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
      # Get array of Nexthops and ifnames. Nexthops and ifnames are mapped one to one
      STATIC_ROUTE_NEXTHOPS=($(echo $ARP_UPDATE_VARS | jq -r '.static_route_nexthops'))
      STATIC_ROUTE_IFNAMES=($(echo $ARP_UPDATE_VARS | jq -r '.static_route_ifnames'))
      # on supervisor/rp exit the script gracefully
      if [[ -z "$STATIC_ROUTE_NEXTHOPS" ]] || [[ -z "$STATIC_ROUTE_IFNAMES" ]]; then
          logger "arp_update: exiting as no static route in packet based chassis"
          exit 0
      fi
      for i in ${!STATIC_ROUTE_NEXTHOPS[@]}; do
          nexthop="${STATIC_ROUTE_NEXTHOPS[i]}"
          if [[ $nexthop == *"."* ]]; then
              neigh_state=$(ip -4 neigh show | grep -w $nexthop | tr -s ' ')
              ping_prefix=ping
          elif [[ $nexthop == *":"* ]] ; then
              neigh_state=$(ip -6 neigh show | grep -w $nexthop | tr -s ' ')
              ping_prefix=ping6
          fi
          # Check if there is an INCOMPLETE, FAILED, or STALE entry and try to resolve it again.
          # STALE entries may be present if there is no traffic on a path. A far-end down event may not
          # clear the STALE entry. Refresh the STALE entry to clear the table.
          if [[ -z "${neigh_state}" ]] || [[ -n $(echo ${neigh_state} | grep 'INCOMPLETE\|FAILED\|STALE') ]]; then
              interface="${STATIC_ROUTE_IFNAMES[i]}"
              if [[ -z "$interface" ]]; then
                  # should never be here, handling just in case
                  logger "ERR: arp_update: missing interface entry for static route $nexthop"
                  continue
              fi
              intf_up=$(ip link show $interface | grep "state UP")
              if [[ -n "$intf_up" ]]; then
                  pingcmd="timeout 0.2 $ping_prefix -I ${interface} -n -q -i 0 -c 1 -W 1 $nexthop >/dev/null"
                  eval $pingcmd
                  # STALE entries may appear more often, not logging to prevent periodic syslogs
                  if [[ -z $(echo ${neigh_state} | grep 'STALE') ]]; then
                      logger "arp_update: static route nexthop not resolved ($neigh_state), pinging $nexthop on $interface"
                  fi
              fi
          fi
      done

      sleep 150
      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 [[ $SUBTYPE == "dualtor" ]]; then
        # capture all current failed/incomplete IPv6 neighbors in the kernel to avoid situations where new neighbors are learned
        # in the middle of the below sequence of commands
        unresolved_kernel_neighbors=$(ip -6 neigh show | grep -v fe80 | grep $vlan | grep -E 'FAILED|INCOMPLETE')
        failed_kernel_neighbors=$(echo "$unresolved_kernel_neighbors" | grep FAILED | cut -d ' ' -f 1)

        # it's possible for kernel neighbors to fall out of sync with the hardware
        # this can result in failed neighbors entries that don't have corresponding zero MAC neighbor entries
        # and therefore don't have tunnel routes installed in the hardware
        # flush these neighbors from the kernel to force relearning and resync them to the hardware:
        # 1. for every FAILED or INCOMPLETE neighbor in the kernel, check if there is a corresponding zero MAC neighbor in APPL_DB
        # 2. if no zero MAC neighbor entry exists, flush the kernel neighbor entry
        #     - generates the command 'ip neigh flush <neighbor IPv6>' for all such neighbors
        unsync_neighbors=$(echo "$unresolved_kernel_neighbors" | cut -d ' ' -f 1 | xargs -I{} bash -c "if [[ -z \"\$(sonic-db-cli APPL_DB hget NEIGH_TABLE:$vlan:{} neigh)\" ]]; then echo '{}'; fi")
        if [[ ! -z "$unsync_neighbors" ]]; then
            ip_neigh_flush_cmd="echo \"$unsync_neighbors\" | sed -e 's/^/ip neigh flush /' -e 's/$/;/'"
            eval `eval "$ip_neigh_flush_cmd"`
            sleep 2
        fi

        # 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
        if [[ ! -z "$unresolved_kernel_neighbors" ]]; then
            ping6_template="sed -e 's/^/timeout 0.2 ping /' -e 's/,/ -n -q -i 0 -c 1 -W 1 -I /' -e 's/$/ >\/dev\/null;/'"
            failed_ip6_neigh_cmd="echo \"$unresolved_kernel_neighbors\" | cut -d ' ' -f 1,3 --output-delimiter=',' | $ping6_template"
            eval `eval "$failed_ip6_neigh_cmd"`
            # allow some time for any transient INCOMPLETE neighbors to transition to FAILED
            sleep 5
        fi

        # manually set any remaining FAILED entries to permanently INCOMPLETE
        # once these entries are INCOMPLETE, any subsequent neighbor advertisement messages are able to resolve the entry
        # ignore INCOMPLETE neighbors since if they are transiently incomplete (i.e. new kernel neighbors that we are attempting to resolve for the first time),
        # setting them to permanently incomplete here means the kernel will never generate a netlink message for that neighbor
        # generates the following command for each FAILED IPv6 neighbor
        # ip neigh replace <neighbor IPv6> dev <VLAN name> nud incomplete
        failed_kernel_neighbors=$(ip -6 neigh show | grep -v fe80 | grep $vlan | grep -E 'FAILED')
        if [[ ! -z "$failed_kernel_neighbors" ]]; then
            neigh_replace_template="sed -e 's/^/ip neigh replace /' -e 's/,/ dev /' -e 's/$/ nud incomplete;/'" 
            ip_neigh_replace_cmd="echo \"$failed_kernel_neighbors\" | cut -d ' ' -f 1,3 --output-delimiter=',' | $neigh_replace_template"
            eval `eval "$ip_neigh_replace_cmd"`
        fi
      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*)

  # resolve neighbor entries from CONFIG_DB in case of mismatch with kernel
  DBNEIGH="$DBNEIGH $(sonic-db-cli CONFIG_DB keys NEIGH* | sed -e 's/|/:/g')"

  KERNEIGH4=$(ip -4 neigh show | grep Vlan | grep -v 'FAILED\|INCOMPLETE' | cut -d ' ' -f 1,3  --output-delimiter=',')
  KERNEIGH6=$(ip -6 neigh show | grep -v fe80 | grep Vlan | grep -v 'FAILED\|INCOMPLETE' | 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