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server.go
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server.go
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package server
//go:generate go run $GOPATH/src/v2ray.com/core/tools/generrorgen/main.go -pkg server -path App,DNS,Server
import (
"context"
"sync"
"time"
dnsmsg "github.com/miekg/dns"
"v2ray.com/core/app"
"v2ray.com/core/app/dispatcher"
"v2ray.com/core/app/dns"
"v2ray.com/core/app/log"
"v2ray.com/core/common"
"v2ray.com/core/common/net"
)
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())
}
func (r *DomainRecord) Inactive() bool {
now := time.Now()
return r.Expire.Before(now) || r.LastAccess.Add(time.Minute*5).Before(now)
}
type CacheServer struct {
sync.Mutex
hosts map[string]net.IP
records map[string]*DomainRecord
servers []NameServer
}
func NewCacheServer(ctx context.Context, config *dns.Config) (*CacheServer, error) {
space := app.SpaceFromContext(ctx)
if space == nil {
return nil, newError("no space in context")
}
server := &CacheServer{
records: make(map[string]*DomainRecord),
servers: make([]NameServer, len(config.NameServers)),
hosts: config.GetInternalHosts(),
}
space.OnInitialize(func() error {
disp := dispatcher.FromSpace(space)
if disp == nil {
return newError("dispatcher is not found in the space")
}
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, disp)
}
}
}
if len(config.NameServers) == 0 {
server.servers = append(server.servers, &LocalNameServer{})
}
return nil
})
return server, nil
}
func (*CacheServer) Interface() interface{} {
return (*dns.Server)(nil)
}
func (*CacheServer) Start() error {
return nil
}
func (*CacheServer) Close() {}
func (s *CacheServer) 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 *CacheServer) tryCleanup() {
s.Lock()
defer s.Unlock()
if len(s.records) > 256 {
domains := make([]string, 0, 256)
for d, r := range s.records {
if r.Expired() {
domains = append(domains, d)
}
}
for _, d := range domains {
delete(s.records, d)
}
}
}
func (s *CacheServer) Get(domain string) []net.IP {
if ip, found := s.hosts[domain]; found {
return []net.IP{ip}
}
domain = dnsmsg.Fqdn(domain)
ips := s.GetCached(domain)
if ips != nil {
return ips
}
s.tryCleanup()
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()
log.Trace(newError("returning ", len(a.IPs), " IPs for domain ", domain).AtDebug())
return a.IPs
case <-time.After(QueryTimeout):
}
}
log.Trace(newError("returning nil for domain ", domain).AtDebug())
return nil
}
func init() {
common.Must(common.RegisterConfig((*dns.Config)(nil), func(ctx context.Context, config interface{}) (interface{}, error) {
return NewCacheServer(ctx, config.(*dns.Config))
}))
}