Add static CNI plugin

This changes to add 'static' CNI plugin, which provides to assign
IPv4/v6 address statically from given config file. See README.md
for the details.

plugins/ipam/static/main.go

@@ -0,0 +1,142 @@
+// Copyright 2018 CNI authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net"
+
+	"github.com/containernetworking/cni/pkg/skel"
+	"github.com/containernetworking/cni/pkg/types"
+	"github.com/containernetworking/cni/pkg/types/current"
+	"github.com/containernetworking/cni/pkg/version"
+
+	types020 "github.com/containernetworking/cni/pkg/types/020"
+)
+
+// The top-level network config - IPAM plugins are passed the full configuration
+// of the calling plugin, not just the IPAM section.
+type Net struct {
+	Name       string      `json:"name"`
+	CNIVersion string      `json:"cniVersion"`
+	IPAM       *IPAMConfig `json:"ipam"`
+}
+
+type IPAMConfig struct {
+	Name      string
+	Type      string         `json:"type"`
+	Routes    []*types.Route `json:"routes"`
+	Addresses []Address      `json:"addresses"`
+	DNS       types.DNS      `json:"dns"`
+}
+
+type Address struct {
+	AddressStr string `json:"address"`
+	Gateway    net.IP `json:"gateway,omitempty"`
+	Address    net.IPNet
+	Version    string
+}
+
+func main() {
+	skel.PluginMain(cmdAdd, cmdDel, version.All)
+}
+
+// canonicalizeIP makes sure a provided ip is in standard form
+func canonicalizeIP(ip *net.IP) error {
+	if ip.To4() != nil {
+		*ip = ip.To4()
+		return nil
+	} else if ip.To16() != nil {
+		*ip = ip.To16()
+		return nil
+	}
+	return fmt.Errorf("IP %s not v4 nor v6", *ip)
+}
+
+// NewIPAMConfig creates a NetworkConfig from the given network name.
+func LoadIPAMConfig(bytes []byte, envArgs string) (*IPAMConfig, string, error) {
+	n := Net{}
+	if err := json.Unmarshal(bytes, &n); err != nil {
+		return nil, "", err
+	}
+
+	if n.IPAM == nil {
+		return nil, "", fmt.Errorf("IPAM config missing 'ipam' key")
+	}
+
+	// Validate all ranges
+	numV4 := 0
+	numV6 := 0
+	for i := range n.IPAM.Addresses {
+		ip, addr, err := net.ParseCIDR(n.IPAM.Addresses[i].AddressStr)
+		if err != nil {
+			return nil, "", fmt.Errorf("invalid CIDR %s: %s", n.IPAM.Addresses[i].AddressStr, err)
+		}
+		n.IPAM.Addresses[i].Address = *addr
+		n.IPAM.Addresses[i].Address.IP = ip
+
+		if err := canonicalizeIP(&n.IPAM.Addresses[i].Address.IP); err != nil {
+			return nil, "", fmt.Errorf("invalid address %d: %s", i, err)
+		}
+
+		if n.IPAM.Addresses[i].Address.IP.To4() != nil {
+			n.IPAM.Addresses[i].Version = "4"
+			numV4++
+		} else {
+			n.IPAM.Addresses[i].Version = "6"
+			numV6++
+		}
+	}
+
+	// CNI spec 0.2.0 and below supported only one v4 and v6 address
+	if numV4 > 1 || numV6 > 1 {
+		for _, v := range types020.SupportedVersions {
+			if n.CNIVersion == v {
+				return nil, "", fmt.Errorf("CNI version %v does not support more than 1 address per family", n.CNIVersion)
+			}
+		}
+	}
+
+	// Copy net name into IPAM so not to drag Net struct around
+	n.IPAM.Name = n.Name
+
+	return n.IPAM, n.CNIVersion, nil
+}
+
+func cmdAdd(args *skel.CmdArgs) error {
+	ipamConf, confVersion, err := LoadIPAMConfig(args.StdinData, args.Args)
+	if err != nil {
+		return err
+	}
+
+	result := &current.Result{}
+	result.DNS = ipamConf.DNS
+	result.Routes = ipamConf.Routes
+	for _, v := range ipamConf.Addresses {
+		result.IPs = append(result.IPs, &current.IPConfig{
+			Version: v.Version,
+			Address: v.Address,
+			Gateway: v.Gateway})
+	}
+
+	result.Routes = ipamConf.Routes
+	return types.PrintResult(result, confVersion)
+}
+
+func cmdDel(args *skel.CmdArgs) error {
+	// Nothing required because of no resource allocation in static plugin.
+	return nil
+}