# $FreeBSD$
#
# This is an example that shows how to send ASCII formatted control
# messages to a node using ngctl(8).
#
# What we will do here create a divert(4) tap. This simply dumps
# out all packets diverted by some ipfw(8) divert rule to the console.
#
# Lines that begin with ``$'' (shell prompt) or ``+'' (ngctl prompt)
# indicate user input
#
# First, start up ngctl in interactive mode:
$ ngctl
Available commands:
connect Connects hook <peerhook> of the node at <relpath> to <hook>
debug Get/set debugging verbosity level
help Show command summary or get more help on a specific command
list Show information about all nodes
mkpeer Create and connect a new node to the node at "path"
msg Send a netgraph control message to the node at "path"
name Assign name <name> to the node at <path>
read Read and execute commands from a file
rmhook Disconnect hook "hook" of the node at "path"
show Show information about the node at <path>
shutdown Shutdown the node at <path>
status Get human readable status information from the node at <path>
types Show information about all installed node types
quit Exit program
+
# Now let's create a ng_ksocket(4) node, in the family PF_INET,
# of type SOCK_RAW, and protocol IPPROTO_DIVERT:
+ mkpeer ksocket foo inet/raw/divert
# Note that ``foo'' is the hook name on the socket node, which can be
# anything. The ``inet/raw/divert'' is the hook name on the ksocket
# node, which tells it what kind of socket to create.
# Lets give our ksocket node a global name. How about ``fred'':
+ name foo fred
# Note that we used ngctl's ``name'' command to do this. However,
# the following manually constructed netgraph message would have
# accomplished the exact same thing:
+ msg foo name { name="fred" }
# Here we are using the ASCII <-> binary control message conversion
# routines. ngctl does this for us automatically when we use the
# ``msg'' command.
# Now lets bind the socket associated with the ksocket node to a port
# supplied by the system. We do this by sending the ksocket node a
# ``bind'' control message. Again, ngctl does the conversion of the
# control message from ASCII to binary behind the scenes.
+ msg fred: bind inet/192.168.1.1
# The ksocket accepts arbitrary sockaddr structures, but also has
# special support for the PF_LOCAL and PF_INET protocol families.
# That is why we can specify the struct sockaddr argument to the
# ``bind'' command as ``inet/192.168.1.1'' (since we didn't specify
# a port number, it's assumed to be zero). We could have also
# relied on the generic sockaddr syntax and instead said this:
+ msg fred: bind { family=2 len=16 data=[ 2=192 168 1 1 ] }
# This is what you would have to do for protocol families other
# that PF_INET and PF_LOCAL, at least until special handling for
# new ones is added.
# The reason for the ``2=192'' is to skip the two byte IP port number,
# which causes it to be set to zero, the default value for integral
# types when parsing. Now since we didn't ask for a specific port
# number, we need to do a ``getname'' to see what port number we got:
+ msg fred: getname
Rec'd response "getname" (5) from "fred:":
Args: inet/192.168.1.1:1029
# As soon as we sent the message, we got back a response. Here
# ngctl is telling us that it received a control message with the
# NGF_RESP (response) flag set, the response was to a prior ``getname''
# control message, that the originator was the node addressable
# as ``fred:''. The message arguments field is then displayed to
# us in its ASCII form. In this case, what we get back is a struct
# sockaddr, and there we see that our port number is 1029.
# So now let's add the ipfw divert rule for whatever packets we
# want to see. How about anything from 192.168.1.129.
+ ^Z
Suspended
$ ipfw add 100 divert 1029 ip from 192.168.1.129 to any
00100 divert 1029 ip from 192.168.1.129 to any
$ fg
# Now watch what happens when we try to ping from that machine:
+
Rec'd data packet on hook "foo":
0000: 45 00 00 3c 57 00 00 00 20 01 bf ee c0 a8 01 81 E..<W... .......
0010: c0 a8 01 01 08 00 49 5c 03 00 01 00 61 62 63 64 ......I\....abcd
0020: 65 66 67 68 69 6a 6b 6c 6d 6e 6f 70 71 72 73 74 efghijklmnopqrst
0030: 75 76 77 61 62 63 64 65 66 67 68 69 uvwabcdefghi
+
Rec'd data packet on hook "foo":
0000: 45 00 00 3c 58 00 00 00 20 01 be ee c0 a8 01 81 E..<X... .......
0010: c0 a8 01 01 08 00 48 5c 03 00 02 00 61 62 63 64 ......H\....abcd
0020: 65 66 67 68 69 6a 6b 6c 6d 6e 6f 70 71 72 73 74 efghijklmnopqrst
0030: 75 76 77 61 62 63 64 65 66 67 68 69 uvwabcdefghi
+
Rec'd data packet on hook "foo":
0000: 45 00 00 3c 59 00 00 00 20 01 bd ee c0 a8 01 81 E..<Y... .......
0010: c0 a8 01 01 08 00 47 5c 03 00 03 00 61 62 63 64 ......G\....abcd
0020: 65 66 67 68 69 6a 6b 6c 6d 6e 6f 70 71 72 73 74 efghijklmnopqrst
0030: 75 76 77 61 62 63 64 65 66 67 68 69 uvwabcdefghi
+
# So we're seeing the output from the ksocket socket appear on the ``foo''
# hook of ngctl's socket node. Since the packets are getting diverted,
# the 192.168.1.129 machine doesn't see any response from us.
# Of course, any type of socket can be used, even TCP:
+ mkpeer ksocket bar inet/stream/tcp
+ msg bar connect inet/192.168.1.33:13
ngctl: send msg: Operation now in progress
+
Rec'd data packet on hook "foo":
0000: 4d 6f 6e 20 4e 6f 76 20 32 39 20 31 37 3a 34 38 Mon Nov 29 17:48
0010: 3a 33 37 20 31 39 39 39 0d 0a :37 1999..
+
# Or, UNIX domain:
+ mkpeer ksocket bar local/stream/0
+ msg bar bind local/"/tmp/bar.socket"
+
# Here's an example of a more complicated ASCII control message argument.
# If you look in /sys/netgraph/ng_message.h, you will see that a node
# responds to a NGM_LISTHOOKS with a struct hooklist, which contains
# an array of struct linkinfo:
#
# /* Structure used for NGM_LISTHOOKS */
# struct linkinfo {
# char ourhook[NG_HOOKSIZ]; /* hook name */
# char peerhook[NG_HOOKSIZ]; /* peer hook */
# struct nodeinfo nodeinfo;
# };
#
# struct hooklist {
# struct nodeinfo nodeinfo; /* node information */
# struct linkinfo link[0]; /* info about each hook */
# };
#
# By sending a node the ``listhooks'' command using ngctl, we can see
# this structure in ASCII form (lines wrapped for readability):
+ msg bar bind local/"/tmp/bar.socket"
+ msg bar listhooks
Rec'd response "listhooks" (7) from "bar":
Args: { nodeinfo={ type="ksocket" id=9 hooks=1 }
linkinfo=[ { ourhook="local/stream/0" peerhook="bar"
nodeinfo={ name="ngctl1327" type="socket" id=8 hooks=1 } } ] }