sonic-buildimage/files/scripts/arp_update

#!/bin/bash
#
# usage:
# arp_update:
# Send ipv6 multicast pings to all "UP" L3 interfaces including vlan interfaces to
# refresh link-local addresses from neighbors.
# Send gratuitous ARP/NDP requests to VLAN member neighbors to refresh
# the ipv4/ipv6 neighbors state.

while /bin/true; do
  # find L3 interfaces which are UP, send ipv6 multicast pings
  echo "{% for (name, prefix) in INTERFACE|pfx_filter %} {{name}} {% endfor %}" > /tmp/intf_tmp.j2
  INTERFACE=`sonic-cfggen -d -t /tmp/intf_tmp.j2`
  echo "{% for (name, prefix) in PORTCHANNEL_INTERFACE|pfx_filter %} {{name}} {% endfor %}" > /tmp/pc_intf_tmp.j2
  PC_INTERFACE=`sonic-cfggen -d -t /tmp/pc_intf_tmp.j2`

  ALL_INTERFACE="$INTERFACE $PC_INTERFACE"
  for intf in $ALL_INTERFACE; do
      ping6cmd="ping6 -I $intf -n -q -i 0 -c 1 -W 0 ff02::1 >/dev/null"
      intf_up=$(ip link show $intf | grep "state UP")
      if [[ -n "$intf_up" ]]; then
          eval $ping6cmd
      fi
  done

  VLAN=`sonic-cfggen -d -v 'VLAN.keys() | join(" ") if VLAN'`
  for vlan in $VLAN; do
      # generate a list of arping commands:
      #   arping -q -w 0 -c 1 -i <VLAN interface> <IP 1>;
      #   arping -q -w 0 -c 1 -i <VLAN interface> <IP 2>;
      #   ...
      arpingcmd="sed -e 's/ / -i /' -e 's/^/arping -q -w 0 -c 1 /' -e 's/$/;/'"
      ipcmd="ip -4 neigh show | grep $vlan | cut -d ' ' -f 1,3 | $arpingcmd"

      eval `eval $ipcmd`

      # send ipv6 multicast pings to Vlan interfaces to get/refresh link-local addrs
      ping6cmd="ping6 -I $vlan -n -q -i 0 -c 1 -W 0 ff02::1 >/dev/null"
      eval $ping6cmd

      # generate a list of ndisc6 commands (exclude link-local addrs since it is done above):
      #   ndisc6 -q -w 0 -1 <IP 1> <VLAN interface>;
      #   ndisc6 -q -w 0 -1 <IP 2> <VLAN interface>;
      #   ...
      ndisc6cmd="sed -e 's/^/ndisc6 -q -w 0 -1 /' -e 's/$/;/'"
      ip6cmd="ip -6 neigh show | grep -v fe80 | grep $vlan | cut -d ' ' -f 1,3 | $ndisc6cmd"
      eval `eval $ip6cmd`
  done
  sleep 300
done