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 protocol on a
router running FreeBSD. The ng_netflow node listens for incoming 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 specified 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. By default (ingress NetFlow enabled) node does
NetFlow accounting of data received on iface* hooks. If corresponding
out hook is connected, 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 (egress NetFlow disabled
by default). When full export datagram is built it is sent to the export
hook. In normal operation, the export hook is connected 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 message 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 capturing 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_SETCONFIG
Sets configuration for the specified interface. This message
requires struct ng_netflow_setconfig as an argument:
struct ng_netflow_setconfig {
u_int16_t iface;
u_int32_t conf;
#define NG_NETFLOW_CONF_INGRESS 1
#define NG_NETFLOW_CONF_EGRESS 2
#define NG_NETFLOW_CONF_ONCE 4
#define NG_NETFLOW_CONF_THISONCE 8
};
Configuration is a bitmask of several options. Option
NG_NETFLOW_CONF_INGRESS enabled by default enables ingress
NetFlow generation (for data coming from ifaceX hook). Option
NG_NETFLOW_CONF_EGRESS enables egress NetFlow (for data coming
from outX hook). Option NG_NETFLOW_CONF_ONCE defines that packet
should be accounted only once if it several times passes via
netflow node. Option NG_NETFLOW_CONF_THISONCE defines that packet
should be accounted only once if it several times passes via
exactly this netflow node. Last two options are important to
avoid duplicate accounting when both ingress and egress NetFlow
are enabled.
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 }"
NGM_NETFLOW_SETCONFIG "setconfig { iface = %u conf = %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 interface, 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 NetFlow-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 packets, 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 configure 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 future releases.