Merge lp:~mpontillo/maas/fix-random-failure--bug-1683503 into lp:~maas-committers/maas/trunk

[Mike Pontillo]

Fix dynamic range suggestion code to prevent suggesting a very small dynamic range.

[Lee Trager (ltrager)]

LGTM!

review: Approve

=== modified file 'src/provisioningserver/utils/network.py'
--- src/provisioningserver/utils/network.py	2016-12-07 12:46:14 +0000
+++ src/provisioningserver/utils/network.py	2017-04-17 23:20:00 +0000
@@ -267,6 +267,8 @@
         suggested_gateway = None
         first_address = self.first_address_value
         last_address = self.last_address_value
+        if self.ip_version == 6 and self.total_addresses <= 2:
+            return None
         if self.ip_version == 6:
             # For IPv6 addresses, always return the subnet-router anycast
             # address. (See RFC 4291 section 2.6.1 for more information.)
@@ -315,20 +317,23 @@
                         candidate.first, candidate.last - 1,
                         purpose=IPRANGE_TYPE.PROPOSED_DYNAMIC)
         if candidate is not None:
+            first = candidate.first
             one_fourth_range = self.total_addresses >> 2
             half_remaining_space = self.num_available >> 1
             if candidate.size > one_fourth_range:
                 # Prevent the proposed range from taking up too much available
                 # space in the subnet.
-                candidate = MAASIPRange(
-                    candidate.last - one_fourth_range, candidate.last,
-                    purpose=IPRANGE_TYPE.PROPOSED_DYNAMIC)
+                first = candidate.last - one_fourth_range
             elif candidate.size >= half_remaining_space:
                 # Prevent the proposed range from taking up the remainder of
                 # the available IP addresses. (take at most half.)
-                candidate = MAASIPRange(
-                    candidate.last - half_remaining_space + 1, candidate.last,
-                    purpose=IPRANGE_TYPE.PROPOSED_DYNAMIC)
+                first = candidate.last - half_remaining_space + 1
+            if first >= candidate.last:
+                # Calculated an impossible range.
+                return None
+            candidate = MAASIPRange(
+                first, candidate.last,
+                purpose=IPRANGE_TYPE.PROPOSED_DYNAMIC)
         return candidate
 
     @property
 
=== modified file 'src/provisioningserver/utils/tests/test_network.py'
--- src/provisioningserver/utils/tests/test_network.py	2017-04-04 07:42:31 +0000
+++ src/provisioningserver/utils/tests/test_network.py	2017-04-17 23:20:00 +0000
@@ -825,6 +825,12 @@
         self.assertThat(u['10.0.0.2'].purpose, Not(Contains('unused')))
         self.assertThat(u['10.0.0.254'].purpose, Contains('unused'))
 
+    def test__calculates_full_range_for_small_ipv6(self):
+        s = MAASIPSet([])
+        u = s.get_full_range('2001:db8::/127')
+        self.assertThat(u['2001:db8::'].purpose, Contains('unused'))
+        self.assertThat(u['2001:db8::1'].purpose, Contains('unused'))
+
     def test__supports_ior(self):
         s1 = MAASIPSet(['10.0.0.2', '10.0.0.4', '10.0.0.6', '10.0.0.8'])
         s2 = MAASIPSet(['10.0.0.1', '10.0.0.3', '10.0.0.5', '10.0.0.7'])
@@ -1082,6 +1088,25 @@
             stats.suggested_dynamic_range, Not(Contains(
                 "2001:db8::bfff:ffff:ffff:ffff")))
 
+    def test__no_suggestion_for_small_ipv6_slash_126(self):
+        s = MAASIPSet([])
+        u = s.get_full_range('2001:db8::/126')
+        stats = IPRangeStatistics(u)
+        self.assertThat(stats.suggested_gateway, Equals("2001:db8::"))
+        self.assertThat(stats.suggested_dynamic_range, Is(None))
+
+    def test__no_suggestion_for_small_ipv6_slash_127(self):
+        s = MAASIPSet([])
+        u = s.get_full_range('2001:db8::/127')
+        stats = IPRangeStatistics(u)
+        self.assertThat(stats.suggested_gateway, Equals(None))
+
+    def test__no_suggestion_and_no_gateway_for_small_ipv6_slash_128(self):
+        s = MAASIPSet([])
+        u = s.get_full_range('2001:db8::/128')
+        stats = IPRangeStatistics(u)
+        self.assertThat(stats.suggested_gateway, Is(None))
+
     def test__suggests_half_available_for_ipv6(self):
         s = MAASIPSet([MAASIPRange(
             "2001:db8::1", "2001:db8::ffff:ffff:ffff:ff00")])