NG_ATM(4) FreeBSD Kernel Interfaces Manual NG_ATM(4)


ng_atmnetgraph 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:

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

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 headers.


This node type supports the generic messages plus the following:
NGM_ATM_GET_IFNAME ( getifname)
Return the name of the interface as a NUL-terminated string. This is normally the same name as that of the node.
NGM_ATM_GET_CONFIG ( getconfig)
Returns a structure defining the configuration of the interface:

struct ngm_atm_config { 
 uint32_t pcr;  /* peak cell rate */ 
 uint32_t vpi_bits; /* number of active VPI bits */ 
 uint32_t vci_bits; /* number of active VCI bits */ 
 uint32_t max_vpcs; /* maximum number of VPCs */ 
 uint32_t max_vccs; /* maximum number of VCCs */ 
NGM_ATM_GET_VCCS ( getvccs)
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: ABR/VBR/UBR+MCR 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:

use AAL5 instead of AAL0
if AAL5 use LLC SNAP encapsulation
this is a netgraph VCC
this is a HARP VCC
transmit only VCC
receive only VCC
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:

AAL 0 (raw cells)
AAL 3 or AAL 4
device specific raw cells

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

NGM_ATM_CPCS_INIT ( cpcsinit)
Initialize a VCC for sending and receiving. The argument is a structure:

struct ngm_atm_cpcs_init { 
 char  name[NG_HOOKSIZ]; 
 uint32_t flags;  /* flags. (if_atm.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_atm.h) */ 
 uint8_t  traffic; /* traffic type (if_atm.h) */ 
 uint32_t pcr;  /* Peak cell rate */ 
 uint32_t scr;  /* VBR: Sustainable cell rate */ 
 uint32_t mbs;  /* VBR: Maximum burst rate */ 
 uint32_t mcr;  /* UBR+: 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.

NGM_ATM_CPCS_TERM ( cpcsterm)
Stop sending and receiving on the indicated hook. The argument is a

struct ngm_atm_cpcs_term { 
 char  name[NG_HOOKSIZ]; 
NGM_ATM_GET_STATS ( getstats)
This command returns a message, containing node statistics. The structure of the message is:

struct ngm_atm_stats { 
 uint64_t        in_packets; 
 uint64_t        in_errors; 
 uint64_t        out_packets; 
 uint64_t        out_errors; 


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.
NGM_ATM_VCC_CHANGE ( vcc_change)
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 ngm_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 modified.


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.


Harti Brandt <harti@FreeBSD.org>
November 2, 2012 FreeBSD