ng_source
—
netgraph node for traffic generation
The source
node acts as a source of
packets according to the parameters set up using control messages and input
packets. The ng_source
node type is used primarily
for testing and benchmarking.
The source
node has two hooks:
input and output. The
output hook must remain connected, its disconnection
will shutdown the node.
The operation of the node is as follows. Packets received on the
input hook are queued internally. When
output hook is connected,
ng_source
node assumes that its neighbour node is of
ng_ether(4)
node type. The neighbour is queried for its interface name. The
ng_source
node then uses queue of the interface for
its evil purposes. The ng_source
node also disables
autosrc option on neighbour
ng_ether(4)
node. If interface name cannot be obtained automatically, it should be
configured explicitly with the NGM_SOURCE_SETIFACE
control message, and autosrc should be turned off on
ng_ether(4)
node manually.
If the node is connected to a netgraph network, which does not
terminate in a real
ng_ether(4)
interface, limit the packet injection rate explicitly with the
NGM_SOURCE_SETPPS control message.
Upon receipt of a NGM_SOURCE_START
control
message the node starts sending the previously queued packets out the
output hook on every clock tick as fast as the
connected interface will take them. While active, on every clock tick the
node checks the available space in the interface queue and sends that many
packets out its output hook. Once the number of
packets indicated in the start message has been sent, or upon receipt of a
NGM_SOURCE_STOP
message, the node stops sending
data.
This node type supports the generic control messages as well as
the following, which must be sent with the
NGM_SOURCE_COOKIE
attached.
NGM_SOURCE_GET_STATS
(getstats
)
- Returns a structure containing the following fields:
- outOctets
- The number of octets/bytes sent out the output
hook.
- outFrames
- The number of frames/packets sent out the output
hook.
- queueOctets
- The number of octets queued from the input
hook.
- queueFrames
- The number of frames queued from the input
hook.
- startTime
- The time the last start message was received.
- endTime
- The time the last end message was received or the output packet count
was reached.
- elapsedTime
- Either endTime
-
startTime or current time -
startTime.
NGM_SOURCE_CLR_STATS
(clrstats
)
- Clears and resets the statistics returned by
getstats
(except queueOctets
and queueFrames).
NGM_SOURCE_GETCLR_STATS
(getclrstats
)
- As
getstats
but clears the statistics at the same
time.
NGM_SOURCE_START
(start
)
- This message requires a single uint64_t parameter
which is the number of packets to send before stopping. Node starts
sending the queued packets out the output hook. The
output hook must be connected and node must have
interface configured.
NGM_SOURCE_STOP
(stop
)
- Stops the node if it is active.
NGM_SOURCE_CLR_DATA
(clrdata
)
- Clears the packets queued from the input hook.
NGM_SOURCE_SETIFACE
(setiface
)
- This message requires the name of the interface to be configured as an
argument.
NGM_SOURCE_SETPPS
(setpps
)
- This message requires a single uint32_t parameter
which puts upper limit on the amount of packets sent per second.
NGM_SOURCE_SET_TIMESTAMP
(settimestamp
)
- This message specifies that a timestamp (in the format of a
struct timeval) should be inserted in the
transmitted packets. This message requires a structure containing the
following fields:
- offset
- The offset from the beginning of the packet at which the timestamp is
to be inserted.
- flags
- Set to 1 to enable the timestamp.
NGM_SOURCE_GET_TIMESTAMP
(gettimestamp
)
- Returns the current timestamp settings in the form of the structure
described above.
NGM_SOURCE_SET_COUNTER
(setcounter
)
- This message specifies that a counter should be embedded in transmitted
packets. Up to four counters may be independently configured. This message
requires a structure containing the following fields:
- offset
- The offset from the beginning of the packet at which the counter is to
be inserted.
- flags
- Set to 1 to enable the counter.
- width
- The byte width of the counter. It may be 1, 2, or 4.
- next_val
- The value for the next insertion of the counter.
- min_val
- The minimum value to be used by the counter.
- max_val
- The maximum value to be used by the counter.
- increment
- The value to be added to the counter after each insertion. It may be
negative.
- index
- The counter to be configured, from 0 to 3.
NGM_SOURCE_GET_COUNTER
(getcounter
)
- This message requires a single uint8_t parameter
which specifies the counter to query. Returns the current counter settings
in the form of the structure described above.
This node shuts down upon receipt of a
NGM_SHUTDOWN
control message, when all hooks have
been disconnected, or when the output hook has been
disconnected.
Attach the node to an
ng_ether(4)
node for an interface. If ng_ether
is not already
loaded you will 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.
kldload ng_ether
ngctl mkpeer bge0: source orphans output
At this point the new node can be referred to as
“bge0:orphans
”. The node can be given
its own name like this:
ngctl name bge0:orphans
src0
After which it can be referred to as
“src0:
”.
Once created, packets can be sent to the node as raw binary data.
Each packet must be delivered in a separate netgraph message.
The following example uses a short Perl script to convert the hex
representation of an ICMP packet to binary and deliver it to the
source
node's input hook via
nghook(8):
perl -pe 's/(..)[ \t\n]*/chr(hex($1))/ge' <<EOF | nghook src0: input
ff ff ff ff ff ff 00 00 00 00 00 00 08 00 45 00
00 54 cb 13 00 00 40 01 b9 87 c0 a8 2b 65 0a 00
00 01 08 00 f8 d0 c9 76 00 00 45 37 01 73 00 01
04 0a 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 14 15
16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25
26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33 34 35
36 37
EOF
To check that the node has queued these packets you can get the
node statistics:
ngctl msg bge0:orphans getstats
Args: { queueOctets=64 queueFrames=1 }
Send as many packets as required out the
output hook:
ngctl msg bge0:orphans start
16
Either wait for them to be sent (periodically fetching stats if
desired) or send the stop message:
ngctl msg bge0:orphans
stop
Check the statistics (here we use
getclrstats
to also clear the statistics):
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 } }
The times are from struct timevals, 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
date(1)
command:
date -r 1035305880
Tue Oct 22 12:58:00 EDT 2002
The ng_source
node type was implemented in
FreeBSD 4.8.