netdir(3N) netdir(3N)
NAME
netdir_getbyname, netdir_getbyaddr, netdir_free, netdir_mergeaddr,
taddr2uaddr, uaddr2taddr, netdir_perror, netdir_sperror - generic
transport name-to-address translation
SYNOPSIS
#include <netdir.h>
int
netdir_getbyname(config, service, addrs)
struct netconfig *config;
struct nd_hostserv *service;
struct nd_addrlist **addrs;
int
netdir_getbyaddr(config, service, netaddr)
struct netconfig *config;
struct nd_hostservlist **service;
struct netbuf *netaddr;
void
netdir_free(ptr, ident)
void *ptr;
int ident;
int
netdir_mergeaddr(config, mrg_uaddr, s_uaddr, c_uaddr)
struct netconfig *config;
char **mrg_uaddr, *s_uaddr, *c_uaddr;
char *
taddr2uaddr(config, addr)
struct netconfig *config;
struct netbuf *addr;
struct netbuf *
uaddr2taddr(config, uaddr)
struct netconfig *config;
char *uaddr;
int
netdir_options(netconfig, option, fd, pointer_to_args)
struct netconfig *netconfig;
int option;
int fd;
char *point_to_args;
void
netdir_perror(s)
char *s;
char *
netdir_sperror()
DESCRIPTION
These routines 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.
7/91 Page 1
netdir(3N) netdir(3N)
The netdir_getbyname() routine 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 routine returns all addresses that are valid for that transport
in the nd_addrlist structure. The nd_hostserv and nd_addrlist
structures have the following elements. The netconfig structure is
described on the netconfig(4) manual page.
struct nd_addrlist {
int n_cnt;
struct netbuf *n_addrs;
}
struct nd_hostserv {
char *h_host;
char *h_serv;
]
netdir_getbyname() accepts some special-case host names. These host
names are hints to the underlying mapping routines that define the
intent of the request. This information is required for some
transport provider developers to provide the correct information back
to the caller. The host names are defined in /usr/include/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(3), which represents the address
to which remote programs will bind their endpoints.
HOST_ANY Represents any host accessible by this transport
provider. HOST_ANY allows applications to specify a
required service without specifying a particular host
name.
HOST_BROADCAST
Represents the address for all hosts accessible by this
transport provider. Network requests to this address
will be received by all machines.
All fields of the nd_hostserv structure must be initialized.
To find all available transports, call the netdir_getbyname() routine
with each struct netconfig structure returned by the getnetpath(3N)
call.
The netdir_getbyaddr() routine maps addresses to service names. This
routine returns a list of host and service pairs that would yield
this address. If more than one tuple of host and service name is
returned then the first tuple contains the preferred host and service
names.
struct nd_hostservlist {
int *h_cnt;
Page 2 7/91
netdir(3N) netdir(3N)
struct hostserv *h_hostservs;
}
The netdir_free() structure is used to free the structures allocated
by the name to address translation routines.
The netdir_mergeaddr() routine is used by a network service to return
an optimized network addresses to a client. This routine takes the
universal address of the endpoint that the service has bound to,
which is pointed to by the s_uaddr parameter, and the address of the
endpoint that a request came in on, which is pointed to by the
c_uaddr paramter, to create an optimized address for communication
with the service. The service address should be an address returned
by the netdir_getbyname() call, specified with the special host name
HOST_SELF.
The taddr2uaddr() and uaddr2taddr() routines support translation
between universal addresses and TLI type netbufs. The take and
return character string pointers. The taddr2uaddr() routine returns
a pointer to a string that contains the universal address and returns
NULL if the conversion is not possible. This is not a fatal
condition as some transports may not suppose a universal address
form.
option, fd, and pointer_to_args are passed to the netdir_options
routine for the transport specified in netconfigp. There are four
values for option:
ND_SET_BROADCAST
ND_SET_RESERVEDPORT
ND_CHECK_RESERVEDPORT
ND_MERGEADDR
If a transport provider does not support an option, netdir_options
returns -1 and sets _nderror to ND_NOCTRL.
The specific actions of each option follow.
ND_SET_BROADCAST Sets the transport provider up to allow
broadcast, if the transport supports broadcast.
fd is a file descriptor into the transport (i.e.,
the result of a t_open of /dev/udp).
pointer_to_args is not used. If this completes,
broadcast operations may be performed on file
descriptor fd.
ND_SET_RESERVEDPORT Allows the application to bind to a reserved
port, if that concept exists for the transport
provider. fd is a file descriptor into the
transport (it must not be bound to an address).
If pointer_to_args is NULL, fd will be bound to a
reserved port. If pointer_to_args is a pointer
to a netbuf structure, an attempt will be made to
7/91 Page 3
netdir(3N) netdir(3N)
bind to a reserved port on the specified address.
ND_CHECK_RESERVEDPORT
Used to verify that an address corresponds to a
reserved port, if that concept exists for the
transport provider. fd is not used.
pointer_to_args is a pointer to a netbuf
structure that contains an address. This option
returns 0 only if the address specified in
pointer_to_args is reserved.
ND_MERGEADDR Used to take a ``local address'' (like the
0.0.0.0 address that TCP uses) and return a
``real address'' that client machines can connect
to. fd is not used. pointer_to_args is a
pointer to a struct nd_mergearg, which has the
following form:
struct nd_mergearg {
char *s_uaddr; /* server's universal address */
char *c_uaddr; /* client's universal address */
char *m_uaddr; /* the result */
}
s_uaddr is something like 0.0.0.0.1.12, and, if
the call is successful, m_uaddr will be set to
something like 192.11.109.89.1.12. For most
transports, m_uaddr is exactly what s_uaddr is.
The netdir_perror() routine prints an error message on the standard
output stating why one of the name-to-address mapping routines
failed. The error message is preceded by the string given as an
argument.
The netdir_sperror() routine returns a string containing an error
message stating why one of the name-to-address mapping routines
failed.
SEE ALSO
getnetpath(3N)
Page 4 7/91