1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
|
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
}
|
