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====== FromDevice Element Documentation ======

===== NAME =====

**FromDevice** -- Click element;
reads packets from network device (Linux kernel)

===== SYNOPSIS =====

FromDevice(DEVNAME [, //keywords// PROMISC, BURST, TIMESTAMP...])

**Ports**: no inputs, 1 output\\ 
**Processing**: push\\ 
**Drivers**: linuxmodule\\ 
**Package**: linuxmodule (core)\\ 

===== DESCRIPTION =====

This manual page describes the Linux kernel module version of the FromDevice
element. For the user-level element, read the [[FromDevice.u]] manual page.
Intercepts all packets received by the Linux network interface named DEVNAME
and pushes them out output 0. The packets include the link-level header.
DEVNAME may also be an Ethernet address, in which case FromDevice searches for
a device with that address.
FromDevice receives packets at interrupt time. As this happens, FromDevice
simply stores the packets in an internal queue. Later, in the Click kernel
thread -- that is, not at interrupt time -- FromDevice emits packets from that
queue as it is scheduled by the driver. It emits at most BURST packets per
scheduling; BURST is 8 by default.
Keyword arguments are:


 ? **PROMISC**
 ! Boolean.  If true, the device is put into promiscuous mode while FromDevice is
active.  Default is false.

 ? **BURST**
 ! Unsigned integer.  Sets the BURST parameter.

 ? **TIMESTAMP**
 ! Boolean.  If true, then ensure that received packets have correctly-set
timestamp annotations.  Default is true.

 ? **QUIET**
 ! Boolean.  If true, then suppress device up/down messages.  Default is false.

 ? **ALLOW_NONEXISTENT**
 ! Allow nonexistent devices. If true, and no device named DEVNAME exists when
the router is initialized, then FromDevice will report a warning (rather than
an error). Later, while the router is running, if a device named DEVNAME
appears, FromDevice will seamlessly begin outputing its packets. Default is
false.


===== NOTES =====

Linux won't see any packets from the device. If you want Linux to process
packets, you should hand them to [[ToHost]].
FromDevice accesses packets the same way Linux does: through interrupts.
This is bad for performance. If you care about performance and have a
polling-capable device, use [[PollDevice]] instead.
Linux device drivers, and thus FromDevice, should set packets' timestamp,
packet-type, and device annotations.


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

[[PollDevice]], [[ToDevice]], [[FromHost]], [[ToHost]], [[FromDevice.u]]


Generated by 'click-elem2man' from '../elements/linuxmodule/fromdevice.hh' on 18/Sep/2007.


===== COMMENTS =====