Merge ~smoser/cloud-init:fix/1796917-ignore-all-zero-macs into cloud-init:master

[Scott Moser]

net: ignore nics that have "zero" mac address.

Previously we explicitly excluded mac address '00:00:00:00:00:00'.
But then some nics (tunl0 and sit0) ended up having a mac address like
'00:00:00:00'.

The change here just ignores all 00[:00[:00...]].

LP: #1796917

see commit message

[Ryan Harper (raharper)]

Interesting, I was wondering why the output in the bug showed a "truncated" MAC. And I figured we would have already ignored empty MAC as well.

This looks good plus unittest!

review: Approve

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:935d2de80d5847f5aee4e59a882179bbdd350489
https://jenkins.ubuntu.com/server/job/cloud-init-ci/377/
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    SUCCESS: Checkout
    SUCCESS: Unit & Style Tests
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review: Approve (continuous-integration)

0206d10... by Scott Moser on 2018-10-09

rharper feedback: consistent use of tick or double quote on single line.

3d91eaa... by Scott Moser on 2018-10-09

change the comparison.

This should be slightly faster. Compute the string once and then
just do substring matching rather than computing the "zero mac"
for the given length each time.

[Chad Smith (chad.smith)]

Ahh my brain parsed that tunl mac as 6 bytes, not 4. Thanks for this fix and the inline comments to shed light on this issue in the future.
+1

review: Approve

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:0206d1067345cfa531133e27582a1236b245f318
https://jenkins.ubuntu.com/server/job/cloud-init-ci/378/
Executed test runs:
    SUCCESS: Checkout
    SUCCESS: Unit & Style Tests
    SUCCESS: Ubuntu LTS: Build
    SUCCESS: Ubuntu LTS: Integration
    IN_PROGRESS: Declarative: Post Actions

Click here to trigger a rebuild:
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review: Approve (continuous-integration)

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:3d91eaade62a6f427c948c40b6d0a618e6351311
https://jenkins.ubuntu.com/server/job/cloud-init-ci/379/
Executed test runs:
    SUCCESS: Checkout
    SUCCESS: Unit & Style Tests
    SUCCESS: Ubuntu LTS: Build
    SUCCESS: Ubuntu LTS: Integration
    IN_PROGRESS: Declarative: Post Actions

Click here to trigger a rebuild:
https://jenkins.ubuntu.com/server/job/cloud-init-ci/379/rebuild

review: Approve (continuous-integration)

diff --git a/cloudinit/net/__init__.py b/cloudinit/net/__init__.py
index f83d368..ad98a59 100644
--- a/cloudinit/net/__init__.py
+++ b/cloudinit/net/__init__.py
@@ -612,7 +612,8 @@ def get_interfaces():
     Bridges and any devices that have a 'stolen' mac are excluded."""
     ret = []
     devs = get_devicelist()
-    empty_mac = '00:00:00:00:00:00'
+    # 16 somewhat arbitrarily chosen.  Normally a mac is 6 '00:' tokens.
+    zero_mac = ':'.join(('00',) * 16)
     for name in devs:
         if not interface_has_own_mac(name):
             continue
@@ -624,7 +625,8 @@ def get_interfaces():
         # some devices may not have a mac (tun0)
         if not mac:
             continue
-        if mac == empty_mac and name != 'lo':
+        # skip nics that have no mac (00:00....)
+        if name != 'lo' and mac == zero_mac[:len(mac)]:
             continue
         ret.append((name, mac, device_driver(name), device_devid(name)))
     return ret
diff --git a/tests/unittests/test_net.py b/tests/unittests/test_net.py
index 5d9c7d9..8e38373 100644
--- a/tests/unittests/test_net.py
+++ b/tests/unittests/test_net.py
@@ -3339,9 +3339,23 @@ class TestGetInterfacesByMac(CiTestCase):
         addnics = ('greptap1', 'lo', 'greptap2')
         self.data['macs'].update(dict((k, empty_mac) for k in addnics))
         self.data['devices'].update(set(addnics))
+        self.data['own_macs'].extend(list(addnics))
         ret = net.get_interfaces_by_mac()
         self.assertEqual('lo', ret[empty_mac])
 
+    def test_skip_all_zeros(self):
+        """Any mac of 00:... should be skipped."""
+        self._mock_setup()
+        emac1, emac2, emac4, emac6 = (
+            '00', '00:00', '00:00:00:00', '00:00:00:00:00:00')
+        addnics = {'empty1': emac1, 'emac2a': emac2, 'emac2b': emac2,
+                   'emac4': emac4, 'emac6': emac6}
+        self.data['macs'].update(addnics)
+        self.data['devices'].update(set(addnics))
+        self.data['own_macs'].extend(addnics.keys())
+        ret = net.get_interfaces_by_mac()
+        self.assertEqual('lo', ret['00:00:00:00:00:00'])
+
     def test_ib(self):
         ib_addr = '80:00:00:28:fe:80:00:00:00:00:00:00:00:11:22:03:00:33:44:56'
         ib_addr_eth_format = '00:11:22:33:44:56'