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Add stream isolation via EDNS0 #4

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Oct 11, 2019
Merged

Add stream isolation via EDNS0 #4

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15 changes: 13 additions & 2 deletions madns.go
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,8 @@ var log, Log = xlog.New("madns")

const version string = "1.0.0"

const EDNS0STREAMISOLATION uint16 = 65312

var (
cNumQueries = expvar.NewInt("madns.numQueries")
cNumQueriesNoEDNS = expvar.NewInt("madns.numQueriesNoEDNS")
Expand All @@ -33,7 +35,7 @@ type Backend interface {
// The existence of wildcard records will be determined by doing a lookup for a name
// like "*.example.com", so there is no need to process the wildcard logic other than
// to make sure such a lookup functions correctly.
Lookup(qname string) (rrs []dns.RR, err error)
Lookup(qname, streamIsolationID string) (rrs []dns.RR, err error)
}

// DNS query engine implementing dns.Handler. Suitable for exposure directly to
Expand Down Expand Up @@ -92,8 +94,15 @@ func (e *engine) ServeDNS(rw dns.ResponseWriter, reqMsg *dns.Msg) {
tx.typesAtQname = map[uint16]struct{}{}
tx.additionalQueue = map[string]struct{}{}

tx.streamIsolationID = []byte{}

opt := tx.req.IsEdns0()
if opt != nil {
for _, edns0 := range opt.Option {
if edns0.Option() == EDNS0STREAMISOLATION {
tx.streamIsolationID = edns0.(*dns.EDNS0_LOCAL).Data
}
}
tx.res.Extra = append(tx.res.Extra, opt)
} else {
cNumQueriesNoEDNS.Add(1)
Expand Down Expand Up @@ -145,6 +154,8 @@ type stx struct {
e *engine
rcode int

streamIsolationID []byte

typesAtQname map[uint16]struct{}
additionalQueue map[string]struct{}
soa *dns.SOA
Expand All @@ -170,7 +181,7 @@ type stx struct {
func (tx *stx) blookup(qname string) (rrs []dns.RR, err error) {
cBackendLookups.Add(1)

rrs, err = tx.e.cfg.Backend.Lookup(qname)
rrs, err = tx.e.cfg.Backend.Lookup(qname, string(tx.streamIsolationID))
if err == nil && len(rrs) == 0 {
err = merr.ErrNoResults
}
Expand Down