Add traffic plugin

This allows for advanced loadbalancing and maybe geoIP loadbalancing.

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

plugin/traffic/setup.go

@@ -0,0 +1,40 @@
+package traffic
+
+import (
+	"math/rand"
+	"time"
+
+	"github.com/coredns/coredns/core/dnsserver"
+	"github.com/coredns/coredns/plugin"
+	clog "github.com/coredns/coredns/plugin/pkg/log"
+
+	"github.com/caddyserver/caddy"
+)
+
+var log = clog.NewWithPlugin("traffic")
+
+func init() { plugin.Register("traffic", setup) }
+
+func setup(c *caddy.Controller) error {
+	rand.Seed(int64(time.Now().Nanosecond()))
+	if err := parse(c); err != nil {
+		return plugin.Error("traffic", err)
+	}
+
+	dnsserver.GetConfig(c).AddPlugin(func(next plugin.Handler) plugin.Handler {
+		return &Traffic{Next: next, assignments: make(map[string]assignment)}
+	})
+
+	return nil
+}
+
+func parse(c *caddy.Controller) error {
+	for c.Next() {
+		args := c.RemainingArgs()
+		if len(args) != 0 {
+			return c.ArgErr()
+
+		}
+	}
+	return nil
+}