Old versions of ircu did not have very good means of dealing with
logging.  In u2.10.11, an entirely new logging subsystem was written,
allowing a server administrator much more power in determining what
actions are to be logged where.  The new logging subsystem permits log
messages to go to syslog, to a file, and to server operators via
server notices, simultaneously (though having output to multiple log
files is not presently supported).

All log messages have two values that are passed in with them: the
logging level, which must be one of the values in enum LogLevel, and a
logging subsystem, which must be one of the values in enum LogSys;
these values are used as indexes into arrays within ircd_log.c, so be
careful should you change them.

In addition to the LogLevel and LogSys, there is also a set of three
flags that may be passed to the log_write() logging function; these
flags may be used to suppress certain types of logging that may be
undesirable.  For instance, when a server links, a log may be written
containing the server's IP address; to prevent this IP address from
ever showing up in a server notice, that invocation of log_write() is
passed the LOG_NOSNOTICE flag.

<enum>
enum LogLevel {
  L_CRIT,
  L_ERROR,
  L_WARNING,
  L_NOTICE,
  L_TRACE,
  L_INFO,
  L_DEBUG,
  L_LAST_LEVEL
};

This enum describes the severity levels of a log message.  The
severity decreases as you proceed downwards in the list, so L_DEBUG is
less severe than L_INFO, and L_CRIT in the most severe of all.  The
special value L_LAST_LEVEL should never be used; it merely marks the
end of the list.
</enum>

<enum>
enum LogSys {
  LS_SYSTEM, LS_CONFIG, LS_OPERMODE, LS_GLINE, LS_JUPE, LS_WHO, LS_NETWORK,
  LS_OPERKILL, LS_SERVKILL, LS_USER, LS_OPER, LS_RESOLVER, LS_SOCKET,
  LS_DEBUG, LS_OLDLOG,
  LS_LAST_SYSTEM
};

These are the various logging subsystems recognized by the logging
subsystem.  Again, order is important, and again, LS_LAST_SYSTEM
should never be used.
</enum>

<function>
void log_debug_init(int usetty);

This initializes the special-purpose debug logging code in the
server.  If the _usetty_ parameter is non-zero, then all debugging
output will go to the terminal regardless of file settings for the
LS_DEBUG subsystem.  This function is not defined unless the server is
compiled with -DDEBUGMODE.
</function>

<function>
void log_init(const char *process_name);

This initializes the entire logging subsystem, including special
things such as storing the process name and opening syslog with the
open_log() function.  It may only be called once.
</function>

<function>
void log_reopen(void);

All log files are persistently open, in order to avoid the overhead of
re-opening the log file each time.  This function is used to close all
the log files and to close and reopen syslog.  (Log files are opened
again only when there is something to write to them.)
</function>

<function>
void log_close(void);

This closes all log files and the syslog prior to the server
terminating.  Should logs need to be reopened after calling this
function, call log_reopen() instead of log_init().
</function>

<function>
void log_write(enum LogSys subsys, enum LogLevel severity,
	       unsigned int flags, const char *fmt, ...);

This is the actual logging function.  The _flags_ parameter is 0 or
the bitwise OR of LOG_NOSYSLOG (suppresses syslogging), LOG_NOFILELOG
(suppresses logging to a file) and LOG_NOSNOTICE (suppresses logging
via server notices).  The _fmt_ parameter is a format string
acceptable to ircd_snprintf(), which is the function called to
actually format the log message.
</function>

<function>
void log_vwrite(enum LogSys subsys, enum LogLevel severity,
		unsigned int flags, const char *fmt, va_list vl);

This is similar to log_write() except that it takes a va_list
parameter.
</function>

<function>
char *log_cannon(const char *subsys);

This returns the canonical name for logging subsystem.  This probably
should not be exposed here, but it is needed in ircd_features.c at
present.
</function>

<function>
int log_set_file(const char *subsys, const char *filename);

This sets the file name for the specified logging subsystem to
_filename_; returns 2 if the subsystem was undefined, 1 if the value
of _filename_ was not understood, or 0 if there was no error.
</function>

<function>
char *log_get_file(const char *subsys);

This returns the current log file name for the given subsystem.
</function>

<function>
int log_set_facility(const char *subsys, const char *facility);

This sets the syslog facility for the specified logging subsystem to
_facility_; returns 2 if the subsystem was undefined, 1 if the value
of _facility_ was not understood, or 0 if there was no error.  Two
special facility names may be given; "NONE" specifies that no
syslogging should be performed, and "DEFAULT" specifies that ircd's
default syslog facility should be used.
</function>

<function>
char *log_get_facility(const char *subsys);

This returns the current syslog facility for the given subsystem.  See
the documentation for log_set_facility() for a description of the
special facility names "NONE" and "DEFAULT."
</function>

<function>
int log_set_snomask(const char *subsys, const char *snomask);

This sets the server notice type for the specified logging subsystem
to _snomask_; returns 2 if the subsystem was undefined, 1 if the value
of _snomask_ was not understood, or 0 if there was no error.  The
special server notice type "NONE" indicates that no server notices
should be generated.  The other valid values for _snomask_ are:
"OLDSNO," "SERVKILL," "OPERKILL," "HACK2," "HACK3," "UNAUTH,"
"TCPCOMMON," "TOOMANY," "HACK4," "GLINE," "NETWORK," "IPMISMATCH,"
"THROTTLE," "OLDREALOP," "CONNEXIT," and "DEBUG."
</function>

<function>
char *log_get_snomask(const char *subsys);

This returns the current server notice type for the given subsystem.
See the documentation for log_set_snomask() for a description of the
return values.
</function>

<function>
int log_set_level(const char *subsys, const char *level);

This function is used to set the minimum log level for a particular
subsystem; returns 2 if the subsystem was undefined, 1 if the value of
_level_ was not understood, or 0 if there was no error.  Any log
notices generated with lower severity than that set with this function
will not be logged.  Valid values are "CRIT," "ERROR," "WARNING,"
"NOTICE," "TRACE," "INFO," and "DEBUG."
</function>

<function>
char *log_get_level(const char *subsys);

This returns the current minimum log level for the given subsystem.
See the documentation for log_set_level() for a description of the
return values.
</function>

<function>
int log_set_default(const char *facility);

This function sets the default syslog facility for all of ircd.  Valid
values for _facility_ are as described for log_set_facility() with the
exclusion of the "NONE" and "DEFAULT" facilities; returns 1 if the
facility name was unrecognized (or proscribed) or 0 if there was no
error.
</function>

<function>
char *log_get_default(void);

This simply returns ircd's default syslog facility.
</function>

<function>
void log_feature_unmark(void);

This function is called by the ircd_features.c subsystem and should
not be called by any other part of ircd.  See the features API
documentation for notes on what this function does.
</function>

<function>
void log_feature_mark(int flag);

This function is called by the ircd_features.c subsystem and should
not be called by any other part of ircd.  See the features API
documentation for notes on what this function does.
</function>

<function>
void log_feature_report(struct Client *to, int flag);

This function is called by the ircd_features.c subsystem and should
not be called by any other part of ircd.  See the features API
documentation for notes on what this function does.
</function>

<authors>
Kev <klmitch@mit.edu>
</authors>

<changelog>
[2001-06-13 Kev] Fix a minor typo.

[2000-12-18 Kev] Wrote some documentation on how to use the logging
subsystem.
</changelog>