ng_netflow(4)

NAME

ng_netflow - Cisco's NetFlow implementation

SYNOPSIS

#include <sys/types.h>
#include <netinet/in.h>
#include <netgraph/netflow/ng_netflow.h>

DESCRIPTION

The ng_netflow node implements Cisco's NetFlow export proto

col on a
router running FreeBSD. The ng_netflow node listens for in

coming traffic
and identifies unique flows in it. Flows are distinguished

by endpoint
IP addresses, TCP/UDP port numbers, ToS and input interface.

Expired
flows are exported out of the node in NetFlow version 5 UDP

datagrams.
Expiration reason can be one of the following:

- RST or FIN TCP segment.

- Active timeout. Flows cannot live more than the speci

fied period of

time. The default is 1800 seconds (30 minutes).

- Inactive timeout. A flow was inactive for the specified

period of

time. The default is 15 seconds.

Export information is stored in NetFlow version 5 datagrams.

HOOKS

This node type supports up to NG_NETFLOW_MAXIFACES hooks

named iface0,
iface1, etc., and the same number of hooks named out0, out1,

etc., plus a
single hook named export. The node does NetFlow accounting

of data
received on iface* hooks. If corresponding out hook is con

nected, unmodified data is bypassed to it, otherwise data is freed. If

data is
received on out hook, it is bypassed to corresponding iface

hook without
any processing. When full export datagram is built it is

sent to the
export hook. In normal operation, the export hook is con

nected to the
inet/dgram/udp hook of the ng_ksocket(4) node.

CONTROL MESSAGES

This node type supports the generic control messages, plus

the following:

NGM_NETFLOW_INFO

Returns some node statistics and the current timeout

values in a
struct ng_netflow_info.

NGM_NETFLOW_IFINFO

Returns information about the ifaceN hook. The hook

number is
passed as an argument.

NGM_NETFLOW_SETDLT

Sets data link type on the ifaceN hook. Currently,

supported
types are raw IP datagrams and Ethernet. This mess

sage type uses
struct ng_netflow_setdlt as an argument:

struct ng_netflow_setdlt {

uint16_t iface; /* which iface

to operate on */
uint8_t dlt; /* DLT_XXX from

bpf.h */

};

The requested ifaceN hook must already be connected,

otherwise
message send operation will return an error.

NGM_NETFLOW_SETIFINDEX

In some cases, ng_netflow may be unable to determine

the input
interface index of a packet. This can happen if

traffic enters
the ng_netflow node before it comes to the system

interface's
input queue. An example of such a setup is captur

ing a traffic
between synchronous data line and ng_iface(4). In

this case, the
input index should be associated with a given hook.

The interface's index can be determined via if_nametoindex(3)

from userland. This message requires struct

ng_netflow_setifindex as an
argument:

struct ng_netflow_setifindex {

u_int16_t iface; /* which iface

to operate on */
u_int16_t index; /* new index */

};

The requested ifaceN hook must already be connected,

otherwise
the message send operation will return an error.

NGM_NETFLOW_SETTIMEOUTS

Sets values in seconds for NetFlow active/inactive

timeouts.
This message requires struct ng_netflow_settimeouts

as an argument:

struct ng_netflow_settimeouts {

uint32_t inactive_timeout;
uint32_t active_timeout;

};

NGM_NETFLOW_SHOW

This control message asks a node to dump the entire

contents of
the flow cache. It is called from flowctl(8), not

directly from
ngctl(8). See also BUGS section.

ASCII CONTROL MESSAGES

Most binary control messages have an ASCII equivalent. The

supported
ASCII commands are:

NGM_NETFLOW_INFO "info"
NGM_NETFLOW_IFINFO "ifinfo %u"
NGM_NETFLOW_SETDLT "setdlt { iface = %u dlt = %u

}"
NGM_NETFLOW_SETIFINDEX "setifindex { iface = %u index

= %u }"
NGM_NETFLOW_SETTIMEOUTS "settimeouts { inactive = %u

active = %u }"

SHUTDOWN

This node shuts down upon receipt of a NGM_SHUTDOWN control

message, or
when all hooks have been disconnected.

EXAMPLES

The simplest possible configuration is one Ethernet inter

face, where flow
collecting is enabled.

/usr/sbin/ngctl -f- <<-SEQ

mkpeer fxp0: netflow lower iface0
name fxp0:lower netflow
connect fxp0: netflow: upper out0
mkpeer netflow: ksocket export inet/dgram/udp
msg netflow:export connect inet/10.0.0.1:4444

SEQ

This is a more complicated example of a router with 2 Net

Flow-enabled
interfaces fxp0 and ng0. Note that the ng0: node in this

example is connected to ng_tee(4). The latter sends us a copy of IP pack

ets, which we
analyze and free. On fxp0: we do not use tee, but send

packets back to
ether node.

/usr/sbin/ngctl -f- <<-SEQ

# connect ng0's tee to iface0 hook
mkpeer ng0:inet netflow right2left iface0
name ng0:inet.right2left netflow
# set DLT to raw mode
msg netflow: setdlt { iface=0 dlt=12 }
# set interface index (5 in this example)
msg netflow: setifindex { iface=0 index=5 }

# Connect fxp0: to iface1 and out1 hook
connect fxp0: netflow: lower iface1
connect fxp0: netflow: upper out1

# Create ksocket node on export hook, and con

figure it
# to send exports to proper destination
mkpeer netflow: ksocket export inet/dgram/udp
msg netflow:export connect inet/10.0.0.1:4444

SEQ

SEE ALSO

netgraph(4), ng_ether(4), ng_iface(4), ng_ksocket(4),

ng_tee(4),
flowctl(8), ngctl(8)

http://www.cisco.com/univercd/cc/td/doc/cisintwk/intsolns/netflsol/nfwhite.htm

AUTHORS

The ng_netflow node type was written by Gleb Smirnoff <glebius@FreeBSD.org>, based on ng_ipacct written by Roman

V. Palagin
<romanp@unshadow.net>.

BUGS

Cache snapshot obtained via NGM_NETFLOW_SHOW command may

lack some percentage of entries under severe load.

The ng_netflow node type does not fill in AS numbers. This

is due to the
lack of necessary information in the kernel routing table.

However, this
information can be injected into the kernel from a routing

daemon such as
GNU Zebra. This functionality may become available in fu

ture releases.

BSD March 2, 2006

BSD