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NETGRAPH(3)		     Library Functions Manual		     NETGRAPH(3)

NAME
     NgMkSockNode,   NgNameNode,   NgSendMsg,	NgSendAsciiMsg,  NgSendReplyMsg,
     NgRecvMsg, NgAllocRecvMsg, NgRecvAsciiMsg, NgAllocRecvAsciiMsg, NgSendData,
     NgRecvData, NgAllocRecvData, NgSetDebug, NgSetErrLog -- netgraph  user  li-
     brary

LIBRARY
     Netgraph User Library (libnetgraph, -lnetgraph)

SYNOPSIS
     #include <netgraph.h>

     int
     NgMkSockNode(const char *name, int *csp, int *dsp);

     int
     NgNameNode(int cs, const char *path, const char *fmt, ...);

     int
     NgSendMsg(int cs, const char *path, int cookie, int cmd, const void *arg,
	 size_t arglen);

     int
     NgSendAsciiMsg(int cs, const char *path, const char *fmt, ...);

     int
     NgSendReplyMsg(int cs, const char *path, struct ng_mesg *msg,
	 const void *arg, size_t arglen);

     int
     NgRecvMsg(int cs, struct ng_mesg *rep, size_t replen, char *path);

     int
     NgAllocRecvMsg(int cs, struct ng_mesg **rep, char *path);

     int
     NgRecvAsciiMsg(int cs, struct ng_mesg *rep, size_t replen, char *path);

     int
     NgAllocRecvAsciiMsg(int cs, struct ng_mesg **rep, char *path);

     int
     NgSendData(int ds, const char *hook, const u_char *buf, size_t len);

     int
     NgRecvData(int ds, u_char *buf, size_t len, char *hook);

     int
     NgAllocRecvData(int ds, u_char **buf, char *hook);

     int
     NgSetDebug(int level);

     void
     NgSetErrLog(void (*log)(const char *fmt, ...),
	 void (*logx)(const char *fmt, ...));

DESCRIPTION
     These  functions  facilitate  user-mode program participation in the kernel
     netgraph(4) graph-based networking system, by utilizing the netgraph socket
     node type (see ng_socket(4)).

     The NgMkSockNode() function should be called first, to create a new  socket
     type  netgraph  node  with associated control and data sockets.  If name is
     non-NULL, the node will have that global name assigned to it.  The csp  and
     dsp  arguments will be set to the newly opened control and data sockets as-
     sociated with the node; either csp or dsp may be NULL if only one socket is
     desired.  The NgMkSockNode() function loads the socket node type KLD if  it
     is not already loaded.

     The  NgNameNode()	function  assigns a global name to the node addressed by
     path.

     The NgSendMsg() function sends a binary control  message  from  the  socket
     node  associated with control socket cs to the node addressed by path.  The
     cookie indicates how to interpret cmd, which indicates a specific	command.
     Extra  argument  data (if any) is specified by arg and arglen.  The cookie,
     cmd, and argument data are defined by the header file corresponding to  the
     type  of  the  node  being addressed.  The unique, non-negative token value
     chosen for use in the message header is returned.	This value is  typically
     used to associate replies.

     Use  NgSendReplyMsg()  to	send reply to a previously received control mes-
     sage.  The original message header should be pointed to by msg.

     The NgSendAsciiMsg() function performs the same  function	as  NgSendMsg(),
     but  adds	support for ASCII encoding of control messages.  The NgSendAsci-
     iMsg() function formats its input a la printf(3) and then sends the result-
     ing ASCII string to the node in a NGM_ASCII2BINARY  control  message.   The
     node  returns  a  binary version of the message, which is then sent back to
     the node just as with NgSendMsg().  As with NgSendMsg(), the message  token
     value  is returned.  Note that ASCII conversion may not be supported by all
     node types.

     The NgRecvMsg() function reads the next control  message  received  by  the
     node associated with control socket cs.  The message and any extra argument
     data  must  fit  in  replen bytes.  If path is non-NULL, it must point to a
     buffer of at least NG_PATHSIZ bytes, which will be filled in (and NUL  ter-
     minated) with the path to the node from which the message was received.

     The  length of the control message is returned.  A return value of zero in-
     dicates that the socket was closed.

     The NgAllocRecvMsg() function works exactly like NgRecvMsg(),  except  that
     the  buffer for a message is dynamically allocated to guarantee that a mes-
     sage is not truncated.  The size of the buffer is equal to the socket's re-
     ceive buffer size.  The caller is responsible for freeing the  buffer  when
     it is no longer required.

     The  NgRecvAsciiMsg()  function works exactly like NgRecvMsg(), except that
     after the message is received, any binary arguments are converted to  ASCII
     by  sending  a  NGM_BINARY2ASCII request back to the originating node.  The
     result is the same as NgRecvMsg(), with the exception that the reply  argu-
     ments  field  will  contain a NUL-terminated ASCII version of the arguments
     (and the reply header argument length field will be adjusted).

     The NgAllocRecvAsciiMsg() function works exactly like NgRecvAsciiMsg(), ex-
     cept that the buffer for a message is dynamically	allocated  to  guarantee
     that  a  message  is not truncated.  The size of the buffer is equal to the
     socket's receive buffer size.  The caller is responsible  for  freeing  the
     buffer when it is no longer required.

     The NgSendData() function writes a data packet out on the specified hook of
     the  node	corresponding  to data socket ds.  The node must already be con-
     nected to some other node via that hook.

     The NgRecvData() function reads the next data packet (of up to  len  bytes)
     received  by the node corresponding to data socket ds and stores it in buf,
     which must be large enough to hold the entire packet.  If hook is non-NULL,
     it must point to a buffer of at  least  NG_HOOKSIZ  bytes,  which	will  be
     filled  in (and NUL terminated) with the name of the hook on which the data
     was received.

     The length of the packet is returned.  A return  value  of  zero  indicates
     that the socket was closed.

     The NgAllocRecvData() function works exactly like NgRecvData(), except that
     the  buffer  for a data packet is dynamically allocated to guarantee that a
     data packet is not truncated.  The size of  the  buffer  is  equal  to  the
     socket's  receive	buffer	size.  The caller is responsible for freeing the
     buffer when it is no longer required.

     The NgSetDebug() and NgSetErrLog() functions are used for	debugging.   The
     NgSetDebug()  function  sets the debug level (if non-negative), and returns
     the old setting.  Higher debug levels result in more  verbosity.	The  de-
     fault  is	zero.  All debug and error messages are logged via the functions
     specified in the most recent call to NgSetErrLog().   The	default  logging
     functions are vwarn(3) and vwarnx(3).

     At debug level 3, the library attempts to display control message arguments
     in  ASCII	format;  however, this results in additional messages being sent
     which may interfere with debugging.  At even higher levels, even these  ad-
     ditional messages will be displayed, etc.

     Note  that select(2) can be used on the data and the control sockets to de-
     tect the presence of incoming  data  and  control	messages,  respectively.
     Data  and	control packets are always written and read atomically, i.e., in
     one whole piece.

     User mode programs must be linked with the -lnetgraph flag to link in  this
     library.

INITIALIZATION
     To enable netgraph in your kernel, either your kernel must be compiled with
     options  NETGRAPH in the kernel configuration file, or else the netgraph(4)
     and ng_socket(4) KLD modules must have been loaded via kldload(8).

RETURN VALUES
     The NgSetDebug() function returns the previous debug setting.

     The NgSetErrLog() function has no return value.

     All other functions return -1 if there was an error and set  errno  accord-
     ingly.

     A	return value of zero from NgRecvMsg() or NgRecvData() indicates that the
     netgraph socket has been closed.

     For NgSendAsciiMsg() and NgRecvAsciiMsg(), the following additional  errors
     are possible:

     [ENOSYS]		The  node type does not know how to encode or decode the
			control message.

     [ERANGE]		The encoded or decoded arguments were too long	for  the
			supplied buffer.

     [ENOENT]		An  unknown structure field was seen in an ASCII control
			message.

     [EALREADY] 	The same structure field was specified twice in an ASCII
			control message.

     [EINVAL]		ASCII control message parse error or illegal value.

     [E2BIG]		ASCII control message array or fixed width string buffer
			overflow.

SEE ALSO
     select(2), socket(2), warnx(3), kld(4), netgraph(4), ng_socket(4)

HISTORY
     The netgraph system was designed and first implemented at Whistle	Communi-
     cations, Inc. in a version of FreeBSD 2.2 customized for the Whistle Inter-
     Jet.

AUTHORS
     Archie Cobbs <archie@FreeBSD.org>

FreeBSD ports 15.quarterly	  May 15, 2020			     NETGRAPH(3)

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