Xray-core/app/dns/fakedns/fake.go

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package fakedns
import (
"context"
"math"
"math/big"
gonet "net"
"time"
"github.com/xtls/xray-core/common"
"github.com/xtls/xray-core/common/cache"
"github.com/xtls/xray-core/common/net"
"github.com/xtls/xray-core/features/dns"
)
type Holder struct {
domainToIP cache.Lru
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ipRange *gonet.IPNet
config *FakeDnsPool
}
func (*Holder) Type() interface{} {
return (*dns.FakeDNSEngine)(nil)
}
func (fkdns *Holder) Start() error {
return fkdns.initializeFromConfig()
}
func (fkdns *Holder) Close() error {
fkdns.domainToIP = nil
fkdns.ipRange = nil
return nil
}
func NewFakeDNSHolder() (*Holder, error) {
var fkdns *Holder
var err error
if fkdns, err = NewFakeDNSHolderConfigOnly(nil); err != nil {
return nil, newError("Unable to create Fake Dns Engine").Base(err).AtError()
}
err = fkdns.initialize("240.0.0.0/8", 65535)
if err != nil {
return nil, err
}
return fkdns, nil
}
func NewFakeDNSHolderConfigOnly(conf *FakeDnsPool) (*Holder, error) {
return &Holder{nil, nil, conf}, nil
}
func (fkdns *Holder) initializeFromConfig() error {
return fkdns.initialize(fkdns.config.IpPool, int(fkdns.config.LruSize))
}
func (fkdns *Holder) initialize(ipPoolCidr string, lruSize int) error {
var ipRange *gonet.IPNet
var err error
if _, ipRange, err = gonet.ParseCIDR(ipPoolCidr); err != nil {
return newError("Unable to parse CIDR for Fake DNS IP assignment").Base(err).AtError()
}
ones, bits := ipRange.Mask.Size()
rooms := bits - ones
if math.Log2(float64(lruSize)) >= float64(rooms) {
return newError("LRU size is bigger than subnet size").AtError()
}
fkdns.domainToIP = cache.NewLru(lruSize)
fkdns.ipRange = ipRange
return nil
}
// GetFakeIPForDomain check and generate a fake IP for a domain name
func (fkdns *Holder) GetFakeIPForDomain(domain string) []net.Address {
if v, ok := fkdns.domainToIP.Get(domain); ok {
return []net.Address{v.(net.Address)}
}
var currentTimeMillis = uint64(time.Now().UnixNano() / 1e6)
ones, bits := fkdns.ipRange.Mask.Size()
rooms := bits - ones
if rooms < 64 {
currentTimeMillis %= (uint64(1) << rooms)
}
var bigIntIP = big.NewInt(0).SetBytes(fkdns.ipRange.IP)
bigIntIP = bigIntIP.Add(bigIntIP, new(big.Int).SetUint64(currentTimeMillis))
var ip net.Address
for {
ip = net.IPAddress(bigIntIP.Bytes())
// if we run for a long time, we may go back to beginning and start seeing the IP in use
if _, ok := fkdns.domainToIP.PeekKeyFromValue(ip); !ok {
break
}
bigIntIP = bigIntIP.Add(bigIntIP, big.NewInt(1))
if !fkdns.ipRange.Contains(bigIntIP.Bytes()) {
bigIntIP = big.NewInt(0).SetBytes(fkdns.ipRange.IP)
}
}
fkdns.domainToIP.Put(domain, ip)
return []net.Address{ip}
}
// GetDomainFromFakeDNS check if an IP is a fake IP and have corresponding domain name
func (fkdns *Holder) GetDomainFromFakeDNS(ip net.Address) string {
if !ip.Family().IsIP() || !fkdns.ipRange.Contains(ip.IP()) {
return ""
}
if k, ok := fkdns.domainToIP.GetKeyFromValue(ip); ok {
return k.(string)
}
newError("A fake ip request to ", ip, ", however there is no matching domain name in fake DNS").AtInfo().WriteToLog()
return ""
}
// GetFakeIPRange return fake IP range from configuration
func (fkdns *Holder) GetFakeIPRange() *gonet.IPNet {
return fkdns.ipRange
}
func init() {
common.Must(common.RegisterConfig((*FakeDnsPool)(nil), func(ctx context.Context, config interface{}) (interface{}, error) {
var f *Holder
var err error
if f, err = NewFakeDNSHolderConfigOnly(config.(*FakeDnsPool)); err != nil {
return nil, err
}
return f, nil
}))
}