src/log4net/Appender/LocalSyslogAppender.cs (132 lines of code) (raw):
#region Apache License
//
// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.
// The ASF licenses this file to you under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with
// the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#endregion
using System;
using System.Runtime.InteropServices;
using log4net.Core;
using log4net.Util;
namespace log4net.Appender;
/// <summary>
/// Logs events to a local syslog service.
/// </summary>
/// <remarks>
/// <note>
/// This appender uses the POSIX libc library functions <c>openlog</c>, <c>syslog</c>, and <c>closelog</c>.
/// If these functions are not available on the local system then this appender will not work!
/// </note>
/// <para>
/// The functions <c>openlog</c>, <c>syslog</c>, and <c>closelog</c> are specified in SUSv2 and
/// POSIX 1003.1-2001 standards. These are used to log messages to the local syslog service.
/// </para>
/// <para>
/// This appender talks to a local syslog service. If you need to log to a remote syslog
/// daemon and you cannot configure your local syslog service to do this you may be
/// able to use the <see cref="RemoteSyslogAppender"/> to log via UDP.
/// </para>
/// <para>
/// Syslog messages must have a facility and and a severity. The severity
/// is derived from the Level of the logging event.
/// The facility must be chosen from the set of defined syslog
/// <see cref="SyslogFacility"/> values. The facilities list is predefined
/// and cannot be extended.
/// </para>
/// <para>
/// An identifier is specified with each log message. This can be specified
/// by setting the <see cref="Identity"/> property. The identity (also know
/// as the tag) must not contain white space. The default value for the
/// identity is the application name (from <see cref="SystemInfo.ApplicationFriendlyName"/>).
/// </para>
/// </remarks>
/// <author>Rob Lyon</author>
/// <author>Nicko Cadell</author>
public class LocalSyslogAppender : AppenderSkeleton
{
/// <summary>
/// syslog severities
/// </summary>
/// <remarks>
/// <para>
/// The log4net Level maps to a syslog severity using the
/// <see cref="LocalSyslogAppender.AddMapping"/> method and the <see cref="LevelSeverity"/>
/// class. The severity is set on <see cref="LevelSeverity.Severity"/>.
/// </para>
/// </remarks>
public enum SyslogSeverity
{
/// <summary>
/// system is unusable
/// </summary>
Emergency = 0,
/// <summary>
/// action must be taken immediately
/// </summary>
Alert = 1,
/// <summary>
/// critical conditions
/// </summary>
Critical = 2,
/// <summary>
/// error conditions
/// </summary>
Error = 3,
/// <summary>
/// warning conditions
/// </summary>
Warning = 4,
/// <summary>
/// normal but significant condition
/// </summary>
Notice = 5,
/// <summary>
/// informational
/// </summary>
Informational = 6,
/// <summary>
/// debug-level messages
/// </summary>
Debug = 7
};
/// <summary>
/// syslog facilities
/// </summary>
/// <remarks>
/// <para>
/// The syslog facility defines which subsystem the logging comes from.
/// This is set on the <see cref="Facility"/> property.
/// </para>
/// </remarks>
public enum SyslogFacility
{
/// <summary>
/// kernel messages
/// </summary>
Kernel = 0,
/// <summary>
/// random user-level messages
/// </summary>
User = 1,
/// <summary>
/// mail system
/// </summary>
Mail = 2,
/// <summary>
/// system daemons
/// </summary>
Daemons = 3,
/// <summary>
/// security/authorization messages
/// </summary>
Authorization = 4,
/// <summary>
/// messages generated internally by syslogd
/// </summary>
Syslog = 5,
/// <summary>
/// line printer subsystem
/// </summary>
Printer = 6,
/// <summary>
/// network news subsystem
/// </summary>
News = 7,
/// <summary>
/// UUCP subsystem
/// </summary>
Uucp = 8,
/// <summary>
/// clock (cron/at) daemon
/// </summary>
Clock = 9,
/// <summary>
/// security/authorization messages (private)
/// </summary>
Authorization2 = 10,
/// <summary>
/// ftp daemon
/// </summary>
Ftp = 11,
/// <summary>
/// NTP subsystem
/// </summary>
Ntp = 12,
/// <summary>
/// log audit
/// </summary>
Audit = 13,
/// <summary>
/// log alert
/// </summary>
Alert = 14,
/// <summary>
/// clock daemon
/// </summary>
Clock2 = 15,
/// <summary>
/// reserved for local use
/// </summary>
Local0 = 16,
/// <summary>
/// reserved for local use
/// </summary>
Local1 = 17,
/// <summary>
/// reserved for local use
/// </summary>
Local2 = 18,
/// <summary>
/// reserved for local use
/// </summary>
Local3 = 19,
/// <summary>
/// reserved for local use
/// </summary>
Local4 = 20,
/// <summary>
/// reserved for local use
/// </summary>
Local5 = 21,
/// <summary>
/// reserved for local use
/// </summary>
Local6 = 22,
/// <summary>
/// reserved for local use
/// </summary>
Local7 = 23
}
/// <summary>
/// Message identity
/// </summary>
/// <remarks>
/// <para>
/// An identifier is specified with each log message. This can be specified
/// by setting the <see cref="Identity"/> property. The identity (also known
/// as the tag) must not contain white space. The default value for the
/// identity is the application name (from <see cref="SystemInfo.ApplicationFriendlyName"/>).
/// </para>
/// </remarks>
public string? Identity { get; set; }
/// <summary>
/// Syslog facility
/// </summary>
/// <remarks>
/// Set to one of the <see cref="SyslogFacility"/> values. The list of
/// facilities is predefined and cannot be extended. The default value
/// is <see cref="SyslogFacility.User"/>.
/// </remarks>
public SyslogFacility Facility { get; set; } = SyslogFacility.User;
/// <summary>
/// Add a mapping of level to severity
/// </summary>
/// <param name="mapping">The mapping to add</param>
/// <remarks>
/// <para>
/// Adds a <see cref="LevelSeverity"/> to this appender.
/// </para>
/// </remarks>
public void AddMapping(LevelSeverity mapping)
{
_levelMapping.Add(mapping);
}
/// <summary>
/// Initialize the appender based on the options set.
/// </summary>
/// <remarks>
/// <para>
/// This is part of the <see cref="IOptionHandler"/> delayed object
/// activation scheme. The <see cref="ActivateOptions"/> method must
/// be called on this object after the configuration properties have
/// been set. Until <see cref="ActivateOptions"/> is called this
/// object is in an undefined state and must not be used.
/// </para>
/// <para>
/// If any of the configuration properties are modified then
/// <see cref="ActivateOptions"/> must be called again.
/// </para>
/// </remarks>
[System.Security.SecuritySafeCritical]
public override void ActivateOptions()
{
base.ActivateOptions();
_levelMapping.ActivateOptions();
// Set to app name by default
string? identString = Identity ?? SystemInfo.ApplicationFriendlyName;
// create the native heap ansi string. Note this is a copy of our string
// so we do not need to hold on to the string itself, holding on to the
// handle will keep the heap ansi string alive.
_handleToIdentity = Marshal.StringToHGlobalAnsi(identString);
// open syslog
NativeMethods.openlog(_handleToIdentity, 1, Facility);
}
/// <summary>
/// This method is called by the <see cref="AppenderSkeleton.DoAppend(LoggingEvent)"/> method.
/// </summary>
/// <param name="loggingEvent">The event to log.</param>
/// <remarks>
/// <para>
/// Writes the event to a remote syslog daemon.
/// </para>
/// <para>
/// The format of the output will depend on the appender's layout.
/// </para>
/// </remarks>
[System.Security.SecuritySafeCritical]
[System.Security.Permissions.SecurityPermission(System.Security.Permissions.SecurityAction.Demand, UnmanagedCode = true)]
protected override void Append(LoggingEvent loggingEvent)
{
int priority = GeneratePriority(Facility, GetSeverity(loggingEvent.EnsureNotNull().Level));
string message = RenderLoggingEvent(loggingEvent);
// Call the local libc syslog method
// The second argument is a printf style format string
NativeMethods.syslog(priority, "%s", message);
}
/// <summary>
/// Close the syslog when the appender is closed
/// </summary>
/// <remarks>
/// <para>
/// Close the syslog when the appender is closed
/// </para>
/// </remarks>
[System.Security.SecuritySafeCritical]
protected override void OnClose()
{
base.OnClose();
try
{
// close syslog
NativeMethods.closelog();
}
catch (DllNotFoundException)
{
// Ignore dll not found at this point
}
if (_handleToIdentity != IntPtr.Zero)
{
// free global ident
Marshal.FreeHGlobal(_handleToIdentity);
}
}
/// <summary>
/// This appender requires a <see cref="AppenderSkeleton.Layout"/> to be set.
/// </summary>
protected override bool RequiresLayout => true;
/// <summary>
/// Translates a log4net level to a syslog severity.
/// </summary>
/// <param name="level">A log4net level.</param>
/// <returns>A syslog severity.</returns>
protected virtual SyslogSeverity GetSeverity(Level? level)
{
if (_levelMapping.Lookup(level) is LevelSeverity levelSeverity)
{
return levelSeverity.Severity;
}
//
// Fall back to sensible default values
//
if (level is null)
{
// Default setting
return SyslogSeverity.Debug;
}
if (level >= Level.Alert)
{
return SyslogSeverity.Alert;
}
else if (level >= Level.Critical)
{
return SyslogSeverity.Critical;
}
else if (level >= Level.Error)
{
return SyslogSeverity.Error;
}
else if (level >= Level.Warn)
{
return SyslogSeverity.Warning;
}
else if (level >= Level.Notice)
{
return SyslogSeverity.Notice;
}
else if (level >= Level.Info)
{
return SyslogSeverity.Informational;
}
// Default setting
return SyslogSeverity.Debug;
}
/// <summary>
/// Generate a syslog priority.
/// </summary>
/// <param name="facility">The syslog facility.</param>
/// <param name="severity">The syslog severity.</param>
/// <returns>A syslog priority.</returns>
private static int GeneratePriority(SyslogFacility facility, SyslogSeverity severity)
=> ((int)facility * 8) + (int)severity;
/// <summary>
/// Marshaled handle to the identity string. We have to hold on to the
/// string as the <c>openlog</c> and <c>syslog</c> APIs just hold the
/// pointer to the ident and dereference it for each log message.
/// </summary>
private IntPtr _handleToIdentity = IntPtr.Zero;
/// <summary>
/// Mapping from level object to syslog severity
/// </summary>
private readonly LevelMapping _levelMapping = new();
/// <summary>
/// A class to act as a mapping between the level that a logging call is made at and
/// the syslog severity that is should be logged at.
/// </summary>
public class LevelSeverity : LevelMappingEntry
{
/// <summary>
/// The mapped syslog severity for the specified level
/// </summary>
public SyslogSeverity Severity { get; set; }
}
}