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package loop
import (
"context"
"sync"
"github.com/coredns/coredns/plugin"
clog "github.com/coredns/coredns/plugin/pkg/log"
"github.com/coredns/coredns/request"
"github.com/miekg/dns"
)
var log = clog.NewWithPlugin("loop")
// Loop is a plugin that implements loop detection by sending a "random" query.
type Loop struct {
Next plugin.Handler
zone string
qname string
addr string
sync.RWMutex
i int
off bool
}
// New returns a new initialized Loop.
func New(zone string) *Loop { return &Loop{zone: zone, qname: qname(zone)} }
// ServeDNS implements the plugin.Handler interface.
func (l *Loop) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
if r.Question[0].Qtype != dns.TypeHINFO {
return plugin.NextOrFailure(l.Name(), l.Next, ctx, w, r)
}
if l.disabled() {
return plugin.NextOrFailure(l.Name(), l.Next, ctx, w, r)
}
state := request.Request{W: w, Req: r}
zone := plugin.Zones([]string{l.zone}).Matches(state.Name())
if zone == "" {
return plugin.NextOrFailure(l.Name(), l.Next, ctx, w, r)
}
if state.Name() == l.qname {
l.inc()
}
if l.seen() > 2 {
log.Fatalf(`Loop (%s -> %s) detected for zone %q, see https://coredns.io/plugins/loop#troubleshooting. Query: "HINFO %s"`, state.RemoteAddr(), l.address(), l.zone, l.qname)
}
return plugin.NextOrFailure(l.Name(), l.Next, ctx, w, r)
}
// Name implements the plugin.Handler interface.
func (l *Loop) Name() string { return "loop" }
func (l *Loop) exchange(addr string) (*dns.Msg, error) {
m := new(dns.Msg)
m.SetQuestion(l.qname, dns.TypeHINFO)
return dns.Exchange(m, addr)
}
func (l *Loop) seen() int {
l.RLock()
defer l.RUnlock()
return l.i
}
func (l *Loop) inc() {
l.Lock()
defer l.Unlock()
l.i++
}
func (l *Loop) reset() {
l.Lock()
defer l.Unlock()
l.i = 0
}
func (l *Loop) setDisabled() {
l.Lock()
defer l.Unlock()
l.off = true
}
func (l *Loop) disabled() bool {
l.RLock()
defer l.RUnlock()
return l.off
}
func (l *Loop) setAddress(addr string) {
l.Lock()
defer l.Unlock()
l.addr = addr
}
func (l *Loop) address() string {
l.RLock()
defer l.RUnlock()
return l.addr
}
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