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NETGRAPH(3)            FreeBSD Library Functions Manual            NETGRAPH(3)

     NgMkSockNode, NgNameNode, NgSendMsg, NgRecvMsg, NgSendData, NgRecvData,
     NgSetDebug, NgSetErrLog - netgraph user library

     Netgraph User Library (libnetgraph, -lnetgraph)

     #include <netgraph.h>

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

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

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

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

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

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

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

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

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

     NgSetDebug(int level);

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

     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's not already loaded.

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

     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 NgSendMsgReply() to send reply to a previously received control
     message.  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
     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 terminated) with the path to the node from which the message was

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

     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 NgRecvAsciiMsg(), with the exception that the
     reply arguments field will contain a NUL-terminated ASCII version of the
     arguments (and the reply header argument length field will be adjusted).

     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 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
     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 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.

     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

     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 accordingly.  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.

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

     The netgraph system was designed and first implemented at Whistle
     Communications, Inc. in a version of FreeBSD 2.2 customized for the
     Whistle InterJet.

     Archie Cobbs <>

FreeBSD 11.0-PRERELEASE        January 19, 1999        FreeBSD 11.0-PRERELEASE


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