65 lines
1.2 KiB
Go
65 lines
1.2 KiB
Go
// Copyright (C) 2019 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this file,
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// You can obtain one at https://mozilla.org/MPL/2.0/.
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package stun
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import (
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"bytes"
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"net"
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"sync"
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"time"
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)
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const (
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stunFilterPriority = 10
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otherDataPriority = 100
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)
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type stunFilter struct {
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ids map[string]time.Time
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mut sync.Mutex
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}
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func (f *stunFilter) Outgoing(out []byte, _ net.Addr) {
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if !f.isStunPayload(out) {
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panic("not a stun payload")
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}
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f.mut.Lock()
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f.ids[string(out[8:20])] = time.Now().Add(time.Minute)
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f.reap()
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f.mut.Unlock()
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}
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func (f *stunFilter) ClaimIncoming(in []byte, _ net.Addr) bool {
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if f.isStunPayload(in) {
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f.mut.Lock()
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_, ok := f.ids[string(in[8:20])]
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f.reap()
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f.mut.Unlock()
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return ok
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}
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return false
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}
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func (f *stunFilter) isStunPayload(data []byte) bool {
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// Need at least 20 bytes
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if len(data) < 20 {
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return false
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}
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// First two bits always unset, and should always send magic cookie.
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return data[0]&0xc0 == 0 && bytes.Equal(data[4:8], []byte{0x21, 0x12, 0xA4, 0x42})
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}
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func (f *stunFilter) reap() {
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now := time.Now()
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for id, timeout := range f.ids {
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if timeout.Before(now) {
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delete(f.ids, id)
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}
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}
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}
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