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 */ 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. 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. 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