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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. The process must have
55 root privileges to be able to create netgraph sockets however once created,
56 any process that has one may use it.
60 node is created by creating a new socket of type
62 in the protocol family
67 Any control messages received by the node
68 and not having a cookie value of
70 are received by the process, using
72 the socket address argument is a
73 .Dv "struct sockaddr_ng"
74 containing the sender's netgraph address. Conversely, control messages
75 can be sent to any node by calling
77 supplying the recipient's address in a
78 .Dv "struct sockaddr_ng" .
81 system call may be used to assign a global netgraph name to the node.
83 To transmit and receive netgraph data packets, a
85 socket must also be created using
90 .Dv NG_DATA sockets do not automatically
91 have nodes associated with them; they are bound to a specific node via the
93 system call. The address argument is the netgraph address of the
95 node already created. Once a data socket is associated with a node,
96 any data packets received by the node are read using
98 and any packets to be sent out from the node are written using
100 In the case of data sockets, the
101 .Dv "struct sockaddr_ng"
102 contains the name of the
104 on which the data was received or should be sent.
106 As a special case, to allow netgraph data sockets to be used as stdin or stdout
109 with a NULL sockaddr pointer, a
113 will succeed in the case where there is exactly ONE hook attached to
114 the socket node, (and thus the path is unambiguous).
116 There is a user library that simplifies using netgraph sockets; see
119 This node type supports hooks with arbitrary names (as long as
120 they are unique) and always accepts hook connection requests.
122 This node type supports the generic control messages, plus the following:
124 .It Dv NGM_SOCK_CMD_NOLINGER
125 When the last hook is removed from this node, it will shut down as
128 message. Attempts to access the sockets associated will return
130 .It Dv NGM_SOCK_CMD_LINGER
131 This is the default mode. When the last hook is removed, the node will
132 continue to exist, ready to accept new hooks until it
133 is explicitly shut down.
138 .Dv NGM_SOCKET_COOKIE
140 .Dv NGM_GENERIC_COOKIE
141 will be passed unaltered up the
145 This node type shuts down and disappears when both the associated
149 sockets have been closed, or a
151 control message is received. In the latter case, attempts to write
152 to the still-open sockets will return
155 .Dv NGM_SOCK_CMD_NOLINGER
156 message has been received, closure of the last hook will also initiate
157 a shutdown of the node.
159 It is not possible to reject the connection of a hook, though any
160 data received on that hook can certainly be ignored.
162 The controlling process is not notified of all events that an in-kernel node
163 would be notified of, e.g. a new hook, or hook removal. We should define
164 some node-initiated messages for this purpose (to be sent up the control
175 node type was implemented in
178 .An Julian Elischer Aq julian@whistle.com