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====== ARPQuerier Element Documentation ======

===== NAME =====

**ARPQuerier** -- Click element;
encapsulates IP packets in Ethernet headers found via ARP

===== SYNOPSIS =====

ARPQuerier(IP, ETH, //keywords//)\\ ARPQuerier(NAME, //keywords//)

**Ports**: 2 inputs, 1-2 outputs\\ 
**Processing**: push\\ 
**Package**: ethernet (core)\\ 

===== DESCRIPTION =====

Handles most of the ARP protocol. Argument IP should be
this host's IP address, and ETH should be this host's
Ethernet address. (In
the one-argument form, NAME should be shorthand for
both an IP and an Ethernet address; see [[AddressInfo]].)
Packets arriving on input 0 should be IP packets, and must have their
destination address annotations set.
If an Ethernet address is already known
for the destination, the IP packet is wrapped in an Ethernet
header and sent to output 0. Otherwise the IP packet is saved and
an ARP query is sent instead. If an ARP response arrives
on input 1 for an IP address that we need, the mapping is
recorded and any saved IP packets are sent.
The ARP reply packets on input 1 should include the Ethernet header.
ARPQuerier may have one or two outputs. If it has two, then ARP queries
are sent to the second output.
ARPQuerier will not send queries for packets addressed to 0.0.0.0,
255.255.255.255, or, if specified, any BROADCAST address.  Packets addressed
to 0.0.0.0 are dropped; packets for broadcast addresses are forwarded with
destination Ethernet address FF:FF:FF:FF:FF:FF.
Keyword arguments are:


 ? **CAPACITY**
 ! Unsigned integer.  The maximum number of saved IP packets the element will
hold at a time.  Default is 2048.  Note that, unlike the number of packets,
the total number of ARP entries the element will hold is currently unlimited.

 ? **BROADCAST**
 ! IP address.  Local broadcast IP address.  Packets sent to this address will be
forwarded to Ethernet address FF:FF:FF:FF:FF:FF.  Defaults to the local
broadcast address that can be extracted from the IP address's corresponding
prefix, if any.


===== EXAMPLES =====


     c :: Classifier(12/0806 20/0002, 12/0800, ...);
     a :: ARPQuerier(18.26.4.24, 00:00:C0:AE:67:EF);
     c[0] -> a[1];
     c[1] -> ... -> a[0];
     a[0] -> ... -> ToDevice(eth0);


===== NOTES =====

If a host has multiple interfaces, it will need multiple
instances of ARPQuerier.
ARPQuerier uses packets' destination IP address annotations, and can destroy
their next packet annotations.
ARPQuerier will send at most 10 queries a second for any IP address.


===== ELEMENT HANDLERS =====


 ? **ipaddr (read/write)**
 ! Returns or sets the ARPQuerier's source IP address.

 ? **table (read-only)**
 ! Returns a textual representation of the ARP table.

 ? **stats (read-only)**
 ! Returns textual statistics (queries and drops).

 ? **queries (read-only)**
 ! Returns the number of queries sent.

 ? **responses (read-only)**
 ! Returns the number of responses received.

 ? **drops (read-only)**
 ! Returns the number of packets dropped.


===== SEE ALSO =====

[[ARPResponder]], [[ARPFaker]], [[AddressInfo]]


Generated by 'click-elem2man' from '../elements/ethernet/arpquerier.hh' on 18/Sep/2007.


===== COMMENTS =====