Add iptables testing framework.

It would be preferrable to test iptables via syscall tests, but there are some
problems with that approach:

* We're limited to loopback-only, as syscall tests involve only a single
  container. Other link interfaces (e.g. fdbased) should be tested.
* We'd have to shell out to call iptables anyways, as the iptables syscall
  interface itself is too large and complex to work with alone.
* Running the Linux/native version of the syscall test will require root, which
  is a pain to configure, is inherently unsafe, and could leave host iptables
  misconfigured.

Using the go_test target allows there to be no new test runner.

PiperOrigin-RevId: 285274275

1 files changed, 82 insertions, 0 deletions

diff --git a/test/iptables/iptables_util.go b/test/iptables/iptables_util.go
new file mode 100644
index 000000000..3a4d11f1a
--- /dev/null
+++ b/test/iptables/iptables_util.go
@@ -0,0 +1,82 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package iptables
+
+import (
+	"fmt"
+	"net"
+	"os/exec"
+	"time"
+)
+
+const iptablesBinary = "iptables"
+
+// filterTable calls `iptables -t filter` with the given args.
+func filterTable(args ...string) error {
+	args = append([]string{"-t", "filter"}, args...)
+	cmd := exec.Command(iptablesBinary, args...)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		return fmt.Errorf("error running iptables with args %v\nerror: %v\noutput: %s", args, err, string(out))
+	}
+	return nil
+}
+
+// listenUDP listens on a UDP port and returns the value of net.Conn.Read() for
+// the first read on that port.
+func listenUDP(port int, timeout time.Duration) error {
+	localAddr := net.UDPAddr{
+		Port: port,
+	}
+	conn, err := net.ListenUDP(network, &localAddr)
+	if err != nil {
+		return err
+	}
+	defer conn.Close()
+	conn.SetDeadline(time.Now().Add(timeout))
+	_, err = conn.Read([]byte{0})
+	return err
+}
+
+// sendUDPLoop sends 1 byte UDP packets repeatedly to the IP and port specified
+// over a duration.
+func sendUDPLoop(ip net.IP, port int, duration time.Duration) error {
+	// Send packets for a few seconds.
+	remote := net.UDPAddr{
+		IP:   ip,
+		Port: port,
+	}
+	conn, err := net.DialUDP(network, nil, &remote)
+	if err != nil {
+		return err
+	}
+	defer conn.Close()
+
+	to := time.After(duration)
+	for timedOut := false; !timedOut; {
+		// This may return an error (connection refused) if the remote
+		// hasn't started listening yet or they're dropping our
+		// packets. So we ignore Write errors and depend on the remote
+		// to report a failure if it doesn't get a packet it needs.
+		conn.Write([]byte{0})
+		select {
+		case <-to:
+			timedOut = true
+		default:
+			time.Sleep(200 * time.Millisecond)
+		}
+	}
+
+	return nil
+}