Finish implementing AARP

aarp.go

@@ -14,8 +14,12 @@ import (
 	"github.com/sfiera/multitalk/pkg/ethertalk"
 )
 
-// TODO: verify this parameter
+const (
-const maxAMTEntryAge = 30 * time.Second
+	// TODO: verify parameters
+	maxAMTEntryAge        = 30 * time.Second
+	aarpRequestRetransmit = 1 * time.Second
+	aarpRequestTimeout    = 10 * time.Second
+)
 
 // AARPMachine maintains both an Address Mapping Table and handles AARP packets
 // (sending and receiving requests, responses, and probes). This process assumes
@@ -30,8 +34,7 @@ type AARPMachine struct {
 	state  aarpState
 	probes int
 
-	myHWAddr  ethernet.Addr
+	myAddr aarp.AddrPair
-	myDDPAddr ddp.Addr
 }
 
 type aarpState int
@@ -49,7 +52,7 @@ func (a *AARPMachine) Run(ctx context.Context, incomingCh <-chan *ethertalk.Pack
 	a.probes = 0
 
 	// Initialise our DDP address with a preferred address (first network.1)
-	a.myDDPAddr = ddp.Addr{
+	a.myAddr.Proto = ddp.Addr{
 		Network: ddp.Network(a.cfg.EtherTalk.NetStart),
 		Node:    1,
 	}
@@ -95,7 +98,7 @@ func (a *AARPMachine) Run(ctx context.Context, incomingCh <-chan *ethertalk.Pack
 				a.AMT.Learn(aapkt.Src.Proto, aapkt.Src.Hardware)
 				log.Printf("AARP: Gleaned that %v -> %v", aapkt.Src.Proto, aapkt.Src.Hardware)
 
-				if aapkt.Dst.Proto != a.myDDPAddr {
+				if aapkt.Dst.Proto != a.myAddr.Proto {
 					continue
 				}
 				if a.state != aarpStateAssigned {
@@ -111,7 +114,7 @@ func (a *AARPMachine) Run(ctx context.Context, incomingCh <-chan *ethertalk.Pack
 				log.Printf("AARP: %v is at %v", aapkt.Dst.Proto, aapkt.Dst.Hardware)
 				a.AMT.Learn(aapkt.Dst.Proto, aapkt.Dst.Hardware)
 
-				if aapkt.Dst.Proto != a.myDDPAddr {
+				if aapkt.Dst.Proto != a.myAddr.Proto {
 					continue
 				}
 				if a.state == aarpStateProbing {
@@ -122,7 +125,7 @@ func (a *AARPMachine) Run(ctx context.Context, incomingCh <-chan *ethertalk.Pack
 				log.Printf("AARP: %v probing to see if %v is available", aapkt.Src.Hardware, aapkt.Src.Proto)
 				// AMT should not be updated, because the address is tentative
 
-				if aapkt.Dst.Proto != a.myDDPAddr {
+				if aapkt.Dst.Proto != a.myAddr.Proto {
 					continue
 				}
 				switch a.state {
@@ -142,30 +145,69 @@ func (a *AARPMachine) Run(ctx context.Context, incomingCh <-chan *ethertalk.Pack
 	}
 }
 
+// Resolve resolves an AppleTalk node address to an Ethernet address.
+// If the address is in the cache (AMT) and is still valid, that is used.
+// Otherwise, the address is resolved using AARP.
+func (a *AARPMachine) Resolve(ctx context.Context, ddpAddr ddp.Addr) (ethernet.Addr, error) {
+	// try the cache first
+	result, ok := a.AMT.Lookup(ddpAddr)
+	if ok {
+		return result, nil
+	}
+
+	if err := a.request(ddpAddr); err != nil {
+		return ethernet.Addr{}, err
+	}
+
+	ticker := time.NewTicker(aarpRequestRetransmit)
+	defer ticker.Stop()
+
+	ctx, cancel := context.WithTimeout(ctx, aarpRequestTimeout)
+	defer cancel()
+
+	for {
+		// We might have a result already
+		result, ok := a.AMT.Lookup(ddpAddr)
+		if ok {
+			return result, nil
+		}
+
+		select {
+		case <-ctx.Done():
+			return ethernet.Addr{}, ctx.Err()
+
+		case <-a.AMT.Wait(ddpAddr):
+			// Should have a result now.
+
+		case <-ticker.C:
+			if err := a.request(ddpAddr); err != nil {
+				return ethernet.Addr{}, err
+			}
+		}
+	}
+}
+
 // Re-roll a local address
 func (a *AARPMachine) reroll() {
 	if a.cfg.EtherTalk.NetStart != a.cfg.EtherTalk.NetEnd {
 		// Pick a new network number at random
-		a.myDDPAddr.Network = rand.N[ddp.Network](
+		a.myAddr.Proto.Network = rand.N[ddp.Network](
 			a.cfg.EtherTalk.NetEnd-a.cfg.EtherTalk.NetStart+1,
 		) + a.cfg.EtherTalk.NetStart
 	}
 
 	// Can't use: 0x00, 0xff, 0xfe, or the existing node number
 	newNode := rand.N[ddp.Node](0xfd) + 1
-	for newNode != a.myDDPAddr.Node {
+	for newNode != a.myAddr.Proto.Node {
 		newNode = rand.N[ddp.Node](0xfd) + 1
 	}
-	a.myDDPAddr.Node = newNode
+	a.myAddr.Proto.Node = newNode
 	a.probes = 0
 }
 
 // Send an AARP response
 func (a *AARPMachine) heyThatsMe(targ aarp.AddrPair) error {
-	respFrame, err := ethertalk.AARP(a.myHWAddr, aarp.Response(targ, aarp.AddrPair{
+	respFrame, err := ethertalk.AARP(a.myAddr.Hardware, aarp.Response(targ, a.myAddr))
-		Proto:    a.myDDPAddr,
-		Hardware: a.myHWAddr,
-	}))
 	if err != nil {
 		return err
 	}
@@ -180,7 +222,7 @@ func (a *AARPMachine) heyThatsMe(targ aarp.AddrPair) error {
 
 // Broadcast an AARP Probe
 func (a *AARPMachine) probe() error {
-	probeFrame, err := ethertalk.AARP(a.myHWAddr, aarp.Probe(a.myHWAddr, a.myDDPAddr))
+	probeFrame, err := ethertalk.AARP(a.myAddr.Hardware, aarp.Probe(a.myAddr.Hardware, a.myAddr.Proto))
 	if err != nil {
 		return err
 	}
@@ -191,16 +233,30 @@ func (a *AARPMachine) probe() error {
 	return a.pcapHandle.WritePacketData(probeFrameRaw)
 }
 
+// Broadcast an AARP Request
+func (a AARPMachine) request(ddpAddr ddp.Addr) error {
+	reqFrame, err := ethertalk.AARP(a.myAddr.Hardware, aarp.Request(a.myAddr, ddpAddr))
+	if err != nil {
+		return err
+	}
+	reqFrameRaw, err := ethertalk.Marshal(*reqFrame)
+	if err != nil {
+		return err
+	}
+	return a.pcapHandle.WritePacketData(reqFrameRaw)
+}
+
 type amtEntry struct {
 	hwAddr  ethernet.Addr
 	last    time.Time
+	updated chan struct{}
 }
 
 // AMT implements a concurrent-safe Address Mapping Table for AppleTalk (DDP)
 // addresses to Ethernet hardware addresses.
 type AMT struct {
 	mu    sync.RWMutex
-	table map[ddp.Addr]amtEntry
+	table map[ddp.Addr]*amtEntry
 }
 
 // Learn adds or updates an AMT entry.
@@ -208,12 +264,44 @@ func (t *AMT) Learn(ddpAddr ddp.Addr, hwAddr ethernet.Addr) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 	if t.table == nil {
-		t.table = make(map[ddp.Addr]amtEntry)
+		t.table = make(map[ddp.Addr]*amtEntry)
 	}
-	t.table[ddpAddr] = amtEntry{
+	oldEnt := t.table[ddpAddr]
+	if oldEnt == nil {
+		t.table[ddpAddr] = &amtEntry{
 			hwAddr:  hwAddr,
 			last:    time.Now(),
+			updated: make(chan struct{}),
 		}
+		return
+	}
+
+	if oldEnt.hwAddr == hwAddr && time.Since(oldEnt.last) < maxAMTEntryAge {
+		oldEnt.last = time.Now()
+		return
+	}
+	oldEnt.hwAddr = hwAddr
+	oldEnt.last = time.Now()
+	close(oldEnt.updated)
+	oldEnt.updated = make(chan struct{})
+}
+
+// Wait returns a channel that is closed when the entry for ddpAddr is updated.
+func (t *AMT) Wait(ddpAddr ddp.Addr) <-chan struct{} {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.table == nil {
+		t.table = make(map[ddp.Addr]*amtEntry)
+	}
+	oldEnt := t.table[ddpAddr]
+	if oldEnt != nil {
+		return oldEnt.updated
+	}
+	ch := make(chan struct{})
+	t.table[ddpAddr] = &amtEntry{
+		updated: ch,
+	}
+	return ch
 }
 
 // Lookup searches for a non-expired entry in the table only. It does not send

main.go

@@ -31,6 +31,7 @@ import (
 
 	"gitea.drjosh.dev/josh/jrouter/atalk"
 	"gitea.drjosh.dev/josh/jrouter/aurp"
+	"github.com/sfiera/multitalk/pkg/aarp"
 	"github.com/sfiera/multitalk/pkg/ddp"
 	"github.com/sfiera/multitalk/pkg/ethernet"
 	"github.com/sfiera/multitalk/pkg/ethertalk"
@@ -154,7 +155,9 @@ func main() {
 		AMT:        new(AMT),
 		cfg:        cfg,
 		pcapHandle: pcapHandle,
-		myHWAddr:   myHWAddr,
+		myAddr: aarp.AddrPair{
+			Hardware: myHWAddr,
+		},
 	}
 	aarpCh := make(chan *ethertalk.Packet, 1024)
 	go aarpMachine.Run(ctx, aarpCh)

peer.go

@@ -256,8 +256,8 @@ func (p *peer) handle(ctx context.Context) error {
 				nets := aurp.NetworkTuples{
 					{
 						Extended:   true,
-						RangeStart: p.cfg.EtherTalk.NetStart,
+						RangeStart: uint16(p.cfg.EtherTalk.NetStart),
-						RangeEnd:   p.cfg.EtherTalk.NetEnd,
+						RangeEnd:   uint16(p.cfg.EtherTalk.NetEnd),
 						Distance:   0,
 					},
 				}
@@ -312,7 +312,7 @@ func (p *peer) handle(ctx context.Context) error {
 				if pkt.Flags&aurp.RoutingFlagSendZoneInfo != 0 {
 					zones := aurp.ZoneTuples{
 						{
-							Network: p.cfg.EtherTalk.NetStart,
+							Network: uint16(p.cfg.EtherTalk.NetStart),
 							Name:    p.cfg.EtherTalk.ZoneName,
 						},
 					}
@@ -346,7 +346,7 @@ func (p *peer) handle(ctx context.Context) error {
 				// ZI-Req
 				zones := aurp.ZoneTuples{
 					{
-						Network: p.cfg.EtherTalk.NetStart,
+						Network: uint16(p.cfg.EtherTalk.NetStart),
 						Name:    p.cfg.EtherTalk.ZoneName,
 					},
 				}