de0fa53379
* Doc: add package docs Add short package level docs to make godoc looks nicer. Add some badges to the README. * correct url
46 lines
1.1 KiB
Go
46 lines
1.1 KiB
Go
// Package edns provides function usefull for adding/inspecting OPT records to/in messages.
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package edns
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import (
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"errors"
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"github.com/miekg/dns"
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)
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// Version checks the EDNS version in the request. If error
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// is nil everything is OK and we can invoke the middleware. If non-nil, the
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// returned Msg is valid to be returned to the client (and should). For some
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// reason this response should not contain a question RR in the question section.
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func Version(req *dns.Msg) (*dns.Msg, error) {
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opt := req.IsEdns0()
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if opt == nil {
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return nil, nil
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}
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if opt.Version() == 0 {
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return nil, nil
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}
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m := new(dns.Msg)
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m.SetReply(req)
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// zero out question section, wtf.
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m.Question = nil
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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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o.SetVersion(0)
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o.SetExtendedRcode(dns.RcodeBadVers)
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m.Extra = []dns.RR{o}
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return m, errors.New("EDNS0 BADVERS")
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}
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// Size returns a normalized size based on proto.
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func Size(proto string, size int) int {
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if proto == "tcp" {
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return dns.MaxMsgSize
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}
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if size < dns.MinMsgSize {
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return dns.MinMsgSize
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}
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return size
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}
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