lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr — lightweight resolver utility functions
#include <lwres/lwres.h>
lwres_result_t
lwres_string_parse( |
, | |
, | ||
) ; |
lwres_result_t
lwres_addr_parse( |
, | |
) ; |
lwres_result_t
lwres_getaddrsbyname( |
, | |
, | ||
, | ||
) ; |
lwres_result_t
lwres_getnamebyaddr( |
, | |
, | ||
, | ||
, | ||
) ; |
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
.
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.