ns3::TapBridge Class Reference
[Bridge]

A bridge to make it appear that a real host process is connected to an ns-3 net device. More...

#include <tap-bridge.h>

Inheritance diagram for ns3::TapBridge:

[legend]

Collaboration diagram for ns3::TapBridge:

[legend]

List of all members.

Public Types
enum	Mode { ILLEGAL, CONFIGURE_LOCAL, USE_LOCAL, USE_BRIDGE }
Public Member Functions
Ptr< NetDevice >	GetBridgedNetDevice (void)
	Get the bridged net device.
void	SetBridgedNetDevice (Ptr< NetDevice > bridgedDevice)
	Set the ns-3 net device to bridge.
void	Start (Time tStart)
	Set a start time for the device.
void	Stop (Time tStop)
void	SetMode (TapBridge::Mode mode)
TapBridge::Mode	GetMode (void)
virtual void	SetIfIndex (const uint32_t index)
virtual uint32_t	GetIfIndex (void) const
virtual Ptr< Channel >	GetChannel (void) const
virtual void	SetAddress (Address address)
virtual Address	GetAddress (void) const
virtual bool	SetMtu (const uint16_t mtu)
virtual uint16_t	GetMtu (void) const
virtual bool	IsLinkUp (void) const
virtual void	SetLinkChangeCallback (Callback< void > callback)
virtual bool	IsBroadcast (void) const
virtual Address	GetBroadcast (void) const
virtual bool	IsMulticast (void) const
virtual Address	GetMulticast (Ipv4Address multicastGroup) const
	Make and return a MAC multicast address using the provided multicast group.
virtual bool	IsPointToPoint (void) const
	Return true if the net device is on a point-to-point link.
virtual bool	IsBridge (void) const
	Return true if the net device is acting as a bridge.
virtual bool	Send (Ptr< Packet > packet, const Address &dest, uint16_t protocolNumber)
virtual bool	SendFrom (Ptr< Packet > packet, const Address &source, const Address &dest, uint16_t protocolNumber)
virtual Ptr< Node >	GetNode (void) const
virtual void	SetNode (Ptr< Node > node)
virtual bool	NeedsArp (void) const
virtual void	SetReceiveCallback (NetDevice::ReceiveCallback cb)
virtual void	SetPromiscReceiveCallback (NetDevice::PromiscReceiveCallback cb)
virtual bool	SupportsSendFrom () const
virtual Address	GetMulticast (Ipv6Address addr) const
	Get the MAC multicast address corresponding to the IPv6 address provided.
Static Public Member Functions
static TypeId	GetTypeId (void)
	This method returns the TypeId associated to ns3::TapBridge.
Protected Member Functions
virtual void	DoDispose (void)

---

Detailed Description

A bridge to make it appear that a real host process is connected to an ns-3 net device.

• The Tap Bridge lives in a kind of a gray world somewhere between a Linux host and an ns-3 bridge device. From the Linux perspective, this code appears as the user mode handler for a Tap net device. That is, when the Linux host writes to a /dev/tap device (that is either manually or automatically created depending on basic operating mode -- more on this later), the write is redirected into the TapBridge that lives in the ns-3 world; and from this perspective, becomes a read. In other words, a Linux process writes a packet to a tap device and this packet is redirected to an ns-3 process where it is received by the TapBridge as a result of a read operation there. The TapBridge then sends the packet to the ns-3 net device to which it is bridged. In the other direction, a packet received by an ns-3 net device is bridged to the TapBridge (it appears via a callback from that net device. The TapBridge then takes that packet and writes it back to the host using the Linux TAP mechanism. This write to the device will then appear to the Linux host as if a packet has arrived on its device.

The upshot is that the Tap Bridge appears to bridge a tap device on a Linux host in the "real world" to an ns-3 net device in the simulation and make is appear that a ns-3 net device is actually installed in the Linux host. In order to do this on the ns-3 side, we need a "ghost node" in the simulation to hold the bridged ns-3 net device and the TapBridge. This node should not actually do anything else in the simulation since its job is simply to make the net device appear in Linux. This is not just arbitrary policy, it is because:

• Bits sent to the Tap Bridge from higher layers in the ghost node (using the TapBridge Send() method) are completely ignored. The Tap Bridge is not, itself, connected to any network, neither in Linux nor in ns-3;
• The bridged ns-3 net device is has had its receive callback disconnected from the ns-3 node and reconnected to the Tap Bridge. All data received by a bridged device will be sent to the Linux host and will not be received by the node. From the perspective of the ghost node, you can send over this device but you cannot ever receive.

Of course, if you understand all of the issues you can take control of your own destiny and do whatever you want -- we do not actively prevent you from using the ghost node for anything you decide. You will be able to perform typical ns-3 operations on the ghost node if you so desire. The internet stack, for example, must be there and functional on that node in order to participate in IP address assignment and global routing. However, as mentioned above, interfaces talking any Tap Bridge or associated bridged net devices will not work completely. If you understand exactly what you are doing, you can set up other interfaces and devices on the ghost node and use them; or take advantage of the operational send side of the bridged devices to create traffic generators. We generally recommend that you treat this node as a ghost of the Linux host and leave it to itself, though.

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Member Enumeration Documentation

enum ns3::TapBridge::Mode

Enumeration of the operating modes supported in the class.

Enumerator:

ILLEGAL	mode not set
CONFIGURE_LOCAL	ns-3 creates and configures tap device
USE_LOCAL	ns-3 uses a pre-created tap, without configuring it
USE_BRIDGE	ns-3 uses a pre-created tap, and bridges to a bridging net device

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Member Function Documentation

virtual void ns3::TapBridge::DoDispose

(

void

)

[protected, virtual]

This method is called by Object::Dispose or by the object's destructor, whichever comes first.

Subclasses are expected to implement their real destruction code in an overriden version of this method and chain up to their parent's implementation once they are done. i.e., for simplicity, the destructor of every subclass should be empty and its content should be moved to the associated DoDispose method.

Reimplemented from ns3::Object.

virtual Address ns3::TapBridge::GetAddress

(

void

)

const [virtual]

Returns:

the current Address of this interface.

Implements ns3::NetDevice.

Ptr<NetDevice> ns3::TapBridge::GetBridgedNetDevice

(

void

)

Get the bridged net device.

The bridged net device is the ns-3 device to which this bridge is connected,

Returns:

the bridged net device.

virtual Address ns3::TapBridge::GetBroadcast

(

void

)

const [virtual]

Returns:

the broadcast address supported by this netdevice.

Calling this method is invalid if IsBroadcast returns not true.

Implements ns3::NetDevice.

virtual Ptr<Channel> ns3::TapBridge::GetChannel

(

void

)

const [virtual]

Returns:

the channel this NetDevice is connected to. The value returned can be zero if the NetDevice is not yet connected to any channel or if the underlying NetDevice has no concept of a channel. i.e., callers _must_ check for zero and be ready to handle it.

Implements ns3::NetDevice.

virtual uint32_t ns3::TapBridge::GetIfIndex

(

void

)

const [virtual]

Returns:

index ifIndex of the device

Implements ns3::NetDevice.

TapBridge::Mode ns3::TapBridge::GetMode

(

void

)

Get the operating mode of this device.

Returns:

The operating mode of this device.

virtual uint16_t ns3::TapBridge::GetMtu

(

void

)

const [virtual]

Returns:

the link-level MTU in bytes for this interface.

This value is typically used by the IP layer to perform IP fragmentation when needed.

Implements ns3::NetDevice.

virtual Address ns3::TapBridge::GetMulticast

(

Ipv6Address

addr

)

const [virtual]

Get the MAC multicast address corresponding to the IPv6 address provided.

Parameters:

addr

IPv6 address

Returns:

the MAC multicast address

Warning:

Calling this method is invalid if IsMulticast returns not true.

Implements ns3::NetDevice.

virtual Address ns3::TapBridge::GetMulticast

(

Ipv4Address

multicastGroup

)

const [virtual]

Make and return a MAC multicast address using the provided multicast group.

RFC 1112 says that an Ipv4 host group address is mapped to an Ethernet multicast address by placing the low-order 23-bits of the IP address into the low-order 23 bits of the Ethernet multicast address 01-00-5E-00-00-00 (hex). Similar RFCs exist for Ipv6 and Eui64 mappings. This method performs the multicast address creation function appropriate to the underlying MAC address of the device. This MAC address is encapsulated in an abstract Address to avoid dependencies on the exact MAC address format.

A default imlementation of GetMulticast is provided, but this method simply NS_ASSERTS. In the case of net devices that do not support multicast, clients are expected to test NetDevice::IsMulticast and avoid attempting to map multicast packets. Subclasses of NetDevice that do support multicasting are expected to override this method and provide an implementation appropriate to the particular device.

Parameters:

multicastGroup

The IP address for the multicast group destination of the packet.

Returns:

The MAC multicast Address used to send packets to the provided multicast group.

Warning:

Calling this method is invalid if IsMulticast returns not true.

See also:

Ipv4Address

Address

NetDevice::IsMulticast

Implements ns3::NetDevice.

virtual Ptr<Node> ns3::TapBridge::GetNode

(

void

)

const [virtual]

Returns:

the node base class which contains this network interface.

When a subclass needs to get access to the underlying node base class to print the nodeid for example, it can invoke this method.

Implements ns3::NetDevice.

static TypeId ns3::TapBridge::GetTypeId

(

void

)

[static]

This method returns the TypeId associated to ns3::TapBridge.

This object is accessible through the following paths with Config::Set and Config::Connect:

• /NodeList/[i]/DeviceList/[i]/$ns3::TapBridge

Attributes defined for this type:

• DeviceName: The name of the tap device to create.
  • Set with class: StringValue
  • Underlying type: std::string
  • Initial value:
  • Flags: construct write read
• Gateway: The IP address of the default gateway to assign to the host machine, when in ConfigureLocal mode.
  • Set with class: Ipv4AddressValue
  • Underlying type: Ipv4Address
  • Initial value: 255.255.255.255
  • Flags: construct write read
• IpAddress: The IP address to assign to the tap device, when in ConfigureLocal mode. This address will override the discovered IP address of the simulated device.
  • Set with class: Ipv4AddressValue
  • Underlying type: Ipv4Address
  • Initial value: 255.255.255.255
  • Flags: construct write read
• MacAddress: The MAC address to assign to the tap device, when in ConfigureLocal mode. This address will override the discovered MAC address of the simulated device.
  • Set with class: Mac48AddressValue
  • Underlying type: Mac48Address
  • Initial value: ff:ff:ff:ff:ff:ff
  • Flags: construct write read
• Netmask: The network mask to assign to the tap device, when in ConfigureLocal mode. This address will override the discovered MAC address of the simulated device.
  • Set with class: Ipv4MaskValue
  • Underlying type: Ipv4Mask
  • Initial value: 255.255.255.255
  • Flags: construct write read
• Start: The simulation time at which to spin up the tap device read thread.
  • Set with class: TimeValue
  • Underlying type: Time
  • Initial value: 0ns
  • Flags: construct write read
• Stop: The simulation time at which to tear down the tap device read thread.
  • Set with class: TimeValue
  • Underlying type: Time
  • Initial value: 0ns
  • Flags: construct write read
• Mode: The operating and configuration mode to use.
  • Set with class: ns3::EnumValue
  • Underlying type: ConfigureLocal|UseLocal|UseBridge
  • Initial value: UseLocal
  • Flags: construct write

Attributes defined in parent class ns3::NetDevice:

• Mtu: The MAC-level Maximum Transmission Unit
  • Set with class: ns3::UintegerValue
  • Underlying type: uint16_t 0:65535
  • Flags: write read

No TraceSources defined for this type.

Reimplemented from ns3::NetDevice.

virtual bool ns3::TapBridge::IsBridge

(

void

)

const [virtual]

Return true if the net device is acting as a bridge.

Returns:

value of m_isBridge flag

Implements ns3::NetDevice.

virtual bool ns3::TapBridge::IsBroadcast

(

void

)

const [virtual]

Returns:

true if this interface supports a broadcast address, false otherwise.

Implements ns3::NetDevice.

virtual bool ns3::TapBridge::IsLinkUp

(

void

)

const [virtual]

Returns:

true if link is up; false otherwise

Implements ns3::NetDevice.

virtual bool ns3::TapBridge::IsMulticast

(

void

)

const [virtual]

Returns:

value of m_isMulticast flag

Implements ns3::NetDevice.

virtual bool ns3::TapBridge::IsPointToPoint

(

void

)

const [virtual]

Return true if the net device is on a point-to-point link.

Returns:

value of m_isPointToPoint flag

Implements ns3::NetDevice.

virtual bool ns3::TapBridge::NeedsArp

(

void

)

const [virtual]

Returns:

true if ARP is needed, false otherwise.

Called by higher-layers to check if this NetDevice requires ARP to be used.

Implements ns3::NetDevice.

virtual bool ns3::TapBridge::Send	(	Ptr< Packet >	packet,
		const Address &	dest,
		uint16_t	protocolNumber
	)			[virtual]

Parameters:

	packet	packet sent from above down to Network Device
	dest	mac address of the destination (already resolved)
	protocolNumber	identifies the type of payload contained in this packet. Used to call the right L3Protocol when the packet is received.

Called from higher layer to send packet into Network Device to the specified destination Address

Returns:

whether the Send operation succeeded

Implements ns3::NetDevice.

virtual bool ns3::TapBridge::SendFrom	(	Ptr< Packet >	packet,
		const Address &	source,
		const Address &	dest,
		uint16_t	protocolNumber
	)			[virtual]

Parameters:

	packet	packet sent from above down to Network Device
	source	source mac address (so called "MAC spoofing")
	dest	mac address of the destination (already resolved)
	protocolNumber	identifies the type of payload contained in this packet. Used to call the right L3Protocol when the packet is received.

Called from higher layer to send packet into Network Device with the specified source and destination Addresses.

Returns:

whether the Send operation succeeded

Implements ns3::NetDevice.

virtual void ns3::TapBridge::SetAddress

(

Address

address

)

[virtual]

Set the address of this interface

Implements ns3::NetDevice.

void ns3::TapBridge::SetBridgedNetDevice

(

Ptr< NetDevice >

bridgedDevice

)

Set the ns-3 net device to bridge.

This method tells the bridge which ns-3 net device it should use to connect the simulation side of the bridge.

Attention:

The ns-3 net device that is being set as the device must have an an IP address assigned to it before the simulation is run. This address will be used to set the hardware address of the host Linux device.

virtual void ns3::TapBridge::SetIfIndex

(

const uint32_t

index

)

[virtual]

Parameters:

index

ifIndex of the device

Implements ns3::NetDevice.

virtual void ns3::TapBridge::SetLinkChangeCallback

(

Callback< void >

callback

)

[virtual]

Parameters:

callback

the callback to invoke

Register a callback invoked whenever the link status changes to UP. This callback is typically used by the IP/ARP layer to flush the ARP cache whenever the link goes up.

Implements ns3::NetDevice.

void ns3::TapBridge::SetMode

(

TapBridge::Mode

mode

)

Set the operating mode of this device.

Parameters:

mode

The operating mode of this device.

virtual bool ns3::TapBridge::SetMtu

(

const uint16_t

mtu

)

[virtual]

Parameters:

mtu

MTU value, in bytes, to set for the device

Returns:

whether the MTU value was within legal bounds

Override for default MTU defined on a per-type basis.

Implements ns3::NetDevice.

virtual void ns3::TapBridge::SetNode

(

Ptr< Node >

node

)

[virtual]

Parameters:

node

the node associated to this netdevice.

This method is called from ns3::Node::AddDevice.

Implements ns3::NetDevice.

virtual void ns3::TapBridge::SetPromiscReceiveCallback

(

NetDevice::PromiscReceiveCallback

cb

)

[virtual]

Parameters:

cb

callback to invoke whenever a packet has been received in promiscuous mode and must be forwarded to the higher layers.

Enables netdevice promiscuous mode and sets the callback that will handle promiscuous mode packets. Note, promiscuous mode packets means _all_ packets, including those packets that can be sensed by the netdevice but which are intended to be received by other hosts.

Implements ns3::NetDevice.

virtual void ns3::TapBridge::SetReceiveCallback

(

NetDevice::ReceiveCallback

cb

)

[virtual]

Parameters:

cb

callback to invoke whenever a packet has been received and must be forwarded to the higher layers.

Implements ns3::NetDevice.

void ns3::TapBridge::Start

(

Time

tStart

)

Set a start time for the device.

The tap bridge consumes a non-trivial amount of time to start. It starts up in the context of a scheduled event to ensure that all configuration has been completed before extracting the configuration (IP addresses, etc.) In order to allow a more reasonable start-up sequence than a thundering herd of devices, the time at which each device starts is also configurable bot via the Attribute system and via this call.

Parameters:

tStart

the start time

void ns3::TapBridge::Stop

(

Time

tStop

)

Set a stop time for the device.

Parameters:

tStop

the stop time

See also:

TapBridge::Start

virtual bool ns3::TapBridge::SupportsSendFrom

(

)

const [virtual]

Returns:

true if this interface supports a bridging mode, false otherwise.

Implements ns3::NetDevice.

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The documentation for this class was generated from the following files:

• src/devices/tap-bridge/tap-bridge.h
• doc/introspected-doxygen.h