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
|
// Package middleware provides some types and functions common among middleware.
package middleware
import (
"fmt"
"github.com/miekg/dns"
"golang.org/x/net/context"
)
type (
// Middleware is the middle layer which represents the traditional
// idea of middleware: it chains one Handler to the next by being
// passed the next Handler in the chain.
Middleware func(Handler) Handler
// Handler is like dns.Handler except ServeDNS may return an rcode
// and/or error.
//
// If ServeDNS writes to the response body, it should return a status
// code. If the status code is not one of the following:
//
// * SERVFAIL (dns.RcodeServerFailure)
//
// * REFUSED (dns.RecodeRefused)
//
// * FORMERR (dns.RcodeFormatError)
//
// * NOTIMP (dns.RcodeNotImplemented)
//
// CoreDNS assumes *no* reply has yet been written. All other response
// codes signal other handlers above it that the response message is
// already written, and that they should not write to it also.
//
// If ServeDNS encounters an error, it should return the error value
// so it can be logged by designated error-handling middleware.
//
// If writing a response after calling another ServeDNS method, the
// returned rcode SHOULD be used when writing the response.
//
// If handling errors after calling another ServeDNS method, the
// returned error value SHOULD be logged or handled accordingly.
//
// Otherwise, return values should be propagated down the middleware
// chain by returning them unchanged.
Handler interface {
ServeDNS(context.Context, dns.ResponseWriter, *dns.Msg) (int, error)
Name() string
}
// HandlerFunc is a convenience type like dns.HandlerFunc, except
// ServeDNS returns an rcode and an error. See Handler
// documentation for more information.
HandlerFunc func(context.Context, dns.ResponseWriter, *dns.Msg) (int, error)
)
// ServeDNS implements the Handler interface.
func (f HandlerFunc) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
return f(ctx, w, r)
}
func (f HandlerFunc) Name() string { return "handlerfunc" }
// Error returns err with 'middleware/name: ' prefixed to it.
func Error(name string, err error) error { return fmt.Errorf("%s/%s: %s", "middleware", name, err) }
// Namespace is the namespace used for the metrics.
const Namespace = "coredns"
|
