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Refactor to make this much less confusing

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This commit is contained in:
Matt Keeler 2018-07-03 11:04:19 -04:00
parent 4d1bdd8fdb
commit e9390fb5c7
1 changed files with 14 additions and 37 deletions
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51
agent/dns.go
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@ -1143,8 +1143,7 @@ func (d *DNSServer) serviceNodeRecords(dc string, nodes structs.CheckServiceNode
qType := req.Question[0].Qtype
handled := make(map[string]struct{})
edns := req.IsEdns0() != nil
haveCNAME := false
allowCNAME := true
var answerCNAME []dns.RR = nil
count := 0
for _, node := range nodes {
@ -1171,49 +1170,27 @@ func (d *DNSServer) serviceNodeRecords(dc string, nodes structs.CheckServiceNode
// Add the node record
records := d.formatNodeRecord(node.Node, addr, qName, qType, ttl, edns, true)
if records != nil {
// only allow at most 1 CNAME record
//
// The general rules are:
// 1 - if any nodes have actual address for the service ignore CNAMEs (set allowCNAME to false)
// 2 - if non nodes have actual addresses for the service only return the first CNAME record and ignore others
//
// We have to track 2 things, whether we have a CNAME in our Answer list and whether or not they are allowed.
// The reason we can't just track one vs the other is due to needing to clear out existing CNAMEs when we come
// upon more A/AAAA RRs
switch records[0].(type) {
case *dns.CNAME:
if haveCNAME || !allowCNAME {
// This checks whether we have a CNAME in our Answer list already or other non-CNAME data
// In both cases we need to ignore the new CNAME RR
continue
} else {
// This case basically can only happen for the very first node when CNAMEs are allowed but
// we don't have one yet.
haveCNAME = true
allowCNAME = false
// keep track of the first CNAME + associated RRs but don't add to the resp.Answer yet
// this will only be added if no non-CNAME RRs are found
if len(answerCNAME) == 0 {
answerCNAME = records
}
default:
if haveCNAME {
// This case handles when we previously had a CNAME record but now we have come across
// other non-CNAME data. We want to clear the CNAME data and start fresh. Additionally
// we need to mark that we no longer have CNAME data in the Answer list to make sure
// we don't clear out any more data in the future.
resp.Answer = nil
haveCNAME = false
resp.Answer = append(resp.Answer, records...)
count++
if count == d.config.ARecordLimit {
// We stop only if greater than 0 or we reached the limit
return
}
// once we see a non-CNAME node then we disallow setting any in the future.
allowCNAME = false
}
resp.Answer = append(resp.Answer, records...)
count++
if count == d.config.ARecordLimit {
// We stop only if greater than 0 or we reached the limit
return
}
}
}
if len(resp.Answer) == 0 && len(answerCNAME) > 0 {
resp.Answer = answerCNAME
}
}
// serviceARecords is used to add the SRV records for a service lookup