From d03cb6b85d120ea886bb03a84c141bff4e62a80a Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Fri, 20 Nov 2020 22:48:59 +0900
Subject: [PATCH 1/3] link-config: make MACAddressPolicy= accept an empty
 string

---
 src/udev/net/link-config.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/udev/net/link-config.c b/src/udev/net/link-config.c
index afb2cd4d1c..0519635748 100644
--- a/src/udev/net/link-config.c
+++ b/src/udev/net/link-config.c
@@ -668,8 +668,12 @@ static const char* const mac_address_policy_table[_MAC_ADDRESS_POLICY_MAX] = {
 };
 
 DEFINE_STRING_TABLE_LOOKUP(mac_address_policy, MACAddressPolicy);
-DEFINE_CONFIG_PARSE_ENUM(config_parse_mac_address_policy, mac_address_policy, MACAddressPolicy,
-                         "Failed to parse MAC address policy");
+DEFINE_CONFIG_PARSE_ENUM_WITH_DEFAULT(
+        config_parse_mac_address_policy,
+        mac_address_policy,
+        MACAddressPolicy,
+        MAC_ADDRESS_POLICY_NONE,
+        "Failed to parse MAC address policy");
 
 static const char* const name_policy_table[_NAMEPOLICY_MAX] = {
         [NAMEPOLICY_KERNEL] = "kernel",

From a7a12bf4040cd140376bb12700d3920884bc803c Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Fri, 20 Nov 2020 22:58:23 +0900
Subject: [PATCH 2/3] link-config: warn when MACAddress= is set with
 MACAddressPolicy=persistent or random

---
 src/udev/net/link-config.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/udev/net/link-config.c b/src/udev/net/link-config.c
index 0519635748..d12fd0e299 100644
--- a/src/udev/net/link-config.c
+++ b/src/udev/net/link-config.c
@@ -181,6 +181,13 @@ int link_load_one(link_config_ctx *ctx, const char *filename) {
                 return 0;
         }
 
+        if (IN_SET(link->mac_address_policy, MAC_ADDRESS_POLICY_PERSISTENT, MAC_ADDRESS_POLICY_RANDOM) && link->mac) {
+                log_warning("%s: MACAddress= in [Link] section will be ignored when MACAddressPolicy= "
+                            "is set to \"persistent\" or \"random\".",
+                            filename);
+                link->mac = mfree(link->mac);
+        }
+
         log_debug("Parsed configuration file %s", filename);
 
         LIST_PREPEND(links, ctx->links, TAKE_PTR(link));

From 6ca4a070778e3f6c049c59b29a4432ea4c2d72fb Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Fri, 20 Nov 2020 22:43:45 +0900
Subject: [PATCH 3/3] man: to make MACAddress= take effect, MACAddressPolicy=
 must be "none"

---
 man/systemd.link.xml | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/man/systemd.link.xml b/man/systemd.link.xml
index 504977c862..24271ea65a 100644
--- a/man/systemd.link.xml
+++ b/man/systemd.link.xml
@@ -273,18 +273,21 @@
             <varlistentry>
               <term><option>none</option></term>
               <listitem>
-                <para>Keeps the MAC address assigned by the kernel.</para>
+                <para>Keeps the MAC address assigned by the kernel. Or use the MAC address specified in
+                <varname>MACAddress=</varname>.</para>
               </listitem>
             </varlistentry>
           </variablelist>
+
+          <para>An empty string assignment is equivalent to setting <literal>none</literal>.</para>
         </listitem>
       </varlistentry>
       <varlistentry>
         <term><varname>MACAddress=</varname></term>
         <listitem>
-          <para>The MAC address to use, if no
-          <varname>MACAddressPolicy=</varname>
-          is specified.</para>
+          <para>The interface MAC address to use. For this setting to take effect,
+          <varname>MACAddressPolicy=</varname> must either be unset, empty, or <literal>none</literal>.
+          </para>
         </listitem>
       </varlistentry>
       <varlistentry>