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arp: set and check arp state #27

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arp: set and check arp state #27

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12 changes: 7 additions & 5 deletions arp.go
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Original file line number Diff line number Diff line change
Expand Up @@ -54,12 +54,12 @@ const (
)

// Add either adds a new entry or updates an ArpEntry in the ArpTable syncmap.
func (t *ArpTable) Add(IP string, mac net.HardwareAddr, timeNow time.Time) error {
func (t *ArpTable) Add(IP string, mac net.HardwareAddr, timeNow time.Time, status ArpStatus) error {
if IP == "" {
return errors.New("valid IP address must be provided")
}
ip := net.ParseIP(IP)
t.ArpMap.Store(IP, &ArpEntry{IP: ip, Mac: mac, Status: StatusReady, Timestamp: timeNow})
t.ArpMap.Store(IP, &ArpEntry{IP: ip, Mac: mac, Status: status, Timestamp: timeNow})
return nil
}

Expand All @@ -78,8 +78,10 @@ func (t *ArpTable) Get(IP string) (*ArpEntry, bool, error) {
return nil, false, errors.New("invalid ARP entry type")
}

if arpEntry.Mac == nil {
return nil, false, errors.New("invalid ARP entry")
// Update the status from waiting to stale to express that the waiting time (2seconds) has expired
// This will allow us to send again an ARP request
if arpEntry.Status == StatusWaiting && arpEntry.Timestamp.Add(time.Second*2).Before(time.Now()) {
arpEntry.Status = StatusStale
}

return arpEntry, found, nil
Expand Down Expand Up @@ -138,7 +140,7 @@ func GenerateARPRequest(arpTable *ArpTable, srcMAC []byte, dstIP string, srcIP s

// FIXME this function should be .Upsert() (Add or Update the entry)
if arpTable != nil {
err := arpTable.Add(dstIP, net.HardwareAddr{}, time.Now())
err := arpTable.Add(dstIP, net.HardwareAddr{}, time.Now(), StatusWaiting)
if err != nil {
return nil, fmt.Errorf("unable to add waiting ARP entry: %v", err)
}
Expand Down
8 changes: 4 additions & 4 deletions network.go
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Original file line number Diff line number Diff line change
Expand Up @@ -148,7 +148,7 @@ func ReadUTUN() {
Lerror.Printf("unable to retrieve ARP entry for %v: %v", dstIP.String(), err)
}

if found {
if found && entry.Status == StatusReady {
// We found the destination MAC in the ARP table, continue to craft
// the ethernet header of the IP packet.

Expand All @@ -163,7 +163,7 @@ func ReadUTUN() {
}
Ldebug.Printf("wrote %d bytes to vswitch\n", b)

} else {
} else if !found || found && entry.Status == StatusStale {

// TODO: Queue ethernet frame while ARP is being resolving the dst MAC address

Expand Down Expand Up @@ -394,7 +394,7 @@ func connSwitch(ctx context.Context, cancel context.CancelFunc, config *tls.Conf
if oper == OperationReply {
Ldebug.Printf("Received ARP response\n")
// We received an ARP response
err := arpTable.Add(spa.String(), sha, time.Now())
err := arpTable.Add(spa.String(), sha, time.Now(), StatusReady)
if err != nil {
Lerror.Printf("unable to update ARP entry: %v", err)
}
Expand All @@ -405,7 +405,7 @@ func connSwitch(ctx context.Context, cancel context.CancelFunc, config *tls.Conf
// ETH src MAC match the arp SHA AND arp SPA match TPA
if bytes.Equal(frameBuf[10:16], frameBuf[26:32]) && bytes.Equal(frameBuf[32:36], frameBuf[42:46]) {
Ldebug.Printf("we received an GARP")
arpTable.Add(spa.String(), sha, time.Now())
arpTable.Add(spa.String(), sha, time.Now(), StatusReady)
} else {
// We received an ARP request, send a response
sendBuf := GenerateARPReply(gMAC[0:6], sha, tpa, spa)
Expand Down