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https://github.com/coredns/coredns.git
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ebef64280a
This implements stubzones in the same way as SkyDNS. This also works with multiple configured domains and has tests. Also add more configuration parameters for TLS and path prefix and enabling stubzones. Run StubUpdates as a startup command to keep up to date with the list in etcd.
79 lines
1.9 KiB
Go
79 lines
1.9 KiB
Go
package etcd
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import (
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"github.com/miekg/coredns/middleware"
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"github.com/miekg/dns"
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"golang.org/x/net/context"
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)
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// Stub wraps an Etcd. We have this type so that it can have a ServeDNS method.
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type Stub struct {
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Etcd
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Zone string // for what zone (and thus what nameservers are we called)
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}
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func (s Stub) ServeDNS(ctx context.Context, w dns.ResponseWriter, req *dns.Msg) (int, error) {
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if hasStubEdns0(req) {
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// TODO(miek): actual error here
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return dns.RcodeServerFailure, nil
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}
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req = addStubEdns0(req)
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proxy, ok := (*s.Etcd.Stubmap)[s.Zone]
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if !ok { // somebody made a mistake..
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return dns.RcodeServerFailure, nil
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}
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state := middleware.State{W: w, Req: req}
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m1, e1 := proxy.Forward(state)
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if e1 != nil {
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return dns.RcodeServerFailure, e1
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}
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m1.RecursionAvailable, m1.Compress = true, true
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state.W.WriteMsg(m1)
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return dns.RcodeSuccess, nil
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}
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// hasStubEdns0 checks if the message is carrying our special edns0 zero option.
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func hasStubEdns0(m *dns.Msg) bool {
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option := m.IsEdns0()
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if option == nil {
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return false
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}
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for _, o := range option.Option {
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if o.Option() == ednsStubCode && len(o.(*dns.EDNS0_LOCAL).Data) == 1 &&
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o.(*dns.EDNS0_LOCAL).Data[0] == 1 {
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return true
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}
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}
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return false
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}
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// addStubEdns0 adds our special option to the message's OPT record.
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func addStubEdns0(m *dns.Msg) *dns.Msg {
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option := m.IsEdns0()
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// Add a custom EDNS0 option to the packet, so we can detect loops when 2 stubs are forwarding to each other.
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if option != nil {
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option.Option = append(option.Option, &dns.EDNS0_LOCAL{ednsStubCode, []byte{1}})
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} else {
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m.Extra = append(m.Extra, ednsStub)
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}
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return m
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}
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const (
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ednsStubCode = dns.EDNS0LOCALSTART + 10
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stubDomain = "stub.dns"
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)
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var ednsStub = func() *dns.OPT {
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o := new(dns.OPT)
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o.Hdr.Name = "."
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o.Hdr.Rrtype = dns.TypeOPT
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e := new(dns.EDNS0_LOCAL)
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e.Code = ednsStubCode
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e.Data = []byte{1}
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o.Option = append(o.Option, e)
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return o
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}()
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