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NG_NETFLOW(4) FreeBSD Kernel Interfaces Manual NG_NETFLOW(4)
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[править] NAME
ng_netflow -- Cisco's NetFlow implementation
[править] SYNOPSIS
#include <sys/types.h>
#include <netinet/in.h>
#include <netgraph/netflow/ng_netflow.h>
[править] 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 5/9 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.
Node supports IPv6 accounting (NetFlow v9 only) and is aware of multiple
fibs. Different fibs are mapped to different domain_id in NetFlow V9 and
different engine_id in NetFlow V5.
[править] HOOKS
This node type supports up to NG_NETFLOW_MAXIFACES (default 65536) hooks
named iface0, iface1, etc., and the same number of hooks named out0,
out1, etc., plus two export hooks: export (for NetFlow version 5) and
export9 (for NetFlow version 9). Export can be done simultaneously for
all supported export hooks. By default (ingress NetFlow enabled) node
does NetFlow accounting of data received on iface* hooks. If correspond-
ing 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 corre-
sponding iface hook without any processing (egress NetFlow disabled by
default). When full export datagram for an export protocol is built it
is sent to the export or export9 hook. In normal operation, one (or
more) export hook is connected to the inet/dgram/udp hook of the
ng_ksocket(4) node.
[править] 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 inter-
face's index can be determined via if_nametoindex(3) from user-
land. 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 argu-
ment:
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_NET-
FLOW_CONF_INGRESS enabled by default enables ingress NetFlow gen-
eration (for data coming from ifaceX hook). Option NG_NET-
FLOW_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 net-
flow 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_SETTEMPLATE
Sets various timeouts to announce data flow templates (NetFlow
v9-specific). This message requires struct ng_netflow_settemplate
as an argument:
struct ng_netflow_settemplate {
uint16_t time;
uint16_t packets;
};
Value of time field represents time in seconds to re-announce
data templates. Value of packets field represents maximum pack-
ets count between re-announcing data templates.
NGM_NETFLOW_SETMTU
Sets export interface MTU to build packets of specified size
(NetFlow v9-specific). This message requires struct
ng_netflow_setmtu as an argument:
struct ng_netflow_settemtu {
uint16_t mtu;
};
Default is 1500 bytes
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.
[править] 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 }"
NGM_NETFLOW_SETTEMPLATE "settemplate { time = %u packets = %u }"
NGM_NETFLOW_SETMTU "setmtu { mtu = %u }"
[править] SHUTDOWN
This node shuts down upon receipt of a NGM_SHUTDOWN control message, or
when all hooks have been disconnected.
[править] 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 con-
nected 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
[править] SEE ALSO
netgraph(4) • setfib(2) • ng_ether(4) • ng_iface(4) • ng_ksocket(4) • ng_tee(4) • flowctl(8) • ngctl(8)
B. Claise, Ed, Cisco Systems NetFlow Services Export Version 9, RFC 3954.
http://www.cisco.com/en/US/docs/ios/solutions_docs/netflow/nfwhite.html
[править] AUTHORS
The ng_netflow node type was written by Gleb Smirnoff
<glebius@FreeBSD.org>, Alexander Motin <mav@FreeBSD.org>, Alexander
Chernikov <melifaro@ipfw.ru>. The initial code was based on ng_ipacct
written by Roman V. Palagin <romanp@unshadow.net>.
[править] BUGS
Cache snapshot obtained via NGM_NETFLOW_SHOW command may lack some per-
centage of entries under severe load. IPv6 flows are not shown.
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.
FreeBSD 9.0 March 2, 2011 FreeBSD 9.0
