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_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); |
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.