105 lines
2.5 KiB
Go
105 lines
2.5 KiB
Go
package net
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import (
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"context"
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"fmt"
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"log"
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"math/rand"
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"net"
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"strconv"
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"time"
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"github.com/hashicorp/packer/common/filelock"
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"github.com/hashicorp/packer/common/retry"
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"github.com/hashicorp/packer/packer"
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)
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var _ net.Listener = &Listener{}
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// Listener wraps a net.Lister with some magic packer capabilies. For example
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// until you call Listener.Close, any call to ListenRangeConfig.Listen cannot
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// bind to Port. Packer tries tells moving parts which port they can use, but
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// often the port has to be released before a 3rd party is started, like a VNC
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// server.
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type Listener struct {
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// Listener can be closed but Port will be file locked by packer until
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// Close is called.
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net.Listener
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Port int
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Address string
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lock *filelock.Flock
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}
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func (l *Listener) Close() error {
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err := l.lock.Unlock()
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if err != nil {
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log.Printf("cannot unlock lockfile %#v: %v", l, err)
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}
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return l.Listener.Close()
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}
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// ListenRangeConfig contains options for listening to a free address [Min,Max)
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// range. ListenRangeConfig wraps a net.ListenConfig.
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type ListenRangeConfig struct {
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// like "tcp" or "udp". defaults to "tcp".
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Network string
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Addr string
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Min, Max int
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net.ListenConfig
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}
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// Listen tries to Listen to a random open TCP port in the [min, max) range
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// until ctx is cancelled.
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// Listen uses net.ListenConfig.Listen internally.
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func (lc ListenRangeConfig) Listen(ctx context.Context) (*Listener, error) {
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if lc.Network == "" {
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lc.Network = "tcp"
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}
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portRange := lc.Max - lc.Min
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var listener *Listener
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err := retry.Config{
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RetryDelay: func() time.Duration { return 20 * time.Millisecond },
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}.Run(ctx, func(context.Context) error {
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port := lc.Min
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if portRange > 0 {
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port += rand.Intn(portRange)
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}
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lockFilePath, err := packer.CachePath("port", strconv.Itoa(port))
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if err != nil {
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return err
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}
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lock := filelock.New(lockFilePath)
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locked, err := lock.TryLock()
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if err != nil {
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return err
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}
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if !locked {
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return fmt.Errorf("Port %d is file locked", port)
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}
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log.Printf("Trying port: %d", port)
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l, err := lc.ListenConfig.Listen(ctx, lc.Network, fmt.Sprintf("%s:%d", lc.Addr, port))
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if err != nil {
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if err := lock.Unlock(); err != nil {
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log.Fatalf("Could not unlock file lock for port %d: %v", port, err)
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}
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return fmt.Errorf("Port %d cannot be opened: %v", port, err)
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}
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log.Printf("Found available port: %d on IP: %s", port, lc.Addr)
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listener = &Listener{
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Address: lc.Addr,
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Port: port,
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Listener: l,
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lock: lock,
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}
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return nil
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})
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return listener, err
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}
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