NETGRAPH(3) BSD Library Functions Manual NETGRAPH(3)NAME
NgMkSockNode, NgNameNode, NgSendMsg, NgSendAsciiMsg, NgSendReplyMsg,
NgRecvMsg, NgRecvAsciiMsg, NgSendData, NgRecvData, NgSetDebug,
NgSetErrLog — netgraph 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
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
NgRecvAsciiMsg(int cs, struct ng_mesg *rep, size_t replen, 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
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)).
NgMkSockNode() should be called first, to create a new socket type net‐
graph 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 associ‐
ated 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.
NgSendAsciiMsg() performs the same function as NgSendMsg(), but adds sup‐
port 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 associ‐
ated 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 termi‐
nated) 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.
NgRecvAsciiMsg() works exactly like NgRecvMsg(), except that after the
message is received, any binary arguments are converted to ASCII by send‐
ing a NGM_BINARY2ASCII request back to the originating node. The result
is the same as NgRecvAsciiMsg(), 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).
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_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.
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 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 VALUESNgSetDebug() 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 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 ALSOselect(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@whistle.com⟩
BSD January 19, 1999 BSD
