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33 .\" Author: Archie Cobbs <archie@FreeBSD.org>
35 .\" $FreeBSD: src/share/man/man4/ng_socket.4,v 1.14.2.1 2001/12/21 09:00:51 ru Exp $
36 .\" $DragonFly: src/share/man/man4/ng_socket.4,v 1.4 2006/05/26 21:39:39 swildner Exp $
37 .\" $Whistle: ng_socket.8,v 1.5 1999/01/25 23:46:27 archie Exp $
44 .Nd netgraph socket node type
46 .In netgraph/ng_message.h
47 .In netgraph/socket/ng_socket.h
53 socket and a netgraph node. The
55 node type allows user-mode processes to participate in the kernel
57 networking subsystem using the
59 socket interface. The process must have
60 root privileges to be able to create netgraph sockets however once created,
61 any process that has one may use it.
65 node is created by creating a new socket of type
67 in the protocol family
72 Any control messages received by the node
73 and not having a cookie value of
75 are received by the process, using
77 the socket address argument is a
78 .Dv "struct sockaddr_ng"
79 containing the sender's netgraph address. Conversely, control messages
80 can be sent to any node by calling
82 supplying the recipient's address in a
83 .Dv "struct sockaddr_ng" .
86 system call may be used to assign a global netgraph name to the node.
88 To transmit and receive netgraph data packets, a
90 socket must also be created using
95 .Dv NG_DATA sockets do not automatically
96 have nodes associated with them; they are bound to a specific node via the
98 system call. The address argument is the netgraph address of the
100 node already created. Once a data socket is associated with a node,
101 any data packets received by the node are read using
103 and any packets to be sent out from the node are written using
105 In the case of data sockets, the
106 .Dv "struct sockaddr_ng"
107 contains the name of the
109 on which the data was received or should be sent.
111 As a special case, to allow netgraph data sockets to be used as stdin or stdout
114 with a NULL sockaddr pointer, a
118 will succeed in the case where there is exactly ONE hook attached to
119 the socket node, (and thus the path is unambiguous).
121 There is a user library that simplifies using netgraph sockets; see
124 This node type supports hooks with arbitrary names (as long as
125 they are unique) and always accepts hook connection requests.
127 This node type supports the generic control messages, plus the following:
129 .It Dv NGM_SOCK_CMD_NOLINGER
130 When the last hook is removed from this node, it will shut down as
133 message. Attempts to access the sockets associated will return
135 .It Dv NGM_SOCK_CMD_LINGER
136 This is the default mode. When the last hook is removed, the node will
137 continue to exist, ready to accept new hooks until it
138 is explicitly shut down.
143 .Dv NGM_SOCKET_COOKIE
145 .Dv NGM_GENERIC_COOKIE
146 will be passed unaltered up the
150 This node type shuts down and disappears when both the associated
154 sockets have been closed, or a
156 control message is received. In the latter case, attempts to write
157 to the still-open sockets will return
160 .Dv NGM_SOCK_CMD_NOLINGER
161 message has been received, closure of the last hook will also initiate
162 a shutdown of the node.
172 node type was implemented in
175 .An Julian Elischer Aq julian@FreeBSD.org
177 It is not possible to reject the connection of a hook, though any
178 data received on that hook can certainly be ignored.
180 The controlling process is not notified of all events that an in-kernel node
181 would be notified of, e.g. a new hook, or hook removal. We should define
182 some node-initiated messages for this purpose (to be sent up the control