d2268d3030
* Test DNAME handling If the DNAME itself matches the QTYPE, and the owner name matches QNAME, the relevant DNAME RR should be included in the answer section. Other parts of RFC 6672 are not implemented yet and hence left untested. * Implement the DNAME substitution As specified in RFC 6672, a DNAME substitution is performed by replacing the suffix labels of the name being sought matching the owner name of the DNAME resource record with the string of labels in the RDATA field. The matching labels end with the root label in all cases. Only whole labels are replaced. * Handle DNAME redirection A CNAME RR is created on-the-fly for the DNAME redirection. Be aware that we do not have all the edge cases covered yet. * Test DNAME owner name matching the QNAME A DNAME RR redirects DNS names subordinate to its owner name; the owner name of a DNAME is NOT redirected itself. * Ignore names next to and below a DNAME record According to RFC 6672, resource records MUST NOT exist at any subdomain of the owner of a DNAME RR. When loading a zone, those names below the DNAME RR will be quietly ignored. * Streamline DNAME processing Instead of checking DNAMEs during lookup, we use a preloaded list of DNAME RRs to streamline the process without any runtime performance penalty: * When loading the zone, keep a record of any DNAME RRs. * If there aren't any DNAMEs in the zone, just do the lookup as usual. * Only when the zone has one or more DNAME records, we look for the matching DNAME and ignore confronting subdomain(s) in the process. * Make it easier to trace back through test errors * Make DNAME handling part of lookup routine DNAME processing is invoked only if the zone has at least one DNAME RR. * Put DNAME resolution inside the searching of a hit We can drop some of the other ideas; we don't need to track if we have DNAMEs in the zone it just follows naturally from the current lookup code. See also: #664
44 lines
1.1 KiB
Go
44 lines
1.1 KiB
Go
package file
|
|
|
|
import (
|
|
"strings"
|
|
|
|
"github.com/miekg/dns"
|
|
)
|
|
|
|
// substituteDNAME performs the DNAME substitution defined by RFC 6672,
|
|
// assuming the QTYPE of the query is not DNAME. It returns an empty
|
|
// string if there is no match.
|
|
func substituteDNAME(qname, owner, target string) string {
|
|
if dns.IsSubDomain(owner, qname) && qname != owner {
|
|
labels := dns.SplitDomainName(qname)
|
|
labels = append(labels[0:len(labels)-dns.CountLabel(owner)], dns.SplitDomainName(target)...)
|
|
|
|
return strings.Join(labels, ".") + "."
|
|
}
|
|
|
|
return ""
|
|
}
|
|
|
|
// synthesizeCNAME returns a CNAME RR pointing to the resulting name of
|
|
// the DNAME substitution. The owner name of the CNAME is the QNAME of
|
|
// the query and the TTL is the same as the corresponding DNAME RR.
|
|
//
|
|
// It returns nil if the DNAME substitution has no match.
|
|
func synthesizeCNAME(qname string, d *dns.DNAME) *dns.CNAME {
|
|
target := substituteDNAME(qname, d.Header().Name, d.Target)
|
|
if target == "" {
|
|
return nil
|
|
}
|
|
|
|
r := new(dns.CNAME)
|
|
r.Hdr = dns.RR_Header{
|
|
Name: qname,
|
|
Rrtype: dns.TypeCNAME,
|
|
Class: dns.ClassINET,
|
|
Ttl: d.Header().Ttl,
|
|
}
|
|
r.Target = target
|
|
|
|
return r
|
|
}
|