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775cf92f03
Show from and to address when detecting a loop they may aid in
debugging.
Hard to create a unit test, but this is a startup run with self induced
loop:
~~~ corefile
.:1053 {
loop
log
forward . 127.0.0.1:1053
}
~~~~
~~~
:1053
2018-12-16T10:11:03.695Z [INFO] CoreDNS-1.3.0
2018-12-16T10:11:03.695Z [INFO] linux/amd64, go1.11,
CoreDNS-1.3.0
linux/amd64, go1.11,
2018-12-16T10:11:03.696Z [FATAL] plugin/loop: Loop (127.0.0.1:51384 -> :1053) detected for zone ".", see https://coredns.io/plugins/loop#troubleshooting. Query: "HINFO 2781022615773629442.4133547885299871809."
~~~
Update the docs and polished that a bit as well.
Signed-off-by: Miek Gieben <miek@miek.nl>
110 lines
2.1 KiB
Go
110 lines
2.1 KiB
Go
package loop
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import (
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"context"
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"sync"
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"github.com/coredns/coredns/plugin"
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clog "github.com/coredns/coredns/plugin/pkg/log"
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"github.com/coredns/coredns/request"
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"github.com/miekg/dns"
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)
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var log = clog.NewWithPlugin("loop")
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// Loop is a plugin that implements loop detection by sending a "random" query.
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type Loop struct {
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Next plugin.Handler
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zone string
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qname string
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addr string
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sync.RWMutex
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i int
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off bool
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}
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// New returns a new initialized Loop.
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func New(zone string) *Loop { return &Loop{zone: zone, qname: qname(zone)} }
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// ServeDNS implements the plugin.Handler interface.
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func (l *Loop) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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if r.Question[0].Qtype != dns.TypeHINFO {
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return plugin.NextOrFailure(l.Name(), l.Next, ctx, w, r)
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}
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if l.disabled() {
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return plugin.NextOrFailure(l.Name(), l.Next, ctx, w, r)
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}
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state := request.Request{W: w, Req: r}
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zone := plugin.Zones([]string{l.zone}).Matches(state.Name())
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if zone == "" {
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return plugin.NextOrFailure(l.Name(), l.Next, ctx, w, r)
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}
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if state.Name() == l.qname {
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l.inc()
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}
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if l.seen() > 2 {
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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)
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}
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return plugin.NextOrFailure(l.Name(), l.Next, ctx, w, r)
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}
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// Name implements the plugin.Handler interface.
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func (l *Loop) Name() string { return "loop" }
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func (l *Loop) exchange(addr string) (*dns.Msg, error) {
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m := new(dns.Msg)
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m.SetQuestion(l.qname, dns.TypeHINFO)
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return dns.Exchange(m, addr)
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}
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func (l *Loop) seen() int {
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l.RLock()
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defer l.RUnlock()
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return l.i
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}
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func (l *Loop) inc() {
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l.Lock()
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defer l.Unlock()
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l.i++
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}
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func (l *Loop) reset() {
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l.Lock()
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defer l.Unlock()
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l.i = 0
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}
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func (l *Loop) setDisabled() {
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l.Lock()
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defer l.Unlock()
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l.off = true
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}
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func (l *Loop) disabled() bool {
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l.RLock()
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defer l.RUnlock()
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return l.off
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}
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func (l *Loop) setAddress(addr string) {
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l.Lock()
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defer l.Unlock()
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l.addr = addr
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}
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func (l *Loop) address() string {
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l.RLock()
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defer l.RUnlock()
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return l.addr
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}
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