dns_client_resource.h

DNS 的实现代码

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/*
 * file:  dns_client_resource.h
 *
 * description:  this file contains typedefs and externs for the resources
 *               used by the dns client.  note that none of this would be
 *               necessary if there was a efficient malloc() and free() as
 *               part of the ISOS package.  if and when one becomes available
 *               this should be replaced.
 */

#ifndef _DNS_CLIENT_RESOURSE_H
#define _DNS_CLIENT_RESOURSE_H

#include "atypes.h"
#include "dns_client_query.h"     /* includes dns_resolv.h for struct dns_hostent */



#define IPSIZE      sizeof(U32)
#define IP6SIZE     sizeof(struct in6_addr)
#define TXBUFMAX    5


/* this structure is used to provide memory for nslookup commands. */

typedef struct {
    long                used;
    struct dns_hostent  hent;
    struct hostent     *hent6;     /* for IPv6 only */
    ATMOS_MESSAGE       amsg;
    char                name[NAMEMAX+1];
    U32                 addrs[ENTADDRS];
} nslook_t;

/* Prototype of callback for QueryState */
typedef void (*dns_client_query_callback)(QueryState *);

/* externs */

#ifdef DNS_DEBUG
extern void print_resource_pool(void);
#endif

extern U8           *dns_ip_alloc(void);
extern U8           *dns_ip6_alloc(void);
extern void         dns_ip_free(U8 *);
extern U8           *dns_name_alloc(void);
extern void         dns_name_free(U8 *);

extern DnsQuestion  *dns_get_question(void);
extern void         dns_free_question(DnsQuestion *);
extern DnsRRec      *dns_get_RR(void);
extern void         dns_free_RR(DnsRRec *);
extern SOArec       *dns_get_SOA(void);
extern void         dns_free_SOA(SOArec *);

extern void         dns_cache_init(void);

/*
 * dns_alloc_struct_hostent()
 *
 * this routine dynamically allocates memory for struct hostent.
 *
 * returns pointer to allocated area
 *         or NULL on failure
 */
extern struct hostent *dns_alloc_struct_hostent(void);

/*
 * dns_alloc_hostname()
 *
 * this routine dynamically allocates memory for 'h_name' field of
 * hostent structure.
 *
 * note, that upon failure, this function RELEASES hostent structure.
 * caller then has to set pointer to this structure to NULL.
 *
 * parameters:
 *     hent     - pointer to hostent structure
 *     hostname - hostname to install
 *
 * returns pointer to allocated area
 *         or NULL on failure
 */
extern const char *dns_alloc_hostname(struct hostent *hent, 
                                      const char *hostname);

/*
 * dns_alloc_aliases()
 *
 * this routine dynamically allocates memory for 'h_aliases' field of
 * hostent structure. 
 *
 * note, however, that memory for aliases themselves is not allocated
 * (since we can not know in advance lengthes of all aliases).
 *
 * note, that on failure, this function RELEASES hostent structure.
 * caller then has to set pointer to this structure to NULL.
 *
 * returns pointer to the allocated area 
 *         or NULL on failure
 */
extern char **dns_alloc_aliases(struct hostent *hent, int num_aliases);

/*
 * dns_alloc_addrlist()
 *
 * this routine dynamically allocates memory for 'h_addr_list' field
 * of hostent structure and for 'num_addr' addresses of type 'type' in
 * it.
 *
 * note, in case of failure, this function RELEASES hostent structure.
 * caller then has to set pointer to this structure to NULL.
 *
 * returns pointer to the allocated area 
 *         or NULL on failure
 */
extern char **dns_alloc_addrlist(struct hostent *hent, 
                                 int num_addr, int afamily);

/*
 * dns_dalloc()
 *
 * this routine will either allocate an IP address or a name.  the IP address
 * is a pointer to a U32 and the name is a character array.
 *
 * return:  pointer to allocated space, or
 *          NULL if none available.
 */

static inline U8 *
dns_dalloc(int size)
{
    if (size <= (int)IPSIZE) 
        return dns_ip_alloc();
    else if (size == (int)IP6SIZE)
        return dns_ip6_alloc();
    else
        return dns_name_alloc();
}   /* end dalloc() */


/*
 * dns_dfree()
 *
 * this routine will release the name or IP address.  the routine uses the
 * size parameter to determine the memory type.
 */
 
static inline void
dns_dfree(U8 *data, int size)
{
    if (size <= (int)IPSIZE || size == (int)IP6SIZE) 
        dns_ip_free(data);
    else
        dns_name_free(data);
}    /* end dns_dfree() */
        

#endif