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NETGRAPH(3)		 BSD Library Functions Manual		   NETGRAPH(3)

NAME
     NgMkSockNode, NgNameNode, NgSendMsg, NgSendAsciiMsg, NgSendMsgReply,
     NgRecvMsg, NgAllocRecvMsg, NgRecvAsciiMsg, NgAllocRecvAsciiMsg,
     NgSendData, NgRecvData, NgAllocRecvData, NgSetDebug, NgSetErrLog — net‐
     graph user library

LIBRARY
     library “libnetgraph”

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
     NgSendMsgReply(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 associated 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 corre‐
     sponding to the type of the node being addressed.	The unique, non-nega‐
     tive token value chosen for use in the message header is returned.	 This
     value is typically used to associate replies.

     Use NgSendMsgReply() 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
     NgSendAsciiMsg() function formats its input a la printf(3) and then sends
     the resulting ASCII string to the node in a NGM_ASCII2BINARY control mes‐
     sage.  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 argu‐
     ment 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 terminated) 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
     indicates 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
     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 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
     arguments field will contain a NUL-terminated ASCII version of the argu‐
     ments (and the reply header argument length field will be adjusted).

     The NgAllocRecvAsciiMsg() function works exactly like NgRecvAsciiMsg(),
     except that the buffer for a message is dynamically allocated to guaran‐
     tee 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
     connected 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
     default is zero.  All debug and error messages are logged via the func‐
     tions 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 argu‐
     ments in ASCII format; however, this results in additional messages being
     sent which may interfere with debugging.  At even higher levels, even
     these additional messages will be displayed, etc.

     Note that select(2) can be used on the data and the control sockets to
     detect 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 con‐
			trol 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 buf‐
			fer 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 Commu‐
     nications, Inc. in a version of FreeBSD 2.2 customized for the Whistle
     InterJet.

AUTHORS
     Archie Cobbs ⟨archie@FreeBSD.org⟩

BSD			       January 27, 2004				   BSD
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