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Author: Dave Chapeskie <dchapeskie@sandvine.com>
$FreeBSD: head/share/man/man4/ng_source.4 106266 2002-10-31 23:03:09Z julian $
.Dd November 1, 2002 .Dt NG_SOURCE 4 .Os .Sh NAME .Nm ng_source .Nd netgraph discard node type .Sh SYNOPSIS n netgraph/ng_source.h .Sh DESCRIPTION The .Nm source node acts as a source of packets according to the parameters set up using control messages and input packets. The 'output' hook must also be connected to a node that responds to the .Em NGM_ETHER_COOKIE / .Em NGM_ETHER_GET_IFINDEX message (e.g. an ng_ether node). node type silently discards all data and control messages it receives. This type is used for testing and debugging.
p The operation of the node is as follows:
p
l -bullet -compact -offset 2n t Packets received on the 'input' hook are queued internally.
t On recpetion of a NGM_SOURCE_START message the node starts sending
the queued packets out the 'output' hook on every clock tick as fast
as the connect interface will take them.
t While active, on every clock tick the node checks the available space
in the ifqueue of the interface connected to the output hook and sends
that many packets out it's output hook.
t Once the number of packets indicated in the start message have been
sent, or on reception of a stop message, the node stops sending data.
.El
.Sh HOOKS
The
.Nm source
node has two hooks: 'input' and 'output'. The 'output'
hook must remain connected, its disconnection will shutdown the node.
.Sh CONTROL MESSAGES
This node type supports the generic control messages as well as the following,
which must be sent with the
.Em NGM_SOURCE_COOKIE
attached.
l -tag -width NGM_SOURCE_GETCLR_STATS t NGM_SOURCE_GET_STATS "getstats":
Returns a structure containing the following fields:
.Bl -bullet -compact -offset 2n
l -tag -width queueFrames: t outOctets: The number of octets/bytes sent out the 'output' hook.
t outFrames: The number of frames/packets sent out the 'output' hook.
t queueOctets: The number of octets queued from the 'input' hook.
t queueFrames: The number of frames queued from the 'input' hook.
t startTime: The time the last start message was recieved.
t endTime: The time the last end message was recieved or
the output packet count was reached.
t elapsedTime: Either endTime-startTime or current time - startTime.
.El
t NGM_SOURCE_CLR_STATS "clrstats":
Clears and resets the statistics returned by getstats (except
queueOctects and queueFrames).
t NGM_SOURCE_GETCLR_STATS "getclrstats":
As getstats but clears the statistics at the same time.
t NGM_SOURCE_START "start":
l -bullet -compact -offset 2n t Takes a single u_int64_t parameter which is the number of packets to
send before stopping.
t Starts sending the queued packets out the output hook.
t The output hook must be connected or EINVAL is returned.
t The node connected to the output hook must respond to
.Em NGM_ETHER_GET_IFINDEX
which is used to get the ifqueue of the attached
interface.
t .Em NGM_ETHER_SET_AUTOSRC
is sent to the node connected to the output hook
to turn off automatic ethernet source address overwriting (any errors
from this message are ignored).
.El
t NGM_SOURCE_STOP "stop":
Stops the node if it is active.
t NGM_SOURCE_CLR_DATA "clrdata":
Clears the packets queued from the 'input' hook.
.El
.Sh SHUTDOWN
This node shuts down upon receipt of a
.Dv NGM_SHUTDOWN
control message, or when the
.Em output
hook has been disconnected.
.Sh EXAMPLE
Build and install the node to /modules (or load it anually).
d -literal -offset 0n $ make obj
$ make depend
$ make
$ make install
.Ed
p Attach the node to an ng_ether node for an interface. If ng_ether is not already loaded you'll need to do so. For example these commands load the ng_ether module and attach the output hook of a new source node to orphans hook of the bge0: ng_ether node. d -literal -offset 0n $ kldload ng_ether $ ngctl mkpeer bge0: source orphans output .Ed
p At this point the new node can be refered to as "bge0:orphans". The node can be given it's own name like this: d -literal -offset 0n $ ngctl name bge0:orphans src0 .Ed
p After which it can be refered to as "src0:".
p Once created packets need to be sent to the node, the TCL net package can be used to generate these packets:
p [Sandvine specific TCL code example omitted]
p To feed the output of the above TCL script to the ng_source node's input hook via nghook: d -literal -offset 0n $ tcl genPacket | nghook bge0:orphans input .Ed
p To check that the node has queued these packets you can get the node statistics: d -literal -offset 0n $ ngctl msg bge0:orphans getstats Args: { queueOctets=64 queueFrames=1 } .Ed
p Send as many packets as required out the output hook: d -literal -offset 0n $ ngctl msg bge0:orphans start 16 .Ed
p Either wait for them to be sent (periodicly fetching stats if desired) or send the stop message: d -literal -offset 0n $ ngctl msg bge0:orphans stop .Ed
p Check the statistics (here we use getclrstats to also clear the statistics): d -literal -offset 0n $ ngctl msg bge0:orphans getclrstats Args: { outOctets=1024 outFrames=16 queueOctets=64 queueFrames=1 startTime={ tv_sec=1035305880 tv_usec=758036 } endTime={ tv_sec=1035305880 tv_usec=759041 } elapsedTime={ tv_usec=1005 } } .Ed
p The times are from "struct timeval"s, the tv_sec field is seconds since the epoch and can be converted into a date string via TCL's [clock format] or via the UNIX date command: d -literal -offset 0n $ date -r 1035305880 Tue Oct 22 12:58:00 EDT 2002 .Ed
p .Sh IMPLEMENTATION NOTES (FreeBSD 4.4 version)
p The use of splimp around the NG_SEND_DATA loop is important. Without it the time taken by a single invocation of ng_source_intr becomes too large and the packet rate drops. Probably due to the NIC starting to send the packets right away.
p Copying all the packets in one loop and sending them in another inside of ng_source_send is done to limit how long we're at splimp and gave minor packet rate increases (~5% at 256 byte packets). However note that if there are errors in the send loop the remaining copied packets are simply freed and discarded thus we skip those packets and ordering of the input queue to the output is not maintained.
p Calling timeout(9) at the end of ng_source_intr instead of near the begining is done to help avoid CPU starvaion if ng_source_intr takes a long time to run.
p The use of splnet may be sub-optimal. It's used for syncronization within the node (e.g. data recieved on the input hook while ng_source_send is active) but we don't want to hold it too long and risk starving the NIC.
p For clarity and simplicity debugging messages and instrumentation code has been removed. On i386 one can include machine/cpufunc.h to have access to the rdtsc() function to read the instruction counter at the start and end of ng_source_intr. Also useful is the packet count returned by ng_source_send. Do not try to report such things from within ng_source_intr, instead include the values in sc->stats. .Sh SEE ALSO .Xr netgraph 4 , .Xr ng_echo 4 , .Xr ng_hole 4 , .Xr ng_tee 4 , .Xr ngctl 8 .Xr nghook 8 .Sh HISTORY The .Nm node type was implemented in .Fx 4.8 . .Sh AUTHORS .An Dave Chapeskie Aq dchapeskie@SANDVINE.com