freebsd-dev/lib/libnetgraph/netgraph.3

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.\" Author: Archie Cobbs <archie@whistle.com>
.\"
.\" $FreeBSD$
.\" $Whistle: netgraph.3,v 1.7 1999/01/25 07:14:06 archie Exp $
.\"
.Dd January 19, 1999
.Dt NETGRAPH 3
.Os FreeBSD 3
.Sh NAME
.Nm NgMkSockNode ,
.Nm NgNameNode ,
.Nm NgSendMsg ,
.Nm NgRecvMsg ,
.Nm NgSendData ,
.Nm NgRecvData ,
.Nm NgSetDebug ,
.Nm NgSetErrLog
.Nd Netgraph user library
.Sh SYNOPSIS
.Fd #include <netgraph.h>
.Ft int
.Fn NgMkSockNode "const char *name" "int *csp" "int *dsp"
.Ft int
.Fn NgNameNode "int cs" "const char *path" "const char *fmt" "..."
.Ft int
.Fn NgSendMsg "int cs" "const char *path" "int cookie" "int cmd" "const void *arg" "size_t arglen"
.Ft int
.Fn NgSendMsgReply "int cs" "const char *path" "struct ng_mesg *msg" "const void *arg" "size_t arglen"
.Ft int
.Fn NgRecvMsg "int cs" "struct ng_mesg *rep" "size_t replen" "char *path"
.Ft int
.Fn NgSendData "int ds" "const char *hook" "const u_char *buf" "size_t len"
.Ft int
.Fn NgRecvData "int ds" "u_char *buf" "size_t len" "char *hook"
.Ft int
.Fn NgSetDebug "int level"
.Ft void
.Fn NgSetErrLog "void (*log)(const char *fmt, ...)" "void (*logx)(const char *fmt, ...)"
.Sh DESCRIPTION
These functions facilitate user-mode program participation in the kernel
.Xr netgraph 4
graph-based networking system, by utilizing the netgraph
.Em socket
node type (see
.Xr ng_socket 8 ")."
.Pp
.Fn NgMkSockNode
should be called first, to create a new
.Em socket
type netgraph node with associated control and data sockets.  If
.Fa name
is non-NULL, the node will have that global name assigned to it.
.Fa "*csp"
and
.Fa "*dsp"
will be set to the newly opened control and data sockets
associated with the node; either
.Fa "csp"
or
.Fa "dsp"
may be NULL if only one socket is desired.
.Pp
.Fn NgNameNode
assigns a global name to the node addressed by
.Fa path .
.Pp
.Fn NgSendMsg
sends a control message from the socket node associated with control socket
.Fa cs
to the node addressed by
.Fa path .
The
.Fa cookie
indicates how to interpret
.Fa cmd ,
which indicates a specific command.
Extra argument data (if any) is specified by
.Fa arg
and
.Fa arglen .
The
.Fa cookie ,
.Fa cmd ,
and argument data are defined by the header file corresponding
to the type of the node being addressed.
.Pp
Use
.Fn NgSendMsgReply
to send reply to a previously received control message.
The original message header should be pointed to by
.Fa msg .
.Pp
.Fn NgRecvMsg
reads the next control message received by the node associated with
control socket
.Fa cs .
The message and any extra argument data must fit in
.Fa replen
bytes.
If
.Fa "path"
is non-NULL, it must point to a buffer of at least
.Dv "NG_PATHLEN + 1"
bytes, which will be filled in (and NUL terminated) with the path to
the node from which the message was received.
.Pp
.Fn NgSendData
writes a data packet out on the specified hook of the node corresponding
to data socket
.Fa ds .
The node must already be connected to some other node via that hook.
.Pp
.Fn NgRecvData
reads the next data packet (of up to
.Fa len
bytes) received by the node corresponding to data socket
.Fa ds
and stores it in
.Fa buf ,
which must be large enough to hold the entire packet.  If
.Fa "hook"
is non-NULL, it must point to a buffer of at least
.Dv "NG_HOOKLEN + 1"
bytes, which will be filled in (and NUL terminated) with the name of
the hook on which the data was received.
.Pp
.Fn NgSetDebug
and
.Fn NgSetErrLog
are used for debugging.
.Fn NgSetDebug
sets the debug level (if non-negative), and returns the old setting.
Higher debug levels result in more verbosity.  The default is zero.
All debug and error messages are logged via the functions
specified in the most recent call to
.Fn NgSetErrLog .
The default logging functions are
.Xr vwarn 3
and
.Xr vwarnx 3 .
.Pp
Note that
.Xr select 2
can be used on the data and the control sockets to detect the presence of
incoming data and control messages, respectively.
Data and control packets are always written and read atomically, i.e.,
in one whole piece.
.Pp
User mode programs must be linked with the
.Dv -lnetgraph
flag to link in this library.
.Sh INITIALIZATION
Netgraph is not part of the standard FreeBSD kernel. To enable it,
either your kernel must be compiled with ``options NETGRAPH''
in the kernel configuration file, or else the
.Xr netgraph 4
and
.Xr ng_socket 8
KLD modules must have been loaded via
.Xr kldload 8 .
.Sh DIAGNOSTICS
All functions except
.Fn NgSetDebug
and
.Fn NgSetErrLog
return -1 if there was an error and set errno accordingly.
.Sh SEE ALSO
.Xr netgraph 4 ,
.Xr socket 2 ,
.Xr select 2 ,
.Xr warnx 3 ,
.Xr ng_socket 8 .
.Sh HISTORY
The
.Em netgraph
system was designed and first implemented at Whistle Communications, Inc.
in a version FreeBSD 2.2 customized for the Whistle InterJet.
.Sh AUTHOR
.An Archie Cobbs <archie@whistle.com>