KRB5_KRBHST_INIT(3)

NAME
krb5_krbhst_init, krb5_krbhst_init_flags, krb5_krbhst_next, krb5_krbhst_next_as_string, krb5_krbhst_reset, krb5_krbhst_free, krb5_krbhst_format_string, krb5_krbhst_get_addrinfo - lookup Kerberos KDC hosts

LIBRARY
Kerberos 5 Library (libkrb5, -lkrb5)

SYNOPSIS
#include <krb5.h>
krb5_error_code
krb5_krbhst_init(krb5_context context, const char *realm, unsigned int type, krb5_krbhst_handle *handle);
krb5_error_code
krb5_krbhst_init_flags(krb5_context context, const char *realm, unsigned int type, int flags, krb5_krbhst_handle *handle);
krb5_error_code
krb5_krbhst_next(krb5_context context, krb5_krbhst_handle handle, krb5_krbhst_info **host);
krb5_error_code
krb5_krbhst_next_as_string(krb5_context context, krb5_krbhst_handle handle, char *hostname, size_t hostlen);
void
krb5_krbhst_reset(krb5_context context, krb5_krbhst_handle handle);
void
krb5_krbhst_free(krb5_context context, krb5_krbhst_handle handle);
krb5_error_code
krb5_krbhst_format_string(krb5_context context, const krb5_krbhst_info *host, char *hostname, size_t hostlen);
krb5_error_code
krb5_krbhst_get_addrinfo(krb5_context context, krb5_krbhst_info *host, struct addrinfo **ai);

DESCRIPTION
These functions are used to sequence through all Kerberos hosts of a particular realm and service. The service type can be the KDCs, the administrative servers, the password changing servers, or the servers for Kerberos 4 ticket conversion.

First a handle to a particular service is obtained by calling krb5_krbhst_init() (or krb5_krbhst_init_flags()) with the realm of interest and the type of service to lookup. The type can be one of:

KRB5_KRBHST_KDC
KRB5_KRBHST_ADMIN
KRB5_KRBHST_CHANGEPW
KRB5_KRBHST_KRB524

The handle is returned to the caller, and should be passed to the other functions.

The flag argument to krb5_krbhst_init_flags is the same flags as krb5_send_to_kdc_flags() uses. Possible values are:

KRB5_KRBHST_FLAGS_MASTER
    only talk to master (readwrite) KDC
KRB5_KRBHST_FLAGS_LARGE_MSG
    this is a large message, so use transport that can handle that.

For each call to krb5_krbhst_next() information on a new host is returned. The former function returns in host a pointer to a structure containing information about the host, such as protocol, hostname, and port:

    typedef struct krb5_krbhst_info {
        enum { KRB5_KRBHST_UDP,
    	   KRB5_KRBHST_TCP,
    	   KRB5_KRBHST_HTTP } proto;
        unsigned short port;
        struct addrinfo *ai;
        struct krb5_krbhst_info *next;
        char hostname[1];
    } krb5_krbhst_info;

The related function, krb5_krbhst_next_as_string(), return the same information as a URL-like string.

When there are no more hosts, these functions return KRB5_KDC_UNREACH.

To re-iterate over all hosts, call krb5_krbhst_reset() and the next call to krb5_krbhst_next() will return the first host.

When done with the handle, krb5_krbhst_free() should be called.

To use a krb5_krbhst_info, there are two functions: krb5_krbhst_format_string() that will return a printable representation of that struct and krb5_krbhst_get_addrinfo() that will return a struct addrinfo that can then be used for communicating with the server mentioned.

EXAMPLES
The following code will print the KDCs of the realm “MY.REALM”:

    krb5_krbhst_handle handle;
    char host[MAXHOSTNAMELEN];
    krb5_krbhst_init(context, "MY.REALM", KRB5_KRBHST_KDC, &handle);
    while(krb5_krbhst_next_as_string(context, handle,
    				 host, sizeof(host)) == 0)
        printf("%s\n", host);
    krb5_krbhst_free(context, handle);

SEE ALSO
getaddrinfo(3), krb5_get_krbhst(3), krb5_send_to_kdc_flags(3)

HISTORY
These functions first appeared in Heimdal 0.3g.