ng_ksocket

NG_KSOCKET(4)             BSD Kernel Interfaces Manual             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.  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 (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 (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 (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 (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 (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 (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 (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 (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.

     Setting socket options example:

     Set FIB 2 for a socket (SOL_SOCKET, SO_SETFIB):
               setopt { level=0xffff name=0x1014 data=[ 2 ] }

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>

BSD                              January 9, 2012                             BSD