Manual Pages  — NG_SOURCE

#include <sys/types.h>

#include <netgraph/ng_source.h>

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.

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

netgraph(4), ng_echo(4), ng_hole(4), ng_tee(4), ngctl(8), nghook(8)