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