my-cni

#!/bin/bash
config=`cat /dev/stdin`

log="/opt/cni/bin/cni.log"
usage() {
cat << EOF
implement a simple kubernetes cni by shell.
Available CNI_COMMAND env:
  ADD        add a container network
  DEL        delete a container network
  VERSION    show cni version
EOF
}

allocateIP(){
  if [ -f /opt/cni/bin/last_allocated_ip ]; then
    ip=$((`cat /opt/cni/bin/last_allocated_ip`+1))
  else
    ip=2
  fi
  echo ${ip} > /opt/cni/bin/last_allocated_ip
  echo ${ip}
}

add() {
  echo config: "$config" >> "$log"
  podcidr=$(echo $config | jq -r ".podcidr")
  podcidr_gw=$(echo $podcidr | sed "s:0/24:1:g")
  net_number=$(echo $podcidr | sed "s:.0/24:$n:g")
  echo podcidr: "$podcidr" >> "$log"
  echo podcidr_gw: "$podcidr_gw" >> "$log"
  echo net_number: "$net_number" >> "$log"
  # ensure bridge cni0 exist
  ip link add cni0 type bridge > /dev/null 2>&1
  ip link set cni0 up
  ip addr add "$podcidr_gw"/24 dev cni0
  veth_id=$(date +%s%N | md5sum | head -c 6)
  ip link add dev veth_"${veth_id}" type veth peer name veth1_"${veth_id}"
  ip link set dev veth_"${veth_id}" up
  ip link set veth_"${veth_id}" master cni0
  ln -sfT ${CNI_NETNS} /var/run/netns/${CNI_CONTAINERID}
  ip link set veth1_"${veth_id}" netns ${CNI_CONTAINERID}
  ip netns exec ${CNI_CONTAINERID} ip link set veth1_"${veth_id}" name ${CNI_IFNAME}
  ip netns exec ${CNI_CONTAINERID} ip link set dev lo up
  host_number=`allocateIP`
  ip netns exec ${CNI_CONTAINERID} ip addr add "$net_number"."$host_number"/24 dev ${CNI_IFNAME}
  echo "allocate ip "$net_number"."$host_number"" >> "$log"
  ip netns exec ${CNI_CONTAINERID} ip link set dev ${CNI_IFNAME} up 
  # set default gw in container
  ip netns exec ${CNI_CONTAINERID} ip route add default via ${podcidr_gw}
  echo "completed exec cni add: ${CNI_CONTAINERID}" >> "$log"
  ip netns exec $CNI_CONTAINERID ip link show >> "$log"
  mac=$(ip netns exec $CNI_CONTAINERID ip link show ${CNI_IFNAME} | awk '/ether/ {print $2}')
  address="$net_number"."$host_number"/24
  output_template='{
  "cniVersion": "0.3.0",
  "interfaces": [                                            
      {
          "name": "%s",
          "mac": "%s",                            
          "sandbox": "%s" 
      }
  ],
  "ips": [
      {
          "version": "4",
          "address": "%s",
          "gateway": "%s",          
          "interface": 0 
      }
  ]
}'
    
    output=$(printf "${output_template}" $CNI_IFNAME $mac $CNI_NETNS $address $podcidr_gw)
    echo $output >> "$log"
    echo "$output"
}

del() {
  ip netns exec ${CNI_CONTAINERID} ip link del dev ${CNI_IFNAME}
}

version() {
  echo "not implement"
}

case "${CNI_COMMAND}" in
  ADD)
    add
    ;;
  DEL)
    del
    ;;
  VERSION)
    version
    ;;
  *)
    usage
    exit 1
    ;;
esac