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plugin/rewrite: apply rcode rewrites to responses with no records (#8421)

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* plugin/rewrite: apply rcode rewrites to record-less responses

An rcode rewrite rewrites the message-level RCODE, but the reverter only ran
response rules from inside the per-record loops in WriteMsg. When a response
carries no answer, authority or additional records - for example a bare
SERVFAIL that a downstream plugin returns to a non-EDNS client - none of the
loops iterate, so the rcode rewrite was silently skipped and the client
received the original RCODE.

Apply message-level response rules once when the response has no records, using
a small marker interface that mirrors the existing requestExtraRevertRule
pattern. This fixes the plugin's documented SERVFAIL-to-NOERROR use case for
responses without records.

Signed-off-by: Sueun Cho <sueun.dev@gmail.com>

* plugin/rewrite: apply fallback rcode rewrites for continue

Signed-off-by: Sueun Cho <sueun.dev@gmail.com>

---------

Signed-off-by: Sueun Cho <sueun.dev@gmail.com>
This commit is contained in:
Sueun Cho
2026-08-18 12:12:32 +09:00
committed by GitHub
parent 897b4ce643
commit 9a623cdeed
5 changed files with 99 additions and 13 deletions
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28
plugin/rewrite/rewrite.go
View File

@@ -57,24 +57,28 @@ func (rw Rewrite) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
if !rw.DoRevert() {
return plugin.NextOrFailure(rw.Name(), rw.Next, ctx, w, r)
}
rcode, err := plugin.NextOrFailure(rw.Name(), rw.Next, ctx, wr, r)
if plugin.ClientWrite(rcode) {
return rcode, err
}
// The next plugins didn't write a response, so write one now with the ResponseReverter.
// If server.ServeDNS does this then it will create an answer mismatch.
res := new(dns.Msg).SetRcode(r, rcode)
state.SizeAndDo(res)
wr.WriteMsg(res)
// return success, so server does not write a second error response to client
return dns.RcodeSuccess, err
return rw.serveWithResponseReverter(ctx, wr, r, state)
}
}
}
if !rw.DoRevert() || len(wr.ResponseRules) == 0 {
return plugin.NextOrFailure(rw.Name(), rw.Next, ctx, w, r)
}
return plugin.NextOrFailure(rw.Name(), rw.Next, ctx, wr, r)
return rw.serveWithResponseReverter(ctx, wr, r, state)
}
func (rw Rewrite) serveWithResponseReverter(ctx context.Context, wr *ResponseReverter, r *dns.Msg, state request.Request) (int, error) {
rcode, err := plugin.NextOrFailure(rw.Name(), rw.Next, ctx, wr, r)
if plugin.ClientWrite(rcode) {
return rcode, err
}
// The next plugins didn't write a response, so write one now with the ResponseReverter.
// If server.ServeDNS does this then it will bypass response rewrite rules.
res := new(dns.Msg).SetRcode(r, rcode)
state.SizeAndDo(res)
wr.WriteMsg(res)
// Return success so server does not write a second error response to the client.
return dns.RcodeSuccess, err
}
// Name implements the Handler interface.