Add new plugin: traffic

Traffic is a plugin that communicates via the xDS protocol to an Envoy
control plane. Using the data from this control plane it hands out IP
addresses. This allows you (via controlling the data in the control
plane) to drain or send more traffic to specific endpoints.

The plugin itself only acts upon this data; it doesn't do anything fancy
by itself.

Code used here is copied from grpc-go and other places, this is clearly
marked in the source files.

Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/traffic/setup_test.go

@@ -0,0 +1,53 @@
+package traffic
+
+import (
+	"testing"
+
+	"github.com/caddyserver/caddy"
+)
+
+func TestSetup(t *testing.T) {
+	/*
+		c := caddy.NewTestController("dns", `traffic grpc://bla`)
+		if err := setup(c); err != nil {
+			t.Fatalf("Test 1, expected no errors, but got: %q", err)
+		}
+	*/
+}
+
+func TestParseTraffic(t *testing.T) {
+	tests := []struct {
+		input     string
+		shouldErr bool
+	}{
+		// ok
+		{`traffic grpc://127.0.0.1:18000 {
+			id test-id
+		}`, false},
+
+		// fail
+		{`traffic`, true},
+		{`traffic tls://1.1.1.1`, true},
+		{`traffic {
+			id bla bla
+		}`, true},
+		{`traffic {
+			node
+		}`, true},
+	}
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", test.input)
+		_, err := parseTraffic(c)
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %v: Expected error but found nil", i)
+			continue
+		} else if !test.shouldErr && err != nil {
+			t.Errorf("Test %v: Expected no error but found error: %v", i, err)
+			continue
+		}
+
+		if test.shouldErr {
+			continue
+		}
+	}
+}