Add traffic plugin

This allows for advanced loadbalancing and maybe geoIP loadbalancing.

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

plugin/traffic/assignment_test.go

@@ -0,0 +1,38 @@
+package traffic
+
+import (
+	"math/rand"
+	"net"
+	"testing"
+	"time"
+)
+
+func TestAssignment(t *testing.T) {
+	rand.Seed(int64(time.Now().Nanosecond()))
+
+	backends := []*backend{
+		{net.IPv4zero, 0, 6},
+		{net.IPv4allrouter, 0, 4},
+		{net.IPv4allsys, 0, 0},
+	}
+	a := assignment{"www.example.org", backends}
+
+	// should never get 0 weight, could be improved to check the difference between 4 and 6.
+	for i := 0; i < 100; i++ {
+		if x := a.Select(); x.weight == 0 {
+			t.Errorf("Expected non-nil weight for Select, got %v", x)
+		}
+	}
+}
+
+func TestAssignmentZero(t *testing.T) {
+	rand.Seed(int64(time.Now().Nanosecond()))
+
+	backends := []*backend{
+		{net.IPv4zero, 0, 0},
+	}
+	a := assignment{"www.example.org", backends}
+	if x := a.Select(); x != nil {
+		t.Errorf("Expected nil for Select, got %v", x)
+	}
+}