LWRES_RESUTIL(3)LWRES_RESUTIL(3)NAME
lwres_string_parse, lwres_addr_parse, lwres_getaddrsby-
name, lwres_getnamebyaddr - lightweight resolver utility
functions
SYNOPSIS
#include <lwres/lwres.h>
lwres_result_t lwres_string_parse(lwres_buffer_t *b, char
**c, lwres_uint16_t *len);
lwres_result_t lwres_addr_parse(lwres_buffer_t *b,
lwres_addr_t *addr);
lwres_result_t lwres_getaddrsbyname(lwres_context_t *ctx,
const char *name, lwres_uint32_t addrtypes, lwres_gabnre-
sponse_t **structp);
lwres_result_t lwres_getnamebyaddr(lwres_context_t *ctx,
lwres_uint32_t addrtype, lwres_uint16_t addrlen, const
unsigned char *addr, lwres_gnbaresponse_t **structp);
DESCRIPTIONlwres_string_parse() retrieves a DNS-encoded string start-
ing the current pointer of lightweight resolver buffer b:
i.e. b->current. When the function returns, the address
of the first byte of the encoded string is returned via *c
and the length of that string is given by *len. The
buffer's current pointer is advanced to point at the char-
acter following the string length, the encoded string, and
the trailing NULL character.
lwres_addr_parse() extracts an address from the buffer b.
The buffer's current pointer b->current is presumed to
point at an encoded address: the address preceded by a
32-bit protocol family identifier and a 16-bit length
field. The encoded address is copied to addr->address and
addr->length indicates the size in bytes of the address
that was copied. b->current is advanced to point at the
next byte of available data in the buffer following the
encoded address.
lwres_getaddrsbyname() and lwres_getnamebyaddr() use the
lwres_gnbaresponse_t structure defined below:
typedef struct {
lwres_uint32_t flags;
lwres_uint16_t naliases;
lwres_uint16_t naddrs;
char *realname;
char **aliases;
lwres_uint16_t realnamelen;
lwres_uint16_t *aliaslen;
lwres_addrlist_t addrs;
void *base;
size_t baselen;
} lwres_gabnresponse_t;
The contents of this structure are not manipulated
directly but they are controlled through the lwres_gabn(3)
functions.
The lightweight resolver uses lwres_getaddrsbyname() to
perform foward lookups. Hostname name is looked up using
the resolver context ctx for memory allocation. addrtypes
is a bitmask indicating which type of addresses are to be
looked up. Current values for this bitmask are LWRES_ADDR-
TYPE_V4 for IPv4 addresses and LWRES_ADDRTYPE_V6 for IPv6
addresses. Results of the lookup are returned in *structp.
lwres_getnamebyaddr() performs reverse lookups. Resolver
context ctx is used for memory allocation. The address
type is indicated by addrtype: LWRES_ADDRTYPE_V4 or
LWRES_ADDRTYPE_V6. The address to be looked up is given by
addr and its length is addrlen bytes. The result of the
function call is made available through *structp.
RETURN VALUES
Successful calls to lwres_string_parse() and
lwres_addr_parse() return LWRES_R_SUCCESS. Both functions
return LWRES_R_FAILURE if the buffer is corrupt or
LWRES_R_UNEXPECTEDEND if the buffer has less space than
expected for the components of the encoded string or
address.
lwres_getaddrsbyname() returns LWRES_R_SUCCESS on success
and it returns LWRES_R_NOTFOUND if the hostname name could
not be found.
LWRES_R_SUCCESS is returned by a successful call to
lwres_getnamebyaddr().
Both lwres_getaddrsbyname() and lwres_getnamebyaddr()
return LWRES_R_NOMEMORY when memory allocation requests
fail and LWRES_R_UNEXPECTEDEND if the buffers used for
sending queries and receiving replies are too small.
SEE ALSOlwres_buffer(3), lwres_gabn(3).
BIND9 Jun 30, 2000 LWRES_RESUTIL(3)
