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NG_ONE2MANY(4) Device Drivers Manual NG_ONE2MANY(4)

ng_one2many — packet multiplexing netgraph node type

#include <netgraph/one2many/ng_one2many.h>

The one2many provides a simple mechanism for routing packets over several links in a one-to-many (and in the reverse direction, many-to-one) fashion. There is a single hook named one, and multiple hooks named many0, many1, etc. Packets received on any of the many hooks are forwarded out the one hook. Packets received on the one hook are forwarded out one of the many hooks; which hook is determined by the node's configured transmit algorithm. Packets are not altered in any way.

Each of the connected many links may be considered to be up or down. Packets are never delivered out a many hook that is down. How a link is determined to be up or down depends on the node's configured link failure detection algorithm.

At this time, the only algorithm for determining the outgoing many hook is a simple round-robin delivery algorithm. Packets are delivered out the many hooks in sequential order.

In the future other algorithms may be added as well.

At this time, the only algorithm for determining when a link has failed, other than the hook being disconnected, is the ``manual'' algorithm: the node is explicitly told which of the links are up via the NGM_ONE2MANY_SET_CONFIG control message (see below). Newly connected links are down until configured otherwise.

In the future other algorithms may be added as well.

This node type supports up to NG_ONE2MANY_MAX_LINKS hooks named many0, many1, etc., plus a single hook named one.

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

Sets the node configuration using a struct ng_one2many_link_config as the control message argument: 
/* Node configuration structure */
struct ng_one2many_config {
  u_int32_t   xmitAlg;        /* how to distribute packets */
  u_int32_t   failAlg;        /* how to detect link failure */
  u_char      enabledLinks[NG_ONE2MANY_MAX_LINKS];
};

Currently, the only valid setting for the xmitAlg field is NG_ONE2MANY_XMIT_ROUNDROBIN; this is also the default setting. The only valid setting for failAlg is NG_ONE2MANY_FAIL_MANUAL; this is also the default setting.

Returns the current node configuration in a struct ng_one2many_link_config.
This command takes a 32 bit link number as an argument and returns a struct ng_one2many_link_stats containing statistics for the corresponding many link, which may or may not be currently connected: 
/* Statistics structure (one for each link) */
struct ng_one2many_link_stats {
  u_int64_t   recvOctets;     /* total octets rec'd on link */
  u_int64_t   recvPackets;    /* total pkts rec'd on link */
  u_int64_t   xmitOctets;     /* total octets xmit'd on link */
  u_int64_t   xmitPackets;    /* total pkts xmit'd on link */
};

To access statistics for the one link, use the link number -1.

This command takes a 32 bit link number as an argument and clears the statistics for that link.
Same as NGM_ONE2MANY_GET_STATS, but also atomically clears the statistics for the link as well.

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

The following commands will set up Ethernet interfaces fxp0 to deliver packets alternating over the physical interfaces corresponding to networking interfaces fxp0 through fxp3:

  # Plumb nodes together
  ngctl mkpeer fxp0: one2many upper one
  ngctl connect fxp0: fxp0:upper lower many0
  ngctl connect fxp1: fxp0:upper lower many1
  ngctl connect fxp2: fxp0:upper lower many2
  ngctl connect fxp3: fxp0:upper lower many3
  # Allow fxp1 through fxp3 to xmit/recv fxp0 frames
  ngctl msg fxp1: setpromisc 1
  ngctl msg fxp2: setpromisc 1
  ngctl msg fxp3: setpromisc 1
  ngctl msg fxp1: setautosrc 0
  ngctl msg fxp2: setautosrc 0
  ngctl msg fxp3: setautosrc 0
  # Configure all four links as up
  ngctl msg fxp0:upper \
    setconfig "{ xmitAlg=1 failAlg=1 enabledLinks=[ 1 1 1 1 ] }"
  # Bring up interface
  ifconfig fxp0 192.168.1.1 netmask 0xfffffffc

With a similar setup on a peer machine (using the address 192.168.1.2), a point-to-point Ethernet connection with four times normal bandwidth is achieved.

netgraph(4), ng_bridge(4), ng_ether(4), ngctl(8)

The ng_one2many node type was implemented in FreeBSD 4.2.

Archie Cobbs <archie@FreeBSD.org>

More transmit and link failure algorithms should be supported. A good candidate is Cisco's Etherchannel.

November 15, 2000 DragonFly-5.6.1