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71 lines
2.1 KiB
Go
71 lines
2.1 KiB
Go
// Package fall handles the fallthrough logic used in plugins that support it. Be careful when including this
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// functionality in your plugin. Why? In the DNS only 1 source is authoritative for a set of names. Fallthrough
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// breaks this convention by allowing a plugin to query multiple sources, depending on the replies it got sofar.
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//
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// This may cause issues in downstream caches, where different answers for the same query can potentially confuse clients.
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// On the other hand this is a powerful feature that can aid in migration or other edge cases.
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//
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// The take away: be mindful of this and don't blindly assume it's a good feature to have in your plugin.
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//
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// See https://github.com/coredns/coredns/issues/2723 for some discussion on this, which includes this quote:
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//
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// TL;DR: `fallthrough` is indeed risky and hackish, but still a good feature of CoreDNS as it allows to quickly answer boring edge cases.
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package fall
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import (
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"github.com/coredns/coredns/plugin"
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)
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// F can be nil to allow for no fallthrough, empty allow all zones to fallthrough or
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// contain a zone list that is checked.
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type F struct {
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Zones []string
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}
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// Through will check if we should fallthrough for qname. Note that we've named the
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// variable in each plugin "Fall", so this then reads Fall.Through().
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func (f F) Through(qname string) bool {
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return plugin.Zones(f.Zones).Matches(qname) != ""
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}
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// setZones will set zones in f.
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func (f *F) setZones(zones []string) {
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z := []string{}
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for i := range zones {
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z = append(z, plugin.Host(zones[i]).NormalizeExact()...)
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}
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f.Zones = z
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}
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// SetZonesFromArgs sets zones in f to the passed value or to "." if the slice is empty.
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func (f *F) SetZonesFromArgs(zones []string) {
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if len(zones) == 0 {
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f.setZones(Root.Zones)
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return
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}
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f.setZones(zones)
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}
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// Equal returns true if f and g are equal.
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func (f *F) Equal(g F) bool {
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if len(f.Zones) != len(g.Zones) {
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return false
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}
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for i := range f.Zones {
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if f.Zones[i] != g.Zones[i] {
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return false
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}
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}
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return true
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}
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// Zero returns a zero valued F.
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var Zero = func() F {
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return F{[]string{}}
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}()
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// Root returns F set to only ".".
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var Root = func() F {
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return F{[]string{"."}}
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}()
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