When authoritative dns servers don't respond properly, retry 3 times

This commit is contained in:
Michael Kroes 2016-02-29 18:43:36 +01:00
parent 14f7ef6b20
commit cb94897e68
1 changed files with 35 additions and 34 deletions

View File

@ -4,7 +4,7 @@
# TLS certificates have been signed, etc., and if not tells the user
# what to do next.
import sys, os, os.path, re, subprocess, datetime, multiprocessing.pool
import sys, os, os.path, re, subprocess, datetime, multiprocessing.pool, time
import dns.reversename, dns.resolver
import dateutil.parser, dateutil.tz
@ -394,37 +394,27 @@ def check_primary_hostname_dns(domain, env, output, dns_domains, dns_zonefiles):
else:
output.print_error("""The DANE TLSA record for incoming mail (%s) is not correct. It is '%s' but it should be '%s'.
It may take several hours for public DNS to update after a change."""
% (tlsa_qname, tlsa25, tlsa25_expected))
% (tlsa_qname, tlsa25, tlsa25_expected))
# Check that the hostmaster@ email address exists.
check_alias_exists("Hostmaster contact address", "hostmaster@" + domain, env, output)
def query_dns_ptr(qname):
# Find the authoritative name server for the address using the default nameservers
resolver = dns.resolver.get_default_resolver()
nameserver = resolver.nameservers[0]
query = dns.message.make_query(qname, dns.rdatatype.PTR)
timeout = 5
response = dns.query.udp(query, nameserver, timeout)
returnCode = response.rcode()
# When looking up PTR records bind will contact the authoritative servers for a response.
# Sometimes these servers don't respond properly, we will give these servers 3 chances
# with a 2 second pause in between.
for attempt in range(3):
result=query_dns(qname, "PTR")
# Check that we were able to query the dns for the authoritative server
if returnCode != dns.rcode.NOERROR:
return "[%s]" % dns.rcode.to_text(returnCode)
# Check if the authoritative servers respond properly
if result == "[nonameservers]":
time.sleep(2)
else:
# There might still be an error, like a timeout, but we will continue
# chances of recovering from those are slim.
break
# If the current DNS server isn't the authority for this address use the one we find in the response
if len(response.authority) > 0:
rrset = response.authority[0]
else:
rrset = response.answer[0]
rr = rrset[0]
if rr.rdtype != dns.rdatatype.SOA:
authority = rr.target
nameserver = query_dns(authority, "A")
# Resolve the PTR record using the proper name server
return query_dns(qname, "PTR", at=nameserver)
return result
def check_alias_exists(alias_name, alias, env, output):
mail_aliases = dict([(address, receivers) for address, receivers, *_ in get_mail_aliases(env)])
@ -672,10 +662,12 @@ def query_dns(qname, rtype, nxdomain='[Not Set]', at=None):
# Do the query.
try:
response = resolver.query(qname, rtype)
except (dns.resolver.NoNameservers, dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
# Host did not have an answer for this query; not sure what the
# difference is between the two exceptions.
except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
# No response was received
return nxdomain
except dns.resolver.NoNameservers:
# No non-broken nameservers were available to respond to the request
return "[nonameservers]"
except dns.exception.Timeout:
return "[timeout]"
@ -946,12 +938,21 @@ if __name__ == "__main__":
run_and_output_changes(env, pool)
elif sys.argv[1] == "--check-ptr":
out = ConsoleOutput()
# Get the list of domains we serve DNS zones for (i.e. does not include subdomains).
dns_zonefiles = dict(get_dns_zones(env))
dns_domains = set(dns_zonefiles)
check_primary_hostname_dns(env["PRIMARY_HOSTNAME"], env, out, dns_domains, dns_zonefiles)
# Run only the primary hostname checks, specifically the ptr check
shell('check_call', ["/usr/sbin/rndc", "flush"], trap=True)
output = ConsoleOutput()
domain=env["PRIMARY_HOSTNAME"]
my_ips = env['PUBLIC_IP'] + ((" / "+env['PUBLIC_IPV6']) if env.get("PUBLIC_IPV6") else "")
existing_rdns_v4 = query_dns_ptr(dns.reversename.from_address(env['PUBLIC_IP']))
existing_rdns_v6 = query_dns_ptr(dns.reversename.from_address(env['PUBLIC_IPV6'])) if env.get("PUBLIC_IPV6") else None
if existing_rdns_v4 == domain and existing_rdns_v6 in (None, domain):
output.print_ok("Reverse DNS is set correctly at ISP. [%s%s]" % (my_ips, env['PRIMARY_HOSTNAME']))
elif existing_rdns_v4 == existing_rdns_v6 or existing_rdns_v6 is None:
output.print_error("""Your box's reverse DNS is currently %s, but it should be %s. Your ISP or cloud provider will have instructions
on setting up reverse DNS for your box.""" % (existing_rdns_v4, domain) )
else:
output.print_error("""Your box's reverse DNS is currently %s (IPv4) and %s (IPv6), but it should be %s. Your ISP or cloud provider will have instructions
on setting up reverse DNS for your box.""" % (existing_rdns_v4, existing_rdns_v6, domain) )
elif sys.argv[1] == "--check-primary-hostname":
# See if the primary hostname appears resolvable and has a signed certificate.