AARP machine improvements
This commit is contained in:
parent
7c3e508dd1
commit
7cb0a31100
SSH key fingerprint:
SHA256:zZji7w1Ilh2RuUpbQcqkLPrqmRwpiCSycbF2EfKm6Kw
1 changed files with 70 additions and 80 deletions
150
aarp.go
150
aarp.go
|
|
@ -21,52 +21,57 @@ const (
|
|||
aarpRequestTimeout = 10 * time.Second
|
||||
)
|
||||
|
||||
type aarpState int
|
||||
|
||||
const (
|
||||
aarpStateProbing aarpState = iota
|
||||
aarpStateAssigned
|
||||
)
|
||||
|
||||
// AARPMachine maintains both an Address Mapping Table and handles AARP packets
|
||||
// (sending and receiving requests, responses, and probes). This process assumes
|
||||
// a particular network range rather than using the startup range, since this
|
||||
// program is a seed router.
|
||||
type AARPMachine struct {
|
||||
*AMT
|
||||
*addressMappingTable
|
||||
|
||||
cfg *config
|
||||
pcapHandle *pcap.Handle
|
||||
|
||||
state aarpState
|
||||
probes int
|
||||
|
||||
// The Run goroutine is responsible for all writes to myAddr.Proto and
|
||||
// probes, so this mutex is not used to enforce a single writer, only
|
||||
// consistent reads
|
||||
mu sync.RWMutex
|
||||
myAddr aarp.AddrPair
|
||||
probes int
|
||||
}
|
||||
|
||||
// NewAARPMachine creates a new AARPMachine.
|
||||
func NewAARPMachine(cfg *config, pcapHandle *pcap.Handle, myHWAddr ethernet.Addr) *AARPMachine {
|
||||
return &AARPMachine{
|
||||
AMT: new(AMT),
|
||||
cfg: cfg,
|
||||
pcapHandle: pcapHandle,
|
||||
addressMappingTable: new(addressMappingTable),
|
||||
cfg: cfg,
|
||||
pcapHandle: pcapHandle,
|
||||
myAddr: aarp.AddrPair{
|
||||
Hardware: myHWAddr,
|
||||
},
|
||||
}
|
||||
}
|
||||
|
||||
// Address returns the address of this node, and reports if the address is valid
|
||||
// (i.e. not tentative).
|
||||
func (a *AARPMachine) Address() (aarp.AddrPair, bool) {
|
||||
a.mu.RLock()
|
||||
defer a.mu.RUnlock()
|
||||
return a.myAddr, a.assigned()
|
||||
}
|
||||
|
||||
// Run executes the machine.
|
||||
func (a *AARPMachine) Run(ctx context.Context, incomingCh <-chan *ethertalk.Packet) error {
|
||||
ticker := time.NewTicker(200 * time.Millisecond) // 200ms is the AARP probe retransmit
|
||||
defer ticker.Stop()
|
||||
|
||||
a.state = aarpStateProbing
|
||||
a.probes = 0
|
||||
|
||||
// Initialise our DDP address with a preferred address (first network.1)
|
||||
a.mu.Lock()
|
||||
a.probes = 0
|
||||
a.myAddr.Proto = ddp.Addr{
|
||||
Network: ddp.Network(a.cfg.EtherTalk.NetStart),
|
||||
Node: 1,
|
||||
}
|
||||
a.mu.Unlock()
|
||||
|
||||
ticker := time.NewTicker(200 * time.Millisecond) // 200ms is the AARP probe retransmit
|
||||
defer ticker.Stop()
|
||||
|
||||
for {
|
||||
select {
|
||||
|
|
@ -74,21 +79,18 @@ func (a *AARPMachine) Run(ctx context.Context, incomingCh <-chan *ethertalk.Pack
|
|||
return ctx.Err()
|
||||
|
||||
case <-ticker.C:
|
||||
switch a.state {
|
||||
case aarpStateAssigned:
|
||||
if a.assigned() {
|
||||
// No need to keep the ticker running if assigned
|
||||
ticker.Stop()
|
||||
continue
|
||||
}
|
||||
|
||||
case aarpStateProbing:
|
||||
if a.probes >= 10 {
|
||||
a.state = aarpStateAssigned
|
||||
continue
|
||||
}
|
||||
a.probes++
|
||||
if err := a.probe(); err != nil {
|
||||
log.Printf("Couldn't broadcast a Probe: %v", err)
|
||||
continue
|
||||
}
|
||||
a.mu.Lock()
|
||||
a.probes++
|
||||
a.mu.Unlock()
|
||||
|
||||
if err := a.probe(); err != nil {
|
||||
log.Printf("Couldn't broadcast a Probe: %v", err)
|
||||
}
|
||||
|
||||
case ethFrame, ok := <-incomingCh:
|
||||
|
|
@ -106,15 +108,13 @@ func (a *AARPMachine) Run(ctx context.Context, incomingCh <-chan *ethertalk.Pack
|
|||
case aarp.RequestOp:
|
||||
log.Printf("AARP: Who has %v? Tell %v", aapkt.Dst.Proto, aapkt.Src.Proto)
|
||||
// Glean that aapkt.Src.Proto -> aapkt.Src.Hardware
|
||||
a.AMT.Learn(aapkt.Src.Proto, aapkt.Src.Hardware)
|
||||
a.addressMappingTable.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.myAddr.Proto {
|
||||
continue
|
||||
}
|
||||
if a.state != aarpStateAssigned {
|
||||
if !(aapkt.Dst.Proto == a.myAddr.Proto && a.assigned()) {
|
||||
continue
|
||||
}
|
||||
|
||||
// Hey that's me! Let them know!
|
||||
if err := a.heyThatsMe(aapkt.Src); err != nil {
|
||||
log.Printf("AARP: Couldn't respond to Request: %v", err)
|
||||
|
|
@ -123,12 +123,12 @@ func (a *AARPMachine) Run(ctx context.Context, incomingCh <-chan *ethertalk.Pack
|
|||
|
||||
case aarp.ResponseOp:
|
||||
log.Printf("AARP: %v is at %v", aapkt.Dst.Proto, aapkt.Dst.Hardware)
|
||||
a.AMT.Learn(aapkt.Dst.Proto, aapkt.Dst.Hardware)
|
||||
a.addressMappingTable.Learn(aapkt.Dst.Proto, aapkt.Dst.Hardware)
|
||||
|
||||
if aapkt.Dst.Proto != a.myAddr.Proto {
|
||||
continue
|
||||
}
|
||||
if a.state == aarpStateProbing {
|
||||
if !a.assigned() {
|
||||
a.reroll()
|
||||
}
|
||||
|
||||
|
|
@ -139,19 +139,17 @@ func (a *AARPMachine) Run(ctx context.Context, incomingCh <-chan *ethertalk.Pack
|
|||
if aapkt.Dst.Proto != a.myAddr.Proto {
|
||||
continue
|
||||
}
|
||||
switch a.state {
|
||||
case aarpStateProbing:
|
||||
if !a.assigned() {
|
||||
// Another node is probing for the same address! Unlucky
|
||||
a.reroll()
|
||||
continue
|
||||
}
|
||||
|
||||
case aarpStateAssigned:
|
||||
if err := a.heyThatsMe(aapkt.Src); err != nil {
|
||||
log.Printf("AARP: Couldn't respond to Probe: %v", err)
|
||||
continue
|
||||
}
|
||||
if err := a.heyThatsMe(aapkt.Src); err != nil {
|
||||
log.Printf("AARP: Couldn't respond to Probe: %v", err)
|
||||
continue
|
||||
}
|
||||
}
|
||||
|
||||
}
|
||||
}
|
||||
}
|
||||
|
|
@ -160,9 +158,8 @@ func (a *AARPMachine) Run(ctx context.Context, incomingCh <-chan *ethertalk.Pack
|
|||
// 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 {
|
||||
result, waitCh := a.addressMappingTable.lookupOrWait(ddpAddr)
|
||||
if waitCh == nil {
|
||||
return result, nil
|
||||
}
|
||||
|
||||
|
|
@ -177,18 +174,15 @@ func (a *AARPMachine) Resolve(ctx context.Context, ddpAddr ddp.Addr) (ethernet.A
|
|||
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 <-waitCh:
|
||||
result, waitCh = a.addressMappingTable.lookupOrWait(ddpAddr)
|
||||
if waitCh == nil {
|
||||
return result, nil
|
||||
}
|
||||
|
||||
case <-ticker.C:
|
||||
if err := a.request(ddpAddr); err != nil {
|
||||
|
|
@ -198,11 +192,15 @@ func (a *AARPMachine) Resolve(ctx context.Context, ddpAddr ddp.Addr) (ethernet.A
|
|||
}
|
||||
}
|
||||
|
||||
func (a *AARPMachine) assigned() bool { return a.probes >= 10 }
|
||||
|
||||
// Re-roll a local address
|
||||
func (a *AARPMachine) reroll() {
|
||||
a.mu.Lock()
|
||||
defer a.mu.Unlock()
|
||||
if a.cfg.EtherTalk.NetStart != a.cfg.EtherTalk.NetEnd {
|
||||
// Pick a new network number at random
|
||||
a.myAddr.Proto.Network = rand.N[ddp.Network](
|
||||
a.myAddr.Proto.Network = rand.N(
|
||||
a.cfg.EtherTalk.NetEnd-a.cfg.EtherTalk.NetStart+1,
|
||||
) + a.cfg.EtherTalk.NetStart
|
||||
}
|
||||
|
|
@ -245,7 +243,7 @@ func (a *AARPMachine) probe() error {
|
|||
}
|
||||
|
||||
// Broadcast an AARP Request
|
||||
func (a AARPMachine) request(ddpAddr ddp.Addr) error {
|
||||
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
|
||||
|
|
@ -263,15 +261,15 @@ type amtEntry struct {
|
|||
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
|
||||
// addressMappingTable implements a concurrent-safe Address Mapping Table for
|
||||
// AppleTalk (DDP) addresses to Ethernet hardware addresses.
|
||||
type addressMappingTable struct {
|
||||
mu sync.Mutex
|
||||
table map[ddp.Addr]*amtEntry
|
||||
}
|
||||
|
||||
// Learn adds or updates an AMT entry.
|
||||
func (t *AMT) Learn(ddpAddr ddp.Addr, hwAddr ethernet.Addr) {
|
||||
func (t *addressMappingTable) Learn(ddpAddr ddp.Addr, hwAddr ethernet.Addr) {
|
||||
t.mu.Lock()
|
||||
defer t.mu.Unlock()
|
||||
if t.table == nil {
|
||||
|
|
@ -297,29 +295,21 @@ func (t *AMT) Learn(ddpAddr ddp.Addr, hwAddr ethernet.Addr) {
|
|||
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{} {
|
||||
// lookupOrWait returns either the valid cached Ethernet address for the given
|
||||
// DDP address, or a channel that is closed when the entry is updated.
|
||||
func (t *addressMappingTable) lookupOrWait(ddpAddr ddp.Addr) (ethernet.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
|
||||
ent, ok := t.table[ddpAddr]
|
||||
if ok && time.Since(ent.last) < maxAMTEntryAge {
|
||||
return ent.hwAddr, nil
|
||||
}
|
||||
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
|
||||
// any packets.
|
||||
func (t *AMT) Lookup(ddpAddr ddp.Addr) (ethernet.Addr, bool) {
|
||||
t.mu.RLock()
|
||||
defer t.mu.RUnlock()
|
||||
ent, ok := t.table[ddpAddr]
|
||||
return ent.hwAddr, ok && time.Since(ent.last) < maxAMTEntryAge
|
||||
return ethernet.Addr{}, ch
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in a new issue