unbound: add odhcpd specific scripts to link DHCP-DNS

The UCI for Unbound already links to dnsmasq, but what
if with Unbound, we want to configure a plain dhcp server.
Most servers can call a script for lease events. That
script can then formulate DNS records and load them
with unbound-control (dependency).

The files added here work with OpenWRT/LEDE odhcpd, such
that it can be run alone. They can be used as examples
for any dhcp server. 'odhcpd.sh' is to be called by
odhcpd when a lease event occurs. 'odhcpd.awk' is called
internal to the shell script. The awk script handles
any tricky reformating that may be required.

/etc/config/dhcp
config odhcpd 'odhcpd'
  option leasetrigger '/usr/lib/unbound/odhcpd.sh'

Signed-off-by: Eric Luehrsen <ericluehrsen@hotmail.com>

net/unbound/files/odhcpd.awk

@@ -0,0 +1,156 @@
+#!/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
+#
+##############################################################################
+
+/^#/ {
+  # We need to pick out DHCP v4 or v6 records
+  net = $2 ; id = $3 ; cls = $4 ; hst = $5 ; adr = $9 ;
+  cdr = adr ;
+  sub( /\/.*/, "", adr ) ;
+  sub( /.*\//, "", cdr ) ;
+
+
+  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 ) ;
+      for( i=1; i<=4; i++ ) { qpr = ( ptr[i] "." qpr) ; }
+
+      # DHCP A and PTR records with FQDN
+      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 ) <= "fd00:" ) {
+            # GA or ULA routed addresses only (not LL or MC)
+            sub( /\/.*/, "", adr ) ;
+            adr = ( adr slaac ) ;
+            if ( split( adr, tmp0, ":" ) >= 8 ) { sub( "::", ":", adr ) ; }
+            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 != "-" )) {
+      # 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 ;
+    }
+  }
+}
+
+##############################################################################
+
+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 ;
+}
+
+##############################################################################
+

net/unbound/files/odhcpd.sh

@@ -0,0 +1,92 @@
+#!/bin/sh
+##############################################################################
+#
+# 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
+#
+##############################################################################
+#
+# This script facilitates alternate installation of Unbound+odhcpd and no
+# need for dnsmasq. There are some limitations, but it works and is small.
+# The lease file is parsed to make "zone-data:" and "local-data:" entries.
+#
+# config odhcpd 'odhcpd'
+#   option leasetrigger '/usr/lib/unbound/odhcpd.sh'
+#
+##############################################################################
+
+# Common file location definitions
+. /usr/lib/unbound/unbound.sh
+
+##############################################################################
+
+odhcpd_settings() {
+  # This trigger is out of normal init context, so we need to read some UCI.
+  local cfg="$1"
+  config_get UNBOUND_D_DHCP_LINK  "$cfg" dhcp_link none
+  config_get_bool UNBOUND_B_SLAAC6_MAC "$cfg" dhcp4_slaac6 0
+}
+
+##############################################################################
+
+odhcpd_zonedata() {
+  local dns_ls_add=$UNBOUND_VARDIR/dhcp_dns.add
+  local dns_ls_del=$UNBOUND_VARDIR/dhcp_dns.del
+  local dhcp_ls_new=$UNBOUND_VARDIR/dhcp_lease.new
+  local dhcp_ls_old=$UNBOUND_VARDIR/dhcp_lease.old
+  local dhcp_ls_add=$UNBOUND_VARDIR/dhcp_lease.add
+  local dhcp_ls_del=$UNBOUND_VARDIR/dhcp_lease.del
+  local dhcp_origin=$( uci get dhcp.@odhcpd[0].leasefile )
+  
+  config_load unbound
+  config_foreach odhcpd_settings unbound
+
+
+  if [ "$UNBOUND_D_DHCP_LINK" = "odhcpd" -a -f "$dhcp_origin" ] ; then
+    # Capture the lease file which could be changing often,
+    # and unbound-control only for changes in hosts (or else...)
+    cat $dhcp_origin | sort > $dhcp_ls_new
+    touch $dhcp_ls_old
+    sort $dhcp_ls_new $dhcp_ls_old $dhcp_ls_old | uniq -u > $dhcp_ls_add
+    sort $dhcp_ls_old $dhcp_ls_new $dhcp_ls_new | uniq -u > $dhcp_ls_del
+
+    # Go through the messy business of coding up A, AAAA, and PTR records.
+    awk -v hostfile=$dns_ls_del -v domain=$UNBOUND_TXT_DOMAIN \
+        -v bslaac=$UNBOUND_B_SLAAC6_MAC -v bisolt=0 \
+        -f /usr/lib/unbound/odhcpd.awk $dhcp_ls_del
+
+    awk -v hostfile=$dns_ls_add -v domain=$UNBOUND_TXT_DOMAIN \
+        -v bslaac=$UNBOUND_B_SLAAC6_MAC -v bisolt=0 \
+        -f /usr/lib/unbound/odhcpd.awk $dhcp_ls_add
+
+
+    if [ -f "$dns_ls_del" ] ; then
+      cat $dns_ls_del | $UNBOUND_CONTROL_CFG local_datas_remove
+    fi
+    
+
+    if [ -f "$dns_ls_add" ] ; then
+      cat $dns_ls_add | $UNBOUND_CONTROL_CFG local_datas
+    fi
+    
+    
+    # prepare next round
+    mv $dhcp_ls_new $dhcp_ls_old
+    rm -f $dns_ls_del $dns_ls_add
+  fi
+}
+
+##############################################################################
+
+odhcpd_zonedata
+
+##############################################################################
+