automaticly generate starting root servers.

Reference: /n/atom/patch/applied2013/genrootservers
Date: Fri Jun 28 19:06:33 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /lib/ndb/genrootservers	Thu Jan  1 00:00:00 1970
+++ /lib/ndb/genrootservers	Fri Jun 28 19:06:16 2013
@@ -0,0 +1,37 @@
+#!/bin/rc
+rfork en
+
+aserver=a.root-servers.net
+letters=(a b c d e f g h i j k l m)
+
+fn fatal {
+	echo $*>[1=2]
+	exit fatal
+}
+
+fn get{
+	ndb/dnsdebug @$aserver $* | awk '
+		$1=="answer" && $(NF-2) == "negative" {next}
+		$1=="answer" {printf "dom=%s	%s=%s\n", $2, $(NF-1), $NF}
+		'
+}
+
+aserver = `{get a.root-servers.net|sed 's/.*=//g'}
+if(~ $#aserver 0)
+	fatal cant find a.root-servers.net
+{
+	echo '#'
+	echo '#  entries defining the dns root.  these will be overridden by any'
+	echo '#  authentic info obtained from the root.'
+	echo '#'
+	echo 'dom='
+	for(letter in $letters)
+		echo '	ns='^$letter^'.root-servers.net'
+	for(letter in $letters)
+		get $letter^.root-servers.net ip
+	{
+		for(letter in $letters){
+			get $letter^.root-servers.net ipv6
+		}
+	} | sed 's/^/# /g'
+}