Revert "bpo-32107 - Better merge of #4494 (#4576)" (#4593)

This reverts commit 9522a218f7dff95c490ff359cc60e8c2af35f5c8.

2 files changed, 28 insertions, 89 deletions

diff --git a/Lib/test/test_uuid.py b/Lib/test/test_uuid.py
index 54d73f7..083c2aa 100644
--- a/Lib/test/test_uuid.py
+++ b/Lib/test/test_uuid.py
@@ -512,69 +512,60 @@ eth0      Link encap:Ethernet  HWaddr 12:34:56:78:90:ab
 
         self.assertEqual(mac, 0x1234567890ab)
 
-    def check_node(self, node, requires=None, *, check_bit=True):
+    def check_node(self, node, requires=None, network=False):
         if requires and node is None:
             self.skipTest('requires ' + requires)
         hex = '%012x' % node
         if support.verbose >= 2:
             print(hex, end=' ')
-        # The MAC address will be universally administered (i.e. the second
-        # least significant bit of the first octet must be unset) for any
-        # physical interface, such as an ethernet port or wireless adapter.
-        # There are some cases where this won't be the case.  Randomly
-        # generated MACs may not be universally administered, but they must
-        # have their multicast bit set, though this is tested in the
-        # `test_random_getnode()` method specifically.  Another case is the
-        # Travis-CI case, which apparently only has locally administered MAC
-        # addresses.
-        if check_bit and not os.getenv('TRAVIS'):
-            self.assertFalse(node & (1 << 41), '%012x' % node)
+        if network:
+            # 47 bit will never be set in IEEE 802 addresses obtained
+            # from network cards.
+            self.assertFalse(node & 0x010000000000, hex)
         self.assertTrue(0 < node < (1 << 48),
                         "%s is not an RFC 4122 node ID" % hex)
 
     @unittest.skipUnless(os.name == 'posix', 'requires Posix')
     def test_ifconfig_getnode(self):
         node = self.uuid._ifconfig_getnode()
-        self.check_node(node, 'ifconfig')
+        self.check_node(node, 'ifconfig', True)
 
     @unittest.skipUnless(os.name == 'posix', 'requires Posix')
     def test_ip_getnode(self):
         node = self.uuid._ip_getnode()
-        self.check_node(node, 'ip')
+        self.check_node(node, 'ip', True)
 
     @unittest.skipUnless(os.name == 'posix', 'requires Posix')
     def test_arp_getnode(self):
         node = self.uuid._arp_getnode()
-        self.check_node(node, 'arp')
+        self.check_node(node, 'arp', True)
 
     @unittest.skipUnless(os.name == 'posix', 'requires Posix')
     def test_lanscan_getnode(self):
         node = self.uuid._lanscan_getnode()
-        self.check_node(node, 'lanscan')
+        self.check_node(node, 'lanscan', True)
 
     @unittest.skipUnless(os.name == 'posix', 'requires Posix')
     def test_netstat_getnode(self):
         node = self.uuid._netstat_getnode()
-        self.check_node(node, 'netstat')
+        self.check_node(node, 'netstat', True)
 
     @unittest.skipUnless(os.name == 'nt', 'requires Windows')
     def test_ipconfig_getnode(self):
         node = self.uuid._ipconfig_getnode()
-        self.check_node(node, 'ipconfig')
+        self.check_node(node, 'ipconfig', True)
 
     @unittest.skipUnless(importable('win32wnet'), 'requires win32wnet')
     @unittest.skipUnless(importable('netbios'), 'requires netbios')
     def test_netbios_getnode(self):
         node = self.uuid._netbios_getnode()
-        self.check_node(node)
+        self.check_node(node, network=True)
 
     def test_random_getnode(self):
         node = self.uuid._random_getnode()
-        # The multicast bit, i.e. the least significant bit of first octet,
-        # must be set for randomly generated MAC addresses.  See RFC 4122,
-        # $4.1.6.
-        self.assertTrue(node & (1 << 40), '%012x' % node)
-        self.check_node(node, check_bit=False)
+        # Least significant bit of first octet must be set.
+        self.assertTrue(node & 0x010000000000, '%012x' % node)
+        self.check_node(node)
 
     @unittest.skipUnless(os.name == 'posix', 'requires Posix')
     def test_unix_getnode(self):
@@ -584,17 +575,13 @@ eth0      Link encap:Ethernet  HWaddr 12:34:56:78:90:ab
             node = self.uuid._unix_getnode()
         except TypeError:
             self.skipTest('requires uuid_generate_time')
-        # Since we don't know the provenance of the MAC address, don't check
-        # whether it is locally or universally administered.
-        self.check_node(node, 'unix', check_bit=False)
+        self.check_node(node, 'unix')
 
     @unittest.skipUnless(os.name == 'nt', 'requires Windows')
     @unittest.skipUnless(importable('ctypes'), 'requires ctypes')
     def test_windll_getnode(self):
         node = self.uuid._windll_getnode()
-        # Since we don't know the provenance of the MAC address, don't check
-        # whether it is locally or universally administered.
-        self.check_node(node, check_bit=False)
+        self.check_node(node)
 
 
 class TestInternalsWithoutExtModule(BaseTestInternals, unittest.TestCase):
diff --git a/Lib/uuid.py b/Lib/uuid.py
index 9e7c672..020c6e7 100644
--- a/Lib/uuid.py
+++ b/Lib/uuid.py
@@ -342,29 +342,11 @@ def _popen(command, *args):
                             env=env)
     return proc
 
-# For MAC (a.k.a. IEEE 802, or EUI-48) addresses, the second least significant
-# bit of the first octet signifies whether the MAC address is universally (0)
-# or locally (1) administered.  Network cards from hardware manufacturers will
-# always be universally administered to guarantee global uniqueness of the MAC
-# address, but any particular machine may have other interfaces which are
-# locally administered.  An example of the latter is the bridge interface to
-# the Touch Bar on MacBook Pros.
-#
-# This bit works out to be the 42nd bit counting from 1 being the least
-# significant, or 1<<41.  We'll skip over any locally administered MAC
-# addresses, as it makes no sense to use those in UUID calculation.
-#
-# See https://en.wikipedia.org/wiki/MAC_address#Universal_vs._local
-
-def _is_universal(mac):
-    return not (mac & (1 << 41))
-
 def _find_mac(command, args, hw_identifiers, get_index):
-    first_local_mac = None
     try:
         proc = _popen(command, *args.split())
         if not proc:
-            return None
+            return
         with proc:
             for line in proc.stdout:
                 words = line.lower().rstrip().split()
@@ -373,9 +355,8 @@ def _find_mac(command, args, hw_identifiers, get_index):
                         try:
                             word = words[get_index(i)]
                             mac = int(word.replace(b':', b''), 16)
-                            if _is_universal(mac):
+                            if mac:
                                 return mac
-                            first_local_mac = first_local_mac or mac
                         except (ValueError, IndexError):
                             # Virtual interfaces, such as those provided by
                             # VPNs, do not have a colon-delimited MAC address
@@ -385,7 +366,6 @@ def _find_mac(command, args, hw_identifiers, get_index):
                             pass
     except OSError:
         pass
-    return first_local_mac or None
 
 def _ifconfig_getnode():
     """Get the hardware address on Unix by running ifconfig."""
@@ -395,7 +375,6 @@ def _ifconfig_getnode():
         mac = _find_mac('ifconfig', args, keywords, lambda i: i+1)
         if mac:
             return mac
-        return None
 
 def _ip_getnode():
     """Get the hardware address on Unix by running ip."""
@@ -403,7 +382,6 @@ def _ip_getnode():
     mac = _find_mac('ip', 'link list', [b'link/ether'], lambda i: i+1)
     if mac:
         return mac
-    return None
 
 def _arp_getnode():
     """Get the hardware address on Unix by running arp."""
@@ -426,10 +404,8 @@ def _arp_getnode():
     # This works on Linux, FreeBSD and NetBSD
     mac = _find_mac('arp', '-an', [os.fsencode('(%s)' % ip_addr)],
                     lambda i: i+2)
-    # Return None instead of 0.
     if mac:
         return mac
-    return None
 
 def _lanscan_getnode():
     """Get the hardware address on Unix by running lanscan."""
@@ -439,36 +415,32 @@ def _lanscan_getnode():
 def _netstat_getnode():
     """Get the hardware address on Unix by running netstat."""
     # This might work on AIX, Tru64 UNIX.
-    first_local_mac = None
     try:
         proc = _popen('netstat', '-ia')
         if not proc:
-            return None
+            return
         with proc:
             words = proc.stdout.readline().rstrip().split()
             try:
                 i = words.index(b'Address')
             except ValueError:
-                return None
+                return
             for line in proc.stdout:
                 try:
                     words = line.rstrip().split()
                     word = words[i]
                     if len(word) == 17 and word.count(b':') == 5:
                         mac = int(word.replace(b':', b''), 16)
-                        if _is_universal(mac):
+                        if mac:
                             return mac
-                        first_local_mac = first_local_mac or mac
                 except (ValueError, IndexError):
                     pass
     except OSError:
         pass
-    return first_local_mac or None
 
 def _ipconfig_getnode():
     """Get the hardware address on Windows by running ipconfig.exe."""
     import os, re
-    first_local_mac = None
     dirs = ['', r'c:\windows\system32', r'c:\winnt\system32']
     try:
         import ctypes
@@ -486,23 +458,18 @@ def _ipconfig_getnode():
             for line in pipe:
                 value = line.split(':')[-1].strip().lower()
                 if re.match('([0-9a-f][0-9a-f]-){5}[0-9a-f][0-9a-f]', value):
-                    mac = int(value.replace('-', ''), 16)
-                    if _is_universal(mac):
-                        return mac
-                    first_local_mac = first_local_mac or mac
-    return first_local_mac or None
+                    return int(value.replace('-', ''), 16)
 
 def _netbios_getnode():
     """Get the hardware address on Windows using NetBIOS calls.
     See http://support.microsoft.com/kb/118623 for details."""
     import win32wnet, netbios
-    first_local_mac = None
     ncb = netbios.NCB()
     ncb.Command = netbios.NCBENUM
     ncb.Buffer = adapters = netbios.LANA_ENUM()
     adapters._pack()
     if win32wnet.Netbios(ncb) != 0:
-        return None
+        return
     adapters._unpack()
     for i in range(adapters.length):
         ncb.Reset()
@@ -521,11 +488,7 @@ def _netbios_getnode():
         bytes = status.adapter_address[:6]
         if len(bytes) != 6:
             continue
-        mac = int.from_bytes(bytes, 'big')
-        if _is_universal(mac):
-            return mac
-        first_local_mac = first_local_mac or mac
-    return first_local_mac or None
+        return int.from_bytes(bytes, 'big')
 
 
 _generate_time_safe = _UuidCreate = None
@@ -638,19 +601,9 @@ def _windll_getnode():
         return UUID(bytes=bytes_(_buffer.raw)).node
 
 def _random_getnode():
-    """Get a random node ID."""
-    # RFC 4122, $4.1.6 says "For systems with no IEEE address, a randomly or
-    # pseudo-randomly generated value may be used; see Section 4.5.  The
-    # multicast bit must be set in such addresses, in order that they will
-    # never conflict with addresses obtained from network cards."
-    #
-    # The "multicast bit" of a MAC address is defined to be "the least
-    # significant bit of the first octet".  This works out to be the 41st bit
-    # counting from 1 being the least significant bit, or 1<<40.
-    #
-    # See https://en.wikipedia.org/wiki/MAC_address#Unicast_vs._multicast
+    """Get a random node ID, with eighth bit set as suggested by RFC 4122."""
     import random
-    return random.getrandbits(48) | (1 << 40)
+    return random.getrandbits(48) | 0x010000000000
 
 
 _node = None
@@ -673,14 +626,13 @@ def getnode():
         getters = [_unix_getnode, _ifconfig_getnode, _ip_getnode,
                    _arp_getnode, _lanscan_getnode, _netstat_getnode]
 
-    for getter in getters:
+    for getter in getters + [_random_getnode]:
         try:
             _node = getter()
         except:
             continue
         if _node is not None:
             return _node
-    return _random_getnode()
 
 
 _last_timestamp = None