freebsd-nq/share/man/man4/ng_source.4

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.\" Author: Dave Chapeskie <dchapeskie@sandvine.com>
.\" $FreeBSD$
.\"
.Dd November 1, 2002
.Dt NG_SOURCE 4
.Os
.Sh NAME
.Nm ng_source
.Nd netgraph discard node type
.Sh SYNOPSIS
.In 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
.Dv output
hook must also be connected to a node that responds to the
.Dv NGM_ETHER_COOKIE Ns / Ns
.Dv NGM_ETHER_GET_IFINDEX
message (e.g., an
.Xr ng_ether 4
node).
This type is used for testing and debugging.
.Pp
The operation of the node is as follows:
.Bl -bullet
.It
Packets received on the
.Dv input
hook are queued internally.
.It
On reception of a
.Dv NGM_SOURCE_START
message the node starts sending
the queued packets out the
.Dv output
hook on every clock tick as fast
as the connect interface will take them.
.It
While active, on every clock tick the node checks the available space
in the
.Va ifqueue
of the interface connected to the output hook and sends
that many packets out its
.Dv output
hook.
.It
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:
.Dv input
and
.Dv output .
The
.Dv 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
.Dv NGM_SOURCE_COOKIE
attached.
.Bl -tag -width indent
.It Dv NGM_SOURCE_GET_STATS Pq Ic getstats
Returns a structure containing the following fields:
.Bl -tag -width indent
.It Va outOctets
The number of octets/bytes sent out the
.Dv output
hook.
.It Va outFrames
The number of frames/packets sent out the
.Dv output
hook.
.It Va queueOctets
The number of octets queued from the
.Dv input
hook.
.It Va queueFrames
The number of frames queued from the
.Dv input
hook.
.It Va startTime
The time the last start message was received.
.It Va endTime
The time the last end message was received or
the output packet count was reached.
.It Va elapsedTime
Either
.Va endTime Li \- Va startTime
or current time
\-
.Va startTime .
.El
.It Dv NGM_SOURCE_CLR_STATS Pq Ic clrstats
Clears and resets the statistics returned by
.Ic getstats
(except
.Va queueOctets
and
.Va queueFrames ) .
.It Dv NGM_SOURCE_GETCLR_STATS Pq Ic getclrstats
As
.Ic getstats
but clears the statistics at the same time.
.It Dv NGM_SOURCE_START Pq Ic start
.Bl -bullet
.It
Takes a single
.Vt u_int64_t
parameter which is the number of packets to
send before stopping.
.It
Starts sending the queued packets out the output hook.
.It
The output hook must be connected or
.Er EINVAL
is returned.
.It
The node connected to the output hook must respond to
.Dv NGM_ETHER_GET_IFINDEX
which is used to get the
.Va ifqueue
of the attached interface.
.It
.Dv NGM_ETHER_SET_AUTOSRC
is sent to the node connected to the
.Dv output
hook
to turn off automatic ethernet source address overwriting (any errors
from this message are ignored).
.El
.It Dv NGM_SOURCE_STOP Pq Ic stop
Stops the node if it is active.
.It Dv NGM_SOURCE_CLR_DATA Pq Ic clrdata
Clears the packets queued from the
.Dv input
hook.
.El
.Sh SHUTDOWN
This node shuts down upon receipt of a
.Dv NGM_SHUTDOWN
control message, or when the
.Dv output
hook has been disconnected.
.Sh EXAMPLES
Attach the node to an
.Xr ng_ether 4
node for an interface.
If
.Nm ng_ether
is
not already loaded you will need to do so.
For example, these commands
load the
.Nm ng_ether
module and attach the
.Dv output
hook of a new
.Nm source
node to
.Dv orphans
hook of the
.Li bge0:
.Nm ng_ether
node.
.Bd -literal -offset indent
kldload ng_ether
ngctl mkpeer bge0: source orphans output
.Ed
.Pp
At this point the new node can be referred to as
.Dq Li bge0:orphans .
The
node can be given its own name like this:
.Pp
.Dl "ngctl name bge0:orphans src0"
.Pp
After which it can be referred to as
.Dq Li src0: .
.Pp
Once created, packets need to be sent to the node, the TCL net package
can be used to generate these packets:
.Pp
[Sandvine specific TCL code example omitted]
.Pp
To feed the output of the above TCL script to the
.Nm source
node's
.Dv input
hook via
.Xr nghook 8 :
.Pp
.Dl "tcl genPacket | nghook bge0:orphans input"
.Pp
To check that the node has queued these packets you can get the node
statistics:
.Bd -literal -offset indent
ngctl msg bge0:orphans getstats
Args:   { queueOctets=64 queueFrames=1 }
.Ed
.Pp
Send as many packets as required out the
.Dv output
hook:
.Pp
.Dl "ngctl msg bge0:orphans start 16"
.Pp
Either wait for them to be sent (periodically fetching stats if desired)
or send the stop message:
.Pp
.Dl "ngctl msg bge0:orphans stop"
.Pp
Check the statistics (here we use
.Ic getclrstats
to also clear the statistics):
.Bd -literal -offset indent
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
.Pp
The times are from
.Vt "struct timeval" Ns s ,
the
.Va tv_sec
field is seconds since
the Epoch and can be converted into a date string via TCL's [clock
format] or via the
.Xr date 1
command:
.Bd -literal -offset indent
date -r 1035305880
Tue Oct 22 12:58:00 EDT 2002
.Ed
.Sh IMPLEMENTATION NOTES
.No ( Fx 4.4
version)
.Pp
The use of
.Xr splimp 9
around the
.Dv NG_SEND_DATA
loop is important.
Without it,
the time taken by a single invocation of
.Fn ng_source_intr
becomes too
large and the packet rate drops.
Probably due to the NIC starting to
send the packets right away.
.Pp
Copying all the packets in one loop and sending them in another inside
of
.Fn ng_source_send
is done to limit how long we are at
.Xr splimp 9
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.
.Pp
Calling
.Xr timeout 9
at the end of
.Fn ng_source_intr
instead of near the
beginning is done to help avoid CPU starvation if
.Fn ng_source_intr
takes a long time to run.
.Pp
The use of
.Xr splnet 9
may be sub-optimal.
It is used for synchronization
within the node (e.g., data received on the
.Dv input
hook while
.Fn ng_source_send
is active) but we do not want to hold it too long and risk
starving the NIC.
.Pp
For clarity and simplicity, debugging messages and instrumentation code
has been removed.
On i386 one can include
.In machine/cpufunc.h
to have access to the
.Fn rdtsc
function to read the instruction counter at the
start and end of
.Fn ng_source_intr .
Also useful is the packet count returned by
.Fn ng_source_send .
Do not try to report such things from within
.Fn ng_source_intr ,
instead include the values in
.Va 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