Add plugin code

This adds basic plugins.
"main" types: veth, bridge, macvlan
"ipam" type: host-local

The code has been ported over from github.com/coreos/rkt project
and adapted to fit the CNI spec.

plugins/ipam/host-local/allocator.go

@@ -0,0 +1,185 @@
+// Copyright 2015 CoreOS, Inc.
+//
+// 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 (
+	"fmt"
+	"net"
+
+	"github.com/appc/cni/pkg/ip"
+	"github.com/appc/cni/pkg/plugin"
+	"github.com/appc/cni/plugins/ipam/host-local/backend"
+)
+
+type IPAllocator struct {
+	start net.IP
+	end   net.IP
+	conf  *IPAMConfig
+	store backend.Store
+}
+
+func NewIPAllocator(conf *IPAMConfig, store backend.Store) (*IPAllocator, error) {
+	var (
+		start net.IP
+		end   net.IP
+		err   error
+	)
+	start, end, err = networkRange((*net.IPNet)(&conf.Subnet))
+	if err != nil {
+		return nil, err
+	}
+
+	// skip the .0 address
+	start = ip.NextIP(start)
+
+	if conf.RangeStart != nil {
+		if err := validateRangeIP(conf.RangeStart, (*net.IPNet)(&conf.Subnet)); err != nil {
+			return nil, err
+		}
+		start = conf.RangeStart
+	}
+	if conf.RangeEnd != nil {
+		if err := validateRangeIP(conf.RangeEnd, (*net.IPNet)(&conf.Subnet)); err != nil {
+			return nil, err
+		}
+		// RangeEnd is inclusive
+		end = ip.NextIP(conf.RangeEnd)
+	}
+
+	return &IPAllocator{start, end, conf, store}, nil
+}
+
+func validateRangeIP(ip net.IP, ipnet *net.IPNet) error {
+	if !ipnet.Contains(ip) {
+		return fmt.Errorf("%s not in network: %s", ip, ipnet)
+	}
+	return nil
+}
+
+// Returns newly allocated IP along with its config
+func (a *IPAllocator) Get(id string) (*plugin.IPConfig, error) {
+	a.store.Lock()
+	defer a.store.Unlock()
+
+	gw := a.conf.Gateway
+	if gw == nil {
+		gw = ip.NextIP(a.conf.Subnet.IP)
+	}
+
+	for cur := a.start; !cur.Equal(a.end); cur = ip.NextIP(cur) {
+		// don't allocate gateway IP
+		if gw != nil && cur.Equal(gw) {
+			continue
+		}
+
+		reserved, err := a.store.Reserve(id, cur)
+		if err != nil {
+			return nil, err
+		}
+		if reserved {
+			return &plugin.IPConfig{
+				IP:      net.IPNet{cur, a.conf.Subnet.Mask},
+				Gateway: gw,
+				Routes:  a.conf.Routes,
+			}, nil
+		}
+	}
+
+	return nil, fmt.Errorf("no IP addresses available in network: %s", a.conf.Name)
+}
+
+// Allocates both an IP and the Gateway IP, i.e. a /31
+// This is used for Point-to-Point links
+func (a *IPAllocator) GetPtP(id string) (*plugin.IPConfig, error) {
+	a.store.Lock()
+	defer a.store.Unlock()
+
+	for cur := a.start; !cur.Equal(a.end); cur = ip.NextIP(cur) {
+		// we're looking for unreserved even, odd pair
+		if !evenIP(cur) {
+			continue
+		}
+
+		gw := cur
+		reserved, err := a.store.Reserve(id, gw)
+		if err != nil {
+			return nil, err
+		}
+		if reserved {
+			cur = ip.NextIP(cur)
+			if cur.Equal(a.end) {
+				break
+			}
+
+			reserved, err := a.store.Reserve(id, cur)
+			if err != nil {
+				return nil, err
+			}
+			if reserved {
+				// found them both!
+				_, bits := a.conf.Subnet.Mask.Size()
+				mask := net.CIDRMask(bits-1, bits)
+
+				return &plugin.IPConfig{
+					IP:      net.IPNet{cur, mask},
+					Gateway: gw,
+					Routes:  a.conf.Routes,
+				}, nil
+			}
+		}
+	}
+
+	return nil, fmt.Errorf("no ip addresses available in network: %s", a.conf.Name)
+}
+
+// Releases all IPs allocated for the container with given ID
+func (a *IPAllocator) Release(id string) error {
+	a.store.Lock()
+	defer a.store.Unlock()
+
+	return a.store.ReleaseByID(id)
+}
+
+func networkRange(ipnet *net.IPNet) (net.IP, net.IP, error) {
+	ip := ipnet.IP.To4()
+	if ip == nil {
+		ip = ipnet.IP.To16()
+		if ip == nil {
+			return nil, nil, fmt.Errorf("IP not v4 nor v6")
+		}
+	}
+
+	if len(ip) != len(ipnet.Mask) {
+		return nil, nil, fmt.Errorf("IPNet IP and Mask version mismatch")
+	}
+
+	var end net.IP
+	for i := 0; i < len(ip); i++ {
+		end = append(end, ip[i]|^ipnet.Mask[i])
+	}
+	return ipnet.IP, end, nil
+}
+
+func evenIP(ip net.IP) bool {
+	i := ip.To4()
+	if i == nil {
+		i = ip.To16()
+		if i == nil {
+			panic("IP is not v4 or v6")
+		}
+	}
+
+	return i[len(i)-1]%2 == 0
+}