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b0b317fdd6
When the plugin chain returns an error rcode without writing a response (it falls off the end, or returns SERVFAIL/REFUSED/FORMERR/NOTIMP), the server generates and sends the error to the client after dnstap's ServeDNS returns, so ResponseWriter.WriteMsg is never called and no CLIENT_RESPONSE dnstap message is emitted. dnstap consumers then see a CLIENT_QUERY with no matching CLIENT_RESPONSE. Synthesize the deferred response and tap it as a CLIENT_RESPONSE, mirroring the deferred-response handling already added to plugin/log. Fixes #6532 Signed-off-by: Saleh <root@lr0.org>
114 lines
3.4 KiB
Go
114 lines
3.4 KiB
Go
package dnstap
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import (
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"context"
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"time"
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"github.com/coredns/coredns/plugin"
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"github.com/coredns/coredns/plugin/dnstap/msg"
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"github.com/coredns/coredns/plugin/pkg/replacer"
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"github.com/coredns/coredns/request"
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tap "github.com/dnstap/golang-dnstap"
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"github.com/miekg/dns"
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)
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// Dnstap is the dnstap handler.
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type Dnstap struct {
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Next plugin.Handler
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io tapper
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listener *listener
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repl replacer.Replacer
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// IncludeRawMessage will include the raw DNS message into the dnstap messages if true.
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IncludeRawMessage bool
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Identity []byte
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Version []byte
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ExtraFormat string
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MultipleTcpWriteBuf int // *Mb
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MultipleQueue int // *10000
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}
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// TapMessage sends the message m to the dnstap interface, without populating "Extra" field.
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func (h *Dnstap) TapMessage(m *tap.Message) {
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if h.ExtraFormat == "" {
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h.tapWithExtra(m, nil)
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} else {
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h.tapWithExtra(m, []byte(h.ExtraFormat))
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}
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}
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// TapMessageWithMetadata sends the message m to the dnstap interface, with "Extra" field being populated.
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func (h *Dnstap) TapMessageWithMetadata(ctx context.Context, m *tap.Message, state request.Request) {
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if h.ExtraFormat == "" {
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h.tapWithExtra(m, nil)
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return
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}
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extraStr := h.repl.Replace(ctx, state, nil, h.ExtraFormat)
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h.tapWithExtra(m, []byte(extraStr))
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}
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func (h *Dnstap) tapWithExtra(m *tap.Message, extra []byte) {
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t := tap.Dnstap_MESSAGE
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payload := &tap.Dnstap{Type: &t, Message: m, Identity: h.Identity, Version: h.Version, Extra: extra}
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// Send to outgoing connection if configured
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if h.io != nil {
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h.io.Dnstap(payload)
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}
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// Broadcast to incoming listeners if configured
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if h.listener != nil {
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h.listener.Dnstap(payload)
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}
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}
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func (h *Dnstap) tapQuery(ctx context.Context, w dns.ResponseWriter, query *dns.Msg, queryTime time.Time) {
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q := new(tap.Message)
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msg.SetQueryTime(q, queryTime)
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msg.SetQueryAddress(q, w.RemoteAddr())
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if h.IncludeRawMessage {
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buf, _ := query.Pack()
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q.QueryMessage = buf
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}
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msg.SetType(q, tap.Message_CLIENT_QUERY)
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state := request.Request{W: w, Req: query}
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h.TapMessageWithMetadata(ctx, q, state)
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}
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// ServeDNS logs the client query and response to dnstap and passes the dnstap Context.
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func (h *Dnstap) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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rw := &ResponseWriter{
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ResponseWriter: w,
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Dnstap: h,
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query: r,
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ctx: ctx,
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queryTime: time.Now(),
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}
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// The query tap message should be sent before sending the query to the
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// forwarder. Otherwise, the tap messages will come out out of order.
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h.tapQuery(ctx, w, r, rw.queryTime)
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rcode, err := plugin.NextOrFailure(h.Name(), h.Next, ctx, rw, r)
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// When the plugin chain returns an error rcode without having written a
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// response (e.g. it falls off the end, or returns SERVFAIL/REFUSED/FORMERR/
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// NOTIMP), the server generates and sends the error response to the client
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// after ServeDNS returns, so ResponseWriter.WriteMsg is never called and no
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// CLIENT_RESPONSE is tapped. Synthesize the deferred response so dnstap
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// consumers see a CLIENT_RESPONSE matching what the client receives, rather
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// than a CLIENT_QUERY with no matching response (#6532).
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if !rw.written && !plugin.ClientWrite(rcode) {
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deferred := new(dns.Msg)
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deferred.SetRcode(r, rcode)
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rw.tapResponse(deferred)
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}
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return rcode, err
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}
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// Name implements the plugin.Plugin interface.
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func (h *Dnstap) Name() string { return "dnstap" }
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