trans‐
port provider. HOST_ANY allows applications to
specify a required service without specifying a
particular host name.
HOST_SELF_CONNECT Represents the host address that can be used to
connect to the local host.
HOST_BROADCAST Represents the address for all hosts accessible
by this transport provider. Network requests to
this address are received by all machines.
All fields of the nd_hostserv structure must be initialized.
To find the address of a given host and service on all available trans‐
ports, call the netdir_getbyname() function with each struct netconfig
structure returned by getnetconfig(3NSL).
The netdir_getbyaddr() function maps addresses to service names. The
function returns service, a list of host and service pairs that yield
these addresses. If more than one tuple of host and service name is
returned, the first tuple contains the preferred host and service
names:
struct nd_hostservlist {
int *h_cnt; /* number of hostservs found */
struct hostserv *h_hostservs;
}
The netdir_free() structure is used to free the structures allocated by
the name to address translation functions. The ptr parameter points to
the structure that has to be freed. The parameter struct_type identi‐
fies the structure:
struct netbuf ND_ADDR
struct nd_addrlist ND_ADDRLIST
struct hostserv ND_HOSTSERV
struct nd_hostservlist ND_HOSTSERVLIST
The free() function is used to free the universal address returned by
the taddr2uaddr() function.
The netdir_options() function is used to do all transport-specific set‐
ups and option management. fildes is the associated file descriptor.
option, fildes, and pointer_to_args are passed to the netdir_options()
function for the transport specified in config. Currently four values
are defined for option:
ND_SET_BROADCAST
ND_SET_RESERVEDPORT
ND_CHECK_RESERVEDPORT
ND_MERGEADDR
The taddr2uaddr() and uaddr2taddr() functions support translation
between universal addresses and TLI type netbufs. The taddr2uaddr()
function takes a struct netbuf data structure and returns a pointer to
a string that contains the universal address. It returns NULL if the
conversion is not possible. This is not a fatal condition as some
transports do not support a universal address form.
The uaddr2taddr() function is the reverse of the taddr2uaddr() func‐
tion. It returns the struct netbuf data structure for the given univer‐
sal address.
If a transport provider does not support an option, netdir_options
returns -1 and the error message can be printed through netdir_perror()
or netdir_sperror().
The specific actions of each option follow.
ND_SET_BROADCAST
Sets the transport provider up to allow broadcast if the transport
supports broadcast. fildes is a file descriptor into the transport,
that is, the result of a t_open of /dev/udp. pointer_to_args is not
used. If this completes, broadcast operations can be performed on
file descriptor fildes.
ND_SET_RESERVEDPORT
Allows the application to bind to a reserved port if that concept
exists for the transport provider. fildes is an unbound file
descriptor into the transport. If pointer_to_args is NULL, fildes
is bound to a reserved port. If pointer_to_args is a pointer to a
netbuf structure, an attempt is made to bind to any reserved port
on the specified address.
ND_CHECK_RESERVEDPORT
Used to verify that the address corresponds to a reserved port if
that concept exists for the transport provider. fildes is not used.
pointer_to_args is a pointer to a netbuf structure that contains
the address. This option returns 0 only if the address specified
in pointer_to_args is reserved.
ND_MERGEADDR
Used to take a ``local address'' such as a 0.0.0.0 TCP address and
return a ``real address'' to which client machines can connect.
fildes is not used. pointer_to_args is a pointer to a struct
nd_mergearg which has the following members:
char s_uaddr; /* server's universal address */
char c_uaddr; /* client's universal address */
char m_uaddr; /* the result */
If s_uaddr is an address such as 0.0.0.0.1.12, and the call is suc‐
cessful m_uaddr is set to an address such as 192.11.109.89.1.12.
For most transports, m_uaddr is identical to s_uaddr.
RETURN VALUES
The netdir_perror() function prints an error message in standard output
that states the cause of a name-to-address mapping failure. The error
message is preceded by the string given as an argument.
The netdir_sperror() function returns a string with an error message
that states the cause of a name-to-address mapping failure.
The netdir_sperror() function returns a pointer to a buffer which con‐
tains the error message string. The buffer is overwritten on each call.
In multithreaded applications, thise buffer is implemented as thread-
specific data.
The netdir_getbyaddr() function returns 0 on success and a non-zero
value on failure.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOgethostname(3C), getnetconfig(3NSL), getnetpath(3NSL), netconfig(4),
attributes(5)SunOS 5.10 28 Jan 2005 netdir(3NSL)
