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

BSD