Plugin/BIND - extend the syntax to allow multiple addresses (#1512)

* Extend bind to allow multiple addresses. UTs added. Changes the log for server starting, adding address when available

* update readme for bind

* fixes after review

* minor fix on readme

* accept multiple BIND directives in blocserver, consolidate the addresses

* fixes after review - format logging server address, variable names

4 files changed, 75 insertions, 28 deletions

diff --git a/plugin/bind/README.md b/plugin/bind/README.md
index 989a65b28..a33a6c8da 100644
--- a/plugin/bind/README.md
+++ b/plugin/bind/README.md
@@ -6,23 +6,46 @@
 
 ## Description
 
-Normally, the listener binds to the wildcard host. However, you may force the listener to bind to
-another IP instead. This directive accepts only an address, not a port.
+Normally, the listener binds to the wildcard host. However, you may want the listener to bind to
+another IP instead.      
+
+If several addresses are provided, a listener will be open on each of the IP provided.
+
+Each address has to be an IP of one of the interfaces of the host.
 
 ## Syntax
 
 ~~~ txt
-bind ADDRESS
+bind ADDRESS  ...
 ~~~
 
-**ADDRESS** is the IP address to bind to.
+**ADDRESS** is an IP address to bind to.
+When several addresses are provided a listener will be opened on each of the addresses.
 
 ## Examples
 
 To make your socket accessible only to that machine, bind to IP 127.0.0.1 (localhost):
 
-~~~
+~~~ corefile
 . {
     bind 127.0.0.1
 }
 ~~~
+
+To allow processing DNS requests only local host on both IPv4 and IPv6 stacks, use the syntax:
+
+~~~ corefile
+. {
+    bind 127.0.0.1 ::1
+}
+~~~
+
+If the configuration comes up with several *bind* directives, all addresses are consolidated together:
+The following sample is equivalent to the preceding:
+ 
+~~~ corefile
+. {
+    bind 127.0.0.1 
+    bind ::1
+}
+~~~
diff --git a/plugin/bind/bind_test.go b/plugin/bind/bind_test.go
index 11556f0bd..9b1dc54aa 100644
--- a/plugin/bind/bind_test.go
+++ b/plugin/bind/bind_test.go
@@ -9,22 +9,38 @@ import (
 )
 
 func TestSetupBind(t *testing.T) {
-	c := caddy.NewTestController("dns", `bind 1.2.3.4`)
-	err := setupBind(c)
-	if err != nil {
-		t.Fatalf("Expected no errors, but got: %v", err)
-	}
-
-	cfg := dnsserver.GetConfig(c)
-	if got, want := cfg.ListenHost, "1.2.3.4"; got != want {
-		t.Errorf("Expected the config's ListenHost to be %s, was %s", want, got)
-	}
-}
-
-func TestBindAddress(t *testing.T) {
-	c := caddy.NewTestController("dns", `bind 1.2.3.bla`)
-	err := setupBind(c)
-	if err == nil {
-		t.Fatalf("Expected errors, but got none")
+	for i, test := range []struct {
+		config   string
+		expected []string
+		failing  bool
+	}{
+		{`bind 1.2.3.4`, []string{"1.2.3.4"}, false},
+		{`bind`, nil, true},
+		{`bind 1.2.3.invalid`, nil, true},
+		{`bind 1.2.3.4 ::5`, []string{"1.2.3.4", "::5"}, false},
+		{`bind ::1 1.2.3.4 ::5 127.9.9.0`, []string{"::1", "1.2.3.4", "::5", "127.9.9.0"}, false},
+		{`bind ::1 1.2.3.4 ::5 127.9.9.0 noone`, nil, true},
+	} {
+		c := caddy.NewTestController("dns", test.config)
+		err := setupBind(c)
+		if err != nil {
+			if !test.failing {
+				t.Fatalf("test %d, expected no errors, but got: %v", i, err)
+			}
+			continue
+		}
+		if test.failing {
+			t.Fatalf("test %d, expected to failed but did not, returned values", i)
+		}
+		cfg := dnsserver.GetConfig(c)
+		if len(cfg.ListenHosts) != len(test.expected) {
+			t.Errorf("test %d : expected the config's ListenHosts size to be %d, was %d", i, len(test.expected), len(cfg.ListenHosts))
+			continue
+		}
+		for i, v := range test.expected {
+			if got, want := cfg.ListenHosts[i], v; got != want {
+				t.Errorf("test %d : expected the config's ListenHost to be %s, was %s", i, want, got)
+			}
+		}
 	}
 }
diff --git a/plugin/bind/setup.go b/plugin/bind/setup.go
index 796377841..a57e8ffce 100644
--- a/plugin/bind/setup.go
+++ b/plugin/bind/setup.go
@@ -12,13 +12,21 @@ import (
 
 func setupBind(c *caddy.Controller) error {
 	config := dnsserver.GetConfig(c)
+
+	// addresses will be consolidated over all BIND directives available in that BlocServer
+	all := []string{}
 	for c.Next() {
-		if !c.Args(&config.ListenHost) {
-			return plugin.Error("bind", c.ArgErr())
+		addrs := c.RemainingArgs()
+		if len(addrs) == 0 {
+			return plugin.Error("bind", fmt.Errorf("at least one address is expected"))
 		}
+		for _, addr := range addrs {
+			if net.ParseIP(addr) == nil {
+				return plugin.Error("bind", fmt.Errorf("not a valid IP address: %s", addr))
+			}
+		}
+		all = append(all, addrs...)
 	}
-	if net.ParseIP(config.ListenHost) == nil {
-		return plugin.Error("bind", fmt.Errorf("not a valid IP address: %s", config.ListenHost))
-	}
+	config.ListenHosts = all
 	return nil
 }
diff --git a/plugin/trace/setup.go b/plugin/trace/setup.go
index 5c6e473c3..2eb93c3a2 100644
--- a/plugin/trace/setup.go
+++ b/plugin/trace/setup.go
@@ -41,7 +41,7 @@ func traceParse(c *caddy.Controller) (*trace, error) {
 	)
 
 	cfg := dnsserver.GetConfig(c)
-	tr.ServiceEndpoint = cfg.ListenHost + ":" + cfg.Port
+	tr.ServiceEndpoint = cfg.HostAddresses()
 	for c.Next() { // trace
 		var err error
 		args := c.RemainingArgs()