This section is an overview of the mapping routines that are available for use. The routines return or convert the network names to their respective network addresses. Note that netdir_getbyname(3NSL), netdir_getbyaddr(3NSL), and taddr2uaddr(3NSL) return pointers to data that must be freed by calls to netdir_free(3NSL).
int netdir_getbyname(struct netconfig *nconf, struct nd_hostserv *service, struct nd_addrlist **addrs);
netdir_getbyname(3NSL) maps the host and service name specified in service to a set of addresses that are consistent with the transport identified in nconf. The nd_hostserv and nd_addrlist structures are defined in the netdir(3NSL) man page. A pointer to the addresses is returned in addrs.
To find all addresses of a host and service on all available transports, call netdir_getbyname(3NSL) with each netconfig(4) structure returned by either getnetpath(3NSL) or getnetconfig(3NSL).
int netdir_getbyaddr(struct netconfig *nconf, struct nd_hostservlist **service, struct netbuf *netaddr);
netdir_getbyaddr(3NSL) maps addresses into host and service names. The interface is called with an address in netaddr and returns a list of host-name and service-name pairs in service. The nd_hostservlist structure is defined in netdir(3NSL).
void netdir_free(void *ptr, int struct_type);
The netdir_free(3NSL) routine frees structures allocated by the name-to-address translation routines. The parameters can take the values that are shown in the following table.
Table 9–2 netdir_free(3NSL) Routines
struct_type |
ptr |
---|---|
ND_HOSTSERV |
Pointer to an nd_hostserv structure |
ND_HOSTSERVLIST |
Pointer to an nd_hostservlist structure |
ND_ADDR |
Pointer to a netbuf structure |
ND_ADDRLIST |
Pointer to an nd_addrlist structure |
char *taddr2uaddr(struct netconfig *nconf, struct netbuf *addr);
taddr2uaddr(3NSL) translates the address pointed to by addr and returns a transport-independent character representation of the address. This character representation is called a universal address. The value that is given in nconf specifies the transport for which the address is valid. The universal address can be freed by free(3C).
struct netbuf *uaddr2taddr(struct netconfig *nconf, char *uaddr);
The universal address pointed to by uaddr is translated into a netbuf structure. nconf specifies the transport for which the address is valid.
int netdir_options(const struct netconfig *config, const int option, const int fildes, char *point_to_args);
netdir_options(3NSL) provides interfaces to transport-specific capabilities, such as the broadcast address and reserved port facilities of TCP and UDP. The value of nconf specifies a transport, while option specifies the transport-specific action to take. The value in option might disable consideration of the value in fd. The fourth argument points to operation-specific data.
The following table shows the values used for option.
Table 9–3 Values for netdir_options
Option |
Description |
---|---|
ND_SET_BROADCAST |
Sets the transport for broadcast if the transport supports broadcast |
ND_SET_RESERVEDPORT |
Enables application binding to reserved ports if allowed by the transport |
ND_CHECK_RESERVEDPORT |
Verifies that an address corresponds to a reserved port if the transport supports reserved ports |
ND_MERGEADDR |
Transforms a locally meaningful address into an address to which client hosts can connect |
The netdir_perror(3NSL) routine displays a message stating why one of the routines that map name-to-address failed on stderr.
void netdir_perror(char *s);
The netdir_sperror(3NSL) routine returns a string containing the error message stating why one of the routines that map name-to-address failed.
char *netdir_sperror(void);
The following example shows network selection and name-to-address mapping.
#include <netconfig.h> #include <netdir.h> #include <sys/tiuser.h> struct nd_hostserv nd_hostserv; /* host and service information */ struct nd_addrlist *nd_addrlistp; /* addresses for the service */ struct netbuf *netbufp; /* the address of the service */ struct netconfig *nconf; /* transport information*/ int i; /* the number of addresses */ char *uaddr; /* service universal address */ void *handlep; /* a handle into network selection */ /* * Set the host structure to reference the "date" * service on host "gandalf" */ nd_hostserv.h_host = "gandalf"; nd_hostserv.h_serv = "date"; /* * Initialize the network selection mechanism. */ if ((handlep = setnetpath()) == (void *)NULL) { nc_perror(argv[0]); exit(1); } /* * Loop through the transport providers. */ while ((nconf = getnetpath(handlep)) != (struct netconfig *)NULL) { /* * Print out the information associated with the * transport provider described in the "netconfig" * structure. */ printf("Transport provider name: %s\n", nconf->nc_netid); printf("Transport protocol family: %s\n", nconf->nc_protofmly); printf("The transport device file: %s\n", nconf->nc_device); printf("Transport provider semantics: "); switch (nconf->nc_semantics) { case NC_TPI_COTS: printf("virtual circuit\n"); break; case NC_TPI_COTS_ORD: printf("virtual circuit with orderly release\n"); break; case NC_TPI_CLTS: printf("datagram\n"); break; } /* * Get the address for service "date" on the host * named "gandalf" over the transport provider * specified in the netconfig structure. */ if (netdir_getbyname(nconf, &nd_hostserv, &nd_addrlistp) != ND_OK) { printf("Cannot determine address for service\n"); netdir_perror(argv[0]); continue; } printf("<%d> addresses of date service on gandalf:\n", nd_addrlistp->n_cnt); /* * Print out all addresses for service "date" on * host "gandalf" on current transport provider. */ netbufp = nd_addrlistp->n_addrs; for (i = 0; i < nd_addrlistp->n_cnt; i++, netbufp++) { uaddr = taddr2uaddr(nconf,netbufp); printf("%s\n",uaddr); free(uaddr); } netdir_free( nd_addrlistp, ND_ADDRLIST ); } endnetconfig(handlep);