AdGuardHome/home/dns.go

275 lines
6.7 KiB
Go

package home
import (
"fmt"
"net"
"os"
"strings"
"sync"
"time"
"github.com/AdguardTeam/AdGuardHome/dnsfilter"
"github.com/AdguardTeam/AdGuardHome/dnsforward"
"github.com/AdguardTeam/dnsproxy/proxy"
"github.com/AdguardTeam/dnsproxy/upstream"
"github.com/AdguardTeam/golibs/log"
"github.com/joomcode/errorx"
"github.com/miekg/dns"
)
var dnsServer *dnsforward.Server
const (
rdnsTimeout = 3 * time.Second // max time to wait for rDNS response
)
type dnsContext struct {
rdnsChannel chan string // pass data from DNS request handling thread to rDNS thread
// contains IP addresses of clients to be resolved by rDNS
// if IP address couldn't be resolved, it stays here forever to prevent further attempts to resolve the same IP
rdnsIP map[string]bool
rdnsLock sync.Mutex // synchronize access to rdnsIP
upstream upstream.Upstream // Upstream object for our own DNS server
}
var dnsctx dnsContext
// initDNSServer creates an instance of the dnsforward.Server
// Please note that we must do it even if we don't start it
// so that we had access to the query log and the stats
func initDNSServer(baseDir string) {
err := os.MkdirAll(baseDir, 0755)
if err != nil {
log.Fatalf("Cannot create DNS data dir at %s: %s", baseDir, err)
}
dnsServer = dnsforward.NewServer(baseDir)
bindhost := config.DNS.BindHost
if config.DNS.BindHost == "0.0.0.0" {
bindhost = "127.0.0.1"
}
resolverAddress := fmt.Sprintf("%s:%d", bindhost, config.DNS.Port)
opts := upstream.Options{
Timeout: rdnsTimeout,
}
dnsctx.upstream, err = upstream.AddressToUpstream(resolverAddress, opts)
if err != nil {
log.Error("upstream.AddressToUpstream: %s", err)
return
}
dnsctx.rdnsIP = make(map[string]bool)
dnsctx.rdnsChannel = make(chan string, 256)
go asyncRDNSLoop()
}
func isRunning() bool {
return dnsServer != nil && dnsServer.IsRunning()
}
func beginAsyncRDNS(ip string) {
if clientExists(ip) {
return
}
// add IP to rdnsIP, if not exists
dnsctx.rdnsLock.Lock()
defer dnsctx.rdnsLock.Unlock()
_, ok := dnsctx.rdnsIP[ip]
if ok {
return
}
dnsctx.rdnsIP[ip] = true
log.Tracef("Adding %s for rDNS resolve", ip)
select {
case dnsctx.rdnsChannel <- ip:
//
default:
log.Tracef("rDNS queue is full")
}
}
// Use rDNS to get hostname by IP address
func resolveRDNS(ip string) string {
log.Tracef("Resolving host for %s", ip)
req := dns.Msg{}
req.Id = dns.Id()
req.RecursionDesired = true
req.Question = []dns.Question{
{
Qtype: dns.TypePTR,
Qclass: dns.ClassINET,
},
}
var err error
req.Question[0].Name, err = dns.ReverseAddr(ip)
if err != nil {
log.Debug("Error while calling dns.ReverseAddr(%s): %s", ip, err)
return ""
}
resp, err := dnsctx.upstream.Exchange(&req)
if err != nil {
log.Error("Error while making an rDNS lookup for %s: %s", ip, err)
return ""
}
if len(resp.Answer) != 1 {
log.Debug("No answer for rDNS lookup of %s", ip)
return ""
}
ptr, ok := resp.Answer[0].(*dns.PTR)
if !ok {
log.Error("not a PTR response for %s", ip)
return ""
}
log.Tracef("PTR response for %s: %s", ip, ptr.String())
if strings.HasSuffix(ptr.Ptr, ".") {
ptr.Ptr = ptr.Ptr[:len(ptr.Ptr)-1]
}
return ptr.Ptr
}
// Wait for a signal and then synchronously resolve hostname by IP address
// Add the hostname:IP pair to "Clients" array
func asyncRDNSLoop() {
for {
var ip string
ip = <-dnsctx.rdnsChannel
host := resolveRDNS(ip)
if len(host) == 0 {
continue
}
dnsctx.rdnsLock.Lock()
delete(dnsctx.rdnsIP, ip)
dnsctx.rdnsLock.Unlock()
_, _ = clientAddHost(ip, host, ClientSourceRDNS)
}
}
func onDNSRequest(d *proxy.DNSContext) {
qType := d.Req.Question[0].Qtype
if qType != dns.TypeA && qType != dns.TypeAAAA {
return
}
ip := dnsforward.GetIPString(d.Addr)
if ip == "" {
// This would be quite weird if we get here
return
}
beginAsyncRDNS(ip)
}
func generateServerConfig() dnsforward.ServerConfig {
filters := []dnsfilter.Filter{}
userFilter := userFilter()
filters = append(filters, dnsfilter.Filter{
ID: userFilter.ID,
Data: userFilter.Data,
})
for _, filter := range config.Filters {
filters = append(filters, dnsfilter.Filter{
ID: filter.ID,
Data: filter.Data,
})
}
newconfig := dnsforward.ServerConfig{
UDPListenAddr: &net.UDPAddr{IP: net.ParseIP(config.DNS.BindHost), Port: config.DNS.Port},
TCPListenAddr: &net.TCPAddr{IP: net.ParseIP(config.DNS.BindHost), Port: config.DNS.Port},
FilteringConfig: config.DNS.FilteringConfig,
Filters: filters,
}
bindhost := config.DNS.BindHost
if config.DNS.BindHost == "0.0.0.0" {
bindhost = "127.0.0.1"
}
newconfig.ResolverAddress = fmt.Sprintf("%s:%d", bindhost, config.DNS.Port)
if config.TLS.Enabled {
newconfig.TLSConfig = config.TLS.TLSConfig
if config.TLS.PortDNSOverTLS != 0 {
newconfig.TLSListenAddr = &net.TCPAddr{IP: net.ParseIP(config.DNS.BindHost), Port: config.TLS.PortDNSOverTLS}
}
}
upstreamConfig, err := proxy.ParseUpstreamsConfig(config.DNS.UpstreamDNS, config.DNS.BootstrapDNS, dnsforward.DefaultTimeout)
if err != nil {
log.Error("Couldn't get upstreams configuration cause: %s", err)
}
newconfig.Upstreams = upstreamConfig.Upstreams
newconfig.DomainsReservedUpstreams = upstreamConfig.DomainReservedUpstreams
newconfig.AllServers = config.DNS.AllServers
newconfig.FilterHandler = applyClientSettings
newconfig.OnDNSRequest = onDNSRequest
return newconfig
}
// If a client has his own settings, apply them
func applyClientSettings(clientAddr string, setts *dnsfilter.RequestFilteringSettings) {
c, ok := clientFind(clientAddr)
if !ok || !c.UseOwnSettings {
return
}
log.Debug("Using settings for client with IP %s", clientAddr)
setts.FilteringEnabled = c.FilteringEnabled
setts.SafeSearchEnabled = c.SafeSearchEnabled
setts.SafeBrowsingEnabled = c.SafeBrowsingEnabled
setts.ParentalEnabled = c.ParentalEnabled
}
func startDNSServer() error {
if isRunning() {
return fmt.Errorf("unable to start forwarding DNS server: Already running")
}
newconfig := generateServerConfig()
err := dnsServer.Start(&newconfig)
if err != nil {
return errorx.Decorate(err, "Couldn't start forwarding DNS server")
}
top := dnsServer.GetStatsTop()
for k := range top.Clients {
beginAsyncRDNS(k)
}
return nil
}
func reconfigureDNSServer() error {
if !isRunning() {
return fmt.Errorf("Refusing to reconfigure forwarding DNS server: not running")
}
config := generateServerConfig()
err := dnsServer.Reconfigure(&config)
if err != nil {
return errorx.Decorate(err, "Couldn't start forwarding DNS server")
}
return nil
}
func stopDNSServer() error {
if !isRunning() {
return fmt.Errorf("Refusing to stop forwarding DNS server: not running")
}
err := dnsServer.Stop()
if err != nil {
return errorx.Decorate(err, "Couldn't stop forwarding DNS server")
}
return nil
}