/
handler.go
270 lines (215 loc) · 5.53 KB
/
handler.go
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package dns
import (
"errors"
"fmt"
"github.com/miekg/dns"
"github.com/yinheli/kungfu/internal"
"net"
"runtime/debug"
"strings"
"sync"
"time"
)
const DEFAULT_TTL = time.Duration(time.Hour * 3)
const DNS_SERVER_NAME = "kungfu-dns-server-helps-you-automatic-climb-the-wall."
type handler struct {
server *Server
client *dns.Client
nameserver []string
lock sync.Mutex
}
func (h *handler) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
defer func() {
if x := recover(); x != nil {
log.Error("ServeDNS error", x)
log.Error("request:\n%v", r)
log.Error("request Extra :\n%v", r.Extra)
log.Error("stack %s", string(debug.Stack()))
dns.HandleFailed(w, r)
}
}()
if r == nil {
return
}
question := r.Question[0]
var msg *dns.Msg
var err error
if question.Qtype == dns.TypePTR {
msg, err = h.resolveInternalPTR(r)
} else {
isIPV4A := isIPV4TypeAQuery(&question)
if isIPV4A {
msg, err = h.resolveInternal(r)
} else {
msg, err = h.resolveUpstream(r)
}
}
if err != nil {
log.Error("process resolve error: %v", err)
}
// log
if msg != nil && msg.Rcode != dns.RcodeSuccess {
log.Debug("resolve remote addr: %s, qname: %s rcode: %d",
w.RemoteAddr().String(), question.Name, msg.Rcode)
}
if err != nil || msg == nil {
dns.HandleFailed(w, r)
} else {
w.WriteMsg(msg)
}
}
func isIPV4TypeAQuery(q *dns.Question) bool {
return q.Qclass == dns.ClassINET && q.Qtype == dns.TypeA
}
func (h *handler) queryDomainCache(r *dns.Msg) *dns.Msg {
qname := r.Question[0].Name
redis := h.server.RedisClient
qnameKey := internal.GetRedisDomainKey(qname)
ttl, err := redis.TTL(qnameKey).Result()
if err != nil {
log.Error("redis check %s error %v", qname, err)
return nil
}
if ttl > 1 {
ip, err := redis.Get(qnameKey).Result()
if err != nil {
log.Error("redis get %s error %v", qname, err)
return nil
}
msg := new(dns.Msg)
msg.SetReply(r)
a := newARecord(qname, net.ParseIP(ip), uint32(ttl.Seconds()))
msg.Answer = append(msg.Answer, a)
log.Debug("internal resolve %s result: %s, ttl: %d", qname, ip, a.Hdr.Ttl)
return msg
}
return nil
}
func (h *handler) resolveInternal(r *dns.Msg) (*dns.Msg, error) {
msg := h.queryDomainCache(r)
if msg != nil {
return msg, nil
}
h.lock.Lock()
defer h.lock.Unlock()
qname := r.Question[0].Name
redis := h.server.RedisClient
if !h.isDomainInGfwlist(qname) {
return h.resolveUpstream(r)
}
// recheck
msg = h.queryDomainCache(r)
if msg != nil {
return msg, nil
}
qnameKey := internal.GetRedisDomainKey(qname)
currentIpKey := internal.GetRedisKey("current-ip")
ipInt, err := redis.Incr(currentIpKey).Result()
if err != nil {
return nil, err
}
ipValue := (h.server.minIp + uint32(ipInt)) % h.server.maxIp
ip := internal.IntToIpv4(ipValue)
ipStr := ip.String()
qnameIpKey := internal.GetRedisIpKey(ipStr)
success, err := redis.SetNX(qnameIpKey, strings.TrimSuffix(qname, "."), DEFAULT_TTL).Result()
if err != nil {
return nil, err
}
if !success {
return nil, errors.New(fmt.Sprintf("update ip cache fail: duplicate key: %s, %s", qnameIpKey, qname))
}
success, err = redis.SetNX(qnameKey, ipStr, DEFAULT_TTL).Result()
if err != nil {
redis.Del(qnameIpKey)
return nil, err
}
if !success {
redis.Del(qnameIpKey)
return nil, errors.New(fmt.Sprintf("update domain cache fail: duplicate key: %s, %s", qnameKey, ipStr))
}
msg = new(dns.Msg)
msg.SetReply(r)
a := newARecord(qname, ip, uint32(DEFAULT_TTL.Seconds()))
msg.Answer = append(msg.Answer, a)
log.Debug("internal *new resolve %s result: %s, ttl: %d", qname, ip, a.Hdr.Ttl)
return msg, nil
}
func (h *handler) resolveInternalPTR(r *dns.Msg) (*dns.Msg, error) {
qname := r.Question[0].Name
if h.server.arpaContains(&qname) {
msg := new(dns.Msg)
msg.SetReply(r)
ptr := new(dns.PTR)
ptr.Hdr = dns.RR_Header{
Name: dns.Fqdn(qname),
Rrtype: dns.TypePTR,
Class: dns.ClassINET,
Ttl: 0,
}
ptr.Ptr = DNS_SERVER_NAME
msg.Answer = append(msg.Answer, ptr)
return msg, nil
}
return h.resolveUpstream(r)
}
func (h *handler) resolveUpstream(r *dns.Msg) (*dns.Msg, error) {
qname := r.Question[0].Name
qtype := dns.Type(r.Question[0].Qtype).String()
var err error
for _, ns := range h.nameserver {
r, _, err = h.client.Exchange(r, ns)
if err != nil {
log.Error("resolve upstream %s on %s qtype: %s error %v", qname, ns, qtype, err)
continue
}
if r.Rcode == dns.RcodeServerFailure {
log.Error("resolve upstream %s on %s qtype: %s fail code %d", qname, ns, qtype, r.Rcode)
continue
}
log.Debug("resolve upstream %s on %s qtype: %s, code: %d", qname, ns, qtype, r.Rcode)
break
}
return r, err
}
func (h *handler) isDomainInGfwlist(domain string) bool {
if domain == "." {
return false
}
domain = strings.TrimSuffix(domain, ".")
if h.isSingleDomainInGfwList(domain) {
return true
}
ds := strings.Split(domain, ".")
n := len(ds)
if n == 1 {
return false
}
for i, j := 1, n-1; i < j; i += 1 {
s := strings.Join(ds[i:], ".")
if h.isSingleDomainInGfwList(s) {
return true
}
}
return false
}
func (h *handler) isSingleDomainInGfwList(domain string) bool {
key := internal.GetRedisProxyDomainSetKey()
v, err := h.server.RedisClient.SIsMember(key, domain).Result()
if err != nil {
log.Warning("check single domain in proxy set error, domain %s, %v", domain, err)
return false
}
return v
}
func newARecord(qname string, ip net.IP, ttl uint32) *dns.A {
a := new(dns.A)
a.Hdr = dns.RR_Header{
Name: dns.Fqdn(qname),
Rrtype: dns.TypeA,
Class: dns.ClassINET,
Ttl: ttl,
}
a.A = ip
return a
}