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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 5/9 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.
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
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 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.
CONTROL MESSAGES
This node type supports the generic control messages, plus the following:
NGM_NETFLOW_INFO (info)
Returns some node statistics and the current timeout values in a struct ng_netflow_info.
NGM_NETFLOW_IFINFO (ifinfo)
Returns information about the ifaceN hook. The hook number is passed as an argument.
NGM_NETFLOW_SETDLT (setdlt)
Sets data link type on the ifaceN hook. Currently, supported types are DLT_RAW (raw IP datagrams)
and DLT_EN10MB (Ethernet). DLT_ definitions can be found in <net/bpf.h> header. Currently used
values are 1 for DLT_EN10MB and 12 for DLT_RAW. This message type uses struct ng_netflow_setdlt as
an argument:
struct ng_netflow_setdlt {
uint16_t iface; /* which iface dlt change */
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 (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 {
uint16_t iface; /* which iface index change */
uint16_t index; /* new index */
};
The requested ifaceN hook must already be connected, otherwise the message send operation will
return an error.
NGM_NETFLOW_SETTIMEOUTS (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; /* flow inactive timeout */
uint32_t active_timeout; /* flow active timeout */
};
NGM_NETFLOW_SETCONFIG (setconfig)
Sets configuration for the specified interface. This message requires struct ng_netflow_setconfig
as an argument:
struct ng_netflow_setconfig {
uint16_t iface; /* which iface config change */
uint32_t conf; /* new config */
#define NG_NETFLOW_CONF_INGRESS 1
#define NG_NETFLOW_CONF_EGRESS 2
#define NG_NETFLOW_CONF_ONCE 4
#define NG_NETFLOW_CONF_THISONCE 8
#define NG_NETFLOW_CONF_NOSRCLOOKUP 16
#define NG_NETFLOW_CONF_NODSTLOOKUP 32
};
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. These two options are important to avoid
duplicate accounting when both ingress and egress NetFlow are enabled. Option
NG_NETFLOW_CONF_NOSRCLOOKUP skips radix lookup on flow source address used to fill in network mask.
Option NG_NETFLOW_CONF_NODSTLOOKUP skips radix lookup on destination (which fills egress interface
id, destination mask and gateway). If one doesn't need data provided by lookups, he/she can disable
them, to reduce load on routers.
NGM_NETFLOW_SETTEMPLATE (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; /* max time between announce */
uint16_t packets; /* max packets between announce */
};
Value of time field represents time in seconds to re-announce data templates. Value of packets
field represents maximum packets count between re-announcing data templates.
NGM_NETFLOW_SETMTU (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_setemtu {
uint16_t mtu; /* MTU for packet */
};
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).
NGM_NETFLOW_V9INFO (v9info)
Returns some NetFlow v9 related values in a
struct ng_netflow_v9info {
uint16_t templ_packets; /* v9 template packets */
uint16_t templ_time; /* v9 template time */
uint16_t mtu; /* v9 MTU */
};
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 either 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), 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
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>.
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.
Debian December 10, 2012 NG_NETFLOW(4)