greendns: compatibility with dnspython v2

Compatibility with dnspython v2:
- `_compute_expiration` was replaced by `_compute_times`
- `dns.query.{tcp,udp}` take new arguments

Main issue for tracking: https://github.com/eventlet/eventlet/issues/619
This patch discussion: https://github.com/eventlet/eventlet/pull/722
This patch deprecates dnspython<2 pin: https://github.com/eventlet/eventlet/issues/629

Co-authored-by: John Vandenberg <jayvdb@gmail.com>
Co-authored-by: Rodolfo Alonso Hernandez <ralonsoh@redhat.com>

6 files changed, 84 insertions, 14 deletions

diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index d5b7c45..3801d2a 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -32,6 +32,7 @@ jobs:
           - { py: 2.7, toxenv: py27-epolls, ignore-error: false }
           - { py: 2.7, toxenv: py27-poll, ignore-error: false }
           - { py: 2.7, toxenv: py27-selects, ignore-error: false }
+          - { py: 2.7, toxenv: py27-dnspython1, ignore-error: false }
           - { py: 3.5, toxenv: py35-epolls, ignore-error: false }
           - { py: 3.5, toxenv: py35-poll, ignore-error: false }
           - { py: 3.5, toxenv: py35-selects, ignore-error: false }
@@ -48,6 +49,7 @@ jobs:
           - { py: 3.9, toxenv: py39-epolls, ignore-error: false }
           - { py: 3.9, toxenv: py39-poll, ignore-error: false }
           - { py: 3.9, toxenv: py39-selects, ignore-error: false }
+          - { py: 3.9, toxenv: py39-dnspython1, ignore-error: false }
           - { py: 3.x, toxenv: ipv6, ignore-error: false }
           - { py: pypy2, toxenv: pypy2-epolls, ignore-error: true }
           - { py: pypy3, toxenv: pypy3-epolls, ignore-error: true }
diff --git a/eventlet/support/greendns.py b/eventlet/support/greendns.py
index 10dd04b..76545c7 100644
--- a/eventlet/support/greendns.py
+++ b/eventlet/support/greendns.py
@@ -120,6 +120,16 @@ def is_ip_addr(host):
     return is_ipv4_addr(host) or is_ipv6_addr(host)
 
 
+# NOTE(ralonsoh): in dnspython v2.0.0, "_compute_expiration" was replaced
+# by "_compute_times".
+if hasattr(dns.query, '_compute_expiration'):
+    def compute_expiration(query, timeout):
+        return query._compute_expiration(timeout)
+else:
+    def compute_expiration(query, timeout):
+        return query._compute_times(timeout)[1]
+
+
 class HostsAnswer(dns.resolver.Answer):
     """Answer class for HostsResolver object"""
 
@@ -660,8 +670,21 @@ def _net_write(sock, data, expiration):
                 raise dns.exception.Timeout
 
 
+# Test if raise_on_truncation is an argument we should handle.
+# It was newly added in dnspython 2.0
+try:
+    dns.message.from_wire("", raise_on_truncation=True)
+except dns.message.ShortHeader:
+    _handle_raise_on_truncation = True
+except TypeError:
+    # Argument error, there is no argument "raise_on_truncation"
+    _handle_raise_on_truncation = False
+
+
 def udp(q, where, timeout=DNS_QUERY_TIMEOUT, port=53,
-        af=None, source=None, source_port=0, ignore_unexpected=False):
+        af=None, source=None, source_port=0, ignore_unexpected=False,
+        one_rr_per_rrset=False, ignore_trailing=False,
+        raise_on_truncation=False, sock=None):
     """coro friendly replacement for dns.query.udp
     Return the response obtained after sending a query via UDP.
 
@@ -686,7 +709,21 @@ def udp(q, where, timeout=DNS_QUERY_TIMEOUT, port=53,
     @type source_port: int
     @param ignore_unexpected: If True, ignore responses from unexpected
     sources.  The default is False.
-    @type ignore_unexpected: bool"""
+    @type ignore_unexpected: bool
+    @param one_rr_per_rrset: If True, put each RR into its own
+    RRset.
+    @type one_rr_per_rrset: bool
+    @param ignore_trailing: If True, ignore trailing
+    junk at end of the received message.
+    @type ignore_trailing: bool
+    @param raise_on_truncation: If True, raise an exception if
+    the TC bit is set.
+    @type raise_on_truncation: bool
+    @param sock: the socket to use for the
+    query.  If None, the default, a socket is created.  Note that
+    if a socket is provided, it must be a nonblocking datagram socket,
+    and the source and source_port are ignored.
+    @type sock: socket.socket | None"""
 
     wire = q.to_wire()
     if af is None:
@@ -708,10 +745,13 @@ def udp(q, where, timeout=DNS_QUERY_TIMEOUT, port=53,
         if source is not None:
             source = (source, source_port, 0, 0)
 
-    s = socket.socket(af, socket.SOCK_DGRAM)
+    if sock:
+        s = sock
+    else:
+        s = socket.socket(af, socket.SOCK_DGRAM)
     s.settimeout(timeout)
     try:
-        expiration = dns.query._compute_expiration(timeout)
+        expiration = compute_expiration(dns.query, timeout)
         if source is not None:
             s.bind(source)
         while True:
@@ -756,14 +796,23 @@ def udp(q, where, timeout=DNS_QUERY_TIMEOUT, port=53,
     finally:
         s.close()
 
-    r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac)
+    if _handle_raise_on_truncation:
+        r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac,
+                                  one_rr_per_rrset=one_rr_per_rrset,
+                                  ignore_trailing=ignore_trailing,
+                                  raise_on_truncation=raise_on_truncation)
+    else:
+        r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac,
+                                  one_rr_per_rrset=one_rr_per_rrset,
+                                  ignore_trailing=ignore_trailing)
     if not q.is_response(r):
         raise dns.query.BadResponse()
     return r
 
 
 def tcp(q, where, timeout=DNS_QUERY_TIMEOUT, port=53,
-        af=None, source=None, source_port=0):
+        af=None, source=None, source_port=0,
+        one_rr_per_rrset=False, ignore_trailing=False, sock=None):
     """coro friendly replacement for dns.query.tcp
     Return the response obtained after sending a query via TCP.
 
@@ -785,7 +834,19 @@ def tcp(q, where, timeout=DNS_QUERY_TIMEOUT, port=53,
     @type source: string
     @param source_port: The port from which to send the message.
     The default is 0.
-    @type source_port: int"""
+    @type source_port: int
+    @type ignore_unexpected: bool
+    @param one_rr_per_rrset: If True, put each RR into its own
+    RRset.
+    @type one_rr_per_rrset: bool
+    @param ignore_trailing: If True, ignore trailing
+    junk at end of the received message.
+    @type ignore_trailing: bool
+    @param sock: the socket to use for the
+    query.  If None, the default, a socket is created.  Note that
+    if a socket is provided, it must be a nonblocking datagram socket,
+    and the source and source_port are ignored.
+    @type sock: socket.socket | None"""
 
     wire = q.to_wire()
     if af is None:
@@ -801,10 +862,13 @@ def tcp(q, where, timeout=DNS_QUERY_TIMEOUT, port=53,
         destination = (where, port, 0, 0)
         if source is not None:
             source = (source, source_port, 0, 0)
-    s = socket.socket(af, socket.SOCK_STREAM)
+    if sock:
+        s = sock
+    else:
+        s = socket.socket(af, socket.SOCK_STREAM)
     s.settimeout(timeout)
     try:
-        expiration = dns.query._compute_expiration(timeout)
+        expiration = compute_expiration(dns.query, timeout)
         if source is not None:
             s.bind(source)
         while True:
@@ -829,7 +893,9 @@ def tcp(q, where, timeout=DNS_QUERY_TIMEOUT, port=53,
         wire = bytes(_net_read(s, l, expiration))
     finally:
         s.close()
-    r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac)
+    r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac,
+                              one_rr_per_rrset=one_rr_per_rrset,
+                              ignore_trailing=ignore_trailing)
     if not q.is_response(r):
         raise dns.query.BadResponse()
     return r
diff --git a/setup.py b/setup.py
index cf5150a..3a446e7 100644
--- a/setup.py
+++ b/setup.py
@@ -15,7 +15,7 @@ setuptools.setup(
     url='http://eventlet.net',
     packages=setuptools.find_packages(exclude=['benchmarks', 'tests', 'tests.*']),
     install_requires=(
-        'dnspython >= 1.15.0, < 2.0.0',
+        'dnspython >= 1.15.0',
         'greenlet >= 0.3',
         'monotonic >= 1.4;python_version<"3.5"',
         'six >= 1.10.0',
diff --git a/tests/greendns_test.py b/tests/greendns_test.py
index a6faae5..7419b35 100644
--- a/tests/greendns_test.py
+++ b/tests/greendns_test.py
@@ -901,7 +901,7 @@ class TinyDNSTests(tests.LimitedTestCase):
             resolver.nameserver_ports[dnsaddr[0]] = dnsaddr[1]
             response = resolver.query('host.example.com', 'a', tcp=True)
             self.assertIsInstance(response, Answer)
-            self.assertEqual(response.rrset.items[0].address, expected_ip)
+            self.assertEqual(list(response.rrset.items)[0].address, expected_ip)
 
 
 def test_reverse_name():
diff --git a/tests/isolated/socket_resolve_green.py b/tests/isolated/socket_resolve_green.py
index 6017d5e..611d7dc 100644
--- a/tests/isolated/socket_resolve_green.py
+++ b/tests/isolated/socket_resolve_green.py
@@ -7,6 +7,7 @@ if __name__ == '__main__':
     import time
     import dns.message
     import dns.query
+    import dns.flags
 
     n = 10
     delay = 0.01
@@ -17,7 +18,7 @@ if __name__ == '__main__':
         addr = addr_map[qname.to_text()]
         r = dns.message.make_response(q)
         r.index = None
-        r.flags = 256
+        r.flags = dns.flags.QR | dns.flags.RD
         r.answer.append(dns.rrset.from_text(str(qname), 60, 'IN', 'A', addr))
         r.time = 0.001
         eventlet.sleep(delay)
diff --git a/tox.ini b/tox.ini
index 59fd833..3697f7e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -16,7 +16,7 @@ statistics = 1
 [tox]
 minversion=2.5
 envlist =
-    ipv6, pep8, py{27,35,36,37,38,39,py2,py3}-{selects,poll,epolls}, py38-openssl
+    ipv6, pep8, py{27,35,36,37,38,39,py2,py3}-{selects,poll,epolls}, py38-openssl, py27-dnspython1, py39-dnspython1
 skipsdist = True
 
 [testenv:ipv6]
@@ -74,6 +74,7 @@ deps =
     py{38,39}: psycopg2-binary==2.8.4
     setuptools==38.5.1
     {selects,poll,epolls}: pyzmq==19.0.2
+    dnspython1: dnspython<2
 usedevelop = True
 commands =
     nosetests --verbose {env:tox_cover_args} {posargs:tests/}