python: Add async DNS support.

This adds a Python version of the async DNS support added in: 771680d DNS: Add basic support for asynchronous DNS resolving The above version uses the unbound C library, and this implimentation uses the SWIG-wrapped Python version of that. In the event that the Python unbound library is not available, a warning will be logged and the resolve() method will just return None. For the case where inet_parse_active() is passed an IP address, it will not try to resolve it, so existing behavior should be preserved in the case that the unbound library is unavailable. Intentional differences from the C version are as follows: OVS_HOSTS_FILE environment variable can bet set to override the system 'hosts' file. This is primarily to allow testing to be done without requiring network connectivity. Since resolution can still be done via hosts file lookup, DNS lookups are not disabled when resolv.conf cannot be loaded. The Python socket_util module has fallen behind its C equivalent. The bare minimum change was done to inet_parse_active() to support sync/async dns, as there is no equivalent to parse_sockaddr_components(), inet_parse_passive(), etc. A TODO was added to bring socket_util.py up to equivalency to the C version. Signed-off-by: Terry Wilson <[email protected]> Signed-off-by: Ilya Maximets <[email protected]>
openvswitch · Jul 14, 2023 · 4d55a36 · 4d55a36
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diff --git a/.github/workflows/build-and-test.yml b/.github/workflows/build-and-test.yml
@@ -183,10 +183,10 @@ jobs:
       run:  sudo apt update || true
     - name: install common dependencies
       run:  sudo apt install -y ${{ env.dependencies }}
-    - name: install libunbound libunwind
+    - name: install libunbound libunwind python3-unbound
       # GitHub Actions doesn't have 32-bit versions of these libraries.
       if:   matrix.m32 == ''
-      run:  sudo apt install -y libunbound-dev libunwind-dev
+      run:  sudo apt install -y libunbound-dev libunwind-dev python3-unbound
     - name: install 32-bit libraries
       if:   matrix.m32 != ''
       run:  sudo apt install -y gcc-multilib

diff --git a/Documentation/intro/install/general.rst b/Documentation/intro/install/general.rst
@@ -90,7 +90,7 @@ need the following software:
   If libcap-ng is installed, then Open vSwitch will automatically build with
   support for it.
 
-- Python 3.4 or later.
+- Python 3.6 or later.
 
 - Unbound library, from http://www.unbound.net, is optional but recommended if
   you want to enable ovs-vswitchd and other utilities to use DNS names when
@@ -208,7 +208,7 @@ simply install and run Open vSwitch you require the following software:
   from iproute2 (part of all major distributions and available at
   https://wiki.linuxfoundation.org/networking/iproute2).
 
-- Python 3.4 or later.
+- Python 3.6 or later.
 
 On Linux you should ensure that ``/dev/urandom`` exists. To support TAP
 devices, you must also ensure that ``/dev/net/tun`` exists.

diff --git a/Documentation/intro/install/rhel.rst b/Documentation/intro/install/rhel.rst
@@ -92,7 +92,7 @@ Once that is completed, remove the file ``/tmp/ovs.spec``.
 If python3-sphinx package is not available in your version of RHEL, you can
 install it via pip with 'pip install sphinx'.
 
-Open vSwitch requires python 3.4 or newer which is not available in older
+Open vSwitch requires python 3.6 or newer which is not available in older
 distributions. In the case of RHEL 6.x and its derivatives, one option is
 to install python34 from `EPEL`_.
 

diff --git a/Documentation/intro/install/windows.rst b/Documentation/intro/install/windows.rst
@@ -56,7 +56,7 @@ The following explains the steps in some detail.
 
       'C:/MinGW /mingw'.
 
-- Python 3.4 or later.
+- Python 3.6 or later.
 
   Install the latest Python 3.x from python.org and verify that its path is
   part of Windows' PATH environment variable.

diff --git a/NEWS b/NEWS
@@ -50,6 +50,9 @@ Post-v3.1.0
        table to check the status.
    - Linux TC offload:
      * Add support for offloading VXLAN tunnels with the GBP extensions.
+   - Python
+     * Added async DNS support.
+     * Dropped support for Python < 3.6.
 
 
 v3.1.0 - 16 Feb 2023

diff --git a/debian/control.in b/debian/control.in
@@ -287,6 +287,7 @@ Depends:
 Suggests:
  python3-netaddr,
  python3-pyparsing,
+ python3-unbound,
 Description: Python 3 bindings for Open vSwitch
  Open vSwitch is a production quality, multilayer, software-based,
  Ethernet virtual switch. It is designed to enable massive network

diff --git a/m4/openvswitch.m4 b/m4/openvswitch.m4
@@ -375,16 +375,16 @@ dnl Checks for valgrind/valgrind.h.
 AC_DEFUN([OVS_CHECK_VALGRIND],
   [AC_CHECK_HEADERS([valgrind/valgrind.h])])
 
-dnl Checks for Python 3.4 or later.
+dnl Checks for Python 3.6 or later.
 AC_DEFUN([OVS_CHECK_PYTHON3],
   [AC_CACHE_CHECK(
-     [for Python 3 (version 3.4 or later)],
+     [for Python 3 (version 3.6 or later)],
      [ovs_cv_python3],
      [if test -n "$PYTHON3"; then
         ovs_cv_python3=$PYTHON3
       else
         ovs_cv_python3=no
-        for binary in python3 python3.4 python3.5 python3.6 python3.7; do
+        for binary in python3 python3.6 python3.7 python3.8 python3.9 python3.10 python3.11 python3.12; do
           ovs_save_IFS=$IFS; IFS=$PATH_SEPARATOR
           for dir in $PATH; do
             IFS=$ovs_save_IFS
@@ -401,7 +401,7 @@ else:
         done
       fi])
    if test "$ovs_cv_python3" = no; then
-     AC_MSG_ERROR([Python 3.4 or later is required but not found in $PATH, please install it or set $PYTHON3 to point to it])
+     AC_MSG_ERROR([Python 3.6 or later is required but not found in $PATH, please install it or set $PYTHON3 to point to it])
    fi
    AC_ARG_VAR([PYTHON3])
    PYTHON3=$ovs_cv_python3])

diff --git a/python/TODO.rst b/python/TODO.rst
@@ -32,3 +32,10 @@ Python Bindings To-do List
 
   * Support write-only-changed monitor mode (equivalent of
     OVSDB_IDL_WRITE_CHANGED_ONLY).
+
+* socket_util:
+
+  * Add equivalent fuctions to inet_parse_passive, parse_sockaddr_components,
+    et al. to better support using async dns. The reconnect code will
+    currently log a warning when inet_parse_active() returns w/o yet having
+    resolved an address, but will continue to connect and eventually succeed.
diff --git a/python/automake.mk b/python/automake.mk
@@ -16,6 +16,7 @@ ovs_pyfiles = \
 	python/ovs/compat/sortedcontainers/sorteddict.py \
 	python/ovs/compat/sortedcontainers/sortedset.py \
 	python/ovs/daemon.py \
+	python/ovs/dns_resolve.py \
 	python/ovs/db/__init__.py \
 	python/ovs/db/custom_index.py \
 	python/ovs/db/data.py \
@@ -55,6 +56,7 @@ ovs_pyfiles = \
 
 ovs_pytests = \
 	python/ovs/tests/test_decoders.py \
+	python/ovs/tests/test_dns_resolve.py \
 	python/ovs/tests/test_filter.py \
 	python/ovs/tests/test_kv.py \
 	python/ovs/tests/test_list.py \