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|
package zdns
import (
"fmt"
"io"
"log"
"net"
"net/http"
"net/url"
"os"
"os/signal"
"sync"
"syscall"
"time"
"github.com/mpolden/zdns/dns"
"github.com/mpolden/zdns/hosts"
)
// A Server defines parameters for running a DNS server.
type Server struct {
Config Config
Logger *log.Logger
proxy *dns.Proxy
matcher *hosts.Matcher
ticker *time.Ticker
done chan bool
signal chan os.Signal
mu sync.RWMutex
}
// NewServer returns a new server configured according to config.
func NewServer(config Config) (*Server, error) {
server := &Server{
Config: config,
signal: make(chan os.Signal, 1),
done: make(chan bool, 1),
}
if config.Filter.RefreshInterval.Duration > 0 {
server.ticker = time.NewTicker(config.Filter.RefreshInterval.Duration)
go server.reloadHosts()
}
signal.Notify(server.signal)
go server.readSignal()
proxy := dns.NewProxy(server.handler, config.Resolvers, config.Resolver.Timeout.Duration)
server.proxy = proxy
return server, nil
}
func readHosts(name string) (hosts.Hosts, error) {
url, err := url.Parse(name)
if err != nil {
return nil, err
}
var rc io.ReadCloser
switch url.Scheme {
case "file":
f, err := os.Open(url.Path)
if err != nil {
return nil, err
}
rc = f
case "http", "https":
client := http.Client{Timeout: 10 * time.Second}
res, err := client.Get(url.String())
if err != nil {
return nil, err
}
rc = res.Body
default:
return nil, fmt.Errorf("%s: invalid scheme: %s", url, url.Scheme)
}
defer rc.Close()
return hosts.Parse(rc)
}
func nonFqdn(s string) string {
sz := len(s)
if sz > 0 && s[sz-1:] == "." {
return s[:sz-1]
}
return s
}
func (s *Server) logf(format string, v ...interface{}) {
if s.Logger != nil {
s.Logger.Printf(format, v...)
}
}
func (s *Server) readSignal() {
for {
select {
case <-s.done:
signal.Stop(s.signal)
return
case sig := <-s.signal:
switch sig {
case syscall.SIGHUP:
s.logf("received signal %s: reloading filters", sig)
s.loadHosts()
case syscall.SIGTERM, syscall.SIGINT:
s.logf("received signal %s: shutting down", sig)
s.Close()
default:
s.logf("received signal %s: ignoring", sig)
}
}
}
}
func (s *Server) reloadHosts() {
for {
select {
case <-s.done:
s.ticker.Stop()
return
case <-s.ticker.C:
s.loadHosts()
}
}
}
func (s *Server) loadHosts() {
var hs []hosts.Hosts
var size int
for _, f := range s.Config.Filters {
h, err := readHosts(f.URL)
if err != nil {
s.logf("failed to read hosts from %s: %s", f.URL, err)
continue
}
if f.Reject {
hs = append(hs, h)
s.logf("loaded %d hosts from %s", len(h), f.URL)
size += len(h)
} else {
var removed int
for hostToRemove := range h {
for _, h := range hs {
if _, ok := h.Get(hostToRemove); ok {
removed++
h.Del(hostToRemove)
}
}
}
size -= removed
if removed > 0 {
s.logf("removed %d hosts from %s", len(h), f.URL)
}
}
}
m := hosts.NewMatcher(hs...)
s.mu.Lock()
defer s.mu.Unlock()
s.matcher = m
s.logf("loaded %d hosts in total", size)
}
// Close terminates all active operations and shuts down the DNS server.
func (s *Server) Close() {
s.done <- true
s.done <- true
if err := s.proxy.Close(); err != nil {
s.logf("error during close: %s", err)
}
}
func (s *Server) handler(r *dns.Request) *dns.Reply {
s.mu.RLock()
defer s.mu.RUnlock()
if !s.matcher.Match(nonFqdn(r.Name)) {
return nil // No match
}
switch s.Config.Filter.RejectMode {
case "zero":
switch r.Type {
case dns.TypeA:
return dns.ReplyA(r.Name, net.IPv4zero)
case dns.TypeAAAA:
return dns.ReplyAAAA(r.Name, net.IPv6zero)
}
case "no-data":
return &dns.Reply{}
case "hosts":
// TODO: Provide answer from hosts
}
return nil
}
// ListenAndServe listens on the network address addr and uses the server to process requests.
func (s *Server) ListenAndServe(addr, network string) error {
return s.proxy.ListenAndServe(addr, network)
}
|
