[nvidia] make sure shared storage with syncd is cleared on restarts (#14547)

Why I did it
Sharing the storage of syncd with other proprietary application extensions allows them to communicate with syncd in differnt ways.
If one container wants to pass some information to syncd then shared storage can be used. However, today the shared storage isn't cleaned on restarts making it possible for syncd to read out-of-date information generated in the past.

NOTE: No plans to use it for standard SONIC dockers and we are working on removing the SDK dependency from PMON docker

How I did it
Implemented new service to clean the shared storage.

How to verify it
Do reboot/fast-reboot/warm-reboot/config-reload/systemctl restart swss and verify /tmp/ is cleaned after each restart in syncd container.

Signed-off-by: Stepan Blyschak <stepanb@nvidia.com>

files/build_templates/docker_image_ctl.j2

@@ -157,9 +157,9 @@ function waitForAllInstanceDatabaseConfigJsonFilesReady()
             done
         fi
         # Delay a second to allow all instance database_config.json files to be completely generated and fully accessible.
-        # This delay is needed to make sure that the database_config.json files are correctly rendered from j2 template 
+        # This delay is needed to make sure that the database_config.json files are correctly rendered from j2 template
         # files ( renderning takes some time )
-        sleep 1 
+        sleep 1
     fi
 }
 {%- endif %}
@@ -240,7 +240,7 @@ function postStartAction()
             mv $WARM_DIR/dump.rdb $WARM_DIR/dump.rdb.old
         else
             # If there is a config_db.json dump file, load it.
-            if [ -r /etc/sonic/config_db$DEV.json ]; then		
+            if [ -r /etc/sonic/config_db$DEV.json ]; then
 
                 if [ -r /etc/sonic/init_cfg.json ]; then
                     $SONIC_CFGGEN -j /etc/sonic/init_cfg.json -j /etc/sonic/config_db$DEV.json --write-to-db
@@ -323,7 +323,7 @@ start() {
 
     {%- if sonic_asic_platform == "broadcom" %}
     {%- if docker_container_name == "syncd" %}
-    # Set the SYNCD_SHM_SIZE if this variable not defined    
+    # Set the SYNCD_SHM_SIZE if this variable not defined
     BRCM_PLATFORM_COMMON_DIR=/usr/share/sonic/device/x86_64-broadcom_common
     SYNCD_SHM_INI=$BRCM_PLATFORM_COMMON_DIR/syncd_shm.ini
 
@@ -545,14 +545,15 @@ start() {
 {%- if docker_container_name == "syncd" %}
         -v /var/log/mellanox:/var/log/mellanox:rw \
         -v mlnx_sdk_socket:/var/run/sx_sdk \
-        -v mlnx_sdk_ready:/tmp \
+        -v /tmp/nv-syncd-shared/:/tmp \
         -v /dev/shm:/dev/shm:rw \
         -v /var/log/sai_failure_dump:/var/log/sai_failure_dump:rw \
         -e SX_API_SOCKET_FILE=/var/run/sx_sdk/sx_api.sock \
 {%- elif docker_container_name == "pmon" %}
         -v /var/run/hw-management:/var/run/hw-management:rw \
         -v mlnx_sdk_socket:/var/run/sx_sdk \
-        -v mlnx_sdk_ready:/tmp \
+        -v /tmp/nv-syncd-shared/:/tmp \
+        -v /dev/shm:/dev/shm:rw \
         -e SX_API_SOCKET_FILE=/var/run/sx_sdk/sx_api.sock \
         -v /dev/shm:/dev/shm:rw \
 {%- else %}

files/build_templates/per_namespace/syncd.service.j2

@@ -19,6 +19,10 @@ After=updategraph.service
 BindsTo=sonic.target
 After=sonic.target
 Before=ntp-config.service
+{% if sonic_asic_platform == 'mellanox' %}
+Requires=nv-syncd-shared.service
+After=nv-syncd-shared.service
+{% endif %}
 
 [Service]
 User=root

files/build_templates/sonic_debian_extension.j2

@@ -946,6 +946,10 @@ MLNX_SONIC_PLATFORM_PY3_WHEEL_NAME=$(basename {{mlnx_platform_api_py3_wheel_path
 sudo cp {{mlnx_platform_api_py3_wheel_path}} $FILESYSTEM_ROOT/$MLNX_SONIC_PLATFORM_PY3_WHEEL_NAME
 sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip3 install $MLNX_SONIC_PLATFORM_PY3_WHEEL_NAME
 sudo rm -rf $FILESYSTEM_ROOT/$MLNX_SONIC_PLATFORM_PY3_WHEEL_NAME
+
+# Install service that manages Nvidia specific shared storage
+sudo cp platform/mellanox/nv-syncd-shared/nv-syncd-shared.service $FILESYSTEM_ROOT_USR_LIB_SYSTEMD_SYSTEM/
+sudo LANG=C chroot $FILESYSTEM_ROOT systemctl enable nv-syncd-shared
 {% endif %}
 
 {%- if SONIC_ROUTING_STACK == "frr" %}

platform/mellanox/nv-syncd-shared/nv-syncd-shared.service

@@ -0,0 +1,17 @@
+[Unit]
+Description=Manage Nvidia specific syncd shared volume
+Requires=docker.service
+After=docker.service
+BindsTo=sonic.target
+After=sonic.target
+PartOf=syncd.service
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=rm -rf /tmp/nv-syncd-shared/
+ExecStart=mkdir -p /tmp/nv-syncd-shared/
+
+[Install]
+WantedBy=sonic.target
+