Support GEVENT_RESOLVER_SERVERS for configuring dnspython nameservers.

Also allow this for ares, and deprecate the GEVENTARES_SERVERS environment variable.

Fixes #1103.

CHANGES.rst

@@ -36,7 +36,10 @@
   :func:`gevent.subprocess.run`.
 
 - Add the ``dnspython`` resolver as a lightweight alternative to
-  c-ares. See :pr:`1088`.
+  c-ares. See :pr:`1088` and :issue:`1103`.
+
+- The ``GEVENTARES_SERVERS`` environment variable is deprecated in
+  favor of ``GEVENT_RESOLVER_SERVERS``. See :issue:`1103`.
 
 - Fix calling ``shutdown`` on a closed socket. It was raising
   ``AttributeError``, now it once again raises the correct

Makefile

@@ -10,6 +10,7 @@ CYTHON?=cython
 
 export PATH:=$(BUILD_RUNTIMES)/snakepit:$(TOOLS):$(PATH)
 export LC_ALL=C.UTF-8
+export GEVENT_RESOLVER_NAMESERVERS=8.8.8.8
 
 
 clean:
@@ -61,7 +62,7 @@ basictest: test_prelim
 
 alltest: basictest
 	@${PYTHON} scripts/travis.py fold_start ares "Running c-ares tests"
-	cd src/greentest && GEVENT_RESOLVER=ares GEVENTARES_SERVERS=8.8.8.8 ${PYTHON} testrunner.py --config known_failures.py --ignore tests_that_dont_use_resolver.txt --quiet
+	cd src/greentest && GEVENT_RESOLVER=ares ${PYTHON} testrunner.py --config known_failures.py --ignore tests_that_dont_use_resolver.txt --quiet
 	@${PYTHON} scripts/travis.py fold_end ares
 	@${PYTHON} scripts/travis.py fold_start dnspython "Running dnspython tests"
 	cd src/greentest && GEVENT_RESOLVER=dnspython ${PYTHON} testrunner.py --config known_failures.py --ignore tests_that_dont_use_resolver.txt --quiet

src/gevent/_config.py

@@ -447,7 +447,67 @@ class AresServers(AresSettingMixin, Setting):
     name = 'ares_servers'
     default = None
     environment_key = 'GEVENTARES_SERVERS'
+    desc = """\
+    A list of strings giving the IP addresses of nameservers for the ares resolver.
+
+    In the environment variable, these strings are separated by commas.
+
+    .. deprecated:: 1.3a2
+       Prefer the :attr:`resolver_nameservers` setting. If both are set,
+       the results are not defined.
+    """
+
+# Generic nameservers, works for dnspython and ares.
+class ResolverNameservers(AresSettingMixin, Setting):
+    document = True
+    name = 'resolver_nameservers'
+    default = None
+    environment_key = 'GEVENT_RESOLVER_NAMESERVERS'
+    desc = """\
+    A list of strings giving the IP addresses of nameservers for the (non-system) resolver.
+
+    In the environment variable, these strings are separated by commas.
+
+    .. rubric:: Resolver Behaviour
+
+    * blocking
+
+      Ignored
 
+    * Threaded
+
+      Ignored
+
+    * dnspython
+
+      If this setting is not given, the dnspython resolver will
+      load nameservers to use from ``/etc/resolv.conf``
+      or the Windows registry. This setting replaces any nameservers read
+      from those means. Note that the file and registry are still read
+      for other settings.
+
+      .. caution:: dnspython does not validate the members of the list.
+         An improper address (such as a hostname instead of IP) has
+         undefined results, including hanging the process.
+
+    * ares
+
+      Similar to dnspython, but with more platform and compile-time
+      options. ares validates that the members of the list are valid
+      addresses.
+    """
+
+    # Normal string-to-list rules. But still validate_anything.
+    _convert = Setting._convert
+
+    # TODO: In the future, support reading a resolv.conf file
+    # *other* than /etc/resolv.conf, and do that both on Windows
+    # and other platforms. Also offer the option to disable the system
+    # configuration entirely.
+
+    @property
+    def kwarg_name(self):
+        return 'servers'
 
 config = Config()
 

src/gevent/resolver/cares.pyx

@@ -9,6 +9,8 @@ import sys
 
 from cpython.ref cimport Py_INCREF
 from cpython.ref cimport Py_DECREF
+from cpython.mem cimport PyMem_Malloc
+from cpython.mem cimport PyMem_Free
 
 from _socket import gaierror
 
@@ -58,8 +60,7 @@ cdef extern from "dnshelper.c":
         pass
     int gevent_make_sockaddr(char* hostp, int port, int flowinfo, int scope_id, sockaddr_in6* sa6)
 
-    void* malloc(int)
-    void free(void*)
+
     void memset(void*, int, int)
 
 
@@ -319,7 +320,7 @@ cdef class channel:
             cares.ares_destroy(self.channel)
             self.channel = NULL
 
-    def set_servers(self, servers=None):
+    cpdef set_servers(self, servers=None):
         if not self.channel:
             raise gaierror(cares.ARES_EDESTRUCTION, 'this ares channel has been destroyed')
         if not servers:
@@ -333,7 +334,7 @@ cdef class channel:
         if length <= 0:
             result = cares.ares_set_servers(self.channel, NULL)
         else:
-            c_servers = <cares.ares_addr_node*>malloc(sizeof(cares.ares_addr_node) * length)
+            c_servers = <cares.ares_addr_node*>PyMem_Malloc(sizeof(cares.ares_addr_node) * length)
             if not c_servers:
                 raise MemoryError
             try:
@@ -357,7 +358,7 @@ cdef class channel:
                 if index:
                     raise ValueError(strerror(index))
             finally:
-                free(c_servers)
+                PyMem_Free(c_servers)
 
     # this crashes c-ares
     #def cancel(self):

src/gevent/resolver/dnspython.py

@@ -81,6 +81,7 @@ from . import hostname_types
 from gevent._compat import string_types
 from gevent._compat import iteritems
 from gevent._patcher import import_patched
+from gevent._config import config
 
 __all__ = [
     'Resolver',
@@ -553,6 +554,8 @@ class Resolver(AbstractResolver):
         self._resolver = _DualResolver()
         if resolver._resolver is None:
             resolver._resolver = self._resolver
+            if config.resolver_nameservers:
+                self._resolver.network_resolver.nameservers[:] = config.resolver_nameservers
         # Different hubs in different threads could be sharing the same
         # resolver.
         assert isinstance(resolver._resolver, _DualResolver)