84ec780ffc
* New plugin: loop Add a plugin that detects loops. It does this by sending an unique query to our selves. If we see the query more than twice we stop the process. If there isn't a loop, the plugin disables it self and becomes a noop plugin. Signed-off-by: Miek Gieben <miek@miek.nl>
90 lines
1.8 KiB
Go
90 lines
1.8 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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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("Seen \"HINFO IN %s\" more than twice, loop detected", 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) 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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