02955d7594
* Add dnsutil.Join * Create dnsutil.Join Create Join helper function and move bits in the code over.
44 lines
1.1 KiB
Go
44 lines
1.1 KiB
Go
package file
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import (
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"github.com/coredns/coredns/middleware/pkg/dnsutil"
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"github.com/miekg/dns"
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)
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// substituteDNAME performs the DNAME substitution defined by RFC 6672,
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// assuming the QTYPE of the query is not DNAME. It returns an empty
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// string if there is no match.
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func substituteDNAME(qname, owner, target string) string {
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if dns.IsSubDomain(owner, qname) && qname != owner {
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labels := dns.SplitDomainName(qname)
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labels = append(labels[0:len(labels)-dns.CountLabel(owner)], dns.SplitDomainName(target)...)
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return dnsutil.Join(labels)
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}
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return ""
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}
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// synthesizeCNAME returns a CNAME RR pointing to the resulting name of
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// the DNAME substitution. The owner name of the CNAME is the QNAME of
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// the query and the TTL is the same as the corresponding DNAME RR.
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//
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// It returns nil if the DNAME substitution has no match.
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func synthesizeCNAME(qname string, d *dns.DNAME) *dns.CNAME {
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target := substituteDNAME(qname, d.Header().Name, d.Target)
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if target == "" {
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return nil
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}
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r := new(dns.CNAME)
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r.Hdr = dns.RR_Header{
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Name: qname,
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Rrtype: dns.TypeCNAME,
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Class: dns.ClassINET,
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Ttl: d.Header().Ttl,
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}
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r.Target = target
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return r
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}
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