Merge pull request #50 from mrozitron/mrozitron-drop-dial-error-checks

simulator: don't treat dial errors as errors

Author: tg

simulator/simulator.go

@@ -72,9 +72,8 @@ func (s *TCPConnectSimulator) Simulate(ctx context.Context, dst string) error {
 	if conn != nil {
 		conn.Close()
 	}
-	// This will likely generate some superfluous io-timeout error messages, but if the
-	// user specifies a misconfigured interface, they'll see the simulation failing.
-	if err != nil && (!isSoftError(err, "connect: connection refused") || isDialError(err)) {
+	// Ignore "connection refused" and timeouts.
+	if err != nil && !isSoftError(err, "connect: connection refused") {
 		return err
 	}
 	return nil
@@ -111,24 +110,14 @@ func (s *DNSResolveSimulator) Simulate(ctx context.Context, dst string) error {
 	host = utils.FQDN(host)
 
 	_, err := r.LookupHost(ctx, host)
-	// Ignore "no such host".  Will ignore timeouts as well, so check for dial errors.
-	if err != nil && (!isSoftError(err, "no such host") || isDialError(err)) {
+	// Ignore "no such host" and timeouts.
+	if err != nil && !isSoftError(err, "no such host") {
 		return err
 	}
 
 	return nil
 }
 
-// isDialError scans an error message for signs of a dial error, returning a boolean.
-func isDialError(err error) bool {
-	// Errors we're after are of the form:
-	// lookup abc.sandbox.alphasoc.xyz. on A.B.C.D:53: dial udp E.F.G.H:0->A.B.C.D:53: i/o timeout
-	// TODO: something more robust?  I don't want to double-dial though.
-	return isTimeout(err) &&
-		strings.Contains(err.Error(), "dial") &&
-		strings.Count(err.Error(), "->") == 1
-}
-
 func isTimeout(err error) bool {
 	netErr, ok := err.(net.Error)
 	if !ok {

simulator/spambot.go

@@ -89,12 +89,11 @@ func (s *Spambot) Hosts(scope string, size int) ([]string, error) {
 	for n := 0; len(hosts) < size && n < len(idx); n++ {
 		ctx, cancel := context.WithTimeout(context.Background(), 300*time.Millisecond)
 		host := utils.FQDN(domains[idx[n]])
-		mx, err := rv.LookupMX(ctx, host)
+		mx, _ := rv.LookupMX(ctx, host)
 		cancel()
 		// Check error message for sign of resolver/routing issue.
-		if err != nil && isDialError(err) {
-			return hosts, err
-		}
+		// TODO: at some point we'll want to check dialer errors for a sign of resolver
+		// problems
 		if len(mx) > 0 {
 			host := strings.TrimSuffix(mx[0].Host, ".")
 			if !seen[host] {

simulator/tunnel-dns.go

@@ -56,8 +56,8 @@ func (s *Tunnel) Simulate(ctx context.Context, host string) error {
 		defer cancelFn()
 		_, err := r.LookupTXT(ctx, fmt.Sprintf("%s.%s", label, host))
 
-		// Ignore "no such host".  Will ignore timeouts as well, so check for dial errors.
-		if err != nil && (!isSoftError(err, "no such host") || isDialError(err)) {
+		// Ignore "no such host".  Will ignore timeouts as well.
+		if err != nil && !isSoftError(err, "no such host") {
 			return err
 		}