From 5c079f6a1427fe24e33c5b55bc0420e06aae2b4c Mon Sep 17 00:00:00 2001
From: Zac Mrowicki <mrowicki@amazon.com>
Date: Wed, 2 Mar 2022 18:58:33 +0000
Subject: [PATCH] release: Include a default .link file for network interfaces

This change adds a default network configuration .link file that
`systemd-udev` will use when configuring new interfaces.  It contains
the default list of policies that are used when naming interfaces, as
well as the policy by which the MAC address should be set.

Bottlerocket packages its own version of this file rather than the
default from systemd for a few reasons. 1) Bottlerocket does not
create/use a udev hwdb (we disable the option in systemd compile flags),
so we remove this option from the NamePolicy list, 2) CNI plugins can be
confused when MAC addresses change for virtual interfaces, so
Bottlerocket sets the default MACAddress Policy to "none" which
directs systemd not to attempt to manage the MAC.  Hardware usually has
a MAC, and veth devices used by CNI generally get a MAC generated by the
plugin.

Additional information about the MAC address issue:
https://github.com/systemd/systemd/issues/3374#issuecomment-288882355
https://github.com/flatcar-linux/Flatcar/issues/278
https://github.com/flatcar-linux/init/pull/33
---
 packages/release/80-release.link | 11 +++++++++++
 packages/release/release.spec    |  7 +++++++
 2 files changed, 18 insertions(+)
 create mode 100644 packages/release/80-release.link

diff --git a/packages/release/80-release.link b/packages/release/80-release.link
new file mode 100644
index 00000000000..4c364bd5d99
--- /dev/null
+++ b/packages/release/80-release.link
@@ -0,0 +1,11 @@
+[Match]
+OriginalName=*
+
+[Link]
+# Bottlerocket disables hwdb so don't include "database" in NamePolicy
+NamePolicy=keep kernel onboard slot path
+AlternativeNamesPolicy=onboard slot path
+
+# Applying a MAC address policy can confuse CNI plugins, which do
+# not expect addresses to change for devices like veth pairs.
+MACAddressPolicy=none
diff --git a/packages/release/release.spec b/packages/release/release.spec
index b637d54b76c..ccf04e336eb 100644
--- a/packages/release/release.spec
+++ b/packages/release/release.spec
@@ -60,6 +60,9 @@ Source1080: runtime.slice
 # Drop-in units to override defaults
 Source1100: systemd-tmpfiles-setup-service-debug.conf
 
+# systemd-udevd default link
+Source1200: 80-release.link
+
 BuildArch: noarch
 Requires: %{_cross_os}acpid
 Requires: %{_cross_os}audit
@@ -114,6 +117,9 @@ install -p -m 0644 %{S:97} %{buildroot}%{_cross_sysctldir}/80-release.conf
 install -d %{buildroot}%{_cross_libdir}/systemd/system.conf.d
 install -p -m 0644 %{S:98} %{buildroot}%{_cross_libdir}/systemd/system.conf.d/80-release.conf
 
+install -d %{buildroot}%{_cross_libdir}/systemd/network
+install -p -m 0644 %{S:1200} %{buildroot}%{_cross_libdir}/systemd/network/80-release.link
+
 install -d %{buildroot}%{_cross_tmpfilesdir}
 install -p -m 0644 %{S:99} %{buildroot}%{_cross_tmpfilesdir}/release.conf
 
@@ -172,6 +178,7 @@ ln -s preconfigured.target %{buildroot}%{_cross_unitdir}/default.target
 %dir %{_cross_libdir}/repart.d
 %{_cross_libdir}/repart.d/80-local.conf
 %{_cross_libdir}/systemd/system.conf.d/80-release.conf
+%{_cross_libdir}/systemd/network/80-release.link
 %{_cross_unitdir}/configured.target
 %{_cross_unitdir}/preconfigured.target
 %{_cross_unitdir}/multi-user.target