Refactor AARP
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SHA256:zZji7w1Ilh2RuUpbQcqkLPrqmRwpiCSycbF2EfKm6Kw
4 changed files with 260 additions and 132 deletions
226
aarp.go
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226
aarp.go
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@ -0,0 +1,226 @@
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package main
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import (
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"context"
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"log"
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"math/rand/v2"
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"sync"
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"time"
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"github.com/google/gopacket/pcap"
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"github.com/sfiera/multitalk/pkg/aarp"
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"github.com/sfiera/multitalk/pkg/ddp"
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"github.com/sfiera/multitalk/pkg/ethernet"
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"github.com/sfiera/multitalk/pkg/ethertalk"
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)
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// TODO: verify this parameter
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const maxAMTEntryAge = 30 * time.Second
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// AARPMachine maintains both an Address Mapping Table and handles AARP packets
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// (sending and receiving requests, responses, and probes). This process assumes
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// a particular network range rather than using the startup range, since this
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// program is a seed router.
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type AARPMachine struct {
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*AMT
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cfg *config
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pcapHandle *pcap.Handle
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state aarpState
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probes int
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myHWAddr ethernet.Addr
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myDDPAddr ddp.Addr
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}
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type aarpState int
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const (
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aarpStateProbing aarpState = iota
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aarpStateAssigned
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)
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func (a *AARPMachine) Run(ctx context.Context, incomingCh <-chan *ethertalk.Packet) error {
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ticker := time.NewTicker(200 * time.Millisecond) // 200ms is the AARP probe retransmit
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defer ticker.Stop()
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a.state = aarpStateProbing
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a.probes = 0
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// Initialise our DDP address with a preferred address (first network.1)
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a.myDDPAddr = ddp.Addr{
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Network: ddp.Network(a.cfg.EtherTalk.NetStart),
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Node: 1,
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}
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for {
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select {
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case <-ctx.Done():
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return ctx.Err()
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case <-ticker.C:
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switch a.state {
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case aarpStateAssigned:
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// No need to keep the ticker running if assigned
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ticker.Stop()
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case aarpStateProbing:
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if a.probes >= 10 {
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a.state = aarpStateAssigned
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continue
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}
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a.probes++
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if err := a.probe(); err != nil {
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log.Printf("Couldn't broadcast a Probe: %v", err)
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continue
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}
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}
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case ethFrame, ok := <-incomingCh:
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if !ok {
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incomingCh = nil
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}
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var aapkt aarp.Packet
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if err := aarp.Unmarshal(ethFrame.Payload, &aapkt); err != nil {
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log.Printf("Couldn't unmarshal AARP packet: %v", err)
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continue
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}
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switch aapkt.Opcode {
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case aarp.RequestOp:
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log.Printf("AARP: Who has %v? Tell %v", aapkt.Dst.Proto, aapkt.Src.Proto)
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// Glean that aapkt.Src.Proto -> aapkt.Src.Hardware
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a.AMT.Learn(aapkt.Src.Proto, aapkt.Src.Hardware)
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log.Printf("AARP: Gleaned that %v -> %v", aapkt.Src.Proto, aapkt.Src.Hardware)
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if aapkt.Dst.Proto != a.myDDPAddr {
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continue
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}
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if a.state != aarpStateAssigned {
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continue
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}
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// Hey that's me! Let them know!
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if err := a.heyThatsMe(aapkt.Src); err != nil {
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log.Printf("AARP: Couldn't respond to Request: %v", err)
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continue
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}
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case aarp.ResponseOp:
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log.Printf("AARP: %v is at %v", aapkt.Dst.Proto, aapkt.Dst.Hardware)
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a.AMT.Learn(aapkt.Dst.Proto, aapkt.Dst.Hardware)
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if aapkt.Dst.Proto != a.myDDPAddr {
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continue
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}
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if a.state == aarpStateProbing {
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a.reroll()
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}
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case aarp.ProbeOp:
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log.Printf("AARP: %v probing to see if %v is available", aapkt.Src.Hardware, aapkt.Src.Proto)
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// AMT should not be updated, because the address is tentative
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if aapkt.Dst.Proto != a.myDDPAddr {
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continue
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}
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switch a.state {
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case aarpStateProbing:
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// Another node is probing for the same address! Unlucky
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a.reroll()
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case aarpStateAssigned:
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if err := a.heyThatsMe(aapkt.Src); err != nil {
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log.Printf("AARP: Couldn't respond to Probe: %v", err)
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continue
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}
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}
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}
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}
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}
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}
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// Re-roll a local address
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func (a *AARPMachine) reroll() {
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if a.cfg.EtherTalk.NetStart != a.cfg.EtherTalk.NetEnd {
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// Pick a new network number at random
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a.myDDPAddr.Network = rand.N[ddp.Network](
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a.cfg.EtherTalk.NetEnd-a.cfg.EtherTalk.NetStart+1,
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) + a.cfg.EtherTalk.NetStart
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}
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// Can't use: 0x00, 0xff, 0xfe, or the existing node number
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newNode := rand.N[ddp.Node](0xfd) + 1
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for newNode != a.myDDPAddr.Node {
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newNode = rand.N[ddp.Node](0xfd) + 1
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}
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a.myDDPAddr.Node = newNode
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a.probes = 0
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}
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// Send an AARP response
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func (a *AARPMachine) heyThatsMe(targ aarp.AddrPair) error {
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respFrame, err := ethertalk.AARP(a.myHWAddr, aarp.Response(targ, aarp.AddrPair{
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Proto: a.myDDPAddr,
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Hardware: a.myHWAddr,
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}))
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if err != nil {
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return err
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}
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// Instead of broadcasting the reply, send it to the target specifically
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respFrame.Dst = targ.Hardware
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respFrameRaw, err := ethertalk.Marshal(*respFrame)
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if err != nil {
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return err
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}
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return a.pcapHandle.WritePacketData(respFrameRaw)
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}
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// Broadcast an AARP Probe
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func (a *AARPMachine) probe() error {
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probeFrame, err := ethertalk.AARP(a.myHWAddr, aarp.Probe(a.myHWAddr, a.myDDPAddr))
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if err != nil {
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return err
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}
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probeFrameRaw, err := ethertalk.Marshal(*probeFrame)
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if err != nil {
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return err
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}
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return a.pcapHandle.WritePacketData(probeFrameRaw)
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}
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type amtEntry struct {
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hwAddr ethernet.Addr
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last time.Time
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}
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// AMT implements a concurrent-safe Address Mapping Table for AppleTalk (DDP)
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// addresses to Ethernet hardware addresses.
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type AMT struct {
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mu sync.RWMutex
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table map[ddp.Addr]amtEntry
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}
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// Learn adds or updates an AMT entry.
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func (t *AMT) Learn(ddpAddr ddp.Addr, hwAddr ethernet.Addr) {
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t.mu.Lock()
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defer t.mu.Unlock()
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if t.table == nil {
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t.table = make(map[ddp.Addr]amtEntry)
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}
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t.table[ddpAddr] = amtEntry{
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hwAddr: hwAddr,
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last: time.Now(),
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}
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}
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// Lookup searches for a non-expired entry in the table only. It does not send
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// any packets.
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func (t *AMT) Lookup(ddpAddr ddp.Addr) (ethernet.Addr, bool) {
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t.mu.RLock()
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defer t.mu.RUnlock()
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ent, ok := t.table[ddpAddr]
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return ent.hwAddr, ok && time.Since(ent.last) < maxAMTEntryAge
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}
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46
amt.go
46
amt.go
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@ -1,46 +0,0 @@
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package main
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import (
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"sync"
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"time"
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"github.com/sfiera/multitalk/pkg/ddp"
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"github.com/sfiera/multitalk/pkg/ethernet"
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)
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// TODO: verify this parameter
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const maxAMTEntryAge = 30 * time.Second
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type amtEntry struct {
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hwAddr ethernet.Addr
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last time.Time
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}
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// AMT implements a concurrent-safe Address Mapping Table for AppleTalk (DDP)
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// addresses to Ethernet hardware addresses.
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type AMT struct {
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mu sync.RWMutex
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table map[ddp.Addr]amtEntry
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}
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// Learn adds or updates an AMT entry.
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func (t *AMT) Learn(ddpAddr ddp.Addr, hwAddr ethernet.Addr) {
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t.mu.Lock()
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defer t.mu.Unlock()
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if t.table == nil {
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t.table = make(map[ddp.Addr]amtEntry)
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}
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t.table[ddpAddr] = amtEntry{
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hwAddr: hwAddr,
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last: time.Now(),
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}
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}
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// Lookup searches for a non-expired entry in the table only. It does not send
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// any packets.
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func (t *AMT) Lookup(ddpAddr ddp.Addr) (ethernet.Addr, bool) {
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t.mu.RLock()
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defer t.mu.RUnlock()
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ent, ok := t.table[ddpAddr]
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return ent.hwAddr, ok && time.Since(ent.last) < maxAMTEntryAge
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}
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@ -19,6 +19,7 @@ package main
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import (
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"os"
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"github.com/sfiera/multitalk/pkg/ddp"
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"gopkg.in/yaml.v3"
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)
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@ -35,10 +36,10 @@ type config struct {
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// Required for routing a local EtherTalk network.
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EtherTalk struct {
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Device string `yaml:"device"`
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ZoneName string `yaml:"zone_name"`
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NetStart uint16 `yaml:"net_start"`
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NetEnd uint16 `yaml:"net_end"`
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Device string `yaml:"device"`
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ZoneName string `yaml:"zone_name"`
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NetStart ddp.Network `yaml:"net_start"`
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NetEnd ddp.Network `yaml:"net_end"`
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} `yaml:"ethertalk"`
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// LocalTalk struct {
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111
main.go
111
main.go
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@ -31,7 +31,6 @@ import (
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"gitea.drjosh.dev/josh/jrouter/atalk"
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"gitea.drjosh.dev/josh/jrouter/aurp"
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"github.com/sfiera/multitalk/pkg/aarp"
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"github.com/sfiera/multitalk/pkg/ddp"
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"github.com/sfiera/multitalk/pkg/ethernet"
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"github.com/sfiera/multitalk/pkg/ethertalk"
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@ -138,101 +137,49 @@ func main() {
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goHandler(peer)
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}
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// AppleTalk packet loop
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var amt AMT
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// AppleTalk packet loops
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iface, err := net.InterfaceByName(cfg.EtherTalk.Device)
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if err != nil {
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log.Fatalf("Couldn't find interface named %q: %v", cfg.EtherTalk.Device, err)
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}
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myHWAddr := ethernet.Addr(iface.HardwareAddr)
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pcapHandle, err := atalk.StartPcap(cfg.EtherTalk.Device)
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if err != nil {
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log.Fatalf("Couldn't open network device for AppleTalk: %v", err)
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}
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defer pcapHandle.Close()
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aarpMachine := &AARPMachine{
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AMT: new(AMT),
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cfg: cfg,
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pcapHandle: pcapHandle,
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myHWAddr: myHWAddr,
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}
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aarpCh := make(chan *ethertalk.Packet, 1024)
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go aarpMachine.Run(ctx, aarpCh)
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go func() {
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iface, err := net.InterfaceByName(cfg.EtherTalk.Device)
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if err != nil {
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log.Fatalf("Couldn't find interface named %q: %v", cfg.EtherTalk.Device, err)
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}
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localMAC := ethernet.Addr(iface.HardwareAddr)
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handle, err := atalk.StartPcap(cfg.EtherTalk.Device)
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if err != nil {
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log.Fatalf("Couldn't open network device for AppleTalk: %v", err)
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}
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defer handle.Close()
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// AARP probe for our preferred address (first network.1)
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localDDPAddr := ddp.Addr{
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Network: ddp.Network(cfg.EtherTalk.NetStart),
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Node: 1,
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}
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probeFrame, err := ethertalk.AARP(localMAC, aarp.Probe(localMAC, localDDPAddr))
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if err != nil {
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log.Fatalf("Couldn't construct AARP Probe: %v", err)
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}
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probeFrameRaw, err := ethertalk.Marshal(*probeFrame)
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if err != nil {
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log.Fatalf("Couldn't marshal AARP Probe: %v", err)
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}
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if err := handle.WritePacketData(probeFrameRaw); err != nil {
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log.Fatalf("Couldn't write packet data: %v", err)
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}
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for {
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rawPkt, _, err := handle.ReadPacketData()
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rawPkt, _, err := pcapHandle.ReadPacketData()
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if err != nil {
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log.Fatalf("Couldn't read AppleTalk / AARP packet data: %v", err)
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}
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var ethFrame ethertalk.Packet
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if err := ethertalk.Unmarshal(rawPkt, ðFrame); err != nil {
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ethFrame := new(ethertalk.Packet)
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if err := ethertalk.Unmarshal(rawPkt, ethFrame); err != nil {
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log.Printf("Couldn't unmarshal EtherTalk frame: %v", err)
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continue
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}
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if ethFrame.Src == localMAC {
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// Ignore if sent by me
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if ethFrame.Src == myHWAddr {
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continue
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}
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switch ethFrame.SNAPProto {
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case ethertalk.AARPProto:
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var aapkt aarp.Packet
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if err := aarp.Unmarshal(ethFrame.Payload, &aapkt); err != nil {
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log.Printf("Couldn't unmarshal AARP packet: %v", err)
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continue
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}
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switch aapkt.Opcode {
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case aarp.RequestOp:
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log.Printf("AARP: Who has %v? Tell %v", aapkt.Dst.Proto, aapkt.Src.Proto)
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// Glean that aapkt.Src.Proto -> aapkt.Src.Hardware
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amt.Learn(aapkt.Src.Proto, aapkt.Src.Hardware)
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log.Printf("AARP: Gleaned that %v -> %v", aapkt.Src.Proto, aapkt.Src.Hardware)
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if aapkt.Dst.Proto != localDDPAddr {
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continue
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}
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// Respond!
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respFrame, err := ethertalk.AARP(localMAC, aarp.Response(aapkt.Src, aarp.AddrPair{
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Proto: localDDPAddr,
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Hardware: localMAC,
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}))
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if err != nil {
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log.Printf("Couldn't construct AARP Response: %v", err)
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continue
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}
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respFrame.Dst = ethFrame.Src
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respFrameRaw, err := ethertalk.Marshal(*respFrame)
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if err != nil {
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log.Printf("Couldn't marshal AARP Response: %v", err)
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continue
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}
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if err := handle.WritePacketData(respFrameRaw); err != nil {
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log.Printf("Couldn't write packet data: %v", err)
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continue
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}
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case aarp.ResponseOp:
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log.Printf("AARP: %v is at %v", aapkt.Dst.Proto, aapkt.Dst.Hardware)
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amt.Learn(aapkt.Dst.Proto, aapkt.Dst.Hardware)
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case aarp.ProbeOp:
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log.Printf("AARP: %v probing to see if %v is available", aapkt.Src.Hardware, aapkt.Src.Proto)
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// AMT should not be updated, because the address is tentative
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}
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aarpCh <- ethFrame
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case ethertalk.AppleTalkProto:
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var ddpkt ddp.ExtPacket
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@ -246,7 +193,7 @@ func main() {
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ddpkt.Proto, len(ddpkt.Data))
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// Glean address info for AMT
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srcAddr := ddp.Addr{Network: ddpkt.SrcNet, Node: ddpkt.SrcNode}
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amt.Learn(srcAddr, ethFrame.Src)
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aarpMachine.Learn(srcAddr, ethFrame.Src)
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log.Printf("DDP: Gleaned that %v -> %v", srcAddr, ethFrame.Src)
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default:
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