freebsd-dev/share/examples/netgraph/ngctl

# $FreeBSD$

#
# 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
# acomplished 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 reponse 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 } } ] }