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 {
                   lwres_uint32_t          length;
                   lwres_uint16_t          version;
                   lwres_uint16_t          pktflags;
                   lwres_uint32_t          serial;
                   lwres_uint32_t          opcode;
                   lwres_uint32_t          result;
                   lwres_uint32_t          recvlength;
                   lwres_uint16_t          authtype;
                   lwres_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 wit 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.

COPYRIGHT

       Copyright © 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
       Copyright © 2000, 2001 Internet Software Consortium.