// +build !confonly package fakedns import ( "context" "math" "math/big" gonet "net" "github.com/v2fly/v2ray-core/v4/common" "github.com/v2fly/v2ray-core/v4/common/cache" "github.com/v2fly/v2ray-core/v4/common/net" "github.com/v2fly/v2ray-core/v4/features/dns" ) type Holder struct { domainToIP cache.Lru nextIP *big.Int 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.nextIP = 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("198.18.0.0/15", 65535) if err != nil { return nil, err } return fkdns, nil } func NewFakeDNSHolderConfigOnly(conf *FakeDnsPool) (*Holder, error) { return &Holder{nil, 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 ipaddr gonet.IP var currentIP *big.Int var err error if ipaddr, ipRange, err = gonet.ParseCIDR(ipPoolCidr); err != nil { return newError("Unable to parse CIDR for Fake DNS IP assignment").Base(err).AtError() } currentIP = big.NewInt(0).SetBytes(ipaddr) if ipaddr.To4() != nil { currentIP = big.NewInt(0).SetBytes(ipaddr.To4()) } 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 fkdns.nextIP = currentIP 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 ip net.Address for { ip = net.IPAddress(fkdns.nextIP.Bytes()) fkdns.nextIP = fkdns.nextIP.Add(fkdns.nextIP, big.NewInt(1)) if !fkdns.ipRange.Contains(fkdns.nextIP.Bytes()) { fkdns.nextIP = big.NewInt(0).SetBytes(fkdns.ipRange.IP) } // if we run for a long time, we may go back to beginning and start seeing the IP in use if _, ok := fkdns.domainToIP.GetKeyFromValue(ip); !ok { break } } 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) } return "" } 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 })) }