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#!/usr/bin/awk
##############################################################################
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# Copyright (C) 2016 Eric Luehrsen
#
##############################################################################
#
# Turn DHCP records into meaningful A, AAAA, and PTR records. Also lift a
# function from dnsmasq and use DHCPv4 MAC to find IPV6 SLAAC hosts.
#
# External Parameters
# "hostfile" = where this script will cache host DNS data
# "domain" = text domain suffix
# "bslaac" = boolean, use DHCPv4 MAC to find GA and ULA IPV6 SLAAC
# "bisolt" = boolean, format <host>.<network>.<domain>. so you can isolate
# "bconf" = boolean, write conf file format rather than pipe records
#
##############################################################################
/^#/ {
# We need to pick out DHCP v4 or v6 records
net = $2 ; id = $3 ; cls = $4 ; hst = $5 ; adr = $9 ; adr2 = $10
cdr = adr ;
cdr2 = adr2 ;
sub( /\/.*/, "", adr ) ;
sub( /.*\//, "", cdr ) ;
sub( /\/.*/, "", adr2 ) ;
sub( /.*\//, "", cdr2 ) ;
if ( bisolt == 1 ) {
# TODO: this might be better with a substituion option,
# or per DHCP pool do-not-DNS option, but its getting busy here.
fqdn = net
fqdn = sub( /\./, "-", fqdn ) ;
fqdn = tolower( hst "." fqdn "." domain ) ;
}
else {
fqdn = tolower( hst "." domain ) ;
}
if ( cls == "ipv4" ) {
if ( NF == 8 ) {
# odhcpd errata in field format without host name
adr = $8 ; hst = "-" ; cdr = adr ;
sub( /\/.*/, "", adr ) ;
sub( /.*\//, "", cdr ) ;
}
if (( cdr == 32 ) && ( hst != "-" )) {
# only for provided hostnames and full /32 assignments
ptr = adr ; qpr = "" ; split( ptr, ptr, "." ) ;
slaac = slaac_eui64( id ) ;
if ( bconf == 1 ) {
x = ( "local-data: \"" fqdn ". 120 IN A " adr "\"" ) ;
y = ( "local-data-ptr: \"" adr " 120 " fqdn "\"" ) ;
print ( x "\n" y "\n" ) > hostfile ;
}
else {
for( i=1; i<=4; i++ ) { qpr = ( ptr[i] "." qpr) ; }
x = ( fqdn ". 120 IN A " adr ) ;
y = ( qpr "in-addr.arpa. 120 IN PTR " fqdn ) ;
print ( x "\n" y ) > hostfile ;
}
if (( bslaac == 1 ) && ( slaac != 0 )) {
# UCI option to discover IPV6 routed SLAAC addresses
# NOT TODO - ping probe take too long when added in awk-rule loop
cmd = ( "ip -6 --oneline route show dev " net ) ;
while ( ( cmd | getline adr ) > 0 ) {
if (( substr( adr, 1, 5 ) <= "fdff:" ) \
&& ( index( adr, "anycast" ) == 0 ) \
&& ( index( adr, "via" ) == 0 )) {
# GA or ULA routed addresses only (not LL or MC)
sub( /\/.*/, "", adr ) ;
adr = ( adr slaac ) ;
if ( split( adr, tmp0, ":" ) >= 8 ) {
sub( "::", ":", adr ) ;
}
if ( bconf == 1 ) {
x = ( "local-data: \"" fqdn ". 120 IN AAAA " adr "\"" ) ;
y = ( "local-data-ptr: \"" adr " 120 " fqdn "\"" ) ;
print ( x "\n" y "\n" ) > hostfile ;
}
else {
qpr = ipv6_ptr( adr ) ;
x = ( fqdn ". 120 IN AAAA " adr ) ;
y = ( qpr ". 120 IN PTR " fqdn ) ;
print ( x "\n" y ) > hostfile ;
}
}
}
close( cmd ) ;
}
}
}
else {
if (( cdr == 128 ) && ( hst != "-" )) {
if ( bconf == 1 ) {
x = ( "local-data: \"" fqdn ". 120 IN AAAA " adr "\"" ) ;
y = ( "local-data-ptr: \"" adr " 120 " fqdn "\"" ) ;
print ( x "\n" y "\n" ) > hostfile ;
}
else {
# only for provided hostnames and full /128 assignments
qpr = ipv6_ptr( adr ) ;
x = ( fqdn ". 120 IN AAAA " adr ) ;
y = ( qpr ". 120 IN PTR " fqdn ) ;
print ( x "\n" y ) > hostfile ;
}
}
if (( cdr2 == 128 ) && ( hst != "-" )) {
if ( bconf == 1 ) {
x = ( "local-data: \"" fqdn ". 120 IN AAAA " adr2 "\"" ) ;
y = ( "local-data-ptr: \"" adr2 " 120 " fqdn "\"" ) ;
print ( x "\n" y "\n" ) > hostfile ;
}
else {
# odhcp puts GA and ULA on the same line (position 9 and 10)
qpr2 = ipv6_ptr( adr2 ) ;
x = ( fqdn ". 120 IN AAAA " adr2 ) ;
y = ( qpr2 ". 120 IN PTR " fqdn ) ;
print ( x "\n" y ) > hostfile ;
}
}
}
}
##############################################################################
function ipv6_ptr( ipv6, arpa, ary, end, i, j, new6, sz, start ) {
# IPV6 colon flexibility is a challenge when creating [ptr].ip6.arpa.
sz = split( ipv6, ary, ":" ) ; end = 9 - sz ;
for( i=1; i<=sz; i++ ) {
if( length(ary[i]) == 0 ) {
for( j=1; j<=end; j++ ) { ary[i] = ( ary[i] "0000" ) ; }
}
else {
ary[i] = substr( ( "0000" ary[i] ), length( ary[i] )+5-4 ) ;
}
}
new6 = ary[1] ;
for( i = 2; i <= sz; i++ ) { new6 = ( new6 ary[i] ) ; }
start = length( new6 ) ;
for( i=start; i>0; i-- ) { arpa = ( arpa substr( new6, i, 1 ) ) ; } ;
gsub( /./, "&\.", arpa ) ; arpa = ( arpa "ip6.arpa" ) ;
return arpa ;
}
##############################################################################
function slaac_eui64( mac, ary, glbit, eui64 ) {
if ( length(mac) >= 12 ) {
# RFC2373 and use DHCPv4 registered MAC to find SLAAC addresses
split( mac , ary , "" ) ;
glbit = ( "0x" ary[2] ) ;
glbit = sprintf( "%d", glbit ) ;
glbit = or( glbit, 2 ) ;
ary[2] = sprintf( "%x", glbit ) ;
eui64 = ( ary[1] ary[2] ary[3] ary[4] ":" ary[5] ary[6] "ff:fe" ) ;
eui64 = ( eui64 ary[7] ary[8] ":" ary[9] ary[10] ary[11] ary[12] ) ;
}
else {
eui64 = 0 ;
}
return eui64 ;
}
##############################################################################
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