62 lines
2.2 KiB
Go
62 lines
2.2 KiB
Go
package natpmp
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import (
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"context"
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"encoding/binary"
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"errors"
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"fmt"
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"net/netip"
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"time"
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)
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var (
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ErrNetworkProtocolUnknown = errors.New("network protocol is unknown")
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ErrLifetimeTooLong = errors.New("lifetime is too long")
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)
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// Add or delete a port mapping. To delete a mapping, set both the
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// requestedExternalPort and lifetime to 0.
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// See https://www.ietf.org/rfc/rfc6886.html#section-3.3
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func (c *Client) AddPortMapping(ctx context.Context, gateway netip.Addr,
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protocol string, internalPort, requestedExternalPort uint16,
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lifetime time.Duration) (durationSinceStartOfEpoch time.Duration,
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assignedInternalPort, assignedExternalPort uint16, assignedLifetime time.Duration,
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err error,
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) {
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lifetimeSecondsFloat := lifetime.Seconds()
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const maxLifetimeSeconds = uint64(^uint32(0))
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if uint64(lifetimeSecondsFloat) > maxLifetimeSeconds {
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return 0, 0, 0, 0, fmt.Errorf("%w: %d seconds must at most %d seconds",
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ErrLifetimeTooLong, uint64(lifetimeSecondsFloat), maxLifetimeSeconds)
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}
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const messageSize = 12
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message := make([]byte, messageSize)
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message[0] = 0 // Version 0
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switch protocol {
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case "udp":
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message[1] = 1 // operationCode 1
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case "tcp":
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message[1] = 2 // operationCode 2
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default:
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return 0, 0, 0, 0, fmt.Errorf("%w: %s", ErrNetworkProtocolUnknown, protocol)
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}
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// [2:3] are reserved.
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binary.BigEndian.PutUint16(message[4:6], internalPort)
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binary.BigEndian.PutUint16(message[6:8], requestedExternalPort)
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binary.BigEndian.PutUint32(message[8:12], uint32(lifetimeSecondsFloat))
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const responseSize = 16
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response, err := c.rpc(ctx, gateway, message, responseSize)
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if err != nil {
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return 0, 0, 0, 0, fmt.Errorf("executing remote procedure call: %w", err)
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}
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secondsSinceStartOfEpoch := binary.BigEndian.Uint32(response[4:8])
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durationSinceStartOfEpoch = time.Duration(secondsSinceStartOfEpoch) * time.Second
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assignedInternalPort = binary.BigEndian.Uint16(response[8:10])
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assignedExternalPort = binary.BigEndian.Uint16(response[10:12])
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lifetimeInSeconds := binary.BigEndian.Uint32(response[12:16])
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assignedLifetime = time.Duration(lifetimeInSeconds) * time.Second
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return durationSinceStartOfEpoch, assignedInternalPort, assignedExternalPort, assignedLifetime, nil
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}
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