From 290afad4e7b17eb4702a896a250046a7df011671 Mon Sep 17 00:00:00 2001
From: Saikrishna Arcot <sarcot@microsoft.com>
Date: Thu, 14 Sep 2023 12:55:50 -0700
Subject: [PATCH] Fix potentially not having any loopback address on lo
 interface (#16490)

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>
---
 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 18e1181c71c..b39331f459b 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 a47c89258e3..90aadce5f44 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 c447cfbc6d3..b38c3692e99 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 b41038fd8d6..705a5a0e209 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 543819734f0..d09e9e741de 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 57bf924ce71..e76aea82618 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 31a6d332577..e5ad2330f3e 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 5777bce1837..1c33cfe819c 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 04490892fe3..8f0f4555781 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 ce3961f1a78..319f25c4e91 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 a47c89258e3..90aadce5f44 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 c447cfbc6d3..b38c3692e99 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 b41038fd8d6..705a5a0e209 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 543819734f0..d09e9e741de 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 57bf924ce71..e76aea82618 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 31a6d332577..e5ad2330f3e 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 5777bce1837..1c33cfe819c 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 04490892fe3..8f0f4555781 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 5e2680854ce..490a27366fd 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