Added new userspace proxy mode specifically for Windows.

pkg/proxy/winuserspace/port_allocator.go

@@ -0,0 +1,153 @@
+/*
+Copyright 2015 The Kubernetes 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 winuserspace
+
+import (
+	"errors"
+	"math/big"
+	"math/rand"
+	"sync"
+	"time"
+
+	"k8s.io/kubernetes/pkg/util/net"
+	"k8s.io/kubernetes/pkg/util/wait"
+)
+
+var (
+	errPortRangeNoPortsRemaining = errors.New("port allocation failed; there are no remaining ports left to allocate in the accepted range")
+)
+
+type PortAllocator interface {
+	AllocateNext() (int, error)
+	Release(int)
+}
+
+// randomAllocator is a PortAllocator implementation that allocates random ports, yielding
+// a port value of 0 for every call to AllocateNext().
+type randomAllocator struct{}
+
+// AllocateNext always returns 0
+func (r *randomAllocator) AllocateNext() (int, error) {
+	return 0, nil
+}
+
+// Release is a noop
+func (r *randomAllocator) Release(_ int) {
+	// noop
+}
+
+// newPortAllocator builds PortAllocator for a given PortRange. If the PortRange is empty
+// then a random port allocator is returned; otherwise, a new range-based allocator
+// is returned.
+func newPortAllocator(r net.PortRange) PortAllocator {
+	if r.Base == 0 {
+		return &randomAllocator{}
+	}
+	return newPortRangeAllocator(r)
+}
+
+const (
+	portsBufSize         = 16
+	nextFreePortCooldown = 500 * time.Millisecond
+	allocateNextTimeout  = 1 * time.Second
+)
+
+type rangeAllocator struct {
+	net.PortRange
+	ports chan int
+	used  big.Int
+	lock  sync.Mutex
+	rand  *rand.Rand
+}
+
+func newPortRangeAllocator(r net.PortRange) PortAllocator {
+	if r.Base == 0 || r.Size == 0 {
+		panic("illegal argument: may not specify an empty port range")
+	}
+	ra := &rangeAllocator{
+		PortRange: r,
+		ports:     make(chan int, portsBufSize),
+		rand:      rand.New(rand.NewSource(time.Now().UnixNano())),
+	}
+	go wait.Until(func() { ra.fillPorts(wait.NeverStop) }, nextFreePortCooldown, wait.NeverStop)
+	return ra
+}
+
+// fillPorts loops, always searching for the next free port and, if found, fills the ports buffer with it.
+// this func blocks until either there are no remaining free ports, or else the stopCh chan is closed.
+func (r *rangeAllocator) fillPorts(stopCh <-chan struct{}) {
+	for {
+		port := r.nextFreePort()
+		if port == -1 {
+			return
+		}
+		select {
+		case <-stopCh:
+			return
+		case r.ports <- port:
+		}
+	}
+}
+
+// nextFreePort finds a free port, first picking a random port. if that port is already in use
+// then the port range is scanned sequentially until either a port is found or the scan completes
+// unsuccessfully. an unsuccessful scan returns a port of -1.
+func (r *rangeAllocator) nextFreePort() int {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+
+	// choose random port
+	j := r.rand.Intn(r.Size)
+	if b := r.used.Bit(j); b == 0 {
+		r.used.SetBit(&r.used, j, 1)
+		return j + r.Base
+	}
+
+	// search sequentially
+	for i := j + 1; i < r.Size; i++ {
+		if b := r.used.Bit(i); b == 0 {
+			r.used.SetBit(&r.used, i, 1)
+			return i + r.Base
+		}
+	}
+	for i := 0; i < j; i++ {
+		if b := r.used.Bit(i); b == 0 {
+			r.used.SetBit(&r.used, i, 1)
+			return i + r.Base
+		}
+	}
+	return -1
+}
+
+func (r *rangeAllocator) AllocateNext() (port int, err error) {
+	select {
+	case port = <-r.ports:
+	case <-time.After(allocateNextTimeout):
+		err = errPortRangeNoPortsRemaining
+	}
+	return
+}
+
+func (r *rangeAllocator) Release(port int) {
+	port -= r.Base
+	if port < 0 || port >= r.Size {
+		return
+	}
+	r.lock.Lock()
+	defer r.lock.Unlock()
+	r.used.SetBit(&r.used, port, 0)
+}