tests:ethernets: Add comments about MAC->EUI64 transformation and mov…

…e method to base.py

tests/integration/base.py

@@ -54,6 +54,23 @@ def resolved_in_use():
     return os.path.isfile('/run/systemd/resolve/resolv.conf')
 
 
+def mac_to_eui64(hwaddr: str) -> ipaddress.IPv6Address:
+    '''
+    Calculate a EUI-64 IPv6 address from a MAC, according to RFC-4291,
+    e.g.: https://www.geeksforgeeks.org/ipv6-eui-64-extended-unique-identifier
+    '''
+    # convert MAC address bytes to a list of base10 decimals
+    mac_addr = [int(h, base=16) for h in hwaddr.split(':')]
+    mac_addr[0] ^= 2  # flip 7th bit of the 1st byte, e.g. XOR 0b00000010 (=2)
+    # inject 0xFFFE in the middle, increasing 48bit MAC to 64bit IPv6 Interface ID
+    mac_addr[3:3] = [0xff, 0xfe]
+    # apply 64bit IPv6 Interface ID on generic IPv6 carrier address (2600::)
+    eui_addr_int = 0x26000000000000000000000000000000
+    for i, h in enumerate(reversed(mac_addr)):
+        eui_addr_int |= h << 8 * i
+    return ipaddress.IPv6Address(eui_addr_int)
+
+
 class IntegrationTestsBase(unittest.TestCase):
     '''Common functionality for network test cases
 

tests/integration/ethernets.py

@@ -23,12 +23,12 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import os
-import sys
 import subprocess
+import sys
 import unittest
-import ipaddress
 
-from base import IntegrationTestsBase, nm_uses_dnsmasq, resolved_in_use, test_backends
+from base import (IntegrationTestsBase, mac_to_eui64, nm_uses_dnsmasq,
+                  resolved_in_use, test_backends)
 
 
 class _CommonTests():
@@ -234,13 +234,9 @@ def test_ip6_stable_privacy(self):
       accept-ra: yes
       ipv6-address-generation: stable-privacy''' % {'r': self.backend, 'ec': self.dev_e_client})
         self.generate_and_settle([self.state_dhcp6(self.dev_e_client)])
-        mac_addr = [int(h, base=16) for h in self.dev_e_client_mac.split(':')]
-        mac_addr[0] ^= 2
-        mac_addr[3:3] = [0xff, 0xfe]
-        eui_addr_int = 0x26000000000000000000000000000000
-        for i, h in enumerate(reversed(mac_addr)):
-            eui_addr_int |= h << 8 * i
-        eui_addr = ipaddress.IPv6Address(eui_addr_int)
+        # Compare to EUI-64 address, to make sure it will NOT match the
+        # (random) stable-privacy address generated.
+        eui_addr = mac_to_eui64(self.dev_e_client_mac)
         self.assert_iface_up(self.dev_e_client, ['inet6 2600::'], [f'inet6 {eui_addr.compressed}/64'])
 
     def test_ip6_eui64(self):
@@ -255,13 +251,8 @@ def test_ip6_eui64(self):
       accept-ra: yes
       ipv6-address-generation: eui64''' % {'r': self.backend, 'ec': self.dev_e_client})
         self.generate_and_settle([self.state_dhcp6(self.dev_e_client)])
-        mac_addr = [int(h, base=16) for h in self.dev_e_client_mac.split(':')]
-        mac_addr[0] ^= 2
-        mac_addr[3:3] = [0xff, 0xfe]
-        eui_addr_int = 0x26000000000000000000000000000000
-        for i, h in enumerate(reversed(mac_addr)):
-            eui_addr_int |= h << 8 * i
-        eui_addr = ipaddress.IPv6Address(eui_addr_int)
+        # Compare to EUI-64 address, to make sure it matches the one generated.
+        eui_addr = mac_to_eui64(self.dev_e_client_mac)
         self.assert_iface_up(self.dev_e_client, [f'inet6 {eui_addr.compressed}/64'])
 
     def test_link_local_all(self):