forked from ginuerzh/gost
/
resolver.go
330 lines (289 loc) · 6.2 KB
/
resolver.go
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package gost
import (
"bufio"
"bytes"
"crypto/tls"
"fmt"
"io"
"net"
"strings"
"sync"
"time"
"github.com/go-log/log"
"github.com/miekg/dns"
)
var (
// DefaultResolverTimeout is the default timeout for name resolution.
DefaultResolverTimeout = 30 * time.Second
// DefaultResolverTTL is the default cache TTL for name resolution.
DefaultResolverTTL = 60 * time.Second
)
// Resolver is a name resolver for domain name.
// It contains a list of name servers.
type Resolver interface {
// Resolve returns a slice of that host's IPv4 and IPv6 addresses.
Resolve(host string) ([]net.IP, error)
}
// ReloadResolver is resolover that support live reloading
type ReloadResolver interface {
Resolver
Reloader
}
// NameServer is a name server.
// Currently supported protocol: TCP, UDP and TLS.
type NameServer struct {
Addr string
Protocol string
Hostname string // for TLS handshake verification
}
func (ns NameServer) String() string {
addr := ns.Addr
prot := ns.Protocol
if _, port, _ := net.SplitHostPort(addr); port == "" {
addr = net.JoinHostPort(addr, "53")
}
if prot == "" {
prot = "udp"
}
return fmt.Sprintf("%s/%s", addr, prot)
}
type resolverCacheItem struct {
IPs []net.IP
ts int64
}
type resolver struct {
Resolver *net.Resolver
Servers []NameServer
mCache *sync.Map
Timeout time.Duration
TTL time.Duration
period time.Duration
domain string
mux sync.RWMutex
}
// NewResolver create a new Resolver with the given name servers and resolution timeout.
func NewResolver(timeout, ttl time.Duration, servers ...NameServer) ReloadResolver {
r := &resolver{
Servers: servers,
Timeout: timeout,
TTL: ttl,
mCache: &sync.Map{},
}
if r.Timeout <= 0 {
r.Timeout = DefaultResolverTimeout
}
if r.TTL == 0 {
r.TTL = DefaultResolverTTL
}
return r
}
func (r *resolver) copyServers() []NameServer {
var servers []NameServer
for i := range r.Servers {
servers = append(servers, r.Servers[i])
}
return servers
}
func (r *resolver) Resolve(host string) (ips []net.IP, err error) {
if r == nil {
return
}
var domain string
var timeout, ttl time.Duration
var servers []NameServer
r.mux.RLock()
domain = r.domain
timeout = r.Timeout
servers = r.copyServers()
r.mux.RUnlock()
if ip := net.ParseIP(host); ip != nil {
return []net.IP{ip}, nil
}
if !strings.Contains(host, ".") && domain != "" {
host = host + "." + domain
}
ips = r.loadCache(host, ttl)
if len(ips) > 0 {
if Debug {
log.Logf("[resolver] cache hit %s: %v", host, ips)
}
return
}
for _, ns := range servers {
ips, err = r.resolve(ns, host, timeout)
if err != nil {
log.Logf("[resolver] %s via %s : %s", host, ns, err)
continue
}
if Debug {
log.Logf("[resolver] %s via %s %v", host, ns, ips)
}
if len(ips) > 0 {
break
}
}
r.storeCache(host, ips)
return
}
func (*resolver) resolve(ns NameServer, host string, timeout time.Duration) (ips []net.IP, err error) {
addr := ns.Addr
if _, port, _ := net.SplitHostPort(addr); port == "" {
addr = net.JoinHostPort(addr, "53")
}
client := dns.Client{
Timeout: timeout,
}
switch strings.ToLower(ns.Protocol) {
case "tcp":
client.Net = "tcp"
case "tls":
cfg := &tls.Config{
ServerName: ns.Hostname,
}
if cfg.ServerName == "" {
cfg.InsecureSkipVerify = true
}
client.Net = "tcp-tls"
client.TLSConfig = cfg
case "udp":
fallthrough
default:
client.Net = "udp"
}
m := dns.Msg{}
m.SetQuestion(dns.Fqdn(host), dns.TypeA)
mr, _, err := client.Exchange(&m, addr)
if err != nil {
return
}
for _, ans := range mr.Answer {
if ar, _ := ans.(*dns.A); ar != nil {
ips = append(ips, ar.A)
}
}
return
}
func (r *resolver) loadCache(name string, ttl time.Duration) []net.IP {
if ttl < 0 {
return nil
}
if v, ok := r.mCache.Load(name); ok {
item, _ := v.(*resolverCacheItem)
if item == nil || time.Since(time.Unix(item.ts, 0)) > ttl {
return nil
}
return item.IPs
}
return nil
}
func (r *resolver) storeCache(name string, ips []net.IP) {
if name == "" || len(ips) == 0 {
return
}
r.mCache.Store(name, &resolverCacheItem{
IPs: ips,
ts: time.Now().Unix(),
})
}
func (r *resolver) Reload(rd io.Reader) error {
var ttl, timeout, period time.Duration
var domain string
var nss []NameServer
split := func(line string) []string {
if line == "" {
return nil
}
if n := strings.IndexByte(line, '#'); n >= 0 {
line = line[:n]
}
line = strings.Replace(line, "\t", " ", -1)
line = strings.TrimSpace(line)
var ss []string
for _, s := range strings.Split(line, " ") {
if s = strings.TrimSpace(s); s != "" {
ss = append(ss, s)
}
}
return ss
}
scanner := bufio.NewScanner(rd)
for scanner.Scan() {
line := scanner.Text()
ss := split(line)
if len(ss) == 0 {
continue
}
switch ss[0] {
case "timeout": // timeout option
if len(ss) > 1 {
timeout, _ = time.ParseDuration(ss[1])
}
case "ttl": // ttl option
if len(ss) > 1 {
ttl, _ = time.ParseDuration(ss[1])
}
case "reload": // reload option
if len(ss) > 1 {
period, _ = time.ParseDuration(ss[1])
}
case "domain":
if len(ss) > 1 {
domain = ss[1]
}
case "search", "sortlist", "options": // we don't support these features in /etc/resolv.conf
case "nameserver": // nameserver option, compatible with /etc/resolv.conf
if len(ss) <= 1 {
break
}
ss = ss[1:]
fallthrough
default:
var ns NameServer
switch len(ss) {
case 0:
break
case 1:
ns.Addr = ss[0]
case 2:
ns.Addr = ss[0]
ns.Protocol = ss[1]
default:
ns.Addr = ss[0]
ns.Protocol = ss[1]
ns.Hostname = ss[2]
}
nss = append(nss, ns)
}
}
if err := scanner.Err(); err != nil {
return err
}
r.mux.Lock()
r.Timeout = timeout
r.TTL = ttl
r.domain = domain
r.period = period
r.Servers = nss
r.mux.Unlock()
return nil
}
func (r *resolver) Period() time.Duration {
r.mux.RLock()
defer r.mux.RUnlock()
return r.period
}
func (r *resolver) String() string {
if r == nil {
return ""
}
r.mux.RLock()
defer r.mux.RUnlock()
b := &bytes.Buffer{}
fmt.Fprintf(b, "Timeout %v\n", r.Timeout)
fmt.Fprintf(b, "TTL %v\n", r.TTL)
fmt.Fprintf(b, "Reload %v\n", r.period)
for i := range r.Servers {
fmt.Fprintln(b, r.Servers[i])
}
return b.String()
}