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>
93 lines
1.7 KiB
Go
93 lines
1.7 KiB
Go
package loop
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import (
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"math/rand"
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"net"
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"strconv"
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"time"
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"github.com/coredns/coredns/core/dnsserver"
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"github.com/coredns/coredns/plugin"
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"github.com/coredns/coredns/plugin/pkg/dnsutil"
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"github.com/mholt/caddy"
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)
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func init() {
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caddy.RegisterPlugin("loop", caddy.Plugin{
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ServerType: "dns",
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Action: setup,
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})
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}
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func setup(c *caddy.Controller) error {
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l, err := parse(c)
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if err != nil {
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return plugin.Error("loop", err)
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}
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dnsserver.GetConfig(c).AddPlugin(func(next plugin.Handler) plugin.Handler {
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l.Next = next
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return l
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})
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// Send query to ourselves and see if it end up with us again.
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c.OnStartup(func() error {
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// Another Go function, otherwise we block startup and can't send the packet.
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go func() {
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deadline := time.Now().Add(30 * time.Second)
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conf := dnsserver.GetConfig(c)
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lh := conf.ListenHosts[0]
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addr := net.JoinHostPort(lh, conf.Port)
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for time.Now().Before(deadline) {
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l.setAddress(addr)
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if _, err := l.exchange(addr); err != nil {
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l.reset()
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time.Sleep(1 * time.Second)
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continue
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}
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go func() {
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time.Sleep(2 * time.Second)
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l.setDisabled()
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}()
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break
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}
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l.setDisabled()
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}()
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return nil
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})
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return nil
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}
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func parse(c *caddy.Controller) (*Loop, error) {
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i := 0
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zone := "."
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for c.Next() {
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if i > 0 {
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return nil, plugin.ErrOnce
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}
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i++
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if c.NextArg() {
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return nil, c.ArgErr()
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}
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if len(c.ServerBlockKeys) > 0 {
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zone = plugin.Host(c.ServerBlockKeys[0]).Normalize()
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}
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}
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return New(zone), nil
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}
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// qname returns a random name. <rand.Int()>.<rand.Int().<zone>.
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func qname(zone string) string {
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l1 := strconv.Itoa(r.Int())
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l2 := strconv.Itoa(r.Int())
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return dnsutil.Join(l1, l2, zone)
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}
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var r = rand.New(rand.NewSource(time.Now().UnixNano()))
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