[swss]: Wait for vlan intf to start ndppd (#10119) (#10153)

202012 version of #10119

Why I did it
If the VLAN interface is not up when ndppd starts, it will fail to enable allmulti mode on the interface and be unable to process received NDP packets

The following logs are seen:

/var/log/syslog.33.gz:Feb 18 10:33:12.825406 sonic INFO swss#/supervisord: ndppd (error) Failed to set allmulti: No such device

How I did it
Use the wait_for_link script currently used by radv to delay ndppd startup until the vlan interface is ready

How to verify it
Apply the changes to a device. config reload the device and confirm that the above error logs are not observed when ndppd starts. Run the arp/test_arp_dualtor.py::test_proxy_arp test case and verify it passes.

dockers/docker-orchagent/docker-init.sh

@@ -10,9 +10,12 @@ CFGGEN_PARAMS=" \
     -t /usr/share/sonic/templates/ports.json.j2,/etc/swss/config.d/ports.json \
     -t /usr/share/sonic/templates/vlan_vars.j2 \
     -t /usr/share/sonic/templates/ndppd.conf.j2,/etc/ndppd.conf \
+    -t /usr/share/sonic/templates/wait_for_link.sh.j2,/usr/bin/wait_for_link.sh \
 "
 VLAN=$(sonic-cfggen $CFGGEN_PARAMS)
 
+chmod +x /usr/bin/wait_for_link.sh
+
 # Executed HWSKU specific initialization tasks.
 if [ -x /usr/share/sonic/hwsku/hwsku-init ]; then
     /usr/share/sonic/hwsku/hwsku-init

dockers/docker-orchagent/ndppd.conf

@@ -6,4 +6,15 @@ autorestart=unexpected
 stdout_logfile=syslog
 stderr_logfile=syslog
 dependent_startup=true
-dependent_startup_wait_for=vlanmgrd:running
+dependent_startup_wait_for=wait_for_link:exited
+
+[program:wait_for_link]
+command=/usr/bin/wait_for_link.sh
+priority=7
+autostart=false
+autorestart=false
+startsecs=0
+stdout_logfile=syslog
+stderr_logfile=syslog
+dependent_startup=true
+dependent_startup_wait_for=swssconfig:exited

dockers/docker-orchagent/wait_for_link.sh.j2

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+
+VLAN_TABLE_PREFIX="VLAN_TABLE"
+
+function wait_until_iface_ready
+{
+    TABLE_PREFIX=$1
+    IFACE=$2
+
+    echo "Waiting until interface $IFACE is ready..."
+
+    # Wait for the interface to come up
+    # (i.e., interface is present in STATE_DB and state is "ok")
+    while true; do
+        RESULT=$(sonic-db-cli STATE_DB HGET "${TABLE_PREFIX}|${IFACE}" "state" 2> /dev/null)
+        if [ x"$RESULT" == x"ok" ]; then
+            break
+        fi
+
+        sleep 1
+    done
+
+    echo "Interface ${IFACE} is ready!"
+}
+
+
+# Wait for all interfaces to be up and ready
+{% for (name, prefix) in VLAN_INTERFACE|pfx_filter %}
+wait_until_iface_ready ${VLAN_TABLE_PREFIX} {{ name }}
+{% endfor %}