val_gethostbyname man page

val_gethostbyname(), val_gethostbyname2(), val_gethostbyname_r(), val_gethostbyname2_r() — get DNSSEC-validated network host entry

Synopsis

#include <validator/validator.h>
extern int h_errno;
struct hostent *val_gethostbyname(const val_context_t *ctx,
                                  const char *name,
                                  val_status_t *val_status);
struct hostent *val_gethostbyname2(const val_context_t *ctx,
                                   const char *name,
                                   int af,
                                   val_status_t *val_status);
int val_gethostbyname_r(const val_context_t *ctx,
                        const char *name,
                        struct hostent *ret,
                        char *buf,
                        size_t buflen,
                        struct hostent **result,
                        int *h_errnop,
                        val_status_t *val_status);
int val_gethostbyname2_r(const val_context_t *ctx,
                         const char *name,
                         int af,
                         struct hostent *ret,
                         char *buf,
                         size_t buflen,
                         struct hostent **result,
                         int *h_errnop,
                         val_status_t *val_status);
  struct hostent *val_gethostbyaddr(val_context_t * ctx,
                                    const char *addr,
                                    int len,
                                    int type, 
                                    val_status_t * val_status);
  int val_gethostbyaddr_r(val_context_t * ctx,
                          const char *addr,
                          int len,
                          int type,
                          struct hostent *ret,
                          char *buf,
                          int buflen,
                          struct hostent **result,
                          int *h_errnop,
                          val_status_t * val_status);

Description

val_gethostbyname(), val_gethostbyname2(), val_gethostbyname_r(), val_gethostbyname2_r(), val_gethostbyaddr() and val_gethostbyaddr_r() perform DNSSEC validation of DNS queries. They return a network host entry value of type struct hostent and are DNSSEC-aware versions of the gethostbyname(3), gethostbyname2(3), gethostbyname_r(), gethostbyname2_r(), gethostbyaddr() and gethostbyaddr_r() functions respectively. (See gethostbyname(3) for more information on type struct hostent).

val_gethostbyname(), val_gethostbyname_r(), val_gethostbyaddr(), and val_gethostbyaddr_r() support only IPv4 addresses. val_gethostbyname2() and val_gethostbyname2_r() support both IPv4 and IPv6 addresses.

The val_gethostbyname_r(), val_gethostbyname2_r() and val_gethostbyaddr_r() functions are reentrant versions and can be safely used in multi-threaded applications.

The ctx parameter specifies the validation context, which can be set to NULL for default values (see libval(3) and dnsval.conf for more details on validation contexts and validation policy).

val_gethostbyname(), val_gethostbyname2() and val_gethostbyaddr() set the global h_errno variable to return the resolver error code. The reentrant versions val_gethostbyname_r(), val_gethostbyname2_r() and val_gethostbyaddr_r() use the h_errnop parameter to return this value. This ensures thread safety, by avoiding the global h_errno variable. h_errnop must not be NULL. (See the man page for gethostbyname(3) for possible values of h_errno.)

The name, af, ret, buf, buflen, and result parameters have the same syntax and semantics as the corresponding parameters for the original gethostbyname*() and gethostbyaddr*() functions. See the manual page for gethostbyname(3) for more details about these parameters.

The val_status parameter is used to return the validator error code and must not be NULL. val_istrusted() and val_isvalidated() can be used to determine the trustworthiness of data and p_val_status() can be used to display the status value to the user in ASCII format (See libval(3) more for information).

Return Values

The val_gethostbyname(), val_gethostbyname2(), and val_gethostbyaddr() functions return a pointer to a hostent structure when they can resolve the given host name (with or without DNSSEC validation), and NULL if data was not available. The memory for the returned value is statically allocated by these two functions. Hence, the caller must not free the memory for the returned value.

The val_gethostbyname_r(), val_gethostbyname2_r() and val_gethostbyaddr_r() functions return 0 when they can resolve the given host name (with or without DNSSEC validation), and a non-zero error-code on failure.

The val_gethostbyaddr() and val_gethostbyaddr_r() functions return 0 when they can resolve the given host name (with or without DNSSEC validation), and a non-zero error-code on failure.

The val_status parameter gives an indication for trustworthiness of data. If the returned hostent structure is NULL, this value gives an indication of whether the non-existence of data can be trusted or not.

Example

#include <stdio.h>
#include <stdlib.h>
#include <validator.h>

   int main(int argc, char *argv[])
   {
        int val_status;
        struct hostent *h = NULL;
        if (argc < 2) {
            printf("Usage: %s <hostname>\n", argv[0]);
            exit(1);
        }
        h = val_gethostbyname(NULL, argv[1], &val_status);
        printf("h_errno = %d [%s]\n", h_errno,
            hstrerror(h_errno));
        if (h) {
            printf("Validation Status = %d [%s]\n", val_status,
                   p_val_status(val_status));
        }
        return 0;
   }

Notes

These functions do not currently read the order of lookup from /etc/hosts.conf. At present, the default order is set to consult the /etc/hosts file first and then query DNS.

The current versions of these functions do not support NIS lookups.

Authors

Abhijit Hayatnagarkar, Suresh Krishnaswamy.

See Also

gethostbyname(3), gethostbyname2(3), gethostbyname_r(3), gethostbyname2_r(3)

val_getaddrinfo(3), val_res_query(3)

libval(3)

http://www.dnssec-tools.org

Referenced By

dnsval.conf(3), val_getaddrinfo(3), val_get_rrset(3), val_res_query(3).

val_gethostbyaddr(3), val_gethostbyaddr_r(3), val_gethostbyname2(3), val_gethostbyname2_r(3) and val_gethostbyname_r(3) are aliases of val_gethostbyname(3).

2013-03-12 perl v5.14.3 Programmer's Manual