Import dnspython modules explicitly in custom servers

Previously, the server relied on the modules being imported by the
isctest.asyncserver module. This is fragile and confuses tooling.

Clean up stray imports in the process.

(cherry picked from commit 5761de5531)

bin/tests/system/chain/ans3/ans.py

@@ -14,6 +14,7 @@ information regarding copyright ownership.
 from typing import AsyncGenerator
 
 import dns.name
+import dns.rcode
 import dns.rdataclass
 import dns.rdatatype
 import dns.rrset

bin/tests/system/chain/ans4/ans.py

@@ -19,8 +19,8 @@ import abc
 import logging
 import re
 
+import dns.name
 import dns.rcode
-import dns.rdata
 import dns.rdataclass
 import dns.rdatatype
 import dns.rrset

bin/tests/system/cookie/cookie_ans.py

@@ -11,7 +11,11 @@
 
 from typing import AsyncGenerator
 
-import dns
+import dns.edns
+import dns.message
+import dns.name
+import dns.rdatatype
+import dns.rrset
 import dns.tsigkeyring
 
 from isctest.asyncserver import (
@@ -68,7 +72,7 @@ def _tld(qctx: QueryContext) -> dns.name.Name:
 
 def _soa(qctx: QueryContext) -> dns.rrset.RRset:
     return dns.rrset.from_text(
-        _tld(qctx), 2, dns.rdataclass.IN, dns.rdatatype.SOA, ". . 0 0 0 0 2"
+        _tld(qctx), 2, qctx.qclass, dns.rdatatype.SOA, ". . 0 0 0 0 2"
     )
 
 
@@ -80,21 +84,19 @@ def _ns(qctx: QueryContext) -> dns.rrset.RRset:
     return dns.rrset.from_text(
         qctx.qname,
         1,
-        dns.rdataclass.IN,
+        qctx.qclass,
         dns.rdatatype.NS,
         _ns_name(qctx).to_text(),
     )
 
 
 def _legit_a(qctx: QueryContext) -> dns.rrset.RRset:
-    return dns.rrset.from_text(
-        qctx.qname, 1, dns.rdataclass.IN, dns.rdatatype.A, "10.53.0.9"
-    )
+    return dns.rrset.from_text(qctx.qname, 1, qctx.qclass, dns.rdatatype.A, "10.53.0.9")
 
 
 def _spoofed_a(qctx: QueryContext) -> dns.rrset.RRset:
     return dns.rrset.from_text(
-        qctx.qname, 1, dns.rdataclass.IN, dns.rdatatype.A, "10.53.0.10"
+        qctx.qname, 1, qctx.qclass, dns.rdatatype.A, "10.53.0.10"
     )
 
 

bin/tests/system/dispatch/ans3/ans.py

@@ -11,7 +11,8 @@
 
 from typing import AsyncGenerator
 
-import dns
+import dns.flags
+import dns.rcode
 
 from isctest.asyncserver import (
     AsyncDnsServer,

bin/tests/system/dnssec/ans10/ans.py

@@ -11,7 +11,8 @@
 
 from typing import AsyncGenerator
 
-import dns
+import dns.rdatatype
+import dns.rrset
 
 from isctest.asyncserver import (
     AsyncDnsServer,
@@ -33,7 +34,7 @@ class AddRrsigToAHandler(ResponseHandler):
             "gB+eISXAhSPZU2i/II0W9ZUhC2SCIrb94mlNvP5092WAeXxqN/vG43/1nmDly2Qs7y5VCjSMOGn85bnaMoAc7w=="
         )
         rrsig_rrset = dns.rrset.from_text(
-            qctx.qname, 1, dns.rdataclass.IN, dns.rdatatype.RRSIG, rrsig
+            qctx.qname, 1, qctx.qclass, dns.rdatatype.RRSIG, rrsig
         )
         qctx.response.answer.append(rrsig_rrset)
         yield DnsResponseSend(qctx.response)
@@ -48,7 +49,7 @@ class AddNsecToTxtHandler(ResponseHandler):
     ) -> AsyncGenerator[DnsResponseSend, None]:
         nsec = f"{qctx.qname.to_text()} A NS SOA RRSIG NSEC"
         nsec_rrset = dns.rrset.from_text(
-            qctx.qname, 1, dns.rdataclass.IN, dns.rdatatype.NSEC, nsec
+            qctx.qname, 1, qctx.qclass, dns.rdatatype.NSEC, nsec
         )
         qctx.response.authority.append(nsec_rrset)
         yield DnsResponseSend(qctx.response)

bin/tests/system/fetchlimit/ans4/ans.py

@@ -13,7 +13,9 @@ information regarding copyright ownership.
 
 from typing import AsyncGenerator
 
-import dns
+import dns.rcode
+import dns.rdatatype
+import dns.rrset
 
 from isctest.asyncserver import (
     ControllableAsyncDnsServer,

bin/tests/system/forward/ans11/ans.py

@@ -14,6 +14,7 @@ information regarding copyright ownership.
 from typing import AsyncGenerator
 
 import dns.rdatatype
+import dns.rrset
 
 from isctest.asyncserver import (
     ControllableAsyncDnsServer,

bin/tests/system/forward/ans6/ans.py

@@ -13,7 +13,10 @@ information regarding copyright ownership.
 
 from typing import AsyncGenerator
 
-import dns
+import dns.name
+import dns.rcode
+import dns.rdatatype
+import dns.rrset
 
 from isctest.asyncserver import (
     ControllableAsyncDnsServer,

bin/tests/system/isctest/asyncserver.py

@@ -38,12 +38,15 @@ import signal
 import struct
 import sys
 
+import dns.exception
 import dns.flags
 import dns.message
 import dns.name
 import dns.node
 import dns.rcode
+import dns.rdata
 import dns.rdataclass
+import dns.rdataset
 import dns.rdatatype
 import dns.rrset
 import dns.tsig

bin/tests/system/qmin/ans2/ans.py

@@ -16,8 +16,8 @@ from typing import AsyncGenerator
 import dns.message
 import dns.name
 import dns.rcode
-import dns.rdataclass
 import dns.rdatatype
+import dns.rrset
 
 from isctest.asyncserver import (
     AsyncDnsServer,
@@ -63,12 +63,8 @@ def send_delegation(
     ADDITIONAL section.
     """
     ns_name = "ns." + zone_cut.to_text()
-    ns_rrset = dns.rrset.from_text(
-        zone_cut, 2, dns.rdataclass.IN, dns.rdatatype.NS, ns_name
-    )
-    a_rrset = dns.rrset.from_text(
-        ns_name, 2, dns.rdataclass.IN, dns.rdatatype.A, target_addr
-    )
+    ns_rrset = dns.rrset.from_text(zone_cut, 2, qctx.qclass, dns.rdatatype.NS, ns_name)
+    a_rrset = dns.rrset.from_text(ns_name, 2, qctx.qclass, dns.rdatatype.A, target_addr)
 
     response = dns.message.make_response(qctx.query)
     response.set_rcode(dns.rcode.NOERROR)

bin/tests/system/qmin/ans4/ans.py

@@ -14,6 +14,7 @@ information regarding copyright ownership.
 from typing import AsyncGenerator
 
 import dns.rcode
+import dns.rdatatype
 
 from isctest.asyncserver import (
     AsyncDnsServer,

bin/tests/system/qmin/qmin_ans.py

@@ -16,7 +16,6 @@ from typing import AsyncGenerator
 import abc
 
 import dns.rcode
-import dns.rdataclass
 import dns.rdatatype
 
 from isctest.asyncserver import (

bin/tests/system/rpzrecurse/ans5/ans.py

@@ -13,7 +13,9 @@ information regarding copyright ownership.
 
 from typing import AsyncGenerator
 
-import dns
+import dns.rcode
+import dns.rdatatype
+import dns.rrset
 
 from isctest.asyncserver import (
     AsyncDnsServer,
@@ -32,7 +34,7 @@ class ReplyA(ResponseHandler):
         self, qctx: QueryContext
     ) -> AsyncGenerator[DnsResponseSend, None]:
         a_rrset = dns.rrset.from_text(
-            qctx.qname, 300, dns.rdataclass.IN, dns.rdatatype.A, "10.53.0.5"
+            qctx.qname, 300, qctx.qclass, dns.rdatatype.A, "10.53.0.5"
         )
         qctx.response.answer.append(a_rrset)
         yield DnsResponseSend(qctx.response)

bin/tests/system/statistics/ans4/ans.py

@@ -13,7 +13,9 @@ information regarding copyright ownership.
 
 from typing import AsyncGenerator
 
-import dns
+import dns.rcode
+import dns.rdatatype
+import dns.rrset
 
 from isctest.asyncserver import (
     AsyncDnsServer,

bin/tests/system/xfer/ans9/ans.py

@@ -14,7 +14,6 @@ information regarding copyright ownership.
 from typing import AsyncGenerator
 
 import dns.message
-import dns.rdataclass
 import dns.rdatatype
 import dns.rrset
 
@@ -52,7 +51,7 @@ class AXFRServer(DomainHandler):
         soa_rrset = dns.rrset.from_text(
             qctx.qname,
             300,
-            dns.rdataclass.IN,
+            qctx.qclass,
             dns.rdatatype.SOA,
             f". . {self.soa_version} 0 0 0 0",
         )
@@ -79,7 +78,7 @@ class AXFRServer(DomainHandler):
         # will already have been done with the mandatory stuff by then.
         ns_message = dns.message.make_response(qctx.query)
         ns_rrset = dns.rrset.from_text(
-            qctx.qname, 300, dns.rdataclass.IN, dns.rdatatype.NS, "."
+            qctx.qname, 300, qctx.qclass, dns.rdatatype.NS, "."
         )
         ns_message.answer.append(ns_rrset)
 
@@ -90,7 +89,7 @@ class AXFRServer(DomainHandler):
         txt_rrset = dns.rrset.from_text(
             qctx.qname,
             300,
-            dns.rdataclass.IN,
+            qctx.qclass,
             dns.rdatatype.TXT,
             "foo bar",
         )

bin/tests/system/zero/ans5/ans.py

@@ -14,10 +14,7 @@ information regarding copyright ownership.
 import ipaddress
 from typing import AsyncGenerator
 
-import dns.flags
-import dns.message
-import dns.rdata
-import dns.rdataclass
+import dns.rcode
 import dns.rdatatype
 import dns.rrset