SNMP_NETGRAPH(3)

NAME
snmp_netgraph, snmp_node, snmp_nodename, ng_cookie_f, ng_hook_f, ng_register_cookie, ng_unregister_cookie, ng_register_hook, ng_unregister_hook, ng_unregister_module, ng_output, ng_output_node, ng_output_id, ng_dialog, ng_dialog_node, ng_dialog_id, ng_send_data, ng_mkpeer_id, ng_connect_node, ng_connect_id, ng_connect2_id, ng_connect2_tee_id, ng_rmhook, ng_rmhook_id, ng_rmhook_tee_id, ng_shutdown_id, ng_next_node_id, ng_node_id, ng_node_id_node, ng_node_name, ng_node_type, ng_peer_hook_id - netgraph module for snmpd.

LIBRARY
(begemotSnmpdModulePath."netgraph" = /usr/lib/snmp_netgraph.so)

SYNOPSIS
#include <bsnmp/snmpmod.h>
#include <bsnmp/snmp_netgraph.h>
extern ng_ID_t snmp_node;
extern u_char *snmp_nodename;
typedef void
ng_cookie_f(const struct ng_mesg *mesg, const char *path, ng_ID_t id, void *uarg);
typedef void
ng_hook_f(const char *hook, const u_char *mesg, size_t len, void *uarg);
void *
ng_register_cookie(const struct lmodule *mod, u_int32_t cookie, ng_ID_t id, ng_cookie_f *func, void *uarg);
void
ng_unregister_cookie(void *reg);
void *
ng_register_hook(const struct lmodule *mod, const char *hook, ng_hook_f *func, void *uarg);
void
ng_unregister_hook(void *reg);
void
ng_unregister_module(const struct lmodule *mod);
int
ng_output(const char *path, u_int cookie, u_int opcode, const void *arg, size_t arglen);
int
ng_output_node(const char *node, u_int cookie, u_int opcode, const void *arg, size_t arglen);
int
ng_output_id(ng_ID_t node, u_int cookie, u_int opcode, const void *arg, size_t arglen);
struct ng_mesg *
ng_dialog(const char *path, u_int cookie, u_int opcode, const void *arg, size_t arglen);
struct ng_mesg *
ng_dialog_node(const char *node, u_int cookie, u_int opcode, const void *arg, size_t arglen);
struct ng_mesg *
ng_dialog_id(ng_ID_t id, u_int cookie, u_int opcode, const void *arg, size_t arglen);
int
ng_send_data(const char *hook, const void *sndbuf, size_t sndlen);
ng_ID_t
ng_mkpeer_id(ng_ID_t id, const char *name, const char *type, const char *hook, const char *peerhook);
int
ng_connect_node(const char *node, const char *ourhook, const char *peerhook);
int
ng_connect_id(ng_ID_t id, const char *ourhook, const char *peerhook);
int
ng_connect2_id(ng_ID_t id, ng_ID_t peer, const char *ourhook, const char *peerhook);
int
ng_connect2_tee_id(ng_ID_t id, ng_ID_t peer, const char *ourhook, const char *peerhook);
int
ng_rmhook(const char *ourhook);
int
ng_rmhook_id(ng_ID_t id, const char *hook);
int
ng_rmhook_tee_id(ng_ID_t id, const char *hook);
int
ng_shutdown_id(ng_ID_t id);
ng_ID_t
ng_next_node_id(ng_ID_t node, const char *type, const char *hook);
ng_ID_t
ng_node_id(const char *path);
ng_ID_t
ng_node_id_node(const char *node);
ng_ID_t
ng_node_name(ng_ID_t id, char *name);
ng_ID_t
ng_node_type(ng_ID_t id, char *type);
int
ng_peer_hook_id(ng_ID_t id, const char *hook, char *peerhook);

DESCRIPTION
The snmp_netgraph module implements a number of tables and scalars that enable remote access to the netgraph subsystem. It also exports a number of global variables and functions, that allow other modules to easily use the netgraph system.

If upon start up of the module the variable begemotNgControlNodeName is not empty the module opens a netgraph socket and names that socket node. If the variable is empty, the socket is created, as soon as the variable is written with a non-empty name. The socket can be closed by writing an empty string to the variable. The socket itself and its name are available in snmp_node and snmp_nodename.

  SENDING AND RECEIVING MESSAGES AND DATA
There are three functions for sending control message:

ng_output()
    sends a control message along the given path.

ng_output_node()
    sends a control message to the node with name node and

ng_output_id()
    sends a control message to the node with node id id.

Each of these functions takes the following arguments:

cookie
    is the node specific command cookie,

opcode
    is the node specific code for the operation to perform,

arg is a pointer to the message itself. This message must start with a struct ng_mesg.

arglen
    is the overall length of the message (header plus arguments).
The functions return the message id that can be used to match incoming responses or -1 if an error occurs.

Another class of functions is used to send a control message and to wait for a matching response. Note, that this operation blocks the daemon, so use it only if you are sure that the response will happen. There is a maximum timeout that is configurable in the MIB variable begemotNgTimeout. Other messages arriving while the functions are waiting for the response are queued and delivered on the next call to the module's idle function.

ng_dialog()
    sends a control message along the given path and waits for a matching response.

ng_dialog_node()
    sends a control message to the node with name node and waits for a matching response.

ng_dialog_id()
    sends a control message to the node with id id and waits for a matching response.

All three functions take the same arguments as the ng_output*() functions. The functions return the response message in a buffer allocated by malloc(3) or NULL in case of an error. The maximum size of the response buffer can be configured in the variable begemotNgResBufSiz.

A data message can be send with the function ng_send_data(). This function takes the name of the snmp_node's hook through which to send the data, a pointer to the message buffer and the size of the message. It returns -1 if an error happens.

  ASYNCHRONOUS CONTROL AND DATA MESSAGES
A module can register functions to asynchronously receive control and data message.

The function ng_register_cookie() registers a control message receive function. If a control message is received, that is not consumed by the dialog functions, the list of registered control message receive functions is scanned. If the cookie in the received message is the same as the cookie argument to the ng_register_cookie() call and the id argument to the ng_register_cookie() call was either 0 or equals the node id which sent the control message, the handler function func is called with a pointer to the received message, the hook on which the message was received (or NULL if it was received not on a hook), the id of the sender's node and the uarg argument of the registration call. The handler function should not modify the contents of the message, because more than one function may be registered to the same cookie and node id.

A control message registration can be undone by calling ng_unregister_cookie() with the return value of the registration call. If an error occurs while registering, ng_register_cookie() returns NULL.

A module can call ng_register_hook() to register a callback for data messages on one of the snmp_node's hooks. If a data message is received on that hook, the callback function func is called with the hook name, a pointer to the data message, the size of the message and the argument uarg to the registration function. The message should be treated as read-only. A data message registration can be undone by calling ng_unregister_hook() with the return value of the registration call. If an error occurs while registering, ng_register_hook() returns NULL.

The function ng_unregister_module() removes all control and data registrations for that module.

  FINDING NODES AND NODE CHARACTERISTICS

The function ng_node_id() returns the id of the node addressed by path or 0 if the node does not exists.

The function ng_node_id_node() returns the id of the node with name node or 0 if the node does not exist.

The function ng_node_node() retrieves the name of the node with id id and writes it to the buffer pointed to by name. This buffer should be at least NG_NODESIZ bytes long. The function returns the node id or 0 if the node is not found.

The function ng_node_type() retrieves the name of the node with id id and writes it to the buffer pointed to by type. This buffer should be at least NG_TYPESIZ bytes long. The function returns the node id or 0 if the node is not found.

The function ng_peer_hook_id() writes the name of the peer hook of the hook hook on the node with id to the buffer pointed to by peer_hook. The buffer should be at least NG_HOOKSIZ bytes long. The function returns 0 if the node and the hook is found, -1 otherwise. The function skips intermediate tee nodes (see ng_tee(4)).

The function ng_next_node_id() returns the node id of the peer node that is on the other side of hook hook of node id. If type is not NULL, the function checks, that the peer node's type is type. The function skips intermediate tee nodes (see ng_tee(4)). It returns the node id of the peer node or 0 if an error occurs or the types do not match.

  CHANGING THE GRAPH
A number of functions can be used to create or destroy nodes and hooks.

The function ng_mkpeer_id() creates a new node of type type whose hook peerhook will be connected to hook of node id. If name is not NULL the new node is named with this name. The function returns The node id of the new node or 0 if an error happens.

The functions ng_connect_node() and ng_connect_id() make a new hook connecting ourhook of the modules socket node snmp_node to peerhook of the node identified by id id or name node. The functions return 0 on success or -1 otherwise.

The function ng_connect2_id() connects hook ourhook of the node with id id to hook peerhook of the node with id peer. The functions return 0 on success or -1 otherwise. The function ng_connect2_tee_id() does the same as ng_connect2_id() except, that it puts an unnamed tee node between the two nodes.

The function ng_rmhook() removes hook hook on the module's snmp_node. The function ng_rmhook_id() removes hook hook on the node with id id. The function ng_rmhook_tee_id() additionally shuts down all tee nodes between the node and the first non-tee peer.

The function ng_shutdown_id() destroys the given node.

FILES

/usr/share/bsnmp/defs/netgraph_tree.def
    The description of the MIB tree implemented by snmp_netgraph.

/usr/share/bsnmp/mibs/BEGEMOT-NETGRAPH.txt
    This is the MIB that is implemented by this module.

SEE ALSO
gensnmptree(1), snmpmod(3)

AUTHORS
Hartmut Brandt <harti@FreeBSD.org>