IP endpoint for dnstap (#1002)

* adds the option to log to a remote endpoint

* examples

* tests

* tcp:// or default to unix://

* cosmetic update

* bad naked returns

5 files changed, 200 insertions, 20 deletions

diff --git a/middleware/dnstap/README.md b/middleware/dnstap/README.md
index a74472156..d91c9422c 100644
--- a/middleware/dnstap/README.md
+++ b/middleware/dnstap/README.md
@@ -24,7 +24,13 @@ dnstap /tmp/dnstap.sock
 Log information including the wire-format DNS message about client requests and responses to */tmp/dnstap.sock*.
 
 ~~~ txt
-dnstap /tmp/dnstap.sock full
+dnstap unix:///tmp/dnstap.sock full
+~~~
+
+Log to a remote endpoint.
+
+~~~ txt
+dnstap tcp://127.0.0.1:6000 full
 ~~~
 
 ## Dnstap command line tool
@@ -47,3 +53,9 @@ The following command listens on the given socket and saves message payloads to
 ~~~ sh
 dnstap -u /tmp/dnstap.sock -w /tmp/test.dnstap
 ~~~
+
+Listen for dnstap messages on port 6000.
+
+~~~ sh
+dnstap -l 127.0.0.1:6000
+~~~
diff --git a/middleware/dnstap/out/tcp.go b/middleware/dnstap/out/tcp.go
new file mode 100644
index 000000000..8d2c25270
--- /dev/null
+++ b/middleware/dnstap/out/tcp.go
@@ -0,0 +1,59 @@
+package out
+
+import (
+	"net"
+	"time"
+
+	fs "github.com/farsightsec/golang-framestream"
+)
+
+// TCP is a Frame Streams encoder over TCP.
+type TCP struct {
+	address string
+	frames  [][]byte
+}
+
+// NewTCP returns a TCP writer.
+func NewTCP(address string) *TCP {
+	s := &TCP{address: address}
+	s.frames = make([][]byte, 0, 13) // 13 messages buffer
+	return s
+}
+
+// Write a single Frame Streams frame.
+func (s *TCP) Write(frame []byte) (n int, err error) {
+	s.frames = append(s.frames, frame)
+	if len(s.frames) == cap(s.frames) {
+		return len(frame), s.Flush()
+	}
+	return len(frame), nil
+}
+
+// Flush the remaining frames.
+func (s *TCP) Flush() error {
+	defer func() {
+		s.frames = s.frames[0:]
+	}()
+	c, err := net.DialTimeout("tcp", s.address, time.Second)
+	if err != nil {
+		return err
+	}
+	enc, err := fs.NewEncoder(c, &fs.EncoderOptions{
+		ContentType:   []byte("protobuf:dnstap.Dnstap"),
+		Bidirectional: true,
+	})
+	if err != nil {
+		return err
+	}
+	for _, frame := range s.frames {
+		if _, err = enc.Write(frame); err != nil {
+			return err
+		}
+	}
+	return enc.Flush()
+}
+
+// Close is an alias to Flush to satisfy io.WriteCloser similarly to type Socket.
+func (s *TCP) Close() error {
+	return s.Flush()
+}
diff --git a/middleware/dnstap/out/tcp_test.go b/middleware/dnstap/out/tcp_test.go
new file mode 100644
index 000000000..d76cd9280
--- /dev/null
+++ b/middleware/dnstap/out/tcp_test.go
@@ -0,0 +1,66 @@
+package out
+
+import (
+	"net"
+	"testing"
+)
+
+func sendOneTcp(tcp *TCP) error {
+	if _, err := tcp.Write([]byte("frame")); err != nil {
+		return err
+	}
+	if err := tcp.Flush(); err != nil {
+		return err
+	}
+	return nil
+}
+func TestTcp(t *testing.T) {
+	tcp := NewTCP("localhost:14000")
+
+	if err := sendOneTcp(tcp); err == nil {
+		t.Fatal("Not listening but no error.")
+		return
+	}
+
+	l, err := net.Listen("tcp", "localhost:14000")
+	if err != nil {
+		t.Fatal(err)
+		return
+	}
+
+	wait := make(chan bool)
+	go func() {
+		acceptOne(t, l)
+		wait <- true
+	}()
+
+	if err := sendOneTcp(tcp); err != nil {
+		t.Fatalf("send one: %s", err)
+		return
+	}
+
+	<-wait
+
+	// TODO: When the server isn't responding according to the framestream protocol
+	// the thread is blocked.
+	/*
+		if err := sendOneTcp(tcp); err == nil {
+			panic("must fail")
+		}
+	*/
+
+	go func() {
+		acceptOne(t, l)
+		wait <- true
+	}()
+
+	if err := sendOneTcp(tcp); err != nil {
+		t.Fatalf("send one: %s", err)
+		return
+	}
+
+	<-wait
+	if err := l.Close(); err != nil {
+		t.Error(err)
+	}
+}
diff --git a/middleware/dnstap/setup.go b/middleware/dnstap/setup.go
index 5c74bd346..63a3eb099 100644
--- a/middleware/dnstap/setup.go
+++ b/middleware/dnstap/setup.go
@@ -2,11 +2,14 @@ package dnstap
 
 import (
 	"fmt"
+	"io"
 	"log"
+	"strings"
 
 	"github.com/coredns/coredns/core/dnsserver"
 	"github.com/coredns/coredns/middleware"
 	"github.com/coredns/coredns/middleware/dnstap/out"
+	"github.com/coredns/coredns/middleware/pkg/dnsutil"
 
 	"github.com/mholt/caddy"
 	"github.com/mholt/caddy/caddyfile"
@@ -26,30 +29,55 @@ func wrapSetup(c *caddy.Controller) error {
 	return nil
 }
 
-func parseConfig(c *caddyfile.Dispenser) (path string, full bool, err error) {
-	c.Next() // directive name
+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 !c.Args(&path) {
-		err = c.ArgErr()
-		return
+	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
 	}
 
-	full = c.NextArg() && c.Val() == "full"
+	c.full = d.NextArg() && d.Val() == "full"
 
 	return
 }
 
 func setup(c *caddy.Controller) error {
-	path, full, err := parseConfig(&c.Dispenser)
+	conf, err := parseConfig(&c.Dispenser)
 	if err != nil {
 		return err
 	}
 
-	dnstap := Dnstap{Pack: full}
+	dnstap := Dnstap{Pack: conf.full}
 
-	o, err := out.NewSocket(path)
-	if err != nil {
-		log.Printf("[WARN] Can't connect to %s at the moment", path)
+	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
 
diff --git a/middleware/dnstap/setup_test.go b/middleware/dnstap/setup_test.go
index fb4bca1f0..fc1dc98e0 100644
--- a/middleware/dnstap/setup_test.go
+++ b/middleware/dnstap/setup_test.go
@@ -6,14 +6,29 @@ import (
 )
 
 func TestConfig(t *testing.T) {
-	file := "dnstap dnstap.sock full"
-	c := caddy.NewTestController("dns", file)
-	if path, full, err := parseConfig(&c.Dispenser); path != "dnstap.sock" || !full {
-		t.Fatalf("%s: %s", file, err)
+	tests := []struct {
+		file   string
+		path   string
+		full   bool
+		socket bool
+		fail   bool
+	}{
+		{"dnstap dnstap.sock full", "dnstap.sock", true, true, false},
+		{"dnstap unix://dnstap.sock", "dnstap.sock", false, true, false},
+		{"dnstap tcp://127.0.0.1:6000", "127.0.0.1:6000", false, false, false},
+		{"dnstap", "fail", false, true, true},
 	}
-	file = "dnstap dnstap.sock"
-	c = caddy.NewTestController("dns", file)
-	if path, full, err := parseConfig(&c.Dispenser); path != "dnstap.sock" || full {
-		t.Fatalf("%s: %s", file, err)
+	for _, c := range tests {
+		cad := caddy.NewTestController("dns", c.file)
+		conf, err := parseConfig(&cad.Dispenser)
+		if c.fail {
+			if err == nil {
+				t.Errorf("%s: %s", c.file, err)
+			}
+		} else if err != nil || conf.target != c.path ||
+			conf.full != c.full || conf.socket != c.socket {
+
+			t.Errorf("expected: %+v\nhave: %+v\nerror: %s\n", c, conf, err)
+		}
 	}
 }