strlog(7) strlog(7)
NAME [Toc] [Back]
strlog - STREAMS log driver
DESCRIPTION [Toc] [Back]
The STREAMS log driver allows user-level processes and STREAMS drivers
and modules to perform error logging and event tracing. These tasks
are done via a user interface and a kernel interface. Further, the
STREAMS log driver delivers error logging and event tracing messages
to the Network Tracing and Logging Facility (NetTL) (see nettl(1M),
netfmt(1M), and nettlconf(1M)).
The interface that this driver presents to user-level processes is a
subset of the ioctl() system calls and STREAMS message formats. These
processes can be error loggers, trace loggers, or other user
processes, that generate error or event messages. The user interface
collects log messages from the log driver, and also generates log
messages from user processes.
The driver also accepts log messages from STREAMS drivers and modules
in the kernel via its function call interface. The kernel interface
enters requests or calls from STREAMS drivers and modules into log
messages.
The log messages accepted by the log driver are also delivered to
NetTL. NetTL can be used to control which types of messages to log,
and to format and filter the logged messages.
Kernel Interface [Toc] [Back]
STREAMS drivers and modules generate log messages by calls to the
strlog function.
#include <sys/strlog.h>
int strlog (mid, sid, level, flags, fmt [, value ]...);
short mid;
short sid;
char level;
ushort flags;
char *fmt;
int value;
mid specifies the STREAMS module ID number for the driver or
module submitting the log message.
sid specifies the sub-ID number of a minor device associated
with the STREAMS module or driver identified by mid.
level specifies a level for screening lower-level event messages
from a tracer.
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strlog(7) strlog(7)
flags contains several flags that can be set in various
combinations. The flags are as follows:
SL_ERROR The message is for the error logger.
SL_TRACE The message is for the tracer.
SL_CONSOLE The message will be printed to the
console.
SL_FATAL Provides a notification of a fatal
error.
SL_NOTIFY Makes a request to mail a copy of a
message to the system administrator.
The following are additional flags. These flags are
not used by strerr or strace. However, they are used
to map STREAMS messages to NetTL messages as described
below in "STREAMS-NetTL Link" section.
SL_WARN The message is a warning.
SL_NOTE The message is a note.
fmt is a printf style format string. This accepts the %x, %l,
%o, %u, %d, %c, and %s conversion specifications.
values are numeric or character arguments for the format string.
There is no maximum number of arguments that can be
specified.
User Interface [Toc] [Back]
User processes access the log driver with an open() call to
/dev/strlog. Each open to the device will obtain a separate stream.
After a process opens /dev/strlog, it indicates whether it is an error
logger or trace logger. It does this by issuing an I_STR ioctl()
system call with the appropriate value in the ic_cmd field of the
strioctl structure, and the appropriate data and control information
in a trace_ids structure:
struct trace_ids {
short ti_mid;
short ti_sid;
char ti_level;
short ti_flags;
};
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strlog(7) strlog(7)
The values for ic_cmd are:
I_ERRLOG Indicates an error logger. No trace_ids data is
needed.
I_TRCLOG Indicates a trace logger. A data buffer consisting of
an array of one or more trace_ids structures must be
included.
If any of the fields of the trace_ids structure contain a value of -1,
/dev/strlog will accept whatever value it receives in that field.
Otherwise, strlog only accepts messages only if the values of mid and
sid are the same as their counterparts in the trace_ids structure, and
if the message's level is equal to or less than the level value in the
trace_ids structure.
Once the logger process has sent the I_STR ioctl() call, the STREAMS
log driver begins to send log messages matching the restrictions to
the logger process. The logger process obtains the log messages via
the getmsg() system call. The control part of the messages passed in
this call includes a log_ctl structure:
struct log_ctl {
short mid;
short sid;
char level;
short flags;
long ltime;
long ttime;
int seq_no;
};
The log_ctl structure indicates the mid, sid, and level time in ticks
since the boot time that the message was submitted, the corresponding
time in seconds since January 1, 1970, and a sequence number. The
time in seconds since January 1, 1970 is provided so that the date and
time of the message can be easily computed. The time in ticks since
boot time is provided so that the relative timing of log messages can
be determined.
A user process, other than an error or trace logger, can send a log
message to strlog. The driver will accept only the flags and level
fields of the log_ctl structure in the control part of the message,
and a properly formatted data part of the message. The data part of
the message is properly formatted if it contains a null-terminated
format string, followed by up to three arguments packed one word each
after the end of the string.
A different series of sequence numbers is provided for error and trace
logging streams. These sequence numbers are intended to help track
the delivery of the messages. A gap in a sequence of numbers
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strlog(7) strlog(7)
indicates that the logger process did not successfully deliver them.
This can happen if the logger process stops sending messages for one
reason or another (see strace(1M) and strerr(1M) command reference
pages for more information). The data part of messages contains text
of the format string (null terminated), followed by up to three
arguments.
STREAMS-NetTL Link [Toc] [Back]
Both STREAMS error logging and event tracing messages are mapped to
NetTL logging messages, and are delivered to NetTL. NetTL classifies
messages into four log classes: DISASTER, ERROR, WARNING, and
INFORMATIVE. The NetTL log class is determined by the flags according
to the following rule:
If (flags & SL_ERROR) NetTL log class
then
if (flags & SL_FATAL) ====> DISASTER
if (flags & SL_WARN) ====> WARNING
if (flags & SL_NOTE) ====> INFORMATIVE
otherwise ====> ERROR
else
all messages ====> INFORMATIVE
As a default, only DISASTER and ERROR messages are logged. This
setting can be altered by the nettl command or the nettlconf command
(see nettl(1M) and nettlconf(1M)).
The STREAMS subsystem ID used by NetTL is STREAMS.
The messages logged by NetTL facility can be formatted to a readable
form by the netfmt command (see netfmt(1M)). The netfmt accepts a
filter configuration file, which can be used to filter on STREAMS
module ID and sub-ID. The filter configuration file syntax for
STREAMS is the following:
STREAMS module_id sub_id
module_id and sub_id can be a decimal number or ``*'' as a wild card.
RETURN VALUE [Toc] [Back]
Unless specified otherwise, upon successful completion, the strlog
ioctl() commands return a value of 0 (zero). Otherwise, a value of -1
is returned.
ERRORS [Toc] [Back]
If any of the following conditions occurs, strlog driver's ioctl()
command sets errno to the corresponding value:
[ENXIO] The I_TRCLOG ioctl() call did not contain any trace_ids
structures.
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strlog(7) strlog(7)
[ENXIO] The I_STR ioctl() call could not be recognized.
The driver does not return any errors for incorrectly formatted
messages that user processes send.
EXAMPLES [Toc] [Back]
The following examples illustrate some basic uses for the strlog
interface.
This code example segment shows how a STREAMS module causes a message
to be printed to the console:
strlog(TMUX,minor(mydev),0,SL_CONSOLE|SL_FATAL,
"TMUX driver (minor:%d) suffers resource shortage.",
minor(mydev));
This code example shows how a user process registers itself with the
STREAMS log driver using the ioctl() command, I_ERRLOG.
struct strioctl iocerr:
int logfd;
if ((logfd = open("/dev/strlog", O_RDWR)) == -1) {
printf("Cannot open /dev/strlog\n");
exit(1);
}
iocerr.ic_cmd = I_ERRLOG;
iocerr.ic_timout = 0;
iocerr.ic_len = 0;
iocerr.ic_dp = NULL;
ioctl(logfd, I_STR, &iocerr);
This code example shows a user-level process sending a message to the
strlog driver.
struct strbuf control, data;
struct log_ctl log;
char *warning = "Fatal error for user level process";
int logfd;
if ((logfd = open("/dev/strlog", O_RDWR)) == -1) {
printf("Cannot open /dev/strlog\n");
exit(1);
}
control.len = control.maxlen = sizeof(log);
control.buf = (char *)&lc;
data.len = data.maxlen = strlen(warning);
data.buf = warning;
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strlog(7) strlog(7)
lc.level = 2;
lc.flags = SL_FATAL|SL_CONSOLE;
putmsg(logfd, &control, &data, 0);
The following examples illustrate how to use the NetTL facility for
the STREAMS. See nettl(1M), netfmt(1M), nettlconf(1M) for the general
NetTL usage. The STREAMS subsystem ID used by NetTL is STREAMS.
The netfmt accepts a filter configuration file as a command argument.
The following filter configuration file example is used to format the
messages whose module ID is 1 and sub-ID is 100:
STREAMS 1 100
This filter configuration file example can be used to display all the
messages whose module ID is 2 and all the messages whose sub-ID is
101:
STREAMS 2 *
STREAMS * 101
FILES [Toc] [Back]
/dev/strlog specifies the clone interface.
<sys/strlog.h> specifies the header file for streams
logging.
<stropts.h> specifies the header file for STREAMS options
and ioctl() commands.
SEE ALSO [Toc] [Back]
strace(1M), strerr(1M), clone(7), streamio(7), getmsg(2), putmsg(2),
write(2), open(2), ioctl(2), nettl(1M), netfmt(1M), nettlconf(1M).
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