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Also: - NSID support - Support for DNS Cookies (closes #115)
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| @@ -0,0 +1,3 @@ | ||
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| This is from github.com/coredns/coredns/plugin/pkg/edns/ |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,137 @@ | ||
| // Package edns provides function useful for adding/inspecting OPT records to/in messages. | ||
| package edns | ||
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| import ( | ||
| "errors" | ||
| "sync" | ||
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| "github.com/miekg/dns" | ||
| ) | ||
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| var sup = &supported{m: make(map[uint16]struct{})} | ||
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| type supported struct { | ||
| m map[uint16]struct{} | ||
| sync.RWMutex | ||
| } | ||
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| // SetSupportedOption adds a new supported option the set of EDNS0 options that we support. Plugins typically call | ||
| // this in their setup code to signal support for a new option. | ||
| // By default we support: | ||
| // dns.EDNS0NSID, dns.EDNS0EXPIRE, dns.EDNS0COOKIE, dns.EDNS0TCPKEEPALIVE, dns.EDNS0PADDING. These | ||
| // values are not in this map and checked directly in the server. | ||
| func SetSupportedOption(option uint16) { | ||
| sup.Lock() | ||
| sup.m[option] = struct{}{} | ||
| sup.Unlock() | ||
| } | ||
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| // SupportedOption returns true if the option code is supported as an extra EDNS0 option. | ||
| func SupportedOption(option uint16) bool { | ||
| sup.RLock() | ||
| _, ok := sup.m[option] | ||
| sup.RUnlock() | ||
| return ok | ||
| } | ||
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| // Version checks the EDNS version in the request. If error | ||
| // is nil everything is OK and we can invoke the plugin. If non-nil, the | ||
| // returned Msg is valid to be returned to the client (and should). For some | ||
| // reason this response should not contain a question RR in the question section. | ||
| func Version(req *dns.Msg) (*dns.Msg, error) { | ||
| opt := req.IsEdns0() | ||
| if opt == nil { | ||
| return nil, nil | ||
| } | ||
| if opt.Version() == 0 { | ||
| return nil, nil | ||
| } | ||
| m := new(dns.Msg) | ||
| m.SetReply(req) | ||
| // zero out question section, wtf. | ||
| m.Question = nil | ||
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| o := new(dns.OPT) | ||
| o.Hdr.Name = "." | ||
| o.Hdr.Rrtype = dns.TypeOPT | ||
| o.SetVersion(0) | ||
| m.Rcode = dns.RcodeBadVers | ||
| o.SetExtendedRcode(dns.RcodeBadVers) | ||
| m.Extra = []dns.RR{o} | ||
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| return m, errors.New("EDNS0 BADVERS") | ||
| } | ||
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| // Size returns a normalized size based on proto. | ||
| func Size(proto string, size uint16) uint16 { | ||
| if proto == "tcp" { | ||
| return dns.MaxMsgSize | ||
| } | ||
| if size < dns.MinMsgSize { | ||
| return dns.MinMsgSize | ||
| } | ||
| return size | ||
| } | ||
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| /* | ||
| The below wasn't from the edns package | ||
| */ | ||
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| // SetSizeAndDo adds an OPT record that the reflects the intent from request. | ||
| func SetSizeAndDo(req, m *dns.Msg) *dns.OPT { | ||
| o := req.IsEdns0() | ||
| if o == nil { | ||
| return nil | ||
| } | ||
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| if mo := m.IsEdns0(); mo != nil { | ||
| mo.Hdr.Name = "." | ||
| mo.Hdr.Rrtype = dns.TypeOPT | ||
| mo.SetVersion(0) | ||
| mo.SetUDPSize(o.UDPSize()) | ||
| mo.Hdr.Ttl &= 0xff00 // clear flags | ||
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| // Assume if the message m has options set, they are OK and represent what an upstream can do. | ||
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| if o.Do() { | ||
| mo.SetDo() | ||
| } | ||
| return mo | ||
| } | ||
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| // Reuse the request's OPT record and tack it to m. | ||
| o.Hdr.Name = "." | ||
| o.Hdr.Rrtype = dns.TypeOPT | ||
| o.SetVersion(0) | ||
| o.Hdr.Ttl &= 0xff00 // clear flags | ||
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| if len(o.Option) > 0 { | ||
| o.Option = SupportedOptions(o.Option) | ||
| } | ||
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| m.Extra = append(m.Extra, o) | ||
| return o | ||
| } | ||
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| func SupportedOptions(o []dns.EDNS0) []dns.EDNS0 { | ||
| var supported = make([]dns.EDNS0, 0, 3) | ||
| // For as long as possible try avoid looking up in the map, because that need an Rlock. | ||
| for _, opt := range o { | ||
| switch code := opt.Option(); code { | ||
| case dns.EDNS0NSID: | ||
| fallthrough | ||
| case dns.EDNS0COOKIE: | ||
| fallthrough | ||
| case dns.EDNS0SUBNET: | ||
| supported = append(supported, opt) | ||
| default: | ||
| if SupportedOption(code) { | ||
| supported = append(supported, opt) | ||
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| } | ||
| } | ||
| } | ||
| return supported | ||
| } |
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