C++ definition

Implements the Address Resolution Protocol for IPv4 and IEEE 802 6-byte MAC addresses.

ARP packets are represented by the ~ArpPacket class.

Communication Between ARP and IPv4 modules: IPv4 module calls the ARP::getMACAddressFor(ipv4Address) method to get the MACAddress of the next hop. If this method could not resolve an IPv4 address to a MAC address, then IPv4 uses the Arp::startAddressResolution() method. ARP emits an arpResolutionCompleted signal when it adds/modifies an entry in the ARP table. ARP emits an arpResolutionFailed signal when an ARP request fails (ARP request sent retryCount times and retryTimeout elapsed).

ARP resolution is used on broadcast interfaces only, that is, on interfaces that have the isBroadcast() flag set in NetworkInterface(1,2) (see ~InterfaceTable). Since routing files (.irt or .mrt files, given as parameters to ~Ipv4RoutingTable) may modify the default interface configuration, you must ensure that these files don't contain the word BROADCAST e.g. for PPP interfaces.

Inheritance diagram

The following diagram shows inheritance relationships for this type. Unresolved types are missing from the diagram.

Extends

Name	Type	Description
SimpleModule	simple module	Base module for all INET simple modules.

Parameters

Name	Type	Default value	Description
displayStringTextFormat	string	""	Determines the text that is written on top of the submodule, supports displaying pars, watches, and module-specific information
interfaceTableModule	string		The path to the InterfaceTable module
routingTableModule	string
retryTimeout	double	1s	Number of seconds ARP waits between retries to resolve an IPv4 address
retryCount	int	3	Number of times ARP will attempt to resolve an IPv4 address
cacheTimeout	double	120s	Number of seconds unused entries in the cache will time out
proxyArpInterfaces	string	"*"	List of interfaces that proxy ARP is enabled on (all interfaces by default)

Properties

Name	Value	Description
class	Arp
display	i=block/layer

Gates

Name	Direction	Size	Description
netwIn	input		Incoming ARP requests and replies
netwOut	output		Outgoing ARP requests/replies, and datagrams with resolved next hop
ifIn	input
ifOut	output

Signals

Name	Type	Unit	Description
arpReplySent	inet::Packet
arpResolutionInitiated	inet::IArp::Notification
arpResolutionFailed	inet::IArp::Notification
arpRequestSent	inet::Packet
arpResolutionCompleted	inet::IArp::Notification

Statistics

Name	Title	Source	Record	Unit	Interpolation Mode	Description
arpReplySent	ARP replies sent	arpReplySent	count, sum(packetBytes), vector(packetBytes)
arpResolutionInitiated	ARP initiated resolutions		count
arpResolutionFailed	ARP failed resolutions		count
arpRequestSent	ARP request sent	arpRequestSent	count, sum(packetBytes), vector(packetBytes)
arpResolutionCompleted	ARP completed resolutions		count

Source code

//
// Implements the Address Resolution Protocol for IPv4 and IEEE 802 6-byte
// MAC addresses.
//
// ARP packets are represented by the ~ArpPacket class.
//
// Communication Between ARP and IPv4 modules:
// IPv4 module calls the `ARP::getMACAddressFor(ipv4Address)` method to get the MACAddress
// of the next hop. If this method could not resolve an IPv4 address to a MAC address, then IPv4
// uses the `Arp::startAddressResolution()` method.
// ARP emits an `arpResolutionCompleted` signal when it adds/modifies an entry in the ARP table.
// ARP emits an `arpResolutionFailed` signal when an ARP request fails (ARP request sent
// `retryCount` times and `retryTimeout` elapsed).
//
// ARP resolution is used on <i>broadcast</i> interfaces only,
// that is, on interfaces that have the `isBroadcast()` flag set in
// `NetworkInterface` (see ~InterfaceTable). Since routing files
// (`.irt` or `.mrt` files, given as parameters to ~Ipv4RoutingTable)
// may modify the default interface configuration, you must ensure that
// these files don't contain the word `BROADCAST` e.g. for PPP
// interfaces.
//
simple Arp extends SimpleModule like IArp
{
    parameters:
        @class(Arp);
        string interfaceTableModule;   // The path to the InterfaceTable module
        string routingTableModule;
        double retryTimeout @unit(s) = default(1s);   // Number of seconds ARP waits between retries to resolve an IPv4 address
        int retryCount = default(3);                  // Number of times ARP will attempt to resolve an IPv4 address
        double cacheTimeout @unit(s) = default(120s); // Number of seconds unused entries in the cache will time out
        string proxyArpInterfaces = default("*");     // List of interfaces that proxy ARP is enabled on (all interfaces by default)
        @display("i=block/layer");
        @signal[arpRequestSent](type=inet::Packet);
        @signal[arpReplySent](type=inet::Packet);
        @signal[arpResolutionInitiated](type=inet::IArp::Notification);
        @signal[arpResolutionCompleted](type=inet::IArp::Notification);
        @signal[arpResolutionFailed](type=inet::IArp::Notification);
        @statistic[arpRequestSent](title="ARP request sent"; source=arpRequestSent; record=count,"sum(packetBytes)","vector(packetBytes)");
        @statistic[arpReplySent](title="ARP replies sent"; source=arpReplySent; record=count,"sum(packetBytes)","vector(packetBytes)");
        @statistic[arpResolutionInitiated](title="ARP initiated resolutions"; record=count);
        @statistic[arpResolutionCompleted](title="ARP completed resolutions"; record=count);
        @statistic[arpResolutionFailed](title="ARP failed resolutions"; record=count);
    gates:
        input netwIn @labels(ArpPacket+Ieee802Ctrl); // Incoming ARP requests and replies
        output netwOut @labels(ArpPacket+Ieee802Ctrl,Ipv4Header+Ieee802Ctrl);  // Outgoing ARP requests/replies, and datagrams with resolved next hop
        input ifIn @labels(ArpPacket,Ieee802Ctrl);
        output ifOut @labels(ArpPacket,Ieee802Ctrl);
}

File: src/inet/networklayer/arp/ipv4/Arp.ned

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