NAME
lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr - lightweight resolver utility functions
SYNOPSIS
I lwres_result_t lwres_string_parse(lwres_buffer_t * b , char ** c , lwres_uint16_t * len );
I lwres_result_t lwres_addr_parse(lwres_buffer_t * b , lwres_addr_t * addr );
I lwres_result_t lwres_getaddrsbyname(lwres_context_t * ctx , const char * name , lwres_uint32_t addrtypes , lwres_gabnresponse_t ** structp );
I 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 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_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).
COPYRIGHT
Copyright 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
Copyright 2000, 2001 Internet Software Consortium.
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