quirk: enforce minimum lease time of 1 hour for Nintendo devices
The Nintendo Switch has been observed to hold on to IP addresses even after their expiration. My guess is that this is an oversight: likely the device enters power saving mode with a configured IP address and just sleeps through the expiration time. As the device seems to wake up once every hour, we enforce a minimum lease time of 1 hour, but only for affected devices. The rest of the network gets short lease times. https://twitter.com/zekjur/status/1263949112036282374
This commit is contained in:
Michael Stapelberg
parent
d81b77a876
commit
53c495091e
@ -16,9 +16,13 @@
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package dhcp4d
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import (
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"bytes"
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"encoding/hex"
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"log"
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"math/rand"
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"net"
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"sort"
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"strings"
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"sync"
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"syscall"
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"time"
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@ -246,17 +250,32 @@ func (h *Handler) leaseHW(hwAddr string) (*Lease, bool) {
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return l, ok && l.HardwareAddr == hwAddr
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}
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func (h *Handler) leasePeriodForDevice(hwAddr string) time.Duration {
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hwAddrPrefix, err := hex.DecodeString(strings.ReplaceAll(hwAddr, ":", ""))
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if err != nil {
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return h.LeasePeriod
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}
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hwAddrPrefix = hwAddrPrefix[:3]
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i := sort.Search(len(nintendoMacPrefixes), func(i int) bool {
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return bytes.Compare(nintendoMacPrefixes[i][:], hwAddrPrefix) >= 0
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})
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if i < len(nintendoMacPrefixes) && bytes.Equal(nintendoMacPrefixes[i][:], hwAddrPrefix) {
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return 1 * time.Hour
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}
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return h.LeasePeriod
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}
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// TODO: is ServeDHCP always run from the same goroutine, or do we need locking?
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func (h *Handler) serveDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options dhcp4.Options) dhcp4.Packet {
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reqIP := net.IP(options[dhcp4.OptionRequestedIPAddress])
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if reqIP == nil {
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reqIP = net.IP(p.CIAddr())
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}
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hwAddr := p.CHAddr().String()
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switch msgType {
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case dhcp4.Discover:
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free := -1
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hwAddr := p.CHAddr().String()
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// try to offer the requested IP, if any and available
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if !reqIP.To4().Equal(net.IPv4zero) {
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@ -284,14 +303,14 @@ func (h *Handler) serveDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options d
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dhcp4.Offer,
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h.serverIP,
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dhcp4.IPAdd(h.start, free),
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h.LeasePeriod,
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h.leasePeriodForDevice(hwAddr),
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h.options.SelectOrderOrAll(options[dhcp4.OptionParameterRequestList]))
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case dhcp4.Request:
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if server, ok := options[dhcp4.OptionServerIdentifier]; ok && !net.IP(server).Equal(h.serverIP) {
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return nil // message not for this dhcp server
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}
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leaseNum := h.canLease(reqIP, p.CHAddr().String())
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leaseNum := h.canLease(reqIP, hwAddr)
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if leaseNum == -1 {
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return dhcp4.ReplyPacket(p, dhcp4.NAK, h.serverIP, nil, 0, nil)
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}
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@ -299,8 +318,8 @@ func (h *Handler) serveDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options d
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lease := &Lease{
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Num: leaseNum,
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Addr: make([]byte, 4),
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HardwareAddr: p.CHAddr().String(),
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Expiry: h.timeNow().Add(h.LeasePeriod),
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HardwareAddr: hwAddr,
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Expiry: h.timeNow().Add(h.leasePeriodForDevice(hwAddr)),
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Hostname: string(options[dhcp4.OptionHostName]),
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}
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copy(lease.Addr, reqIP.To4())
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@ -327,7 +346,12 @@ func (h *Handler) serveDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options d
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h.leasesIP[leaseNum] = lease
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h.leasesHW[lease.HardwareAddr] = leaseNum
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h.callLeasesLocked(lease)
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return dhcp4.ReplyPacket(p, dhcp4.ACK, h.serverIP, reqIP, h.LeasePeriod,
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return dhcp4.ReplyPacket(
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p,
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dhcp4.ACK,
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h.serverIP,
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reqIP,
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h.leasePeriodForDevice(hwAddr),
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h.options.SelectOrderOrAll(options[dhcp4.OptionParameterRequestList]))
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}
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return nil
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@ -15,6 +15,7 @@
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package dhcp4d
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import (
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"encoding/binary"
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"io/ioutil"
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"net"
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"os"
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@ -455,3 +456,47 @@ func TestPersistentStorage(t *testing.T) {
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t.Errorf("DHCPOFFER for wrong IP: got %v, want %v", got, want)
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}
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}
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func TestMinimumLeaseTime(t *testing.T) {
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handler, cleanup := testHandler(t)
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defer cleanup()
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var addr = net.IP{192, 168, 42, 23}
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for _, tt := range []struct {
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hwaddr net.HardwareAddr
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wantLeaseTime time.Duration
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}{
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{
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hwaddr: net.HardwareAddr{0x11, 0x22, 0x33, 0x44, 0x55, 0x66},
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wantLeaseTime: 20 * time.Minute,
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},
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{
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// Nintendo MAC address range for Nintendo Switch specific minimum
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// lease time quirk:
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hwaddr: net.HardwareAddr{0x7c, 0xbb, 0x8a, 0x11, 0x22, 0x33},
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wantLeaseTime: 1 * time.Hour,
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},
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} {
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p := discover(addr, tt.hwaddr)
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resp := handler.serveDHCP(p, dhcp4.Discover, p.ParseOptions())
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if resp == nil {
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t.Fatalf("DHCPDISCOVER(%v) = nil", tt.hwaddr)
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}
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if got, want := messageType(resp), dhcp4.Offer; got != want {
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t.Errorf("DHCPDISCOVER resulted in unexpected message type: got %v, want %v", got, want)
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}
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opts := resp.ParseOptions()
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leaseTimeBytes, ok := opts[dhcp4.OptionIPAddressLeaseTime]
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if !ok {
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t.Fatalf("DHCPDISCOVER(%v): lease time option not set", tt.hwaddr)
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}
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leaseTimeSecs := binary.BigEndian.Uint32(leaseTimeBytes)
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want := uint32(tt.wantLeaseTime.Seconds())
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if got := leaseTimeSecs; got != want {
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t.Errorf("unexpected lease time for hwaddr %v: got %d, want %d", tt.hwaddr, got, want)
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}
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}
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}
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73
internal/dhcp4d/quirks.go
Normal file
73
internal/dhcp4d/quirks.go
Normal file
@ -0,0 +1,73 @@
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package dhcp4d
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// Sorted list of MAC address prefixes assigned to Nintendo.
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// From the IEEE MA-L (MAC Address Block Large, formerly known as OUI) database.
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var nintendoMacPrefixes = [...][3]byte{
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{0x0, 0x9, 0xbf},
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{0x0, 0x16, 0x56},
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{0x0, 0x17, 0xab},
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{0x0, 0x19, 0x1d},
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{0x0, 0x19, 0xfd},
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{0x0, 0x1a, 0xe9},
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{0x0, 0x1b, 0x7a},
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{0x0, 0x1b, 0xea},
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{0x0, 0x1c, 0xbe},
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{0x0, 0x1d, 0xbc},
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{0x0, 0x1e, 0x35},
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{0x0, 0x1e, 0xa9},
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{0x0, 0x1f, 0x32},
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{0x0, 0x1f, 0xc5},
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{0x0, 0x21, 0x47},
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{0x0, 0x21, 0xbd},
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{0x0, 0x22, 0x4c},
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{0x0, 0x22, 0xaa},
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{0x0, 0x22, 0xd7},
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{0x0, 0x23, 0x31},
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{0x0, 0x23, 0xcc},
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{0x0, 0x24, 0x1e},
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{0x0, 0x24, 0x44},
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{0x0, 0x24, 0xf3},
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{0x0, 0x25, 0xa0},
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{0x0, 0x26, 0x59},
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{0x0, 0x27, 0x9},
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{0x4, 0x3, 0xd6},
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{0x18, 0x2a, 0x7b},
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{0x2c, 0x10, 0xc1},
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{0x34, 0x2f, 0xbd},
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{0x34, 0xaf, 0x2c},
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{0x40, 0xd2, 0x8a},
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{0x40, 0xf4, 0x7},
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{0x48, 0xa5, 0xe7},
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{0x58, 0x2f, 0x40},
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{0x58, 0xbd, 0xa3},
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{0x5c, 0x52, 0x1e},
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{0x60, 0x6b, 0xff},
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{0x64, 0xb5, 0xc6},
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{0x70, 0x48, 0xf7},
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{0x78, 0xa2, 0xa0},
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{0x7c, 0xbb, 0x8a},
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{0x8c, 0x56, 0xc5},
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{0x8c, 0xcd, 0xe8},
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{0x94, 0x58, 0xcb},
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{0x98, 0x41, 0x5c},
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{0x98, 0xb6, 0xe9},
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{0x98, 0xe8, 0xfa},
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{0x9c, 0xe6, 0x35},
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{0xa4, 0x38, 0xcc},
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{0xa4, 0x5c, 0x27},
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{0xa4, 0xc0, 0xe1},
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{0xb8, 0x78, 0x26},
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{0xb8, 0x8a, 0xec},
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{0xb8, 0xae, 0x6e},
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{0xcc, 0x9e, 0x0},
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{0xcc, 0xfb, 0x65},
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{0xd4, 0xf0, 0x57},
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{0xd8, 0x6b, 0xf7},
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{0xdc, 0x68, 0xeb},
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{0xe0, 0xc, 0x7f},
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{0xe0, 0xe7, 0x51},
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{0xe0, 0xf6, 0xb5},
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{0xe8, 0x4e, 0xce},
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{0xe8, 0xda, 0x20},
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{0xec, 0xc4, 0xd},
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}
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