Do not reuse dns.Envelope variable

Sending a reference to a dns.Envelope (&env) to a channel and then resetting the env variable to a fresh envelope causes the reference sent over the channel to also reference an empty envelope. Now we maintain a separate slice of dns.RR records and create a new envelope on each send instead. Passing the dns.RR slice over the channel is OK as even if it internally points to data, the slice header itself will be copied and is not affected when we reset "rrs" to a new empty slice.
dnstapir · Jun 3, 2024 · fcd4535 · fcd4535
1 parent e456757
commit fcd4535
Showing 1 changed file with 34 additions and 34 deletions.
diff --git a/xfr.go b/xfr.go
@@ -81,35 +81,35 @@ func (td *TemData) RpzAxfrOut(w dns.ResponseWriter, r *dns.Msg) (uint32, int, er
 
 	count := 0
 	send_count := 0
-	env := dns.Envelope{}
+	rrs := []dns.RR{}
 
 	td.Rpz.Axfr.SOA.Serial = td.Rpz.CurrentSerial
-	env.RR = append(env.RR, dns.RR(&td.Rpz.Axfr.SOA))
+	rrs = append(rrs, dns.RR(&td.Rpz.Axfr.SOA))
 	//	total_sent := 1
 	var total_sent int
 
-	env.RR = append(env.RR, td.Rpz.Axfr.NSrrs...)
+	rrs = append(rrs, td.Rpz.Axfr.NSrrs...)
 
 	for _, rpzn := range td.Rpz.Axfr.Data {
-		env.RR = append(env.RR, *rpzn.RR) // should do proper slice magic instead
+		rrs = append(rrs, *rpzn.RR) // should do proper slice magic instead
 		count++
 		if count >= 500 {
 			send_count++
-			total_sent += len(env.RR)
-			// fmt.Printf("Sending %d RRs\n", len(env.RR))
-			outbound_xfr <- &env
-			// fmt.Printf("Sent %d RRs: done\n", len(env.RR))
-			env = dns.Envelope{}
+			total_sent += len(rrs)
+			// fmt.Printf("Sending %d RRs\n", len(rrs))
+			outbound_xfr <- &dns.Envelope{RR: rrs}
+			rrs = []dns.RR{}
+			// fmt.Printf("Sent %d RRs: done\n", len(rrs))
 			count = 0
 		}
 	}
 
-	env.RR = append(env.RR, dns.RR(&td.Rpz.Axfr.SOA)) // trailing SOA
+	rrs = append(rrs, dns.RR(&td.Rpz.Axfr.SOA)) // trailing SOA
 
-	total_sent += len(env.RR)
+	total_sent += len(rrs)
 	//	td.Logger.Printf("RpzAxfrOut: Zone %s: Sending final %d RRs (including trailing SOA, total sent %d)\n",
-	//		zone, len(env.RR), total_sent)
-	outbound_xfr <- &env
+	//		zone, len(rrs), total_sent)
+	outbound_xfr <- &dns.Envelope{RR: rrs}
 
 	close(outbound_xfr)
 	wg.Wait()        // wait until everything is written out
@@ -214,12 +214,12 @@ func (td *TemData) RpzIxfrOut(w dns.ResponseWriter, r *dns.Msg) (uint32, int, er
 		wg.Done()
 	}()
 
-	env := dns.Envelope{}
+	rrs := []dns.RR{}
 
 	var total_sent int
 
 	td.Rpz.Axfr.SOA.Serial = td.Rpz.CurrentSerial
-	env.RR = append(env.RR, dns.RR(&td.Rpz.Axfr.SOA))
+	rrs = append(rrs, dns.RR(&td.Rpz.Axfr.SOA))
 
 	var totcount, count int
 	var finalSerial uint32
@@ -235,23 +235,23 @@ func (td *TemData) RpzIxfrOut(w dns.ResponseWriter, r *dns.Msg) (uint32, int, er
 			if td.Debug {
 				td.Logger.Printf("IxfrOut: adding FROMSOA to output: %s", fromsoa.String())
 			}
-			env.RR = append(env.RR, fromsoa)
+			rrs = append(rrs, fromsoa)
 			count++
 			td.Logger.Printf("RpzIxfrOut: IXFR[%d,%d] has %d RRs in the removal list",
 				ixfr.FromSerial, ixfr.ToSerial, len(ixfr.Removed))
 			for _, tn := range ixfr.Removed {
 				if td.Debug {
 					td.Logger.Printf("DEL: adding RR to ixfr output: %s", tn.Name)
 				}
-				env.RR = append(env.RR, *tn.RR) // should do proper slice magic instead
+				rrs = append(rrs, *tn.RR) // should do proper slice magic instead
 				count++
 				if count >= 500 {
-					td.Logger.Printf("Sending %d RRs\n", len(env.RR))
-					for _, rr := range env.RR {
+					td.Logger.Printf("Sending %d RRs\n", len(rrs))
+					for _, rr := range rrs {
 						td.Logger.Printf("SEND DELS: %s", rr.String())
 					}
-					outbound_xfr <- &env
-					env = dns.Envelope{}
+					outbound_xfr <- &dns.Envelope{RR: rrs}
+					rrs = []dns.RR{}
 					totcount += count
 					count = 0
 				}
@@ -261,42 +261,42 @@ func (td *TemData) RpzIxfrOut(w dns.ResponseWriter, r *dns.Msg) (uint32, int, er
 			if td.Debug {
 				td.Logger.Printf("RpzIxfrOut: adding TOSOA to output: %s", tosoa.String())
 			}
-			env.RR = append(env.RR, tosoa)
+			rrs = append(rrs, tosoa)
 			count++
 			td.Logger.Printf("RpzIxfrOut: IXFR[%d,%d] has %d RRs in the added list",
 				ixfr.FromSerial, ixfr.ToSerial, len(ixfr.Added))
 			for _, tn := range ixfr.Added {
 				if td.Debug {
 					td.Logger.Printf("ADD: adding RR to ixfr output: %s", tn.Name)
 				}
-				env.RR = append(env.RR, *tn.RR) // should do proper slice magic instead
+				rrs = append(rrs, *tn.RR) // should do proper slice magic instead
 				count++
 				if count >= 500 {
-					td.Logger.Printf("Sending %d RRs\n", len(env.RR))
-					for _, rr := range env.RR {
+					td.Logger.Printf("Sending %d RRs\n", len(rrs))
+					for _, rr := range rrs {
 						td.Logger.Printf("SEND ADDS: %s", rr.String())
 					}
-					outbound_xfr <- &env
-					// fmt.Printf("Sent %d RRs: done\n", len(env.RR))
-					env = dns.Envelope{}
+					outbound_xfr <- &dns.Envelope{RR: rrs}
+					// fmt.Printf("Sent %d RRs: done\n", len(rrs))
+					rrs = []dns.RR{}
 					totcount += count
 					count = 0
 				}
 			}
 		}
 	}
 
-	env.RR = append(env.RR, dns.RR(&td.Rpz.Axfr.SOA)) // trailing SOA
+	rrs = append(rrs, dns.RR(&td.Rpz.Axfr.SOA)) // trailing SOA
 
-	total_sent += len(env.RR)
+	total_sent += len(rrs)
 	td.Logger.Printf("RpzIxfrOut: Zone %s: Sending final %d RRs (including trailing SOA, total sent %d)\n",
-		zone, len(env.RR), total_sent)
+		zone, len(rrs), total_sent)
 
-	//	td.Logger.Printf("Sending %d RRs\n", len(env.RR))
-	//	for _, rr := range env.RR {
+	//	td.Logger.Printf("Sending %d RRs\n", len(rrs))
+	//	for _, rr := range rrs {
 	//		td.Logger.Printf("SEND FINAL: %s", rr.String())
 	//	}
-	outbound_xfr <- &env
+	outbound_xfr <- &dns.Envelope{RR: rrs}
 
 	close(outbound_xfr)
 	wg.Wait()       // wait until everything is written out