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.