Skip site navigation (1)Skip section navigation (2)

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
NG_NETFLOW(4)          FreeBSD Kernel Interfaces Manual          NG_NETFLOW(4)

     ng_netflow - Cisco's NetFlow implementation

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

     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.

     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.

     This node type supports the generic control messages, plus the following:

             Returns some node statistics and the current timeout values in a
             struct ng_netflow_info.

             Returns information about the ifaceN hook.  The hook number is
             passed as an argument.

             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.

             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.

             Sets values in seconds for NetFlow active/inactive timeouts.
             This message requires struct ng_netflow_settimeouts as an

                 struct ng_netflow_settimeouts {
                         uint32_t        inactive_timeout;
                         uint32_t        active_timeout;

             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.

             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
             packets count between re-announcing data templates.

             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

             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.

     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 }"

     This node shuts down upon receipt of a NGM_SHUTDOWN control message, or
     when all hooks have been disconnected.

     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/

     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/

     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.

     The ng_netflow node type was written by Gleb Smirnoff
     <>, Alexander Motin <>, Alexander
     Chernikov <>.  The initial code was based on ng_ipacct
     written by Roman V. Palagin <>.

     Cache snapshot obtained via NGM_NETFLOW_SHOW command may lack some
     percentage 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 11.0-PRERELEASE          March 2, 2011         FreeBSD 11.0-PRERELEASE


Want to link to this manual page? Use this URL:

home | help