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package header
import (
"fmt"
"strings"
clog "github.com/coredns/coredns/plugin/pkg/log"
"github.com/miekg/dns"
)
// Supported flags
const (
authoritative = "aa"
recursionAvailable = "ra"
recursionDesired = "rd"
)
var log = clog.NewWithPlugin("header")
// ResponseHeaderWriter is a response writer that allows modifying dns.MsgHdr
type ResponseHeaderWriter struct {
dns.ResponseWriter
Rules []Rule
}
// WriteMsg implements the dns.ResponseWriter interface.
func (r *ResponseHeaderWriter) WriteMsg(res *dns.Msg) error {
applyRules(res, r.Rules)
return r.ResponseWriter.WriteMsg(res)
}
// Write implements the dns.ResponseWriter interface.
func (r *ResponseHeaderWriter) Write(buf []byte) (int, error) {
log.Warning("ResponseHeaderWriter called with Write: not ensuring headers")
n, err := r.ResponseWriter.Write(buf)
return n, err
}
// Rule is used to set/clear Flag in dns.MsgHdr
type Rule struct {
Flag string
State bool
}
func newRules(key string, args []string) ([]Rule, error) {
if key == "" {
return nil, fmt.Errorf("no flag action provided")
}
if len(args) < 1 {
return nil, fmt.Errorf("invalid length for flags, at least one should be provided")
}
var state bool
action := strings.ToLower(key)
switch action {
case "set":
state = true
case "clear":
state = false
default:
return nil, fmt.Errorf("unknown flag action=%s, should be set or clear", action)
}
var rules []Rule
for _, arg := range args {
flag := strings.ToLower(arg)
switch flag {
case authoritative:
case recursionAvailable:
case recursionDesired:
default:
return nil, fmt.Errorf("unknown/unsupported flag=%s", flag)
}
rule := Rule{Flag: flag, State: state}
rules = append(rules, rule)
}
return rules, nil
}
func applyRules(res *dns.Msg, rules []Rule) {
// handle all supported flags
for _, rule := range rules {
switch rule.Flag {
case authoritative:
res.Authoritative = rule.State
case recursionAvailable:
res.RecursionAvailable = rule.State
case recursionDesired:
res.RecursionDesired = rule.State
}
}
}
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