743 lines
19 KiB
Go
743 lines
19 KiB
Go
package handler
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||
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import (
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"errors"
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"fmt"
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"net"
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"strings"
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"sync"
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||
"time"
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||
"strconv"
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||
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"github.com/miekg/dns"
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||
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"godns/internal/cache"
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"godns/internal/model"
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"godns/internal/stats"
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"godns/pkg/logger"
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)
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type Handler struct {
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strategy int
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commonUpstreams, specialUpstreams []*model.Upstream
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builtInCache cache.Cache
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logger logger.Logger
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stats stats.StatsRecorder
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}
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func NewHandler(strategy int, builtInCache bool,
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upstreams []*model.Upstream,
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dataPath string,
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log logger.Logger,
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statsRecorder stats.StatsRecorder) *Handler {
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var c cache.Cache
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if builtInCache {
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var err error
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c, err = cache.NewBadgerCache(dataPath, log)
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if err != nil {
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log.Printf("Failed to initialize BadgerDB cache: %v", err)
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log.Printf("Cache will be disabled")
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c = nil
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} else {
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log.Printf("BadgerDB cache initialized successfully at %s", dataPath)
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}
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}
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var commonUpstreams, specialUpstreams []*model.Upstream
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for i := 0; i < len(upstreams); i++ {
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if len(upstreams[i].Match) > 0 {
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specialUpstreams = append(specialUpstreams, upstreams[i])
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} else {
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commonUpstreams = append(commonUpstreams, upstreams[i])
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}
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}
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return &Handler{
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strategy: strategy,
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commonUpstreams: commonUpstreams,
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specialUpstreams: specialUpstreams,
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builtInCache: c,
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logger: log,
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stats: statsRecorder,
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}
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}
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func (h *Handler) matchedUpstreams(req *dns.Msg) []*model.Upstream {
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if len(req.Question) == 0 {
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return h.commonUpstreams
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}
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q := req.Question[0]
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var matchedUpstreams []*model.Upstream
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for i := 0; i < len(h.specialUpstreams); i++ {
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if h.specialUpstreams[i].IsMatch(q.Name) {
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matchedUpstreams = append(matchedUpstreams, h.specialUpstreams[i])
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}
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}
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if len(matchedUpstreams) > 0 {
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return matchedUpstreams
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}
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return h.commonUpstreams
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}
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func (h *Handler) LookupIP(host string) (ip net.IP, err error) {
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if ip = net.ParseIP(host); ip != nil {
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return ip, nil
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}
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if !strings.HasSuffix(host, ".") {
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host += "."
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}
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m := new(dns.Msg)
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m.Id = dns.Id()
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m.RecursionDesired = true
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m.Question = make([]dns.Question, 1)
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m.Question[0] = dns.Question{Name: host, Qtype: dns.TypeA, Qclass: dns.ClassINET}
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res := h.exchange(m)
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// 取一个 IPv4 地址
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for i := 0; i < len(res.Answer); i++ {
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if aRecord, ok := res.Answer[i].(*dns.A); ok {
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ip = aRecord.A
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}
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}
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// 选取最后一个（一般是备用，存活率高一些）
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if ip == nil {
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err = errors.New("no ipv4 address found")
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}
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h.logger.Printf("bootstrap LookupIP: %s %v --> %s %v", host, res.Answer, ip, err)
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return
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}
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// removeEDNS 清理请求中的 EDNS 客户端子网信息
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func (h *Handler) removeEDNS(req *dns.Msg) {
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opt := req.IsEdns0()
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if opt == nil {
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return
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}
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// 过滤掉 EDNS Client Subnet 选项
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var newOptions []dns.EDNS0
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for _, option := range opt.Option {
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if _, ok := option.(*dns.EDNS0_SUBNET); !ok {
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// 保留非 ECS 的其他选项
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newOptions = append(newOptions, option)
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} else {
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h.logger.Printf("Removed EDNS Client Subnet from request")
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}
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}
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opt.Option = newOptions
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}
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func (h *Handler) exchange(req *dns.Msg) *dns.Msg {
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// 清理 EDNS 客户端子网信息
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h.removeEDNS(req)
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var msgs []*dns.Msg
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switch h.strategy {
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||
case model.StrategyFullest:
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msgs = h.getTheFullestResults(req)
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||
case model.StrategyFastest:
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||
msgs = h.getTheFastestResults(req)
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case model.StrategyAnyResult:
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msgs = h.getAnyResult(req)
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||
}
|
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var res *dns.Msg
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for i := 0; i < len(msgs); i++ {
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if msgs[i] == nil {
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||
continue
|
||
}
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if res == nil {
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res = msgs[i]
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||
continue
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||
}
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res.Answer = append(res.Answer, msgs[i].Answer...)
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}
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if res == nil {
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// 如果全部上游挂了要返回错误
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res = new(dns.Msg)
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res.Rcode = dns.RcodeServerFailure
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} else {
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res.Answer = uniqueAnswer(res.Answer)
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}
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||
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return res
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}
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func getDnsRequestCacheKey(m *dns.Msg) string {
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if len(m.Question) == 0 {
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return ""
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}
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var b strings.Builder
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||
b.Grow(64)
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b.WriteString(model.GetDomainNameFromDnsMsg(m))
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b.WriteByte('#')
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b.WriteString(strconv.Itoa(int(m.Question[0].Qtype)))
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if o := m.IsEdns0(); o != nil && o.Do() {
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b.WriteString("#DO")
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}
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return b.String()
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}
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func getDnsResponseTtl(m *dns.Msg) time.Duration {
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var ttl uint32
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if len(m.Answer) > 0 {
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ttl = m.Answer[0].Header().Ttl
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}
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||
if ttl < 60 {
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ttl = 60 // 最小 ttl 1 分钟
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||
} else if ttl > 3600 {
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ttl = 3600 // 最大 ttl 1 小时
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}
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return time.Duration(ttl) * time.Second
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}
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// shouldCacheResponse 判断响应是否应该被缓存
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func shouldCacheResponse(m *dns.Msg) bool {
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// 不缓存服务器错误响应
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if m.Rcode == dns.RcodeServerFailure {
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return false
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}
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// 不缓存格式错误的响应
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if m.Rcode == dns.RcodeFormatError {
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return false
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}
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// NXDOMAIN (域名不存在) 可以缓存，但时间较短（由 getDnsResponseTtl 控制）
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// NOERROR 和 NXDOMAIN 都可以缓存
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return m.Rcode == dns.RcodeSuccess || m.Rcode == dns.RcodeNameError
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}
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// validateResponse 验证 DNS 响应，防止缓存投毒
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// 返回 true 表示响应有效，false 表示可能存在投毒风险
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func validateResponse(req *dns.Msg, resp *dns.Msg, debugLogger logger.Logger) bool {
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// 1. 检查响应是否为空
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if resp == nil {
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return false
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}
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// 2. 检查请求和响应的问题数量
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if len(req.Question) == 0 || len(resp.Question) == 0 {
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return true // 如果没有问题部分，跳过验证（某些响应可能没有问题部分）
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}
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// 3. 验证域名匹配（不区分大小写）
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if !strings.EqualFold(req.Question[0].Name, resp.Question[0].Name) {
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debugLogger.Printf("DNS response validation failed: domain mismatch - request: %s, response: %s",
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req.Question[0].Name, resp.Question[0].Name)
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return false
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}
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// 4. 验证查询类型匹配
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if req.Question[0].Qtype != resp.Question[0].Qtype {
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debugLogger.Printf("DNS response validation failed: qtype mismatch - request: %d, response: %d",
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req.Question[0].Qtype, resp.Question[0].Qtype)
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return false
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}
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// 5. 验证查询类别匹配（通常都是 IN - Internet）
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if req.Question[0].Qclass != resp.Question[0].Qclass {
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debugLogger.Printf("DNS response validation failed: qclass mismatch - request: %d, response: %d",
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req.Question[0].Qclass, resp.Question[0].Qclass)
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return false
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}
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// 6. 验证 Answer 部分的域名（防止返回无关域名的记录）
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requestDomain := strings.ToLower(strings.TrimSuffix(req.Question[0].Name, "."))
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validDomains := make(map[string]bool)
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validDomains[requestDomain] = true
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||
// 第一遍：收集所有 CNAME 目标域名
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for _, answer := range resp.Answer {
|
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if answer.Header().Rrtype == dns.TypeCNAME {
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if cname, ok := answer.(*dns.CNAME); ok {
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cnameTarget := strings.ToLower(strings.TrimSuffix(cname.Target, "."))
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validDomains[cnameTarget] = true
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}
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}
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}
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||
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// 第二遍：验证所有应答记录
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for _, answer := range resp.Answer {
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answerDomain := strings.ToLower(strings.TrimSuffix(answer.Header().Name, "."))
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||
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||
// 检查应答记录的域名是否在有效域名列表中
|
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if !validDomains[answerDomain] {
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// 对于 CNAME 记录，域名必须是请求域名
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if answer.Header().Rrtype == dns.TypeCNAME {
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if answerDomain != requestDomain {
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debugLogger.Printf("DNS response validation failed: CNAME domain mismatch - request: %s, CNAME: %s",
|
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requestDomain, answerDomain)
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return false
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}
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} else {
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// 对于其他记录类型，记录警告但不拒绝（某些服务器可能返回额外记录）
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debugLogger.Printf("DNS response validation warning: answer domain not in valid chain - request: %s, answer: %s (type: %d)",
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requestDomain, answerDomain, answer.Header().Rrtype)
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}
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}
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||
}
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||
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// 7. 检查 TTL 值的合理性（防止异常的 TTL 值）
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for _, answer := range resp.Answer {
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ttl := answer.Header().Ttl
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// TTL 不应该超过 7 天（604800 秒）
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if ttl > 604800 {
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debugLogger.Printf("DNS response validation warning: suspiciously high TTL: %d seconds for %s",
|
||
ttl, answer.Header().Name)
|
||
}
|
||
}
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||
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return true
|
||
}
|
||
|
||
// HandleDnsMsg 处理 DNS 查询的核心逻辑（支持缓存和统计）
|
||
// clientIP 和 domain 用于统计，如果为空则自动从请求中提取 domain
|
||
func (h *Handler) HandleDnsMsg(req *dns.Msg, clientIP, domain string) *dns.Msg {
|
||
h.logger.Printf("godns::request %+v\n", req)
|
||
|
||
// 记录查询统计
|
||
if h.stats != nil {
|
||
h.stats.RecordQuery()
|
||
|
||
// 提取域名（如果未提供）
|
||
if domain == "" && len(req.Question) > 0 {
|
||
domain = req.Question[0].Name
|
||
}
|
||
|
||
// 记录客户端查询
|
||
if clientIP != "" || domain != "" {
|
||
h.stats.RecordClientQuery(clientIP, domain)
|
||
}
|
||
}
|
||
|
||
// 检查缓存
|
||
var cacheKey string
|
||
var respCache *dns.Msg
|
||
if h.builtInCache != nil {
|
||
cacheKey = getDnsRequestCacheKey(req)
|
||
if v, ok := h.builtInCache.Get(cacheKey); ok {
|
||
if h.stats != nil {
|
||
h.stats.RecordCacheHit()
|
||
}
|
||
respCache = v.Msg.Copy()
|
||
if v.Expires.After(time.Now()) {
|
||
msg := replyUpdateTtl(req, respCache, uint32(time.Until(v.Expires).Seconds()))
|
||
if len(msg.Answer) > 0 {
|
||
return msg
|
||
}
|
||
}
|
||
} else {
|
||
if h.stats != nil {
|
||
h.stats.RecordCacheMiss()
|
||
}
|
||
}
|
||
}
|
||
|
||
// 从上游获取响应
|
||
resp := h.exchange(req)
|
||
|
||
if resp.Rcode == dns.RcodeServerFailure {
|
||
if h.stats != nil {
|
||
h.stats.RecordFailed()
|
||
}
|
||
// 上游失败时使用任何可用缓存（即使过期）作为降级
|
||
if respCache != nil {
|
||
msg := replyUpdateTtl(req, respCache, 12)
|
||
if len(msg.Answer) > 0 {
|
||
return msg
|
||
}
|
||
}
|
||
}
|
||
|
||
resp.SetReply(req)
|
||
h.logger.Printf("godns::resp: %+v\n", resp)
|
||
|
||
// 验证响应并缓存（防止缓存投毒）
|
||
if h.builtInCache != nil && shouldCacheResponse(resp) && validateResponse(req, resp, h.logger) {
|
||
ttl := getDnsResponseTtl(resp)
|
||
cachedMsg := &cache.CachedMsg{
|
||
Msg: resp,
|
||
Expires: time.Now().Add(ttl),
|
||
}
|
||
if err := h.builtInCache.Set(cacheKey, cachedMsg, ttl+time.Hour); err != nil {
|
||
h.logger.Printf("Failed to cache response: %v", err)
|
||
}
|
||
}
|
||
|
||
return resp
|
||
}
|
||
|
||
// extractClientIPFromDNS 从 DNS 请求中提取客户端 IP
|
||
// 优先级：EDNS Client Subnet > RemoteAddr
|
||
func extractClientIPFromDNS(w dns.ResponseWriter, req *dns.Msg) string {
|
||
// 1. 优先检查 EDNS Client Subnet (ECS)
|
||
// ECS 是 DNS 协议标准，用于传递真实客户端 IP
|
||
if opt := req.IsEdns0(); opt != nil {
|
||
for _, option := range opt.Option {
|
||
if ecs, ok := option.(*dns.EDNS0_SUBNET); ok {
|
||
// ECS 中的 Address 就是客户端真实 IP
|
||
return ecs.Address.String()
|
||
}
|
||
}
|
||
}
|
||
|
||
// 2. 从 RemoteAddr 获取
|
||
var clientIP string
|
||
if addr := w.RemoteAddr(); addr != nil {
|
||
if udpAddr, ok := addr.(*net.UDPAddr); ok {
|
||
clientIP = udpAddr.IP.String()
|
||
} else if tcpAddr, ok := addr.(*net.TCPAddr); ok {
|
||
clientIP = tcpAddr.IP.String()
|
||
}
|
||
}
|
||
|
||
return clientIP
|
||
}
|
||
|
||
func (h *Handler) HandleRequest(w dns.ResponseWriter, req *dns.Msg) {
|
||
// 提取客户端 IP
|
||
clientIP := extractClientIPFromDNS(w, req)
|
||
|
||
// 提取域名
|
||
var domain string
|
||
if len(req.Question) > 0 {
|
||
domain = req.Question[0].Name
|
||
}
|
||
|
||
// 调用核心处理逻辑
|
||
resp := h.HandleDnsMsg(req, clientIP, domain)
|
||
|
||
// 写入响应
|
||
if err := w.WriteMsg(resp); err != nil {
|
||
h.logger.Printf("WriteMsg error: %+v", err)
|
||
}
|
||
}
|
||
|
||
var builderPool = sync.Pool{
|
||
New: func() interface{} {
|
||
b := new(strings.Builder)
|
||
b.Grow(128)
|
||
return b
|
||
},
|
||
}
|
||
|
||
func uniqueAnswer(records []dns.RR) []dns.RR {
|
||
if len(records) == 0 {
|
||
return records
|
||
}
|
||
|
||
seen := make(map[string]bool, len(records))
|
||
result := make([]dns.RR, 0, len(records))
|
||
|
||
for _, rr := range records {
|
||
if rr == nil {
|
||
continue
|
||
}
|
||
|
||
header := rr.Header()
|
||
if header == nil {
|
||
continue
|
||
}
|
||
|
||
builder := builderPool.Get().(*strings.Builder)
|
||
|
||
var key string
|
||
switch v := rr.(type) {
|
||
case *dns.A:
|
||
builder.WriteString(header.Name)
|
||
builder.WriteString("|A|")
|
||
builder.WriteString(v.A.String())
|
||
key = builder.String()
|
||
case *dns.AAAA:
|
||
builder.WriteString(header.Name)
|
||
builder.WriteString("|AAAA|")
|
||
builder.WriteString(v.AAAA.String())
|
||
key = builder.String()
|
||
case *dns.CNAME:
|
||
builder.WriteString(header.Name)
|
||
builder.WriteString("|CNAME|")
|
||
builder.WriteString(v.Target)
|
||
key = builder.String()
|
||
case *dns.MX:
|
||
builder.WriteString(header.Name)
|
||
builder.WriteString("|MX|")
|
||
builder.WriteString(fmt.Sprintf("%d|%s", v.Preference, v.Mx))
|
||
key = builder.String()
|
||
case *dns.NS:
|
||
builder.WriteString(header.Name)
|
||
builder.WriteString("|NS|")
|
||
builder.WriteString(v.Ns)
|
||
key = builder.String()
|
||
case *dns.PTR:
|
||
builder.WriteString(header.Name)
|
||
builder.WriteString("|PTR|")
|
||
builder.WriteString(v.Ptr)
|
||
key = builder.String()
|
||
case *dns.TXT:
|
||
builder.WriteString(header.Name)
|
||
builder.WriteString("|TXT|")
|
||
builder.WriteString(strings.Join(v.Txt, "|"))
|
||
key = builder.String()
|
||
case *dns.SRV:
|
||
builder.WriteString(header.Name)
|
||
builder.WriteString("|SRV|")
|
||
builder.WriteString(fmt.Sprintf("%d|%d|%d|%s", v.Priority, v.Weight, v.Port, v.Target))
|
||
key = builder.String()
|
||
case *dns.SOA:
|
||
builder.WriteString(header.Name)
|
||
builder.WriteString("|SOA|")
|
||
builder.WriteString(v.Ns)
|
||
builder.WriteString("|")
|
||
builder.WriteString(v.Mbox)
|
||
key = builder.String()
|
||
default:
|
||
key = rr.String()
|
||
}
|
||
builder.Reset()
|
||
builderPool.Put(builder)
|
||
|
||
if !seen[key] {
|
||
seen[key] = true
|
||
result = append(result, rr)
|
||
}
|
||
}
|
||
|
||
return result
|
||
}
|
||
|
||
func (h *Handler) getTheFullestResults(req *dns.Msg) []*dns.Msg {
|
||
matchedUpstreams := h.matchedUpstreams(req)
|
||
var wg sync.WaitGroup
|
||
wg.Add(len(matchedUpstreams))
|
||
msgs := make([]*dns.Msg, len(matchedUpstreams))
|
||
|
||
for i := 0; i < len(matchedUpstreams); i++ {
|
||
go func(j int) {
|
||
defer wg.Done()
|
||
msg, _, err := matchedUpstreams[j].Exchange(req.Copy())
|
||
|
||
// 记录上游服务器统计
|
||
if h.stats != nil {
|
||
h.stats.RecordUpstreamQuery(matchedUpstreams[j].Address, err != nil)
|
||
}
|
||
|
||
if err != nil {
|
||
h.logger.Printf("upstream error %s: %v %s", matchedUpstreams[j].Address, model.GetDomainNameFromDnsMsg(req), err)
|
||
return
|
||
}
|
||
if matchedUpstreams[j].IsValidMsg(msg) {
|
||
msgs[j] = msg
|
||
}
|
||
}(i)
|
||
}
|
||
|
||
wg.Wait()
|
||
return msgs
|
||
}
|
||
|
||
func (h *Handler) getTheFastestResults(req *dns.Msg) []*dns.Msg {
|
||
preferUpstreams := h.matchedUpstreams(req)
|
||
msgs := make([]*dns.Msg, len(preferUpstreams))
|
||
|
||
var mutex sync.Mutex
|
||
var finishedCount int
|
||
var finished bool
|
||
var freedomIndex, primaryIndex []int
|
||
|
||
var wg sync.WaitGroup
|
||
wg.Add(1)
|
||
|
||
for i := 0; i < len(preferUpstreams); i++ {
|
||
go func(j int) {
|
||
msg, _, err := preferUpstreams[j].Exchange(req.Copy())
|
||
|
||
if h.stats != nil {
|
||
h.stats.RecordUpstreamQuery(preferUpstreams[j].Address, err != nil)
|
||
}
|
||
|
||
if err != nil {
|
||
h.logger.Printf("upstream error %s: %v %s", preferUpstreams[j].Address, model.GetDomainNameFromDnsMsg(req), err)
|
||
}
|
||
|
||
mutex.Lock()
|
||
defer mutex.Unlock()
|
||
|
||
if finished {
|
||
return
|
||
}
|
||
|
||
finishedCount++
|
||
|
||
if err == nil {
|
||
if preferUpstreams[j].IsValidMsg(msg) {
|
||
if preferUpstreams[j].IsPrimary {
|
||
primaryIndex = append(primaryIndex, j)
|
||
} else {
|
||
freedomIndex = append(freedomIndex, j)
|
||
}
|
||
msgs[j] = msg
|
||
} else if preferUpstreams[j].IsPrimary {
|
||
primaryIndex = append(primaryIndex, j)
|
||
}
|
||
}
|
||
|
||
shouldFinish := finishedCount == len(preferUpstreams) ||
|
||
(len(primaryIndex) > 0 && len(freedomIndex) > 0) ||
|
||
(len(primaryIndex) > 0 && (msgs[primaryIndex[0]] != nil || len(freedomIndex) > 0))
|
||
|
||
if shouldFinish && !finished {
|
||
finished = true
|
||
wg.Done()
|
||
}
|
||
}(i)
|
||
}
|
||
|
||
wg.Wait()
|
||
return msgs
|
||
}
|
||
|
||
func (h *Handler) getAnyResult(req *dns.Msg) []*dns.Msg {
|
||
matchedUpstreams := h.matchedUpstreams(req)
|
||
msgs := make([]*dns.Msg, len(matchedUpstreams))
|
||
|
||
var mutex sync.Mutex
|
||
var finishedCount int
|
||
var finished bool
|
||
|
||
var wg sync.WaitGroup
|
||
wg.Add(1)
|
||
|
||
for i := 0; i < len(matchedUpstreams); i++ {
|
||
go func(j int) {
|
||
msg, _, err := matchedUpstreams[j].Exchange(req.Copy())
|
||
|
||
if h.stats != nil {
|
||
h.stats.RecordUpstreamQuery(matchedUpstreams[j].Address, err != nil)
|
||
}
|
||
|
||
if err != nil {
|
||
h.logger.Printf("upstream error %s: %v %s", matchedUpstreams[j].Address, model.GetDomainNameFromDnsMsg(req), err)
|
||
}
|
||
|
||
mutex.Lock()
|
||
defer mutex.Unlock()
|
||
|
||
if finished {
|
||
return
|
||
}
|
||
|
||
finishedCount++
|
||
shouldFinish := err == nil || finishedCount == len(matchedUpstreams)
|
||
|
||
if shouldFinish && !finished {
|
||
finished = true
|
||
msgs[j] = msg
|
||
wg.Done()
|
||
}
|
||
}(i)
|
||
}
|
||
|
||
wg.Wait()
|
||
return msgs
|
||
}
|
||
|
||
// Close properly shuts down the cache
|
||
func (h *Handler) Close() error {
|
||
if h.builtInCache != nil {
|
||
return h.builtInCache.Close()
|
||
}
|
||
return nil
|
||
}
|
||
|
||
// GetCacheStats returns cache statistics
|
||
func (h *Handler) GetCacheStats() string {
|
||
if h.builtInCache != nil {
|
||
return h.builtInCache.Stats()
|
||
}
|
||
return "Cache disabled"
|
||
}
|
||
|
||
// replyUpdateTtl 准备缓存响应以发送给客户端，执行必要的修正：
|
||
// 1. 设置正确的 Message ID（通过 SetReply）
|
||
// 2. 更新所有 RR 的 TTL 为剩余时间（最低 0）
|
||
// 3. 调整 OPT RR 的 UDP size 为客户端请求的值
|
||
// 4. 清除 ECS Scope Length（标记为缓存答案）
|
||
// 5. 检查过期的 RRSIG 并移除
|
||
func replyUpdateTtl(req *dns.Msg, resp *dns.Msg, ttl uint32) *dns.Msg {
|
||
now := time.Now().Unix()
|
||
|
||
// 辅助函数：更新 RR 列表的 TTL，并检测过期 RRSIG
|
||
updateRRs := func(rrs []dns.RR) []dns.RR {
|
||
var validRRs []dns.RR
|
||
for _, rr := range rrs {
|
||
header := rr.Header()
|
||
if header == nil {
|
||
continue
|
||
}
|
||
|
||
// 检查 RRSIG 是否过期
|
||
if rrsig, ok := rr.(*dns.RRSIG); ok {
|
||
if rrsig.Expiration > 0 && uint32(now) > rrsig.Expiration {
|
||
// RRSIG 已过期，跳过这条记录
|
||
continue
|
||
}
|
||
}
|
||
|
||
// 更新 TTL（最低为 0）
|
||
header.Ttl = ttl
|
||
validRRs = append(validRRs, rr)
|
||
}
|
||
return validRRs
|
||
}
|
||
|
||
// 更新所有部分的 TTL 并移除过期 RRSIG
|
||
resp.Answer = updateRRs(resp.Answer)
|
||
resp.Ns = updateRRs(resp.Ns)
|
||
|
||
// Extra 部分需要特殊处理 OPT RR
|
||
var validExtra []dns.RR
|
||
var reqOpt *dns.OPT
|
||
if reqOpt = req.IsEdns0(); reqOpt != nil {
|
||
// 客户端有 EDNS0，获取其 UDP size
|
||
}
|
||
|
||
for _, rr := range resp.Extra {
|
||
if opt, ok := rr.(*dns.OPT); ok {
|
||
// 处理 OPT RR
|
||
if reqOpt != nil {
|
||
// 使用客户端请求的 UDP size
|
||
opt.SetUDPSize(reqOpt.UDPSize())
|
||
}
|
||
|
||
// 清除 ECS Scope Length
|
||
for i, option := range opt.Option {
|
||
if ecs, ok := option.(*dns.EDNS0_SUBNET); ok {
|
||
// 将 Scope Length 设为 0，表示这是缓存答案
|
||
ecs.SourceScope = 0
|
||
opt.Option[i] = ecs
|
||
}
|
||
}
|
||
validExtra = append(validExtra, opt)
|
||
} else {
|
||
// 非 OPT RR，正常更新 TTL 和检查 RRSIG
|
||
header := rr.Header()
|
||
if header != nil {
|
||
if rrsig, ok := rr.(*dns.RRSIG); ok {
|
||
if rrsig.Expiration > 0 && uint32(now) > rrsig.Expiration {
|
||
continue // 跳过过期的 RRSIG
|
||
}
|
||
}
|
||
header.Ttl = ttl
|
||
}
|
||
validExtra = append(validExtra, rr)
|
||
}
|
||
}
|
||
resp.Extra = validExtra
|
||
|
||
// SetReply 会设置正确的 Message ID 和其他响应标志
|
||
return resp.SetReply(req)
|
||
}
|