2007-06-18
ISC
Internet Systems Consortium, Inc.
lwres_packet
3
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Internet Systems Consortium, Inc. ("ISC")
lwres_lwpacket_renderheader
lwres_lwpacket_parseheader
lightweight resolver packet handling functions
#include <lwres/lwpacket.h>
lwres_result_t
lwres_lwpacket_renderheader
lwres_buffer_t *b
lwres_lwpacket_t *pkt
lwres_result_t
lwres_lwpacket_parseheader
lwres_buffer_t *b
lwres_lwpacket_t *pkt
DESCRIPTION
These functions rely on a
struct lwres_lwpacket
which is defined in
lwres/lwpacket.h.
typedef struct lwres_lwpacket lwres_lwpacket_t;
struct lwres_lwpacket {
uint32_t length;
uint16_t version;
uint16_t pktflags;
uint32_t serial;
uint32_t opcode;
uint32_t result;
uint32_t recvlength;
uint16_t authtype;
uint16_t authlength;
};
The elements of this structure are:
length
the overall packet length, including the entire packet header.
This field is filled in by the lwres_gabn_*() and lwres_gnba_*()
calls.
version
the header format. There is currently only one format,
LWRES_LWPACKETVERSION_0.
This field is filled in by the lwres_gabn_*() and lwres_gnba_*()
calls.
pktflags
library-defined flags for this packet: for instance whether the
packet
is a request or a reply. Flag values can be set, but not defined
by
the caller.
This field is filled in by the application with the exception of
the
LWRES_LWPACKETFLAG_RESPONSE bit, which is set by the library in
the
lwres_gabn_*() and lwres_gnba_*() calls.
serial
is set by the requestor and is returned in all replies. If two
or more
packets from the same source have the same serial number and are
from
the same source, they are assumed to be duplicates and the
latter ones
may be dropped.
This field must be set by the application.
opcode
indicates the operation.
Opcodes between 0x00000000 and 0x03ffffff are
reserved for use by the lightweight resolver library. Opcodes
between
0x04000000 and 0xffffffff are application defined.
This field is filled in by the lwres_gabn_*() and lwres_gnba_*()
calls.
result
is only valid for replies.
Results between 0x04000000 and 0xffffffff are application
defined.
Results between 0x00000000 and 0x03ffffff are reserved for
library use.
This field is filled in by the lwres_gabn_*() and lwres_gnba_*()
calls.
recvlength
is the maximum buffer size that the receiver can handle on
requests
and the size of the buffer needed to satisfy a request when the
buffer
is too large for replies.
This field is supplied by the application.
authtype
defines the packet level authentication that is used.
Authorisation types between 0x1000 and 0xffff are application
defined
and types between 0x0000 and 0x0fff are reserved for library
use.
Currently these are not used and must be zero.
authlen
gives the length of the authentication data.
Since packet authentication is currently not used, this must be
zero.
The following opcodes are currently defined:
NOOP
Success is always returned and the packet contents are echoed.
The lwres_noop_*() functions should be used for this type.
GETADDRSBYNAME
returns all known addresses for a given name.
The lwres_gabn_*() functions should be used for this type.
GETNAMEBYADDR
return the hostname for the given address.
The lwres_gnba_*() functions should be used for this type.
lwres_lwpacket_renderheader()
transfers the contents of lightweight resolver packet structure
lwres_lwpacket_t *pkt in
network byte order to the lightweight resolver buffer,
*b.
lwres_lwpacket_parseheader()
performs the converse operation. It transfers data in network
byte order from buffer *b to resolver
packet *pkt. The contents of the buffer
b should correspond to a
lwres_lwpacket_t.
RETURN VALUES
Successful calls to
lwres_lwpacket_renderheader() and
lwres_lwpacket_parseheader() return
LWRES_R_SUCCESS. If there is insufficient
space to copy data between the buffer *b and
lightweight resolver packet *pkt both
functions
return LWRES_R_UNEXPECTEDEND.