#include "emu-net-device.h"

#include "emu-encode-decode.h"

#include <sys/wait.h>

#include <sys/stat.h>

#include <sys/un.h>

#include <errno.h>

NS_LOG_COMPONENT_DEFINE ("EmuNetDevice");

NS_OBJECT_ENSURE_REGISTERED (EmuNetDevice);

EmuNetDevice::GetTypeId (void)

  static TypeId tid = TypeId ("ns3::EmuNetDevice")

    .AddConstructor<EmuNetDevice> ()

                   MakeMac48AddressAccessor (&EmuNetDevice::m_address),

                   MakeStringAccessor (&EmuNetDevice::m_deviceName),

                   MakeTimeAccessor (&EmuNetDevice::m_tStart),

                   MakeTimeAccessor (&EmuNetDevice::m_tStop),

                   MakePointerAccessor (&EmuNetDevice::m_queue),

                     MakeTraceSourceAccessor (&EmuNetDevice::m_rxTrace))

                     MakeTraceSourceAccessor (&EmuNetDevice::m_dropTrace))

EmuNetDevice::EmuNetDevice () 

  m_name ("Emu NetDevice")

EmuNetDevice::~EmuNetDevice ()

EmuNetDevice::DoDispose()

EmuNetDevice::Start (Time tStart)

  m_startEvent = Simulator::Schedule (tStart, &EmuNetDevice::StartDevice, this);

EmuNetDevice::Stop (Time tStop)

  m_startEvent = Simulator::Schedule (tStop, &EmuNetDevice::StopDevice, this);

EmuNetDevice::StartDevice (void)

  // Spin up the emu net device and start receiving packets.

  NS_ASSERT_MSG (m_sock == -1, "EmuNetDevice::StartDevice(): Device is already started");

  //

  // Call out to a separate process running as suid root in order to get a raw 

  // socket.  We do this to avoid having the entire simulation running as root.

  // If this method returns, we'll have a raw socket waiting for us in m_sock.

  //

  CreateSocket ();

  NS_ASSERT_MSG (rc != -1, "EmuNetDevice::StartDevice(): Can't get interface index");

  NS_ASSERT_MSG (rc != -1, "EmuNetDevice::StartDevice(): Can't bind to specified interface");

  NS_ASSERT_MSG (m_readThread == 0, "EmuNetDevice::StartDevice(): Receive thread is already running");

  m_readThread = Create<SystemThread> (MakeCallback (&EmuNetDevice::ReadThread, this));

EmuNetDevice::CreateSocket (void)

{

  NS_LOG_FUNCTION_NOARGS ();

  //

  // We want to create a raw socket for our net device.  Unfortunately for us

  // you have to have root privileges to do that.  Instead of running the 

  // entire simulation as root, we decided to make a small program who's whole

  // reason for being is to run as suid root and create a raw socket.  We're

  // going to fork and exec that program soon, but we need to have a socket

  // to talk to it with.  So we create a local interprocess (Unix) socket 

  // for that purpose.

  //

  int sock = socket (PF_UNIX, SOCK_DGRAM, 0);

  if (sock == -1)

    {

      NS_FATAL_ERROR ("EmuNetDevice::CreateSocket(): Unix socket creation error, errno = " << strerror (errno));

    }

  //

  // Bind to that socket and let the kernel allocate an endpoint

  //

  struct sockaddr_un un;

  memset (&un, 0, sizeof (un));

  un.sun_family = AF_UNIX;

  int status = bind (sock, (struct sockaddr*)&un, sizeof (sa_family_t));

  if (status == -1)

    {

      NS_FATAL_ERROR ("EmuNetDevice::CreateSocket(): Could not bind(): errno = " << strerror (errno));

    }

  //

  // We have a socket here, but we want to get it there -- to the program we're

  // going to exec.  What we'll do is to do a getsockname and then encode the

  // resulting address information as a string, and then send the string to the

  // program as an argument.  So we need to get the sock name.

  //

  socklen_t len = sizeof (un);

  status = getsockname (sock, (struct sockaddr*)&un, &len);

  if (status == -1)

    {

      NS_FATAL_ERROR ("EmuNetDevice::CreateSocket(): Could not getsockname(): errno = " << strerror (errno));

    }

  //

  // Now encode that socket name (endpoint information) as a string

  //

  std::string endpoint = EmuBufferToString((uint8_t *)&un, len);

  //

  // Fork and exec the process to create our socket.  If we're us (the parent)

  // we wait for the child (the socket creator) to complete and read the 

  // socket it created using the ancillary data mechanism.

  //

  pid_t pid = ::fork ();

  if (pid == 0)

    {

      NS_LOG_DEBUG ("Child process");

      //

      // build a command line argument from the encoded endpoint string that 

      // the socket creation process will use to figure out how to respond to

      // the (now) parent process.

      //

      std::ostringstream oss;

      oss << "-p " << endpoint;

      //

      // Execute the socket creation process image.

      //

      status = ::execl (FindCreator ().c_str (), "emu-sock-creator", oss.str ().c_str (), (char *)NULL);

      //

      // If the execl successfully completes, it never returns.  If it returns it failed or the OS is

      // broken.  In either case, we bail.

      //

      NS_FATAL_ERROR ("EmuNetDevice::CreateSocket(): Back from execl(), errno = " << ::strerror (errno));

    }

  else

    {

      NS_LOG_DEBUG ("Parent process");

      //

      // We're the process running the emu net device.  We need to wait for the

      // socket creator process to finish its job.

      //

      int st;

      pid_t waited = waitpid (pid, &st, 0);

      if (waited == -1)

	{

	  NS_FATAL_ERROR ("EmuNetDevice::CreateSocket(): waitpid() fails, errno = " << strerror (errno));

	}

      NS_ASSERT_MSG (pid == waited, "EmuNetDevice::CreateSocket(): pid mismatch");

      //

      // Check to see if the socket creator exited normally and then take a 

      // look at the exit code.  If it bailed, so should we.  If it didn't

      // even exit normally, we bail too.

      //

      if (WIFEXITED (st))

	{

          int exitStatus = WEXITSTATUS (st);

          if (exitStatus != 0)

            {

              NS_FATAL_ERROR ("EmuNetDevice::CreateSocket(): socket creator exited normally with status " << exitStatus);

            }

	}

      else 

	{

          NS_FATAL_ERROR ("EmuNetDevice::CreateSocket(): socket creator exited abnormally");

	}

      //

      // At this point, the socket creator has run successfully and should 

      // have created our raw socket and sent it back to the socket address

      // we provided.  Our socket should be waiting on the Unix socket.  We've

      // got to do a bunch of grunto work to get at it, though.

      //

      // The struct iovec below is part of a scatter-gather list.  It describes a

      // buffer.  In this case, it describes a buffer (an integer) that will

      // get the data that comes back from the socket creator process.  It will

      // be a magic number that we use as a consistency/sanity check.

      // 

      struct iovec iov;

      uint32_t magic;

      iov.iov_base = &magic;

      iov.iov_len = sizeof(magic);

      //

      // The CMSG macros you'll see below are used to create and access control 

      // messages (which is another name for ancillary data).  The ancillary 

      // data is made up of pairs of struct cmsghdr structures and associated

      // data arrays.

      //

      // First, we're going to allocate a buffer on the stack to receive our 

      // data array (that contains the socket).  Sometimes you'll see this called

      // an "ancillary element" but the msghdr uses the control message termimology

      // so we call it "control."

      //

      size_t msg_size = sizeof(int);

      char control[CMSG_SPACE(msg_size)];

      //

      // There is a msghdr that is used to minimize the number of parameters

      // passed to recvmsg (which we will use to receive our ancillary data).  

      // This structure uses terminology corresponding to control messages, so

      // you'll see msg_control, which is the pointer to the ancillary data and 

      // controllen which is the size of the ancillary data array.

      //

      // So, initialize the message header that describes the ancillary/control

      // data we expect to receive and point it to buffer.

      //

      struct msghdr msg;

      msg.msg_name = 0;

      msg.msg_namelen = 0;

      msg.msg_iov = &iov;

      msg.msg_iovlen = 1;

      msg.msg_control = control;

      msg.msg_controllen = sizeof (control);

      msg.msg_flags = 0;

      //

      // Now we can actually receive the interesting bits from the socket

      // creator process.

      //

      ssize_t bytesRead = recvmsg (sock, &msg, 0);

      if (bytesRead != sizeof(int))

	{

          NS_FATAL_ERROR ("EmuNetDevice::CreateSocket(): Wrong byte count from socket creator");

	}

      //

      // There may be a number of message headers/ancillary data arrays coming in.

      // Let's look for the one with a type SCM_RIGHTS which indicates it' the

      // one we're interested in.

      //

      struct cmsghdr *cmsg;

      for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL; cmsg = CMSG_NXTHDR(&msg, cmsg)) 

	{

	  if (cmsg->cmsg_level == SOL_SOCKET &&

	      cmsg->cmsg_type == SCM_RIGHTS)

	    {

	      int *rawSocket = (int*)CMSG_DATA (cmsg);

	      NS_LOG_INFO ("Got the socket from the socket creator = " << *rawSocket);

              m_sock = *rawSocket;

              return;

	    }

	}

      NS_FATAL_ERROR ("Did not get the raw socket from the socket creator");

    }

}

std::string

EmuNetDevice::FindCreator (void)

{

  struct stat st;

  std::string debug = "./build/debug/src/devices/emu/emu-sock-creator";

  std::string optimized = "./build/optimized/src/devices/emu/emu-sock-creator";

  if (::stat (debug.c_str (), &st) == 0)

    {

      return debug;

    }

  if (::stat (optimized.c_str (), &st) == 0)

    {

      return optimized;

    }

  NS_FATAL_ERROR ("EmuNetDevice::FindCreator(): Couldn't find creator");

  return ""; // quiet compiler

}

void

EmuNetDevice::StopDevice (void)

  NS_ASSERT_MSG (m_readThread != 0, "EmuNetDevice::StopDevice(): Receive thread is not running");

EmuNetDevice::ForwardUp (uint8_t *buf, uint32_t len)