Skip site navigation (1)Skip section navigation (2)

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
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)).

     NgMkSockNode() 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.  *csp and *dsp
     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.
     NgMkSockNode() loads the socket node type KLD if it's not already loaded.

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

     NgSendMsg() 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.

     NgSendAsciiMsg() performs the same function as NgSendMsg(), but adds
     support for ASCII encoding of control messages.  NgSendAsciiMsg() 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.

     NgRecvMsg() 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_PATHLEN + 1 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.

     NgRecvAsciiMsg() 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).

     NgSendData() 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.

     NgRecvData() 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_HOOKLEN + 1 bytes, which will be filled
     in (and NUL terminated) with the name of the hook on which the data was

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

     NgSetDebug() and NgSetErrLog() are used for debugging.  NgSetDebug() 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 messagages 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

     NgSetDebug() returns the previous debug setting.  NgSetErrLog() 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


Want to link to this manual page? Use this URL:

home | help