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.

ARP_UPDATE_VARS_FILE="/usr/share/sonic/templates/arp_update_vars.j2"

while /bin/true; do
  # find L3 interfaces which are UP, send ipv6 multicast pings
  ARP_UPDATE_VARS=$(sonic-cfggen -d -t ${ARP_UPDATE_VARS_FILE})
  SWITCH_TYPE=$(echo $ARP_UPDATE_VARS | jq -r '.switch_type')
  if [[ "$SWITCH_TYPE" == "chassis-packet" ]]; then
      STATIC_ROUTE_NEXTHOPS=$(echo $ARP_UPDATE_VARS | jq -r '.static_route_nexthops')
      # on supervisor/rp exit the script gracefully
      if [[ -z "$STATIC_ROUTE_NEXTHOPS" ]]; then
          logger "arp_update: exiting as no static route in packet based chassis"
          exit 0
      fi
      for nexthop in $STATIC_ROUTE_NEXTHOPS; do
          if [[ $nexthop == *"."* ]]; then
              neigh_state=( $(ip -4 neigh show | grep $nexthop | tr -s ' ' | cut -d ' ' -f 3,4) )
              ping_prefix=ping
          elif [[ $nexthop == *":"* ]] ; then
              neigh_state=( $(ip -6 neigh show | grep $nexthop | tr -s ' ' | cut -d ' ' -f 3,4) )
              ping_prefix=ping6
          fi
       
          if [[ "${neigh_state[1]}" == "INCOMPLETE" ]] || [[ "${neigh_state[1]}" == "FAILED" ]]; then
              pingcmd="timeout 0.2 $ping_prefix -I ${neigh_state[0]} -n -q -i 0 -c 1 -W 1 $nexthop >/dev/null"
              eval $pingcmd
              logger "arp_update: sttaic route nexthop not resolved, pinging $nexthop on ${neigh_state[0]}"
          fi
      done

      sleep 300
      continue
  fi
  # find L3 interfaces which are UP, send ipv6 multicast pings
  INTERFACE=$(echo $ARP_UPDATE_VARS | jq -r '.interface')
  PC_INTERFACE=$(echo $ARP_UPDATE_VARS | jq -r '.pc_interface')
  VLAN_SUB_INTERFACE=$(echo $ARP_UPDATE_VARS | jq -r '.vlan_sub_interface')

  ALL_INTERFACE="$INTERFACE $PC_INTERFACE $VLAN_SUB_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=$(echo $ARP_UPDATE_VARS | jq -r '.vlan')
  SUBTYPE=$(sonic-db-cli CONFIG_DB hget 'DEVICE_METADATA|localhost' 'subtype' | tr '[:upper:]' '[:lower:]')
  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="timeout 1 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`
 
      if [[ $SUBTYPE == "dualtor" ]]; then
        # on dual ToR devices, try to resolve failed neighbor entries since
        # these entries will have tunnel routes installed, preventing normal 
        # neighbor resolution (SWSS PR #2137)

        # since ndisc6 is a userland process, the above ndisc6 commands are 
        # insufficient to update the kernel neighbor table for failed entries

        # we don't need to do this for ipv4 neighbors since arping is able to
        # update the kernel neighbor table

        # generates the following command for each failed or incomplete IPv6 neighbor
        # timeout 0.2 ping <neighbor IPv6> -n -q -i 0 -c 1 -W 1 -I <VLAN name> >/dev/null
        ping6_template="sed -e 's/^/timeout 0.2 ping /' -e 's/,/ -n -q -i 0 -c 1 -W 1 -I /' -e 's/$/ >\/dev\/null;/'"
        failed_ip6_neigh_cmd="ip -6 neigh show | grep -v fe80 | grep $vlan | grep -E 'FAILED|INCOMPLETE' | cut -d ' ' -f 1,3 --output-delimiter=',' | $ping6_template"
        eval `eval $failed_ip6_neigh_cmd`
      fi
  done
  

  # sleep here before handling the mismatch as it is not required during startup
  sleep 300

  # refresh neighbor entries from APP_DB in case of mismatch with kernel
  DBNEIGH=$(sonic-db-cli APPL_DB keys NEIGH_TABLE*)
  KERNEIGH4=$(ip -4 neigh show | grep Vlan | cut -d ' ' -f 1,3  --output-delimiter=',')
  KERNEIGH6=$(ip -6 neigh show | grep -v fe80 | grep Vlan | cut -d ' ' -f 1,3  --output-delimiter=',')
  for neigh in $DBNEIGH; do
      intf="$( cut -d ':' -f 2 <<< "$neigh" )"
      ip="$( cut -d ':' -f 3- <<< "$neigh" )"
      if [[ $intf == *"Vlan"* ]]; then
          if [[ $ip == *"."* ]] && [[ ! $KERNEIGH4 =~ "${ip},${intf}" ]]; then
              pingcmd="timeout 0.2 ping -I $intf -n -q -i 0 -c 1 -W 1 $ip >/dev/null"
              eval $pingcmd
              logger "arp_update: mismatch arp entry, pinging ${ip} on ${intf}"
          elif [[ $ip == *":"* ]] && [[ ! $KERNEIGH6 =~ "${ip},${intf}" ]]; then
              ping6cmd="timeout 0.2 ping6 -I $intf -n -q -i 0 -c 1 -W 1 $ip >/dev/null"
              eval $ping6cmd
              logger "arp_update: mismatch v6 nbr entry, pinging ${ip} on ${intf}"
          fi
      fi
  done

done