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package autopath
import (
"strings"
"github.com/miekg/dns"
)
// Writer 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 Writer.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 Writer struct {
dns.ResponseWriter
original dns.Question
Rcode int
}
// AutoPath enables server side search path lookups for pods.
type AutoPath struct {
NDots int
ResolvConfFile string
HostSearchPath []string
OnNXDOMAIN int
}
// NewWriter returns a pointer to a new Writer
func NewWriter(w dns.ResponseWriter, r *dns.Msg) *Writer {
return &Writer{
ResponseWriter: w,
original: r.Question[0],
Rcode: dns.RcodeSuccess,
}
}
// WriteMsg writes to client, unless response will be NXDOMAIN.
func (apw *Writer) WriteMsg(res *dns.Msg) error {
if res.Rcode == dns.RcodeNameError {
res.Rcode = apw.Rcode
}
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] = CNAME(apw.original.Name, a.Header().Name, a.Header().Ttl)
}
res.Question[0] = apw.original
return apw.ResponseWriter.WriteMsg(res)
}
// Write is a wrapper that records the size of the message that gets written.
func (apw *Writer) Write(buf []byte) (int, error) {
n, err := apw.ResponseWriter.Write(buf)
return n, err
}
func SplitSearch(zone, question, namespace string) (name, search string, ok bool) {
search = strings.Join([]string{namespace, "svc", zone}, ".")
if dns.IsSubDomain(search, question) {
return question[:len(question)-len(search)-1], search, true
}
return "", "", false
}
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