Ipv4Address 

Ipv4L3Protocol::SelectSourceAddress (Ptr<const NetDevice> device,

    Ipv4Address dst, Ipv4InterfaceAddress::InterfaceAddressScope_e scope)

{

  NS_LOG_FUNCTION (device << dst << scope);

  Ipv4Address addr ("0.0.0.0");

  Ipv4InterfaceAddress iaddr; 

  bool found = false;

  if (device != 0)

    {

      int32_t i = GetInterfaceForDevice (device);

      NS_ASSERT_MSG (i >= 0, "No device found on node");

      for (uint32_t j = 0; j < GetNAddresses (i); j++)

        {

          iaddr = GetAddress (i, j);

          if (iaddr.IsSecondary ()) continue;

          if (iaddr.GetScope () > scope) continue; 

          if (dst.CombineMask (iaddr.GetMask ())  == iaddr.GetLocal ().CombineMask (iaddr.GetMask ()) )  

            {

              return iaddr.GetLocal ();

            }

          if (!found)

            {

              addr = iaddr.GetLocal ();

              found = true;

            }

        }

    }

  if (found)

    {

      return addr;

    }

  // Iterate among all interfaces

  for (uint32_t i = 0; i < GetNInterfaces (); i++)

    {

      for (uint32_t j = 0; j < GetNAddresses (i); j++)

        {

          iaddr = GetAddress (i, j);

          if (iaddr.IsSecondary ()) continue;

          if (iaddr.GetScope () != Ipv4InterfaceAddress::LINK 

              && iaddr.GetScope () <= scope) 

            {

              return iaddr.GetLocal ();

            }

        }

    }

  NS_LOG_WARN ("Could not find source address for " << dst << " and scope " 

    << scope << ", returning 0");

  return addr;  

}

  Ipv4Address SelectSourceAddress (Ptr<const NetDevice> device,

    Ipv4Address dst, Ipv4InterfaceAddress::InterfaceAddressScope_e scope);

   * \brief Return the first primary source address with scope less than 

   * or equal to the requested scope, to use in sending a packet to 

   * destination dst out of the specified device.

   *

   * This method mirrors the behavior of Linux inet_select_addr() and is

   * provided because interfaces may have multiple IP addresses configured

   * on them with different scopes, and with a primary and secondary status.

   * Secondary addresses are never returned.

   * \see Ipv4InterfaceAddress

   *

   * If a non-zero device pointer is provided, the method first tries to

   * return a primary address that is configured on that device, and whose

   * subnet matches that of dst and whose scope is less than or equal to

   * the requested scope.  If a primary address does not match the

   * subnet of dst but otherwise matches the scope, it is returned.  

   * If no such address on the device is found, the other devices are 

   * searched in order of their interface index, but not considering dst

   * as a factor in the search.  Because a loopback interface is typically 

   * the first one configured on a node, it will be the first alternate 

   * device to be tried.  Addresses scoped at LINK scope are not returned

   * in this phase.

   * 

   * If no device pointer is provided, the same logic as above applies, only

   * that there is no preferred device that is consulted first.  This means

   * that if the device pointer is null, input parameter dst will be ignored.

   * 

   * If there are no possible addresses to return, a warning log message 

   * is issued and the all-zeroes address is returned.

   *

   * \param device output NetDevice (optionally provided, only to constrain the search)

   * \param dst Destination address to match, if device is provided 

   * \param scope Scope of returned address must be less than or equal to this

   * \returns the first primary Ipv4Address that meets the search criteria

   */

  virtual Ipv4Address SelectSourceAddress (Ptr<const NetDevice> device, 

    Ipv4Address dst, Ipv4InterfaceAddress::InterfaceAddressScope_e scope) = 0;

  /**