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     ng_one2many - packet multiplexing netgraph node type


     #include <sys/types.h>
     #include <netgraph/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 or more of the many hooks; which hook(s) 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.

     Before an interface or link can be plumbed into a group, its status must
     be marked as being “up”.  This is normally setup during the initial boot
     stages by rc.conf(5).  It is also possible to change an interface’s
     status to “up” by using the ifconfig(8) utility.


          Packets are delivered out the many hooks in sequential order.  Each
          packet goes out on a different many hook.

          Packets are delivered out all the many hooks.  Each packet goes out
          each many hook.

     In the future other algorithms may be added as well.


     The node distinguishes between active and failed links.  Data is sent
     only to active links.  The following link failure detection algorithms
     are available:

             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.

             The node listens to flow control message from many hooks, and
             considers link failed if NGM_LINK_IS_DOWN is received.  If the
             NGM_LINK_IS_UP message is received, node considers link active.

     In the future other algorithms may be added as well.

     When all links are considered failed, node sends the NGM_LINK_IS_DOWN
     message towards the one hook.  When at least one link comes up, node
     sends the NGM_LINK_IS_UP message towards the one hook.


     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 valid settings for the xmitAlg field are
          valid settings for failAlg are NG_ONE2MANY_FAIL_MANUAL (default) or

          Returns the current node configuration in a struct

          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

          /* 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 netmask 0xfffffffc

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


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


     The ng_one2many node type was implemented in FreeBSD 4.2.


     The one2many netgraph node (with round-robin algorithm) was written by
     Archie Cobbs 〈〉.  The all algorithm was added by Rogier
     R. Mulhuijzen 〈〉.


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