ec2: Do not enable DHCPv6 on EC2

Enabling DHCPv6 by default on EC2 leads to instance with broken IPv6
connectivity. AWS provides the IP address via DHCPv6 and SLAAC, but
router advertisements are not accepted if the instance has DHCPv6
configured. The accept_ra value is set to 0.

Removing the `dhcp` option from `ipv6.method` and simply using `auto`
(the default) allows the instance to pick up its IPv6 address and accept
router advertisements from the AWS network.

RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=2092459
Pagure: https://pagure.io/cloud-sig/issue/382
Upstream: https://bugs.launchpad.net/cloud-init/+bug/1976526?comments=all

Signed-off-by: Major Hayden <major@redhat.com>

Do-not-enable-dhcp6-on-EC2.patch

@@ -0,0 +1,114 @@
+From 02d0c4852feddb0715cb515e5e552351df3d9e5f Mon Sep 17 00:00:00 2001
+From: Major Hayden <major@redhat.com>
+Date: Tue, 28 Mar 2023 17:16:41 -0500
+Subject: [PATCH] ec2: Do not enable dhcp6 on EC2
+
+When cloud-init finds any ipv6 information in the instance metadata, it
+automatically enables dhcp6 for the network interface. However, this
+brings up the instance with a broken IPv6 configuration because SLAAC
+should be used for almost all situations on EC2.
+
+Red Hat BZ: https://bugzilla.redhat.com/show_bug.cgi?id=2092459
+Fedora Pagure: https://pagure.io/cloud-sig/issue/382
+Upstream: https://bugs.launchpad.net/cloud-init/+bug/1976526
+
+Signed-off-by: Major Hayden <major@redhat.com>
+---
+ cloudinit/sources/DataSourceEc2.py  |  5 -----
+ tests/unittests/sources/test_ec2.py | 15 +++++++--------
+ 2 files changed, 7 insertions(+), 13 deletions(-)
+
+diff --git a/cloudinit/sources/DataSourceEc2.py b/cloudinit/sources/DataSourceEc2.py
+index 44665b26..b78b3e99 100644
+--- a/cloudinit/sources/DataSourceEc2.py
++++ b/cloudinit/sources/DataSourceEc2.py
+@@ -921,8 +921,6 @@ def convert_ec2_metadata_network_config(
+             "set-name": nic_name,
+         }
+         nic_metadata = macs_metadata.get(mac)
+-        if nic_metadata.get("ipv6s"):  # Any IPv6 addresses configured
+-            dev_config["dhcp6"] = True
+         netcfg["ethernets"][nic_name] = dev_config
+         return netcfg
+     # Apply network config for all nics and any secondary IPv4/v6 addresses
+@@ -942,9 +940,6 @@ def convert_ec2_metadata_network_config(
+             "match": {"macaddress": mac.lower()},
+             "set-name": nic_name,
+         }
+-        if nic_metadata.get("ipv6s"):  # Any IPv6 addresses configured
+-            dev_config["dhcp6"] = True
+-            dev_config["dhcp6-overrides"] = dhcp_override
+         dev_config["addresses"] = get_secondary_addresses(nic_metadata, mac)
+         if not dev_config["addresses"]:
+             dev_config.pop("addresses")  # Since we found none configured
+diff --git a/tests/unittests/sources/test_ec2.py b/tests/unittests/sources/test_ec2.py
+index 3fe525e3..9721cab2 100644
+--- a/tests/unittests/sources/test_ec2.py
++++ b/tests/unittests/sources/test_ec2.py
+@@ -432,7 +432,7 @@ class TestEc2(test_helpers.ResponsesTestCase):
+                     "match": {"macaddress": "06:17:04:d7:26:09"},
+                     "set-name": "eth9",
+                     "dhcp4": True,
+-                    "dhcp6": True,
++                    "dhcp6": False,
+                 }
+             },
+         }
+@@ -513,7 +513,7 @@ class TestEc2(test_helpers.ResponsesTestCase):
+                         "2600:1f16:292:100:f153:12a3:c37c:11f9/128",
+                     ],
+                     "dhcp4": True,
+-                    "dhcp6": True,
++                    "dhcp6": False,
+                 }
+             },
+         }
+@@ -593,7 +593,7 @@ class TestEc2(test_helpers.ResponsesTestCase):
+                     "match": {"macaddress": mac1},
+                     "set-name": "eth9",
+                     "dhcp4": True,
+-                    "dhcp6": True,
++                    "dhcp6": False,
+                 }
+             },
+         }
+@@ -1000,7 +1000,7 @@ class TestConvertEc2MetadataNetworkConfig(test_helpers.CiTestCase):
+                     "match": {"macaddress": self.mac1},
+                     "set-name": "eth9",
+                     "dhcp4": True,
+-                    "dhcp6": True,
++                    "dhcp6": False,
+                 }
+             },
+         }
+@@ -1077,7 +1077,7 @@ class TestConvertEc2MetadataNetworkConfig(test_helpers.CiTestCase):
+                     "match": {"macaddress": self.mac1},
+                     "set-name": "eth9",
+                     "dhcp4": True,
+-                    "dhcp6": True,
++                    "dhcp6": False,
+                 }
+             },
+         }
+@@ -1107,8 +1107,7 @@ class TestConvertEc2MetadataNetworkConfig(test_helpers.CiTestCase):
+                     "set-name": "eth9",
+                     "dhcp4": True,
+                     "dhcp4-overrides": {"route-metric": 100},
+-                    "dhcp6": True,
+-                    "dhcp6-overrides": {"route-metric": 100},
++                    "dhcp6": False,
+                 },
+                 "eth10": {
+                     "match": {"macaddress": mac2},
+@@ -1139,7 +1138,7 @@ class TestConvertEc2MetadataNetworkConfig(test_helpers.CiTestCase):
+                     "match": {"macaddress": self.mac1},
+                     "set-name": "eth9",
+                     "dhcp4": True,
+-                    "dhcp6": True,
++                    "dhcp6": False,
+                 }
+             },
+         }
+-- 
+2.39.2
+

cloud-init.spec

@@ -6,7 +6,7 @@
 
 Name:           cloud-init
 Version:        23.1.2
-Release:        5%{?dist}
+Release:        6%{?dist}
 Summary:        Cloud instance init scripts
 License:        Apache-2.0 or GPL-3.0-only
 URL:            https://github.com/canonical/cloud-init
@@ -25,6 +25,10 @@ Patch2:         Fedora-Enable-CA-handling.patch
 # https://bugzilla.redhat.com/show_bug.cgi?id=2068529
 Patch3:         multiple-nameservers.patch
 
+# Enabling dhcp6 on EC2 causes a broken IPv6 configuration.
+# See RHBZ 2092459.
+Patch4:         Do-not-enable-dhcp6-on-EC2.patch
+
 BuildArch:      noarch
 
 BuildRequires:  pkgconfig(systemd)
@@ -200,6 +204,9 @@ python3 -m pytest tests/unittests
 
 
 %changelog
+* Tue May 16 2023 Major Hayden <major@redhat.com> - 23.1.2-6
+- Add patch to disable DHCPv6 on EC2 to fix BZ 2092459.
+
 * Tue May 16 2023 Yaakov Selkowitz <yselkowi@redhat.com> - 23.1.2-5
 - Disable tests by default in RHEL builds