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33 .\" Author: Archie Cobbs <archie@whistle.com>
36 .\" $Whistle: ng_socket.8,v 1.5 1999/01/25 23:46:27 archie Exp $
43 .Nd netgraph socket node type
45 .Fd #include <netgraph/ng_message.h>
46 .Fd #include <netgraph/ng_socket.h>
50 node is both a BSD socket and a netgraph node. The
52 node type allows user-mode processes to participate in the kernel
54 networking subsystem using the BSD socket interface.
58 node is created by creating a new socket of type
60 in the protocol family
65 Any control messages received by the node
66 and not having a cookie value of
68 are received by the process, using
70 the socket address argument is a
71 .Dv "struct sockaddr_ng"
72 containing the sender's netgraph address. Conversely, control messages
73 can be sent to any node by calling
75 supplying the recipient's address in a
76 .Dv "struct sockaddr_ng" .
79 system call may be used to assign a global netgraph name to the node.
81 To transmit and receive netgraph data packets, a
83 socket must also be created using
88 .Dv NG_DATA sockets do not automatically
89 have nodes associated with them; they are bound to a specific node via the
91 system call. The address argument is the netgraph address of the
93 node already created. Once a data socket is associated with a node,
94 any data packets received by the node are read using
96 and any packets to be sent out from the node are written using
98 In the case of data sockets, the
99 .Dv "struct sockaddr_ng"
100 contains the name of the
102 on which the data was received or should be sent.
104 There is a user library that simplifies using netgraph sockets; see
107 This node type supports hooks with arbitrary names (as long as
108 they are unique) and always accepts hook connection requests.
110 This node type supports the generic control messages, plus the following:
112 .It Dv NGM_SOCK_CMD_NOLINGER
113 When the last hook is removed from this node, it will shut down as
116 message. Attempts to access the sockets associated will return
118 .It Dv NGM_SOCK_CMD_LINGER
119 This is the default mode. When the last hook is removed, the node will
120 continue to exist, ready to accept new hooks until it
121 is explicitly shut down.
126 .Dv NGM_SOCKET_COOKIE
128 .Dv NGM_GENERIC_COOKIE
129 will be passed unaltered up the
133 This node type shuts down and disappears when both the associated
137 sockets have been closed, or a
139 control message is received. In the latter case, attempts to write
140 to the still-open sockets will return
143 .Dv NGM_SOCK_CMD_NOLINGER
144 message has been received, closure of the last hook will also initiate
145 a shutdown of the node.
147 It is not possible to reject the connection of a hook, though any
148 data received on that hook can certainly be ignored.
150 The controlling process is not notified of all events that an in-kernel node
151 would be notified of, e.g. a new hook, or hook removal. We should define
152 some node-initiated messages for this purpose (to be sent up the control
161 Julian Elischer <julian@whistle.com>