code review 6482044: go.net/ipv4: new package

ipv4/mocktransponder_test.go

Index: ipv4/mocktransponder_test.go
===================================================================
new file mode 100644
--- /dev/null
+++ b/ipv4/mocktransponder_test.go
@@ -0,0 +1,133 @@
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin freebsd linux netbsd openbsd
+
+package ipv4_test
+
+import (
+	"code.google.com/p/go.net/ipv4"
+	"net"
+	"testing"
+	"time"
+)
+
+// runPayloadTransponder transmits IPv4 datagram payloads to the
+// loopback address or interface and captures the loopback'd datagram
+// payloads.
+func runPayloadTransponder(t *testing.T, c *ipv4.PacketConn, wb []byte, dst net.Addr) {
+	cf := ipv4.FlagTTL | ipv4.FlagDst | ipv4.FlagInterface
+	rb := make([]byte, 1500)
+	for i, toggle := range []bool{true, false, true} {
+		if err := c.SetControlMessage(cf, toggle); err != nil {
+			t.Fatalf("ipv4.PacketConn.SetControlMessage failed: %v", err)
+		}
+		c.SetTOS(i + 1)
+		var ip net.IP
+		switch v := dst.(type) {
+		case *net.UDPAddr:
+			ip = v.IP
+		case *net.IPAddr:
+			ip = v.IP
+		}
+		if ip.IsMulticast() {
+			c.SetMulticastTTL(i + 1)
+		} else {
+			c.SetTTL(i + 1)
+		}
+		c.SetDeadline(time.Now().Add(100 * time.Millisecond))
+		if _, err := c.Write(wb, nil, dst); err != nil {
+			t.Fatalf("ipv4.PacketConn.Write failed: %v", err)
+		}
+		_, cm, _, err := c.Read(rb)
+		if err != nil {
+			t.Fatalf("ipv4.PacketConn.Read failed: %v", err)
+		}
+		t.Logf("rcvd cmsg: %v", cm)
+	}
+}
+
+// runDatagramTransponder transmits ICMP for IPv4 datagrams to the
+// loopback address or interface and captures the response datagrams
+// from the protocol stack within the kernel.
+func runDatagramTransponder(t *testing.T, c *ipv4.RawConn, wb []byte, src, dst net.Addr) {
+	cf := ipv4.FlagTTL | ipv4.FlagDst | ipv4.FlagInterface
+	rb := make([]byte, ipv4.HeaderLen+len(wb))
+	for i, toggle := range []bool{true, false, true} {
+		if err := c.SetControlMessage(cf, toggle); err != nil {
+			t.Fatalf("ipv4.RawConn.SetControlMessage failed: %v", err)
+		}
+		wh := &ipv4.Header{}
+		wh.Version = ipv4.Version
+		wh.Len = ipv4.HeaderLen
+		wh.TOS = i + 1
+		wh.TotalLen = ipv4.HeaderLen + len(wb)
+		wh.TTL = i + 1
+		wh.Protocol = 1
+		if src != nil {
+			wh.Src = src.(*net.IPAddr).IP
+		}
+		if dst != nil {
+			wh.Dst = dst.(*net.IPAddr).IP
+		}
+		c.SetDeadline(time.Now().Add(100 * time.Millisecond))
+		if err := c.Write(wh, wb, nil); err != nil {
+			t.Fatalf("ipv4.RawConn.Write failed: %v", err)
+		}
+		rh, _, cm, err := c.Read(rb)
+		if err != nil {
+			t.Fatalf("ipv4.RawConn.Read failed: %v", err)
+		}
+		t.Logf("rcvd cmsg: %v", cm.String())
+		t.Logf("rcvd hdr: %v", rh.String())
+	}
+}
+
+func loopbackInterface() *net.Interface {
+	ift, err := net.Interfaces()
+	if err != nil {
+		return nil
+	}
+	for _, ifi := range ift {
+		if ifi.Flags&net.FlagLoopback != 0 {
+			return &ifi
+		}
+	}
+	return nil
+}
+
+func isGoodForMulticast(ifi *net.Interface) (net.IP, bool) {
+	if ifi.Flags&net.FlagUp == 0 {
+		return nil, false
+	}
+	// We need a unicast IPv4 address that can be used to specify
+	// the IPv4 multicast interface.
+	ifat, err := ifi.Addrs()
+	if err != nil {
+		return nil, false
+	}
+	if len(ifat) == 0 {
+		return nil, false
+	}
+	var ip net.IP
+	for _, ifa := range ifat {
+		switch v := ifa.(type) {
+		case *net.IPAddr:
+			ip = v.IP
+		case *net.IPNet:
+			ip = v.IP
+		default:
+			continue
+		}
+		if ip.To4() == nil {
+			ip = nil
+			continue
+		}
+		break
+	}
+	if ip == nil {
+		return nil, false
+	}
+	return ip, true
+}