Use the configured resolvers exclusively (caddyserver#131) (fix caddy…

…server#132)

* feature: add optional !important suffix

if !important is added to any of the resolvers, then all are considered
exclusive and no other fallbacks will be added.

* fix: !important can be on it's own

* simplify recursiveNameservers

- use custom OR default nameservers
- add testing

* removed print line

* tests: fixed defaults when resolv.conf is found

dnsutil.go

@@ -313,11 +313,17 @@ func updateDomainWithCName(r *dns.Msg, fqdn string) string {
 }
 
 // recursiveNameservers are used to pre-check DNS propagation. It
-// prepends user-configured nameservers (custom) to the defaults
-// obtained from resolv.conf and defaultNameservers and ensures
-// that all server addresses have a port value.
+// picks user-configured nameservers (custom) OR the defaults
+// obtained from resolv.conf and defaultNameservers if none is
+// configured and ensures that all server addresses have a port value.
 func recursiveNameservers(custom []string) []string {
- servers := append(custom, systemOrDefaultNameservers(defaultResolvConf, defaultNameservers)...)
+ var servers []string
+ if len(custom) == 0 {
+ servers = systemOrDefaultNameservers(defaultResolvConf, defaultNameservers)
+ } else {
+ servers = make([]string, len(custom))
+ copy(servers, custom)
+ }
  populateNameserverPorts(servers)
  return servers
 }

dnsutil_test.go

@@ -7,6 +7,7 @@ package certmagic
 // It has been modified.
 
 import (
+ "net"
  "reflect"
  "sort"
  "strings"
@@ -206,19 +207,48 @@ func TestResolveConfServers(t *testing.T) {
 }
 
 func TestRecursiveNameserversAddsPort(t *testing.T) {
- custom := []string{"127.0.0.1"}
+ type want struct {
+ port string
+ }
+ custom := []string{"127.0.0.1", "ns1.google.com:43"}
+ expectations := []want{{port: "53"}, {port: "43"}}
  results := recursiveNameservers(custom)
 
+ if !reflect.DeepEqual(custom, []string{"127.0.0.1", "ns1.google.com:43"}) {
+ t.Errorf("Expected custom nameservers to be unmodified. got %v", custom)
+ }
+
+ if len(results) != len(expectations) {
+ t.Errorf("%v wrong results length. got %d, want %d", results, len(results), len(expectations))
+ }
+
  var hasCustom bool
  for i, res := range results {
  hasCustom = hasCustom || strings.HasPrefix(res, custom[0])
- if !strings.HasSuffix(res, ":53") {
- t.Errorf("%v Expected all results to have a port, but result %d doesn't: %s", results, i, res)
+ if _, port, err := net.SplitHostPort(res); err != nil {
+ t.Errorf("%v Error splitting result %d into host and port: %v", results, i, err)
+ } else {
+ if port != expectations[i].port {
+ t.Errorf("%v Expected result %d to have port %s but got %s", results, i, expectations[i].port, port)
+ }
  }
  }
  if !hasCustom {
  t.Errorf("%v Expected custom resolvers to be included, but they weren't: %v", results, custom)
  }
+
+}
+
+func TestRecursiveNameserversDefaults(t *testing.T) {
+ results := recursiveNameservers(nil)
+ if len(results) < 1 {
+ t.Errorf("%v Expected at least 1 records as default when nil custom", results)
+ }
+
+ results = recursiveNameservers([]string{})
+ if len(results) < 1 {
+ t.Errorf("%v Expected at least 1 records as default when empty custom", results)
+ }
 }
 
 func clearFqdnCache() {