From e7f49c9bce2bd7b8960b6a61ffe2c8b933423c6b Mon Sep 17 00:00:00 2001
From: mssonicbld <79238446+mssonicbld@users.noreply.github.com>
Date: Thu, 21 Sep 2023 20:40:21 +0800
Subject: [PATCH] Fix potentially not having any loopback address on lo
 interface (#16490) (#16628)

In #15080, there was a command added to re-add 127.0.0.1/8 to the lo
interface when the networking configuration is being brought down.
However, the trigger for that command is `down`, which, looking at
ifupdown2 configuration files, runs immediately after 127.0.0.1/16 is
removed. This means there may be a period of time where there are no
loopback addresses assigned to the lo interface, and redis commands will
fail.

Fix this by changing this to pre-down, which should run well before
127.0.0.1/16 is removed, and should always leave lo with a loopback
address.

Signed-off-by: Saikrishna Arcot <sarcot@microsoft.com>
Co-authored-by: Saikrishna Arcot <sarcot@microsoft.com>
---
 files/image_config/interfaces/interfaces.j2                     | 2 +-
 src/sonic-config-engine/tests/sample_output/py2/interfaces      | 2 +-
 .../tests/sample_output/py2/interfaces_nomgmt                   | 2 +-
 .../tests/sample_output/py2/interfaces_nomgmt_ztp               | 2 +-
 .../tests/sample_output/py2/interfaces_nomgmt_ztp_inband        | 2 +-
 .../tests/sample_output/py2/interfaces_nomgmt_ztp_inband_ip     | 2 +-
 .../tests/sample_output/py2/interfaces_nomgmt_ztp_ip            | 2 +-
 src/sonic-config-engine/tests/sample_output/py2/mvrf_interfaces | 2 +-
 .../tests/sample_output/py2/mvrf_interfaces_nomgmt              | 2 +-
 .../tests/sample_output/py2/two_mgmt_interfaces                 | 2 +-
 src/sonic-config-engine/tests/sample_output/py3/interfaces      | 2 +-
 .../tests/sample_output/py3/interfaces_nomgmt                   | 2 +-
 .../tests/sample_output/py3/interfaces_nomgmt_ztp               | 2 +-
 .../tests/sample_output/py3/interfaces_nomgmt_ztp_inband        | 2 +-
 .../tests/sample_output/py3/interfaces_nomgmt_ztp_inband_ip     | 2 +-
 .../tests/sample_output/py3/interfaces_nomgmt_ztp_ip            | 2 +-
 src/sonic-config-engine/tests/sample_output/py3/mvrf_interfaces | 2 +-
 .../tests/sample_output/py3/mvrf_interfaces_nomgmt              | 2 +-
 .../tests/sample_output/py3/two_mgmt_interfaces                 | 2 +-
 19 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/files/image_config/interfaces/interfaces.j2 b/files/image_config/interfaces/interfaces.j2
index 18e1181c71..b39331f459 100644
--- a/files/image_config/interfaces/interfaces.j2
+++ b/files/image_config/interfaces/interfaces.j2
@@ -26,7 +26,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 {% endblock loopback %}
 {% block mgmt_interface %}
 
diff --git a/src/sonic-config-engine/tests/sample_output/py2/interfaces b/src/sonic-config-engine/tests/sample_output/py2/interfaces
index a47c89258e..90aadce5f4 100644
--- a/src/sonic-config-engine/tests/sample_output/py2/interfaces
+++ b/src/sonic-config-engine/tests/sample_output/py2/interfaces
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt b/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt
index c447cfbc6d..b38c3692e9 100644
--- a/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt
+++ b/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp b/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp
index b41038fd8d..705a5a0e20 100644
--- a/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp
+++ b/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp_inband b/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp_inband
index 543819734f..d09e9e741d 100644
--- a/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp_inband
+++ b/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp_inband
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp_inband_ip b/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp_inband_ip
index 57bf924ce7..e76aea8261 100644
--- a/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp_inband_ip
+++ b/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp_inband_ip
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp_ip b/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp_ip
index 31a6d33257..e5ad2330f3 100644
--- a/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp_ip
+++ b/src/sonic-config-engine/tests/sample_output/py2/interfaces_nomgmt_ztp_ip
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py2/mvrf_interfaces b/src/sonic-config-engine/tests/sample_output/py2/mvrf_interfaces
index 5777bce183..1c33cfe819 100644
--- a/src/sonic-config-engine/tests/sample_output/py2/mvrf_interfaces
+++ b/src/sonic-config-engine/tests/sample_output/py2/mvrf_interfaces
@@ -19,7 +19,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py2/mvrf_interfaces_nomgmt b/src/sonic-config-engine/tests/sample_output/py2/mvrf_interfaces_nomgmt
index 04490892fe..8f0f455578 100644
--- a/src/sonic-config-engine/tests/sample_output/py2/mvrf_interfaces_nomgmt
+++ b/src/sonic-config-engine/tests/sample_output/py2/mvrf_interfaces_nomgmt
@@ -19,7 +19,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py2/two_mgmt_interfaces b/src/sonic-config-engine/tests/sample_output/py2/two_mgmt_interfaces
index ce3961f1a7..319f25c4e9 100644
--- a/src/sonic-config-engine/tests/sample_output/py2/two_mgmt_interfaces
+++ b/src/sonic-config-engine/tests/sample_output/py2/two_mgmt_interfaces
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth1
diff --git a/src/sonic-config-engine/tests/sample_output/py3/interfaces b/src/sonic-config-engine/tests/sample_output/py3/interfaces
index a47c89258e..90aadce5f4 100644
--- a/src/sonic-config-engine/tests/sample_output/py3/interfaces
+++ b/src/sonic-config-engine/tests/sample_output/py3/interfaces
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt b/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt
index c447cfbc6d..b38c3692e9 100644
--- a/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt
+++ b/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp b/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp
index b41038fd8d..705a5a0e20 100644
--- a/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp
+++ b/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp_inband b/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp_inband
index 543819734f..d09e9e741d 100644
--- a/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp_inband
+++ b/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp_inband
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp_inband_ip b/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp_inband_ip
index 57bf924ce7..e76aea8261 100644
--- a/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp_inband_ip
+++ b/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp_inband_ip
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp_ip b/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp_ip
index 31a6d33257..e5ad2330f3 100644
--- a/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp_ip
+++ b/src/sonic-config-engine/tests/sample_output/py3/interfaces_nomgmt_ztp_ip
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py3/mvrf_interfaces b/src/sonic-config-engine/tests/sample_output/py3/mvrf_interfaces
index 5777bce183..1c33cfe819 100644
--- a/src/sonic-config-engine/tests/sample_output/py3/mvrf_interfaces
+++ b/src/sonic-config-engine/tests/sample_output/py3/mvrf_interfaces
@@ -19,7 +19,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py3/mvrf_interfaces_nomgmt b/src/sonic-config-engine/tests/sample_output/py3/mvrf_interfaces_nomgmt
index 04490892fe..8f0f455578 100644
--- a/src/sonic-config-engine/tests/sample_output/py3/mvrf_interfaces_nomgmt
+++ b/src/sonic-config-engine/tests/sample_output/py3/mvrf_interfaces_nomgmt
@@ -19,7 +19,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0
diff --git a/src/sonic-config-engine/tests/sample_output/py3/two_mgmt_interfaces b/src/sonic-config-engine/tests/sample_output/py3/two_mgmt_interfaces
index 5e2680854c..490a27366f 100644
--- a/src/sonic-config-engine/tests/sample_output/py3/two_mgmt_interfaces
+++ b/src/sonic-config-engine/tests/sample_output/py3/two_mgmt_interfaces
@@ -10,7 +10,7 @@ iface lo inet loopback
    netmask 255.255.0.0
    scope host
    post-up ip addr del 127.0.0.1/8 dev lo
-   down ip addr add 127.0.0.1/8 dev lo
+   pre-down ip addr add 127.0.0.1/8 dev lo
 
 # The management network interface
 auto eth0