netgraph(3)

NAME

NgMkSockNode, NgNameNode, NgSendMsg, NgSendAsciiMsg,

NgSendMsgReply

NgRecvMsg, NgAllocRecvMsg, NgRecvAsciiMsg,

NgAllocRecvAsciiMsg

NgSendData, NgRecvData, NgAllocRecvData, NgSetDebug,

NgSetErrLog

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 cre

ate a new
socket type netgraph node with associated control and data

sockets. If
name is non-NULL, the node will have that global name as

signed 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 corresponding to the type of the node being addressed. The

unique, non-negative token value chosen for use in the message header is re

turned. 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

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 re

ceived 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
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

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 NgRecvAsciiMsg() function works exactly like

NgRecvMsg

after the message is received, any binary arguments are con

verted 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 arguments (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 allocat

ed 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
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 ze

ro indicates
that the socket was closed.

The NgAllocRecvData() function works exactly like

NgRecvData

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-nega

tive), and returns
the old setting. Higher debug levels result in more ver

bosity. 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 atomi

cally, 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 set

ting.

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() in

dicates that
the netgraph socket has been closed.

For NgSendAsciiMsg() and NgRecvAsciiMsg(), the following ad

ditional
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 il

legal 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 Communications, Inc. in a version of FreeBSD 2.2 customized for

the Whistle
InterJet.

AUTHORS

Archie Cobbs <archie@FreeBSD.org>

BSD January 27, 2004

BSD