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middleware/kubernetes: autopath in sub package (#848)

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Put the autopath stuff in a separate sub package. Tests are still
included in the main kubernetes directory.

Next steps (after this is merged), is pulling the autopath handling
into the subpackage and fixing the tests.
This commit is contained in:
Miek Gieben 2017-08-07 07:09:32 -07:00 • committed by GitHub
parent 050eccd69e
commit 760e667063
7 changed files with 103 additions and 95 deletions
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77
middleware/kubernetes/autopath.go
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@ -1,77 +0,0 @@
package kubernetes
import "github.com/miekg/dns"
// AutoPathWriter implements a ResponseWriter that also does the following:
// * reverts question section of a packet to its original state.
// This is done to avoid the 'Question section mismatch:' error in client.
// * Defers write to the client if the response code is NXDOMAIN. This is needed
// to enable further search path probing if a search was not successful.
// * Allow forced write to client regardless of response code. This is needed to
// write the packet to the client if the final search in the path fails to
// produce results.
// * Overwrites response code with AutoPathWriter.Rcode if the response code
// is NXDOMAIN (NameError). This is needed to support the AutoPath.OnNXDOMAIN
// function, which returns a NOERROR to client instead of NXDOMAIN if the final
// search in the path fails to produce results.
type AutoPathWriter struct {
dns.ResponseWriter
original dns.Question
Rcode int
Sent bool
}
// NewAutoPathWriter returns a pointer to a new AutoPathWriter
func NewAutoPathWriter(w dns.ResponseWriter, r *dns.Msg) *AutoPathWriter {
return &AutoPathWriter{
ResponseWriter: w,
original: r.Question[0],
Rcode: dns.RcodeSuccess,
}
}
// WriteMsg writes to client, unless response will be NXDOMAIN
func (apw *AutoPathWriter) WriteMsg(res *dns.Msg) error {
return apw.overrideMsg(res, false)
}
// ForceWriteMsg forces the write to client regardless of response code
func (apw *AutoPathWriter) ForceWriteMsg(res *dns.Msg) error {
return apw.overrideMsg(res, true)
}
// overrideMsg overrides rcode, reverts question, adds CNAME, and calls the
// underlying ResponseWriter's WriteMsg method unless the write is deferred,
// or force = true.
func (apw *AutoPathWriter) overrideMsg(res *dns.Msg, force bool) error {
if res.Rcode == dns.RcodeNameError {
res.Rcode = apw.Rcode
}
if res.Rcode != dns.RcodeSuccess && !force {
return nil
}
for _, a := range res.Answer {
if apw.original.Name == a.Header().Name {
continue
}
res.Answer = append(res.Answer, nil)
copy(res.Answer[1:], res.Answer)
res.Answer[0] = newCNAME(apw.original.Name, dns.Fqdn(a.Header().Name), a.Header().Ttl)
}
res.Question[0] = apw.original
apw.Sent = true
return apw.ResponseWriter.WriteMsg(res)
}
// Write is a wrapper that records the size of the message that gets written.
func (apw *AutoPathWriter) Write(buf []byte) (int, error) {
n, err := apw.ResponseWriter.Write(buf)
return n, err
}
// Hijack implements dns.Hijacker. It simply wraps the underlying
// ResponseWriter's Hijack method if there is one, or returns an error.
func (apw *AutoPathWriter) Hijack() {
apw.ResponseWriter.Hijack()
return
}