DNS test: also check a public nameserver to verify that the registrar (or up-host) configuration is correct too

tests/dns.py

@@ -1,7 +1,11 @@
 #!/usr/bin/python3
-# Test DNS configuration.
+#
+# Tests the DNS configuration of a Mail-in-a-Box.
 #
 # tests/dns.py ipaddr hostname
+#
+# where ipaddr is the IP address of your Mail-in-a-Box
+# and hostname is the domain name to check the DNS for.
 
 import sys, subprocess, re, difflib
 
@@ -11,48 +15,64 @@ if len(sys.argv) < 3:
 
 ipaddr, hostname = sys.argv[1:]
 
-def dig(digargs):
-	# run dig and clean the output
-	response = subprocess.check_output(['dig', '@' + ipaddr] + digargs).decode('utf8')
-	response = re.sub('[\r\n]+', '\n', response) # remove blank lines
-	response = re.sub('\n;.*', '', response) # remove comments
-	response = response.strip() + "\n"
-	return response
-
-# call dig a few times with different parameters
-digoutput = \
-   dig([hostname])\
- + dig(["www." + hostname, "+noadditional", "+noauthority"]) \
- + dig(["mx", hostname, "+noadditional", "+noauthority"]) \
- + dig(["txt", hostname, "+noadditional", "+noauthority"]) \
- + dig(["txt", "mail._domainkey." + hostname, "+noadditional", "+noauthority"])
-
-# normalize DKIM key
-digoutput = re.sub(r"(\"p=).*(\")", r"\1__KEY__\2", digoutput)
-
 # construct the expected output
 subs = { "ipaddr": ipaddr, "hostname": hostname }
 expected = """
-{hostname}.	86400	IN	A	{ipaddr}
-{hostname}.	86400	IN	NS	ns1.{hostname}.
-{hostname}.	86400	IN	NS	ns2.{hostname}.
-ns1.{hostname}.	86400	IN	A	{ipaddr}
-ns2.{hostname}.	86400	IN	A	{ipaddr}
-www.{hostname}.	86400	IN	A	{ipaddr}
-{hostname}.	86400	IN	MX	10 {hostname}.
-{hostname}.	300	IN	TXT	"v=spf1 mx -all"
-mail._domainkey.{hostname}. 86400 IN TXT	"v=DKIM1\; k=rsa\; s=email\; " "p=__KEY__"
+{hostname}.	#####	IN	A	{ipaddr}
+{hostname}.	#####	IN	NS	ns1.{hostname}.
+{hostname}.	#####	IN	NS	ns2.{hostname}.
+ns1.{hostname}.	#####	IN	A	{ipaddr}
+ns2.{hostname}.	#####	IN	A	{ipaddr}
+www.{hostname}.	#####	IN	A	{ipaddr}
+{hostname}.	#####	IN	MX	10 {hostname}.
+{hostname}.	#####	IN	TXT	"v=spf1 mx -all"
+mail._domainkey.{hostname}. ##### IN TXT	"v=DKIM1\; k=rsa\; s=email\; " "p=__KEY__"
 """.format(**subs).strip() + "\n"
 
-# Show a diff if there are any changes
-has_diff = False
-def split(s): return [line+"\n" for line in s.split("\n")]
-for line in difflib.unified_diff(split(expected), split(digoutput), fromfile='expected DNS settings', tofile='output from dig'):
-	sys.stdout.write(line)   
+def dig(server, digargs):
+	# run dig and clean the output
+	response = subprocess.check_output(['dig', '@' + server, "+noadditional", "+noauthority"] + digargs).decode('utf8')
+	response = re.sub('[\r\n]+', '\n', response) # remove blank lines
+	response = re.sub('\n;.*', '', response) # remove comments
+	response = re.sub('(\n\S+\s+)(\d+)', r'\1#####', response) # normalize TTLs
+	response = re.sub(r"(\"p=).*(\")", r"\1__KEY__\2", response) # normalize DKIM key
+	response = response.strip() + "\n"
+	return response
+
+def test(server, description):
+	# call dig a few times with different parameters
+	digoutput = \
+	   dig(server, [hostname])\
+	 + dig(server, ["ns", hostname]) \
+	 + dig(server, ["ns1." + hostname]) \
+	 + dig(server, ["ns2." + hostname]) \
+	 + dig(server, ["www." + hostname]) \
+	 + dig(server, ["mx", hostname]) \
+	 + dig(server, ["txt", hostname]) \
+	 + dig(server, ["txt", "mail._domainkey." + hostname])
+
+	# Show a diff if there are any changes
+	has_diff = False
+	def split(s): return [line+"\n" for line in s.split("\n")]
+	for line in difflib.unified_diff(split(expected), split(digoutput), fromfile='expected DNS settings', tofile=description):
+		if not has_diff:
+			print("The response from %s (%s) is not correct:" % (description, server))
+			print()
 		has_diff = True
 
-if not has_diff:
-	print("DNS is OK.")
+		sys.stdout.write(line)   
+
+	return not has_diff
+
+# Test the response from the machine itself.
+if test(ipaddr, "Mail-in-a-Box"):
+	# If those settings are OK, also test Google's Public DNS
+	# to see if the machine is hooked up to recursive DNS properly.
+	if test("8.8.8.8", "Google Public DNS"):
+		print ("DNS is OK.")
 		sys.exit(0)
+	else:
+		print ()
+		print ("Check that the nameserver settings for %s are correct at your domain registrar." % hostname)
 
 sys.exit(1)