fix(handler/dns): buffer pool leak, write deadline, async error logging, EDNS0 buffer
Fix bufpool leak when PackBuffer fails by extracting packResponse helper. Add write deadline before conn.Write to prevent goroutine hangs on slow clients. Log async exchange errors instead of silently discarding them. Raise defaultBufferSize from 1024 to 4096 to match EDNS0 standard. Deduplicate lookupHosts TypeA/TypeAAAA branches.
This commit is contained in:
ginuerzh
+46
-46
@@ -132,6 +132,18 @@ func (h *dnsHandler) Init(md md.Metadata) (err error) {
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return
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}
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// packResponse serializes a DNS message using a pooled buffer.
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// The buffer is returned to the pool if serialization fails.
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func (h *dnsHandler) packResponse(mr *dns.Msg) ([]byte, error) {
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b := bufpool.Get(h.md.bufferSize)
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reply, err := mr.PackBuffer(b)
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if err != nil {
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bufpool.Put(b)
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return nil, err
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}
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return reply, nil
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}
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// Forward implements handler.Forwarder.
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func (h *dnsHandler) Forward(hop hop.Hop) {
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h.hop = hop
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@@ -214,6 +226,9 @@ func (h *dnsHandler) Handle(ctx context.Context, conn net.Conn, opts ...handler.
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}
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defer bufpool.Put(reply)
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if h.md.readTimeout > 0 {
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conn.SetWriteDeadline(time.Now().Add(h.md.readTimeout))
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}
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if _, err = conn.Write(reply); err != nil {
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log.Error(err)
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return err
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@@ -273,15 +288,13 @@ func (h *dnsHandler) request(ctx context.Context, msg []byte, ro *xrecorder.Hand
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if h.options.Bypass.Contains(context.Background(), "udp", strings.Trim(mq.Question[0].Name, "."), bypass.WithService(h.options.Service)) {
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log.Debug("bypass: ", mq.Question[0].Name)
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mr = (&dns.Msg{}).SetReply(&mq)
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b := bufpool.Get(h.md.bufferSize)
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return mr.PackBuffer(b)
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return h.packResponse(mr)
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}
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}
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mr = h.lookupHosts(ctx, &mq, log)
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if mr != nil {
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b := bufpool.Get(h.md.bufferSize)
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return mr.PackBuffer(b)
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return h.packResponse(mr)
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}
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// only cache for single question message.
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@@ -294,8 +307,7 @@ func (h *dnsHandler) request(ctx context.Context, msg []byte, ro *xrecorder.Hand
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ro.DNS.Cached = true
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log.Debugf("message %d (cached): %s", mq.Id, mq.Question[0].String())
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b := bufpool.Get(h.md.bufferSize)
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return mr.PackBuffer(b)
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return h.packResponse(mr)
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}
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}
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}
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@@ -307,15 +319,18 @@ func (h *dnsHandler) request(ctx context.Context, msg []byte, ro *xrecorder.Hand
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ro.Host = ex.String()
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if mr != nil && h.md.async {
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b := bufpool.Get(h.md.bufferSize)
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reply, err := mr.PackBuffer(b)
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reply, err := h.packResponse(mr)
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if err != nil {
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return nil, err
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}
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h.cache.RefreshTTL(resolver_util.NewCacheKey(&mq.Question[0]))
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log.Debugf("exchange message %d (async): %s", mq.Id, mq.Question[0].String())
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go h.exchange(context.WithoutCancel(ctx), ex, &mq)
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go func() {
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if _, err := h.exchange(context.WithoutCancel(ctx), ex, &mq); err != nil {
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log.Debugf("async exchange for %s: %v", mq.Question[0].Name, err)
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}
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}()
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return reply, nil
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}
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@@ -328,8 +343,7 @@ func (h *dnsHandler) request(ctx context.Context, msg []byte, ro *xrecorder.Hand
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return nil, err
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}
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b := bufpool.Get(h.md.bufferSize)
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return mr.PackBuffer(b)
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return h.packResponse(mr)
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}
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func (h *dnsHandler) exchange(ctx context.Context, ex exchanger.Exchanger, mq *dns.Msg) (*dns.Msg, error) {
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@@ -358,7 +372,7 @@ func (h *dnsHandler) exchange(ctx context.Context, ex exchanger.Exchanger, mq *d
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return mr, nil
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}
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// lookup host mapper
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// lookupHosts checks the host mapper for A/AAAA records matching the query.
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func (h *dnsHandler) lookupHosts(ctx context.Context, r *dns.Msg, log logger.Logger) (m *dns.Msg) {
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if h.hostMapper == nil ||
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r.Question[0].Qclass != dns.ClassINET ||
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@@ -366,45 +380,31 @@ func (h *dnsHandler) lookupHosts(ctx context.Context, r *dns.Msg, log logger.Log
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return nil
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}
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m = &dns.Msg{}
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m.SetReply(r)
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host := strings.TrimSuffix(r.Question[0].Name, ".")
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var network, rrType string
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switch r.Question[0].Qtype {
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case dns.TypeA:
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ips, _ := h.hostMapper.Lookup(ctx, "ip4", host)
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if len(ips) == 0 {
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return nil
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}
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log.Debugf("hit host mapper: %s -> %s", host, ips)
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for _, ip := range ips {
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rr, err := dns.NewRR(fmt.Sprintf("%s IN A %s\n", r.Question[0].Name, ip.String()))
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if err != nil {
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log.Error(err)
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return nil
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}
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m.Answer = append(m.Answer, rr)
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}
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network, rrType = "ip4", "IN A"
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case dns.TypeAAAA:
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ips, _ := h.hostMapper.Lookup(ctx, "ip6", host)
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if len(ips) == 0 {
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return nil
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}
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log.Debugf("hit host mapper: %s -> %s", host, ips)
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for _, ip := range ips {
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rr, err := dns.NewRR(fmt.Sprintf("%s IN AAAA %s\n", r.Question[0].Name, ip.String()))
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if err != nil {
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log.Error(err)
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return nil
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}
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m.Answer = append(m.Answer, rr)
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}
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network, rrType = "ip6", "IN AAAA"
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}
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host := strings.TrimSuffix(r.Question[0].Name, ".")
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ips, _ := h.hostMapper.Lookup(ctx, network, host)
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if len(ips) == 0 {
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return nil
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}
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log.Debugf("hit host mapper: %s -> %s", host, ips)
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m = new(dns.Msg)
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m.SetReply(r)
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for _, ip := range ips {
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rr, err := dns.NewRR(fmt.Sprintf("%s %s %s\n", r.Question[0].Name, rrType, ip.String()))
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if err != nil {
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log.Error(err)
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return nil
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}
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m.Answer = append(m.Answer, rr)
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}
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return
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}
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