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server.go
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server.go
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package dns
//go:generate go run $GOPATH/src/v2ray.com/core/common/errors/errorgen/main.go -pkg dns -path App,DNS
import (
"context"
"sync"
"time"
dnsmsg "github.com/miekg/dns"
"v2ray.com/core"
"v2ray.com/core/common"
"v2ray.com/core/common/net"
"v2ray.com/core/common/signal"
)
const (
QueryTimeout = time.Second * 8
)
type DomainRecord struct {
IP []net.IP
Expire time.Time
LastAccess time.Time
}
func (r *DomainRecord) Expired() bool {
return r.Expire.Before(time.Now())
}
type Server struct {
sync.Mutex
hosts map[string]net.IP
records map[string]*DomainRecord
servers []NameServer
task *signal.PeriodicTask
}
func New(ctx context.Context, config *Config) (*Server, error) {
server := &Server{
records: make(map[string]*DomainRecord),
servers: make([]NameServer, len(config.NameServers)),
hosts: config.GetInternalHosts(),
}
server.task = &signal.PeriodicTask{
Interval: time.Minute * 10,
Execute: func() error {
server.cleanup()
return nil
},
}
v := core.MustFromContext(ctx)
if err := v.RegisterFeature((*core.DNSClient)(nil), server); err != nil {
return nil, newError("unable to register DNSClient.").Base(err)
}
for idx, destPB := range config.NameServers {
address := destPB.Address.AsAddress()
if address.Family().IsDomain() && address.Domain() == "localhost" {
server.servers[idx] = &LocalNameServer{}
} else {
dest := destPB.AsDestination()
if dest.Network == net.Network_Unknown {
dest.Network = net.Network_UDP
}
if dest.Network == net.Network_UDP {
server.servers[idx] = NewUDPNameServer(dest, v.Dispatcher())
}
}
}
if len(config.NameServers) == 0 {
server.servers = append(server.servers, &LocalNameServer{})
}
return server, nil
}
// Start implements common.Runnable.
func (s *Server) Start() error {
return s.task.Start()
}
// Close implements common.Closable.
func (s *Server) Close() error {
return s.task.Close()
}
func (s *Server) GetCached(domain string) []net.IP {
s.Lock()
defer s.Unlock()
if record, found := s.records[domain]; found && !record.Expired() {
record.LastAccess = time.Now()
return record.IP
}
return nil
}
func (s *Server) cleanup() {
s.Lock()
defer s.Unlock()
for d, r := range s.records {
if r.Expired() {
delete(s.records, d)
}
}
if len(s.records) == 0 {
s.records = make(map[string]*DomainRecord)
}
}
func (s *Server) LookupIP(domain string) ([]net.IP, error) {
if ip, found := s.hosts[domain]; found {
return []net.IP{ip}, nil
}
domain = dnsmsg.Fqdn(domain)
ips := s.GetCached(domain)
if ips != nil {
return ips, nil
}
for _, server := range s.servers {
response := server.QueryA(domain)
select {
case a, open := <-response:
if !open || a == nil {
continue
}
s.Lock()
s.records[domain] = &DomainRecord{
IP: a.IPs,
Expire: a.Expire,
LastAccess: time.Now(),
}
s.Unlock()
newError("returning ", len(a.IPs), " IPs for domain ", domain).AtDebug().WriteToLog()
return a.IPs, nil
case <-time.After(QueryTimeout):
}
}
return nil, newError("returning nil for domain ", domain)
}
func init() {
common.Must(common.RegisterConfig((*Config)(nil), func(ctx context.Context, config interface{}) (interface{}, error) {
return New(ctx, config.(*Config))
}))
}