shill: LinkMonitor: Add ArpClient code

Add ArpClient class and start hooking it up to LinkMonitor.

BUG=chromium-os:32600
TEST=Unit tests.  Some real-world testing using the test harness
to transmit and receive ARP on a real network.

Change-Id: Ic05d8d7eb921878e3776f35b4be285554ef86456
Reviewed-on: https://gerrit.chromium.org/gerrit/28148
Commit-Ready: Paul Stewart <pstew@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>

1 files changed, 66 insertions, 0 deletions

diff --git a/arp_client.h b/arp_client.h
new file mode 100644
index 00000000..0ae6b7c2
--- /dev/null
+++ b/arp_client.h
@@ -0,0 +1,66 @@
+// Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SHILL_ARP_CLIENT_H_
+#define SHILL_ARP_CLIENT_H_
+
+#include <base/basictypes.h>
+#include <base/memory/scoped_ptr.h>
+
+namespace shill {
+
+class ArpPacket;
+class ByteString;
+class Sockets;
+class ScopedSocketCloser;
+
+// ArpClient task of creating ARP-capable sockets, as well as
+// transmitting requests on and receiving responses from such
+// sockets.
+class ArpClient {
+ public:
+  explicit ArpClient(int interface_index);
+  virtual ~ArpClient();
+
+  // Create a socket for tranmission and reception.  Returns true
+  // if successful, false otherwise.
+  virtual bool Start();
+
+  // Destroy the client socket.
+  virtual void Stop();
+
+  // Receive an ARP reply and parse its contents into |packet|.  Also
+  // return the sender's MAC address (which may be different from the
+  // MAC address in the ARP response) in |sender|.  Returns true on
+  // succes, false otherwise.
+  virtual bool ReceiveReply(ArpPacket *packet, ByteString *sender) const;
+
+  // Send a formatted ARP request from |packet|.  Returns true on
+  // success, false otherwise.
+  virtual bool TransmitRequest(const ArpPacket &packet) const;
+
+  virtual int socket() const { return socket_; }
+
+ private:
+  friend class ArpClientTest;
+
+  // Offset of the ARP OpCode within a captured ARP packet.
+  static const size_t kArpOpOffset;
+
+  // The largest packet we expect to receive as an ARP client.
+  static const size_t kMaxArpPacketLength;
+
+  bool CreateSocket();
+
+  const int interface_index_;
+  scoped_ptr<Sockets> sockets_;
+  scoped_ptr<ScopedSocketCloser> socket_closer_;
+  int socket_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArpClient);
+};
+
+}  // namespace shill
+
+#endif  // SHILL_ARP_CLIENT_H_