netdir(3N) UNIX System V netdir(3N)
NAME
netdirgetbyname, netdirgetbyaddr, netdirfree, netdirmergeaddr,
taddr2uaddr, uaddr2taddr, netdirperror, netdirsperror - generic
transport name-to-address translation
SYNOPSIS
#include <netdir.h>
int netdirgetbyname(struct netconfig *config, struct ndhostserv
*service, struct ndaddrlist *addrs);
int netdirgetbyaddr(struct netconfig *config, struct
ndhostservlist **service, struct netbuf *netaddr);
void netdirfree(void *ptr, int ident);
int netdirmergeaddr(struct netconfig *config, char *mrguaddr,
char *suaddr, char *cuaddr);
char *taddr2uaddr(struct netconfig *config, struct netbuf *addr);
struct netbuf *uaddr2taddr(struct netconfig *config, char *uaddr);
int netdiroptions(struct netconfig *netconfig, int option, int fd,
char *pointertoargs);
void netdirperror(char *s);
char *netdirsperror(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 netdirgetbyname routine maps the machine name and service name in
the ndhostserv 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
ndaddrlist structure. The netconfig structure is described on the
netconfig(4) manual page. The ndhostserv and ndaddrlist structures
have the following elements.
ndaddrlist structure:
int ncnt; /* number of netbufs */
struct netbuf *naddrs; /* the netbufs */
ndhostserv structure:
char *hhost; /* the host name */
char *hserv; /* the service name */
netdirgetbyname 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:
HOSTSELF Represents the address to which local programs will bind
their endpoints. HOSTSELF differs from the host name
provided by gethostname(), which represents the address to
which remote programs will bind their endpoints.
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netdir(3N) UNIX System V netdir(3N)
HOSTANY Represents any host accessible by this transport provider.
HOSTANY allows applications to specify a required service
without specifying a particular host name.
HOSTBROADCAST
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 ndhostserv structure must be initialized.
To find all available transports, call the netdirgetbyname routine with
each netconfig structure returned by the getnetpath call.
The netdirgetbyaddr 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
ndhostservlist structure contains the following members:
int hcnt; /* the number of ndhostservs */
struct hostserv *hhostservs; /* the entries */
The netdirfree structure is used to free the structures allocated by the
name to address translation routines.
The netdirmergeaddr 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 netdirgetbyname
call, specified with the special host name HOSTSELF.
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.
option, fd, and pointer_to_args are passed to the netdiroptions routine
for the transport specified in netconfigp. There are four values for
option:
NDSETBROADCAST
NDSETRESERVEDPORT
NDCHECKRESERVEDPORT
NDMERGEADDR
If a transport provider does not support an option, netdiroptions
returns -1 and sets nderror to NDNOCTRL.
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netdir(3N) UNIX System V netdir(3N)
The specific actions of each option follow.
NDSETBROADCAST 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 topen of /dev/udp). pointer_to_args is not used.
If this completes, broadcast operations may be
performed on file descriptor fd.
NDSETRESERVEDPORT 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.
NDCHECKRESERVEDPORT
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.
NDMERGEADDR 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 ndmergearg,
which has the following members:
char *suaddr; /* server's universal address */
char *cuaddr; /* client's universal address */
char *muaddr; /* merged universal address */
suaddr is something like 0.0.0.0.1.12, and, if the
call is successful, muaddr will be set to something
like 192.11.109.89.1.12. For most transports,
muaddr is exactly what suaddr is.
The netdirperror() 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 netdirsperror routine returns a string containing an error message
stating why one of the name-to-address mapping routines failed.
SEE ALSO
getnetpath(3N)
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