package testutil
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import (
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"container/list"
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"fmt"
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"net"
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"os"
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"sync"
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"time"
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)
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var (
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bindLock sync.Mutex
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freeIPs *list.List
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condNotEmpty *sync.Cond
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)
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const bindLockPort = 10101
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func init() {
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freeIPs = list.New()
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condNotEmpty = sync.NewCond(&bindLock)
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for octet := byte(10); octet < 255; octet++ {
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result := net.IPv4(127, 0, 0, octet)
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freeIPs.PushBack(result)
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}
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}
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func returnIP(ip net.IP) {
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bindLock.Lock()
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defer bindLock.Unlock()
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freeIPs.PushBack(ip)
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condNotEmpty.Broadcast()
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}
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func getBindAddr() net.IP {
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bindLock.Lock()
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defer bindLock.Unlock()
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for freeIPs.Len() == 0 {
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condNotEmpty.Wait()
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}
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elem := freeIPs.Front()
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freeIPs.Remove(elem)
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result := elem.Value.(net.IP)
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return result
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}
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func TakeIP() (ip net.IP, returnFn func()) {
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for attempts := 0; ; attempts++ {
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ip = getBindAddr()
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addr := &net.TCPAddr{IP: ip, Port: bindLockPort}
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ln, err := net.ListenTCP("tcp4", addr)
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if err != nil {
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returnIP(ip)
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continue
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}
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if attempts > 3 {
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logf("took %s after %d attempts", ip, attempts)
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}
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return ip, func() {
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ln.Close()
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time.Sleep(50 * time.Millisecond) // let the kernel cool down
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returnIP(ip)
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}
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}
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}
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func logf(format string, a ...interface{}) {
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fmt.Fprintf(os.Stdout, "testutil: "+format+"\n", a...)
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}
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