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     ng_atm — netgraph ATM node type


     #include <sys/types.h>
     #include <net/if_atm.h>
     #include <netgraph.h>
     #include <netgraph/atm/ng_atm.h>


     The atm netgraph node type allows natm(4) ATM drivers to be connected to
     the netgraph(4) networking subsystem.  When the ng_atm module is loaded a
     node is automatically created for each natm(4) ATM interface.  The nodes
     are named with the same name as the interface.  Nodes are also created if
     a driver for an ATM card is loaded after ng_atm was loaded.

     The atm nodes are persistent.  They are removed when the interface is
     removed.  NGM_SHUTDOWN messages are ignored by the node.


     Four special hooks with fixed names and an unlimited number of hooks with
     user defined names are supported.  Three of the fixed hooks are attached
     to strategic points in the information flow in the natm(4) system and
     support only reading.  The fourth fixed hook behaves like the other user
     hooks, but a number of management messages are sent along the hook.  The
     other hooks can be attached to VCIs dynamically by means of control
     messages to the atm node and can be written and read.

     The four fixed hooks are:

     input    This is a connection to the raw input stream from the network.
              If this hook is connected, all incoming packets are delivered
              out to this hook.  Note that this redirects ALL input.  Neither
              natm(4) nor the user hooks will see any input if input is
              connected.  An atm_pseudohdr (see natm(4)) is prepended to the
              actual data.

     output   This is a connection to the raw output stream to the network
              device.  If this hook is connected, all outgoing packets are
              handed over to the netgraph system and delivered to the hook
              instead of being delivered to the ATM driver.  An atm_pseudohdr
              (see natm(4)) is prepended to the actual data.

     orphans  This hook receives all packets that are unrecognized, i.e., do
              not belong to either a natm(4) socket, a ng_atm VCI or natm(4)
              IP.  Because ATM is connection oriented and packets are received
              on a given VCI only when someone initiates this VCI, packets
              should never be orphaned.  There is however one exception: if
              you use natm(4) IP with LLC/SNAP encapsulation packets with do
              not have the IP protocol indicated in the packet header are
              delivered out of this hook.  An atm_pseudohdr (see natm(4)) is
              prepended to the actual data send out to the hook.

     manage   This hook behaves exactly like a normal user hook (see below)
              except that the node at the other hand will receive management

     Hooks for dynamically initiated VCIs can have whatever name is allowed by
     netgraph(4) as long as the name does not collide with one of the three
     predefined names.

     To initiate packet sending and receiving on a dynamic hook, one has to
     issue a NGM_ATM_CPCS_INIT control message.  To terminate sending and
     receiving one must send a NGM_ATM_CPCS_TERM message (see CONTROL
     MESSAGES).  The data sent and received on these hooks has no additional


     This node type supports the generic messages plus the following:

           Return the name of the interface as a NUL-terminated string.  This
           is normally the same name as that of the node.

           Returns a structure defining the configuration of the interface:

           struct ng_atm_config {
                   uint32_t        pcr;            /* peak cell rate */
                   uint32_t        maxvpi;         /* maximum vpi */
                   uint32_t        maxvci;         /* maximum vci */
                   uint32_t        max_vpcs;       /* maximum number of VPCs */
                   uint32_t        max_vccs;       /* maximum number of VCCs */

           Returns the table of open VCCs from the driver.  This table
           consists of a header and a variable sized array of entries, one for
           each open VCC:

           struct atmio_vcctable {
                   uint32_t        count;          /* number of vccs */
                   struct atmio_vcc vccs[0];       /* array of VCCs */
           struct atmio_vcc {
                   uint16_t        flags;          /* flags */
                   uint16_t        vpi;            /* VPI */
                   uint16_t        vci;            /* VCI */
                   uint16_t        rmtu;           /* Receive maximum CPCS size */
                   uint16_t        tmtu;           /* Transmit maximum CPCS size */
                   uint8_t         aal;            /* aal type */
                   uint8_t         traffic;        /* traffic type */
                   struct atmio_tparam tparam;     /* traffic parameters */
           struct atmio_tparam {
                   uint32_t        pcr;    /* 24bit: Peak Cell Rate */
                   uint32_t        scr;    /* 24bit: VBR Sustainable Cell Rate */
                   uint32_t        mbs;    /* 24bit: VBR Maximum burst size */
                   uint32_t        mcr;    /* 24bit: MCR */
                   uint32_t        icr;    /* 24bit: ABR ICR */
                   uint32_t        tbe;    /* 24bit: ABR TBE (1...2^24-1) */
                   uint8_t         nrm;    /*  3bit: ABR Nrm */
                   uint8_t         trm;    /*  3bit: ABR Trm */
                   uint16_t        adtf;   /* 10bit: ABR ADTF */
                   uint8_t         rif;    /*  4bit: ABR RIF */
                   uint8_t         rdf;    /*  4bit: ABR RDF */
                   uint8_t         cdf;    /*  3bit: ABR CDF */

           Note that this is the driver's table, so all VCCs opened via
           natm(4) sockets and IP are also shown.  They can, however, be
           distinguished by their flags.  The flags field contains the
           following flags:

                 ATM_PH_AAL5     use AAL5 instead of AAL0
                 ATM_PH_LLCSNAP  if AAL5 use LLC SNAP encapsulation
                 ATM_FLAG_NG     this is a netgraph VCC
                 ATM_FLAG_HARP   this is a HARP VCC
                 ATM_FLAG_NORX   transmit only VCC
                 ATM_FLAG_NOTX   receive only VCC
                 ATMIO_FLAG_PVC  treat channel as a PVC

           If the ATM_FLAG_NG flag is set, then traffic and tparam contain
           meaningful information.

           The aal field contains one of the following values:

                 ATMIO_AAL_0     AAL 0 (raw cells)
                 ATMIO_AAL_34    AAL 3 or AAL 4
                 ATMIO_AAL_5     AAL 5
                 ATMIO_AAL_RAW   device specific raw cells

           The traffic field can have one of the following values (not all
           drivers support all traffic types however):


           Initialize a VCC for sending and receiving.  The argument is a

           struct ng_atm_cpcs_init {
                   char            name[NG_HOOKSIZ];
                   uint32_t        flags;          /* flags. (if_natmio.h) */
                   uint16_t        vci;            /* VCI to open */
                   uint16_t        vpi;            /* VPI to open */
                   uint16_t        rmtu;           /* receive maximum PDU */
                   uint16_t        tmtu;           /* transmit maximum PDU */
                   uint8_t         aal;            /* AAL type (if_natmio.h) */
                   uint8_t         traffic;        /* traffic type (if_natmio.h) */
                   uint32_t        pcr;            /* Peak cell rate */
                   uint32_t        scr;            /* Sustainable cell rate */
                   uint32_t        mbs;            /* Maximum burst size */
                   uint32_t        mcr;            /* Minimum cell rate */
                   uint32_t        icr;            /* ABR: Initial cell rate */
                   uint32_t        tbe;            /* ABR: Transmit buffer exposure */
                   uint8_t         nrm;            /* ABR: Nrm */
                   uint8_t         trm;            /* ABR: Trm */
                   uint16_t        adtf;           /* ABR: ADTF */
                   uint8_t         rif;            /* ABR: RIF */
                   uint8_t         rdf;            /* ABR: RDF */
                   uint8_t         cdf;            /* ABR: CDF */

           The name field is the name of the hook for which sending and
           receiving should be enabled.  This hook must already be connected.
           The vpi and vci fields are the respective VPI and VCI values to use
           for the ATM cells.  They must be within the range, given by the
           maxvpi and maxvci fields of the ng_atm_config structure.  The flags
           field contains the flags (see above) and the other fields describe
           the type of traffic.

           Stop sending and receiving on the indicated hook.  The argument is

           struct ng_atm_cpcs_term {
                   char            name[NG_HOOKSIZ];


     If the manage hook is connected, certain messages are sent along the
     hook.  They are received by the peer node with a cookie of NG_ATM_COOKIE.

           The carrier state of the ATM physical interface has changed.  The
           message has the following structure:

           struct ng_atm_carrier_change {
                   uint32_t        node;
                   uint32_t        state;

           The node field is the node ID of the ATM node.  This can be used by
           the managing entity (for example ilmid(8)) to manage several
           interfaces at the same time through the same node.  The state field
           is 1 if the carrier was detected, and 0 if it was lost.

           A permanent VCC has been added, deleted or changed.  This is used
           by ilmid(8) to generate the appropriate ILMI traps.  The structure
           of the message is:

           struct ng_atm_vcc_change {
                   uint32_t        node;
                   uint16_t        vci;
                   uint8_t         vpi;
                   uint8_t         state;
           Where state is 0 if the PVC was deleted, and 1 if it was added or


     If the hardware driver supports it, the node can emit flow control
     messages along a user hook.  The format of these messages is described in
     <netgraph/ng_message.h>.  The atm node may generate NGM_HIGH_WATER_PASSED
     and NGM_LOW_WATER_PASSED messages.  The first one indicates that the
     hardware driver has stopped output on the channel and drops new packets,
     the second one reports that output was reenabled.  Currently, the
     structures are not filled with information.


     The nodes are persistent as long as the corresponding interface exists.
     Upon receipt of a NGM_SHUTDOWN messages, all hooks are disconnected and
     the node is reinitialized.  All VCCs opened via netgraph(4) are closed.
     When the ATM interface is unloaded, the node disappears.  If the node is
     compiled with NGATM_DEBUG there is a sysctl net.graph.atm.allow_shutdown
     which, when set to a non-zero value, allows the nodes to shut down.  Note
     that this is intended for development only and may lead to kernel panics
     if set.


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


     Harti Brandt ⟨