Remove the word middleware (#1067)

* Rename middleware to plugin

first pass; mostly used 'sed', few spots where I manually changed
text.

This still builds a coredns binary.

* fmt error

* Rename AddMiddleware to AddPlugin

* Readd AddMiddleware to remain backwards compat

plugin/dnstap/setup.go

@@ -0,0 +1,98 @@
+package dnstap
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"strings"
+
+	"github.com/coredns/coredns/core/dnsserver"
+	"github.com/coredns/coredns/plugin"
+	"github.com/coredns/coredns/plugin/dnstap/out"
+	"github.com/coredns/coredns/plugin/pkg/dnsutil"
+
+	"github.com/mholt/caddy"
+	"github.com/mholt/caddy/caddyfile"
+)
+
+func init() {
+	caddy.RegisterPlugin("dnstap", caddy.Plugin{
+		ServerType: "dns",
+		Action:     wrapSetup,
+	})
+}
+
+func wrapSetup(c *caddy.Controller) error {
+	if err := setup(c); err != nil {
+		return plugin.Error("dnstap", err)
+	}
+	return nil
+}
+
+type config struct {
+	target string
+	socket bool
+	full   bool
+}
+
+func parseConfig(d *caddyfile.Dispenser) (c config, err error) {
+	d.Next() // directive name
+
+	if !d.Args(&c.target) {
+		return c, d.ArgErr()
+	}
+
+	if strings.HasPrefix(c.target, "tcp://") {
+		// remote IP endpoint
+		servers, err := dnsutil.ParseHostPortOrFile(c.target[6:])
+		if err != nil {
+			return c, d.ArgErr()
+		}
+		c.target = servers[0]
+	} else {
+		// default to UNIX socket
+		if strings.HasPrefix(c.target, "unix://") {
+			c.target = c.target[7:]
+		}
+		c.socket = true
+	}
+
+	c.full = d.NextArg() && d.Val() == "full"
+
+	return
+}
+
+func setup(c *caddy.Controller) error {
+	conf, err := parseConfig(&c.Dispenser)
+	if err != nil {
+		return err
+	}
+
+	dnstap := Dnstap{Pack: conf.full}
+
+	var o io.WriteCloser
+	if conf.socket {
+		o, err = out.NewSocket(conf.target)
+		if err != nil {
+			log.Printf("[WARN] Can't connect to %s at the moment: %s", conf.target, err)
+		}
+	} else {
+		o = out.NewTCP(conf.target)
+	}
+	dnstap.Out = o
+
+	c.OnShutdown(func() error {
+		if err := o.Close(); err != nil {
+			return fmt.Errorf("output: %s", err)
+		}
+		return nil
+	})
+
+	dnsserver.GetConfig(c).AddPlugin(
+		func(next plugin.Handler) plugin.Handler {
+			dnstap.Next = next
+			return dnstap
+		})
+
+	return nil
+}