lwres_resutil(3) BIND9 lwres_resutil(3)
NAME
lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname,
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_gabnresponse_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);
DESCRIPTION
lwres_string_parse() retrieves a DNS-encoded string starting 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
character 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 forward
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_ADDRTYPE_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 ALSO
lwres_buffer(3), lwres_gabn(3).
AUTHOR
Internet Systems Consortium, Inc.
COPYRIGHT
Copyright (C) 2004, 2005, 2007, 2014, 2015 Internet Systems Consortium,
Inc. ("ISC")
Copyright (C) 2000, 2001 Internet Software Consortium.
ISC 2007-06-18 lwres_resutil(3)
bind 9.10.4 - Generated Fri Apr 29 20:51:45 CDT 2016