--- name: "ng_netflow" section: "4" platform: "linux" package: "freebsd-manpages" version: "6.0-5" release: "Debian 4.0 (Etch)" platforms: ["linux", "freebsd"] url: "https://new.carta.tech/ng_netflow" --- # ng\_netflow(4) Cisco's NetFlow implementation ## NAME **ng\_netflow** – Cisco's NetFlow implementation ## SYNOPSIS **#include \** **#include \** **#include \** ## 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*. The 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. 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)](/ng_ksocket/4.md) 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 *iface**N* hook. The hook number is passed as an argument. - NGM\_NETFLOW\_SETDLT Sets data link type on the *iface**N* hook. Currently, supported types are raw IP datagrams and Ethernet. This messsage 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 *iface**N* 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)](/ng_iface/4.md). In this case, the input index should be associated with a given hook. The interface's index can be determined via [if\_nametoindex(3)](/if_nametoindex/3.md) 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 *iface**N* 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\_SHOW This control message asks a node to dump the entire contents of the flow cache. It is called from [flowctl(8)](/flowctl/8.md), not directly from [ngctl(8)](/ngctl/8.md). 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 }" ## 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)](/ng_tee/4.md). 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)](/netgraph/4.md), [ng\_ksocket(4)](/ng_ksocket/4.md), [ng\_tee(4)](/ng_tee/4.md), [flowctl(8)](/flowctl/8.md), [ngctl(8)](/ngctl/8.md) *http://www.cisco.com/warp/public/cc/pd/iosw/ioft/neflct/tech/napps\_wp.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.