NAME¶
lwres_lwpacket_renderheader, lwres_lwpacket_parseheader -
lightweight resolver packet handling functions
SYNOPSIS¶
#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.
AUTHOR¶
Internet Systems Consortium, Inc.
COPYRIGHT¶
Copyright © 2000, 2001, 2004, 2005, 2007, 2014-2016,
2018-2021 Internet Systems Consortium, Inc. ("ISC")