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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.  Connecting 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 arguments to
     socket(2).  Alternately, aliases for the commonly used values 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 received 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, destination struct
     sockaddr must be supplied in an mbuf tag with cookie NGM_KSOCKET_COOKIE
     and type NG_KSOCKET_TAG_SOCKADDR attached to data.  Otherwise 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 supplied as an
          argument.

     NGM_KSOCKET_ACCEPT
          Equivalent to the accept(2) system call on a non-blocking 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 nothing, and a
          connected node will receive the above message asynchronously, 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 reply.

     NGM_KSOCKET_GETPEERNAME
          Equivalent to the getpeername(2) system call.  The name is returned
          as a struct sockaddr in the arguments field of the reply.

     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 argument field,
     the normal ASCII equivalent of the C structure is an acceptable form.
     For the PF_INET and PF_LOCAL address families, a more convenient 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_LOCAL, 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), socket(9)

HISTORY

     The ng_ksocket node type was implemented in FreeBSD 4.0.

AUTHORS

     Archie Cobbs 〈archie@FreeBSD.org