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plugin/loop: show from -> to (#2400)

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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>
This commit is contained in:
Miek Gieben 2018-12-16 21:48:09 +00:00 • committed by Yong Tang
parent 6b8c154441
commit 775cf92f03
3 changed files with 28 additions and 11 deletions
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15
plugin/loop/loop.go
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@ -19,6 +19,7 @@ type Loop struct {
zone string
qname string
addr string
sync.RWMutex
i int
@ -49,7 +50,7 @@ func (l *Loop) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
}
if l.seen() > 2 {
log.Fatalf("Forwarding loop detected in \"%s\" zone. Exiting. See https://coredns.io/plugins/loop#troubleshooting. Probe query: \"HINFO %s\".", l.zone, l.qname)
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)
@ -94,3 +95,15 @@ func (l *Loop) disabled() bool {
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
}