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server.go
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server.go
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package server
import (
"context"
"net"
"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/errors"
v2net "v2ray.com/core/common/net"
)
const (
QueryTimeout = time.Second * 8
)
type DomainRecord struct {
A *ARecord
}
type CacheServer struct {
sync.RWMutex
space app.Space
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, errors.New("DNSCacheServer: 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 errors.New("DNS: 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 == v2net.Network_Unknown {
dest.Network = v2net.Network_UDP
}
if dest.Network == v2net.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() {}
// Private: Visible for testing.
func (v *CacheServer) GetCached(domain string) []net.IP {
v.RLock()
defer v.RUnlock()
if record, found := v.records[domain]; found && record.A.Expire.After(time.Now()) {
return record.A.IPs
}
return nil
}
func (v *CacheServer) Get(domain string) []net.IP {
if ip, found := v.hosts[domain]; found {
return []net.IP{ip}
}
domain = dnsmsg.Fqdn(domain)
ips := v.GetCached(domain)
if ips != nil {
return ips
}
for _, server := range v.servers {
response := server.QueryA(domain)
select {
case a, open := <-response:
if !open || a == nil {
continue
}
v.Lock()
v.records[domain] = &DomainRecord{
A: a,
}
v.Unlock()
log.Debug("DNS: Returning ", len(a.IPs), " IPs for domain ", domain)
return a.IPs
case <-time.After(QueryTimeout):
}
}
log.Debug("DNS: Returning nil for domain ", domain)
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))
}))
}