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(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 ident);
int netdir_mergeaddr(struct netconfig *config, char *mrg_uaddr,
char *s_uaddr, char *c_uaddr);
char *taddr2uaddr(struct netconfig *config, struct netbuf *addr);
struct netbuf *uaddr2taddr(struct netconfig *config, char *uaddr);
int netdir_options(struct netconfig *netconfig, int option, int fd,
char *pointer_to_args);
void netdir_perror(char *s);
char *netdir_sperror(void);
DESCRIPTION
These routines provide a generic interface for name-to-address mapping
that will work with a all transport protocols. This interface provides a
generic way for programs to convert transport specific addresses into
common structures and back again.
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 netconfig structure is described on the
netconfig(4) manual page. The nd_hostserv and nd_addrlist structures
have the following elements.
nd_addrlist structure:
int n_cnt; /* number of netbufs */
struct netbuf *n_addrs; /* the netbufs */
nd_hostserv structure:
char *h_host; /* the host name */
char *h_serv; /* the service name */
Page 1
netdir(3N)netdir(3N)
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 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(), 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 netconfig structure returned by the getnetpath 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. The
nd_hostservlist structure contains the following members:
int h_cnt; /* the number of nd_hostservs */
struct hostserv *h_hostservs; /* the entries */
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 parameter, 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. They 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
support a universal address form.
Page 2
netdir(3N)netdir(3N)
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 (that is, 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 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 members:
char *s_uaddr; /* server's universal address */
char *c_uaddr; /* client's universal address */
char *m_uaddr; /* merged universal address */
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.
Page 3
netdir(3N)netdir(3N)
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 ALSOgetnetpath(3N)
Page 4
