90 lines
1.8 KiB
Go
90 lines
1.8 KiB
Go
package natpmp
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import (
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"fmt"
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"net"
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"time"
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)
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const nAT_PMP_PORT = 5351
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const nAT_TRIES = 9
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const nAT_INITIAL_MS = 250
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// A caller that implements the NAT-PMP RPC protocol.
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type network struct {
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gateway net.IP
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}
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func (n *network) call(msg []byte, timeout time.Duration) (result []byte, err error) {
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var server net.UDPAddr
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server.IP = n.gateway
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server.Port = nAT_PMP_PORT
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conn, err := net.DialUDP("udp", nil, &server)
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if err != nil {
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return
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}
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defer conn.Close()
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// 16 bytes is the maximum result size.
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result = make([]byte, 16)
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var finalTimeout time.Time
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if timeout != 0 {
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finalTimeout = time.Now().Add(timeout)
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}
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needNewDeadline := true
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var tries uint
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for tries = 0; (tries < nAT_TRIES && finalTimeout.IsZero()) || time.Now().Before(finalTimeout); {
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if needNewDeadline {
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nextDeadline := time.Now().Add((nAT_INITIAL_MS << tries) * time.Millisecond)
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err = conn.SetDeadline(minTime(nextDeadline, finalTimeout))
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if err != nil {
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return
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}
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needNewDeadline = false
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}
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_, err = conn.Write(msg)
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if err != nil {
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return
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}
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var bytesRead int
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var remoteAddr *net.UDPAddr
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bytesRead, remoteAddr, err = conn.ReadFromUDP(result)
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if err != nil {
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if err.(net.Error).Timeout() {
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tries++
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needNewDeadline = true
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continue
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}
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return
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}
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if !remoteAddr.IP.Equal(n.gateway) {
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// Ignore this packet.
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// Continue without increasing retransmission timeout or deadline.
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continue
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}
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// Trim result to actual number of bytes received
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if bytesRead < len(result) {
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result = result[:bytesRead]
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}
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return
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}
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err = fmt.Errorf("Timed out trying to contact gateway")
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return
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}
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func minTime(a, b time.Time) time.Time {
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if a.IsZero() {
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return b
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}
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if b.IsZero() {
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return a
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}
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if a.Before(b) {
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return a
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}
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return b
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}
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