freebsd-nq/usr.sbin/bsnmpd/modules/snmp_netgraph/snmp_netgraph.3

.\"
.\" Copyright (c) 2001-2003
.\"	Fraunhofer Institute for Open Communication Systems (FhG Fokus).
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.\" Author: Harti Brandt <harti@freebsd.org>
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.Dd November 14, 2003
.Dt SNMP_NETGRAPH 3
.Os
.Sh NAME
.Nm snmp_netgraph ,
.Nm snmp_node ,
.Nm snmp_nodename ,
.Nm ng_cookie_f ,
.Nm ng_hook_f ,
.Nm ng_register_cookie ,
.Nm ng_unregister_cookie ,
.Nm ng_register_hook ,
.Nm ng_unregister_hook ,
.Nm ng_unregister_module ,
.Nm ng_output ,
.Nm ng_output_node ,
.Nm ng_output_id ,
.Nm ng_dialog ,
.Nm ng_dialog_node ,
.Nm ng_dialog_id ,
.Nm ng_send_data ,
.Nm ng_mkpeer_id ,
.Nm ng_connect_node ,
.Nm ng_connect_id ,
.Nm ng_connect2_id ,
.Nm ng_connect2_tee_id ,
.Nm ng_rmhook ,
.Nm ng_rmhook_id ,
.Nm ng_rmhook_tee_id ,
.Nm ng_shutdown_id ,
.Nm ng_next_node_id ,
.Nm ng_node_id ,
.Nm ng_node_id_node ,
.Nm ng_node_name ,
.Nm ng_node_type ,
.Nm ng_peer_hook_id
.Nd "netgraph module for snmpd.
.Sh LIBRARY
.Pq begemotSnmpdModulePath."netgraph" = "/usr/lib/snmp_netgraph.so"
.Sh SYNOPSIS
.In bsnmp/snmpmod.h
.In bsnmp/snmp_netgraph.h
.Vt extern ng_ID_t snmp_node ;
.Vt extern u_char *snmp_nodename ;
.Ft typedef void
.Fn ng_cookie_f "const struct ng_mesg *mesg" "const char *path" "ng_ID_t id" "void *uarg"
.Ft typedef void
.Fn ng_hook_f "const char *hook" "const u_char *mesg" "size_t len" "void *uarg"
.Ft void *
.Fn ng_register_cookie "const struct lmodule *mod" "u_int32_t cookie" "ng_ID_t id" "ng_cookie_f *func" "void *uarg"
.Ft void
.Fn ng_unregister_cookie "void *reg"
.Ft void *
.Fn ng_register_hook "const struct lmodule *mod" "const char *hook" "ng_hook_f *func" "void *uarg"
.Ft void
.Fn ng_unregister_hook "void *reg"
.Ft void
.Fn ng_unregister_module "const struct lmodule *mod"
.Ft int
.Fn ng_output "const char *path" "u_int cookie" "u_int opcode" "const void *arg" "size_t arglen"
.Ft int
.Fn ng_output_node "const char *node" "u_int cookie" "u_int opcode" "const void *arg" "size_t arglen"
.Ft int
.Fn ng_output_id "ng_ID_t node" "u_int cookie" "u_int opcode" "const void *arg" "size_t arglen"
.Ft struct ng_mesg *
.Fn ng_dialog "const char *path" "u_int cookie" "u_int opcode" "const void *arg" "size_t arglen"
.Ft struct ng_mesg *
.Fn ng_dialog_node "const char *node" "u_int cookie" "u_int opcode" "const void *arg" "size_t arglen"
.Ft struct ng_mesg *
.Fn ng_dialog_id "ng_ID_t id" "u_int cookie" "u_int opcode" "const void *arg" "size_t arglen"
.Ft int
.Fn ng_send_data "const char *hook" "const void *sndbuf" "size_t sndlen"
.Ft ng_ID_t
.Fn ng_mkpeer_id "ng_ID_t id" "const char *name" "const char *type" "const char *hook" "const char *peerhook"
.Ft int
.Fn ng_connect_node "const char *node" "const char *ourhook" "const char *peerhook"
.Ft int
.Fn ng_connect_id "ng_ID_t id" "const char *ourhook" "const char *peerhook"
.Ft int
.Fn ng_connect2_id "ng_ID_t id" "ng_ID_t peer" "const char *ourhook" "const char *peerhook"
.Ft int
.Fn ng_connect2_tee_id "ng_ID_t id" "ng_ID_t peer" "const char *ourhook" "const char *peerhook"
.Ft int
.Fn ng_rmhook "const char *ourhook"
.Ft int
.Fn ng_rmhook_id "ng_ID_t id" "const char *hook"
.Ft int
.Fn ng_rmhook_tee_id "ng_ID_t id" "const char *hook"
.Ft int
.Fn ng_shutdown_id "ng_ID_t id"
.Ft ng_ID_t
.Fn ng_next_node_id "ng_ID_t node" "const char *type" "const char *hook"
.Ft ng_ID_t
.Fn ng_node_id "const char *path"
.Ft ng_ID_t
.Fn ng_node_id_node "const char *node"
.Ft ng_ID_t
.Fn ng_node_name "ng_ID_t id" "char *name"
.Ft ng_ID_t
.Fn ng_node_type "ng_ID_t id" "char *type"
.Ft int
.Fn ng_peer_hook_id "ng_ID_t id" "const char *hook" "char *peerhook"
.Sh DESCRIPTION
The
.Nm 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.
.Pp
If upon start up of the module the variable
.Va 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
.Va snmp_node
and
.Va snmp_nodename .
.Ss SENDING AND RECEIVING MESSAGES AND DATA
There are three functions for sending control message:
.Bl -tag -width ".It Fn ng_output_node"
.It Fn ng_output
sends a control message along the given
.Fa path .
.It Fn ng_output_node
sends a control message to the node with name
.Fa node
and
.It Fn ng_output_id
sends a control message to the node with node id
.Fa id .
.El
.Pp
Each of these functions takes the following arguments:
.Bl -tag -width ".It Fa cookie"
.It Fa cookie
is the node specific command cookie,
.It Fa opcode
is the node specific code for the operation to perform,
.It Fa arg
is a pointer to the message itself.
This message must start with a
.Vt struct ng_mesg .
.It Fa arglen
is the overall length of the message (header plus arguments).
.El
The functions return the message id that can be used to match incoming responses
or -1 if an error occurs.
.Pp
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
.Va 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.
.Bl -tag -width ".It Fn ng_output_node"
.It Fn ng_dialog
sends a control message along the given
.Fa path
and waits for a matching response.
.It Fn ng_dialog_node
sends a control message to the node with name
.Fa node
and waits for a matching response.
.It Fn ng_dialog_id
sends a control message to the node with id
.Fa id
and waits for a matching response.
.El
.Pp
All three functions take the same arguments as the
.Fn ng_output*
functions.
The functions return the response message in a buffer allocated by
.Xr malloc 3
or NULL in case of an error.
The maximum size of the response buffer can be
configured in the variable
.Va begemotNgResBufSiz .
.Pp
A data message can be send with the function
.Fn ng_send_data .
This function takes the name of the
.Va snmp_node Ns '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.
.Ss ASYNCHRONOUS CONTROL AND DATA MESSAGES
A module can register functions to asynchronously receive control and data
message.
.Pp
The function
.Fn 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
.Fa cookie
argument to the
.Fn ng_register_cookie
call and the
.Fa id
argument to the
.Fn ng_register_cookie
call was either 0 or equals the node id which sent the control message, the
handler function
.Fa 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
.Fa 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.
.Pp
A control message registration can be undone by calling
.Fn ng_unregister_cookie
with the return value of the registration call.
If an error occurs while registering,
.Fn ng_register_cookie
returns NULL.
.Pp
A module can call
.Fn ng_register_hook
to register a callback for data messages on one of the
.Va snmp_node Ns 's
hooks.
If a data message is received on that hook, the callback function
.Fa func
is called with the hook name, a pointer to the data message, the size of
the message and the argument
.Fa uarg
to the registration function.
The message should be treated as read-only.
A data message registration can be undone by calling
.Fn ng_unregister_hook
with the return value of the registration call.
If an error occurs while registering,
.Fn ng_register_hook
returns NULL.
.Pp
The function
.Fn ng_unregister_module
removes all control and data registrations for that module.
.Ss FINDING NODES AND NODE CHARACTERISTICS
.Pp
The function
.Fn ng_node_id
returns the id of the node addressed by
.Fa path
or 0 if the node does not exists.
.Pp
The function
.Fn ng_node_id_node
returns the id of the node with name
.Fa node
or 0 if the node does not exist.
.Pp
The function
.Fn ng_node_node
retrieves the name of the node with id
.Fa id
and writes it to the buffer pointed to by
.Fa name .
This buffer should be at least
.Li NG_NODESIZ
bytes long.
The function returns the node id or 0 if the
node is not found
.Pp
The function
.Fn ng_node_type
retrieves the name of the node with id
.Fa id
and writes it to the buffer pointed to by
.Fa type .
This buffer should be at least
.Li NG_TYPESIZ
bytes long.
The function returns the node id or 0 if the
node is not found.
.Pp
The function
.Fn ng_peer_hook_id
writes the name of the peer hook of the hook
.Fa hook
on the node with
.Fa id
to the buffer pointed to by
.Fa peer_hook .
The buffer should be at least
.Li 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
.Xr ng_tee 4 ) .
.Pp
The function
.Fn ng_next_node_id
returns the node id of the peer node that is on the other side of hook
.Fa hook
of node
.Fa id .
If
.Fa type
is not NULL, the function checks, that the peer node's type is
.Fa type .
The function skips intermediate tee nodes (see
.Xr ng_tee 4 ) .
It returns the node id of the peer node or 0 if an error occurs or the
types do not match.
.Ss CHANGING THE GRAPH
A number of functions can be used to create or destroy nodes and hooks.
.Pp
The function
.Fn ng_mkpeer_id
creates a new node of type
.Fa type
whose hook
.Fa peerhook
will be connected to
.Fa hook
of node
.Fa id .
If
.Fa 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.
.Pp
The functions
.Fn ng_connect_node
and
.Fn ng_connect_id
make a new hook connecting
.Fa ourhook
of the modules socket node
.Va snmp_node
to
.Fa peerhook
of the node identified by id
.Fa id
or name
.Fa node .
The functions return 0 on success or -1 otherwise.
.Pp
The function
.Fn ng_connect2_id
connects hook
.Fa ourhook
of the node with id
.Fa id
to hook
.Fa peerhook
of the node with id
.Fa peer .
The functions return 0 on success or -1 otherwise.
The function
.Fn ng_connect2_tee_id does the same as
.Fn ng_connect2_id
except, that it puts an unnamed tee node between the two nodes.
.Pp
The function
.Fn ng_rmhook
removes hook
.Fa hook
on the module's
.Va snmp_node .
The function
.Fn ng_rmhook_id
removes hook
.Fa hook
on the node with id
.Fa id .
The function
.Fn ng_rmhook_tee_id
additionally shuts down all tee nodes between the node and the first non-tee
peer.
.Pp
The function
.Fn ng_shutdown_id
destroys the given node.
.Sh FILES
.Bl -tag -width "XXXXXXXXX"
.It Pa /usr/share/bsnmp/defs/netgraph_tree.def
The description of the MIB tree implemented by
.Nm .
.It Pa /usr/share/bsnmp/mibs/BEGEMOT-NETGRAPH.txt
This is the MIB that is implemented by this module.
.El
.Sh SEE ALSO
.Xr gensnmptree 1 ,
.Xr snmpmod 3
.Sh AUTHORS
.An Hartmut Brandt Aq harti@freebsd.org