179 lines
6.0 KiB
Groff
179 lines
6.0 KiB
Groff
.\" Copyright (c) 1996-1999 Whistle Communications, Inc.
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.\" All rights reserved.
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.\"
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.\" Subject to the following obligations and disclaimer of warranty, use and
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.\" redistribution of this software, in source or object code forms, with or
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.\" without modifications are expressly permitted by Whistle Communications;
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.\" provided, however, that:
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.\" 1. Any and all reproductions of the source or object code must include the
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.\" copyright notice above and the following disclaimer of warranties; and
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.\" 2. No rights are granted, in any manner or form, to use Whistle
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.\" Communications, Inc. trademarks, including the mark "WHISTLE
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.\" COMMUNICATIONS" on advertising, endorsements, or otherwise except as
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.\" such appears in the above copyright notice or in the software.
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.\"
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.\" THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
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.\" TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
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.\" REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
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.\" INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
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.\" WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
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.\" REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
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.\" SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
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.\" IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
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.\" RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
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.\" WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
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.\" PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
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.\" OF SUCH DAMAGE.
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.\"
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.\" Author: Archie Cobbs <archie@whistle.com>
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.\"
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.\" $FreeBSD$
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.\" $Whistle: ng_socket.8,v 1.5 1999/01/25 23:46:27 archie Exp $
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.\"
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.Dd January 19, 1999
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.Dt NG_SOCKET 8
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.Os FreeBSD
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.Sh NAME
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.Nm ng_socket
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.Nd netgraph socket node type
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.Sh SYNOPSIS
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.Fd #include <netgraph/ng_message.h>
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.Fd #include <netgraph/ng_socket.h>
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.Sh DESCRIPTION
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A
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.Nm socket
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node is both a BSD socket and a netgraph node. The
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.Nm
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node type allows user-mode processes to participate in the kernel
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.Xr netgraph 4
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networking subsystem using the BSD socket interface. The process must have
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root privileges to be able to create netgraph sockets however once created,
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any process that has one may use it.
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.Pp
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A new
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.Nm
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node is created by creating a new socket of type
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.Dv NG_CONTROL
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in the protocol family
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.Dv PF_NETGRAPH ,
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using the
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.Xr socket 2
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system call.
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Any control messages received by the node
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and not having a cookie value of
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.Dv NGM_SOCKET_COOKIE
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are received by the process, using
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.Xr recvfrom 2 ;
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the socket address argument is a
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.Dv "struct sockaddr_ng"
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containing the sender's netgraph address. Conversely, control messages
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can be sent to any node by calling
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.Xr sendto 2 ,
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supplying the recipient's address in a
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.Dv "struct sockaddr_ng" .
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The
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.Xr bind 2
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system call may be used to assign a global netgraph name to the node.
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.Pp
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To transmit and receive netgraph data packets, a
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.Dv NG_DATA
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socket must also be created using
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.Xr socket 2
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and associated with a
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.Nm
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node.
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.Dv NG_DATA sockets do not automatically
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have nodes associated with them; they are bound to a specific node via the
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.Xr connect 2
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system call. The address argument is the netgraph address of the
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.Nm
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node already created. Once a data socket is associated with a node,
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any data packets received by the node are read using
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.Xr recvfrom 2
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and any packets to be sent out from the node are written using
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.Xr sendto 2 .
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In the case of data sockets, the
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.Dv "struct sockaddr_ng"
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contains the name of the
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.Em hook
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on which the data was received or should be sent.
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.Pp
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As a special case, to allow netgraph data sockets to be used as stdin or stdout
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on naive programs, a
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.Xr sendto 2
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with a NULL sockaddr pointer, a
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.Xr send 2
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or a
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.Xr write 2
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will succeed in the case where there is exactly ONE hook attached to
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the socket node, (and thus the path is unambiguous).
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.Pp
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There is a user library that simplifies using netgraph sockets; see
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.Xr netgraph 3 .
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.Sh HOOKS
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This node type supports hooks with arbitrary names (as long as
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they are unique) and always accepts hook connection requests.
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.Sh CONTROL MESSAGES
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This node type supports the generic control messages, plus the following:
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.Bl -tag -width foo
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.It Dv NGM_SOCK_CMD_NOLINGER
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When the last hook is removed from this node, it will shut down as
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if it had received a
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.Dv NGM_SHUTDOWN
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message. Attempts to access the sockets associated will return
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.Er ENOTCONN .
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.It Dv NGM_SOCK_CMD_LINGER
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This is the default mode. When the last hook is removed, the node will
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continue to exist, ready to accept new hooks until it
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is explicitly shut down.
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.El
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.Pp
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All other messages
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with neither the
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.Dv NGM_SOCKET_COOKIE
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or
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.Dv NGM_GENERIC_COOKIE
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will be passed unaltered up the
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.Dv NG_CONTROL
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socket.
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.Sh SHUTDOWN
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This node type shuts down and disappears when both the associated
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.Dv NG_CONTROL
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and
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.Dv NG_DATA
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sockets have been closed, or a
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.Dv NGM_SHUTDOWN
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control message is received. In the latter case, attempts to write
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to the still-open sockets will return
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.Er ENOTCONN .
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If the
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.Dv NGM_SOCK_CMD_NOLINGER
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message has been received, closure of the last hook will also initiate
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a shutdown of the node.
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.Sh BUGS
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It is not possible to reject the connection of a hook, though any
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data received on that hook can certainly be ignored.
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.Pp
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The controlling process is not notified of all events that an in-kernel node
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would be notified of, e.g. a new hook, or hook removal. We should define
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some node-initiated messages for this purpose (to be sent up the control
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socket).
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.Sh SEE ALSO
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.Xr socket 2 ,
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.Xr netgraph 3 ,
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.Xr netgraph 4 ,
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.Xr ng_ksocket 8 ,
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.Xr ngctl 8 .
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.Sh HISTORY
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The
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.Nm
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node type was implemented in
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.Fx 4.0 .
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.Sh AUTHORS
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.An Julian Elischer Aq julian@whistle.com
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