ng_ksocket(4)

NAME

ng_ksocket - kernel socket netgraph node type

SYNOPSIS

#include <sys/types.h>
#include <netgraph/ng_ksocket.h>

DESCRIPTION

A ksocket node is both a netgraph node and a BSD socket.
The ng_ksocket
node type allows one to open a socket inside the kernel and
have it
appear as a Netgraph node. The ng_ksocket node type is the
reverse of
the socket node type (see ng_socket(4)): whereas the socket
node type
enables the user-level manipulation (via a socket) of what
is normally a
kernel-level entity (the associated Netgraph node), the
ng_ksocket node
type enables the kernel-level manipulation (via a Netgraph
node) of what
is normally a user-level entity (the associated socket).
A ng_ksocket node allows at most one hook connection. Con
necting to the
node is equivalent to opening the associated socket. The
name given to
the hook determines what kind of socket the node will open
(see below).
When the hook is disconnected and/or the node is shutdown,
the associated
socket is closed.

HOOKS

This node type supports a single hook connection at a time.
The name of
the hook must be of the form <family>/<type>/<proto>, where
the family,
type, and proto are the decimal equivalent of the same argu
ments to
socket(2). Alternately, aliases for the commonly used val
ues are
accepted as well. For example inet/dgram/udp is a more
readable but
equivalent version of 2/2/17.
Data received into socket is sent out via hook. Data re
ceived on hook is
sent out from socket, if the latter is connected (an
NGM_KSOCKET_CONNECT
was sent to node before). If socket is not connected, des
tination struct
sockaddr must be supplied in an mbuf tag with cookie
NGM_KSOCKET_COOKIE
and type NG_KSOCKET_TAG_SOCKADDR attached to data. Other
wise ng_ksocket
will return ENOTCONN to sender.

CONTROL MESSAGES

This node type supports the generic control messages, plus
the following:
NGM_KSOCKET_BIND
This functions exactly like the bind(2) system call.
The struct
sockaddr socket address parameter should be supplied as
an argument.
NGM_KSOCKET_LISTEN
This functions exactly like the listen(2) system call.
The backlog
parameter (a single 32 bit int) should be supplied as
an argument.
NGM_KSOCKET_CONNECT
This functions exactly like the connect(2) system call.
The struct
sockaddr destination address parameter should be sup
plied as an
argument.
NGM_KSOCKET_ACCEPT
Equivalent to the accept(2) system call on a non-block
ing socket.
If there is a pending connection on the queue, a new
socket and a
corresponding cloned node are created. Returned are
the cloned
node's ID and a peer name (as struct sockaddr). If
there are no
pending connections, this control message returns noth
ing, and a
connected node will receive the above message asyn
chronously, when a
connection is established.
A cloned node supports a single hook with an arbitrary
name. If not
connected, a node disappears when its parent node is
destroyed.
Once connected, it becomes an independent node.
NGM_KSOCKET_GETNAME
Equivalent to the getsockname(2) system call. The name
is returned
as a struct sockaddr in the arguments field of the re
ply.
NGM_KSOCKET_GETPEERNAME
Equivalent to the getpeername(2) system call. The name
is returned
as a struct sockaddr in the arguments field of the re
ply.
NGM_KSOCKET_SETOPT
Equivalent to the setsockopt(2) system call, except
that the option
name, level, and value are passed in a struct
ng_ksocket_sockopt.
NGM_KSOCKET_GETOPT
Equivalent to the getsockopt(2) system call, except
that the option
is passed in a struct ng_ksocket_sockopt. When sending
this command, the value field should be empty; upon return, it
will contain
the retrieved value.

ASCII FORM CONTROL MESSAGES

For control messages that pass a struct sockaddr in the ar
gument field,
the normal ASCII equivalent of the C structure is an accept
able form.
For the PF_INET and PF_LOCAL address families, a more conve
nient form is
also used, which is the protocol family name, followed by a
slash, followed by the actual address. For PF_INET, the address is an
IP address
followed by an optional colon and port number. For PF_LO
CAL, the address
is the pathname as a doubly quoted string.
Examples:
PF_LOCAL local/"/tmp/foo.socket"
PF_INET inet/192.168.1.1:1234
Other { family=16 len=16 data=[0x70 0x00 0x01 0x23] }
For control messages that pass a struct ng_ksocket_sockopt,
the normal
ASCII form for that structure is used. In the future, more
convenient
encoding of the more common socket options may be supported.

SHUTDOWN

This node shuts down upon receipt of a NGM_SHUTDOWN control
message, or
when the hook is disconnected. Shutdown of the node closes
the associated socket.

SEE ALSO

socket(2), netgraph(4), ng_socket(4), ngctl(8), mbuf_tags(9)

HISTORY

The ng_ksocket node type was implemented in FreeBSD 4.0.

AUTHORS

Archie Cobbs <archie@FreeBSD.org>
BSD October 28, 2005
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