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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build !windows && !plan9
package syslog
import (
"errors"
"fmt"
"log"
"net"
"os"
"strings"
"sync"
"time"
)
// The Priority is a combination of the syslog facility and
// severity. For example, LOG_ALERT | LOG_FTP sends an alert severity
// message from the FTP facility. The default severity is LOG_EMERG;
// the default facility is LOG_KERN.
type Priority int
const severityMask = 0x07
const facilityMask = 0xf8
const (
// Severity.
// From /usr/include/sys/syslog.h.
// These are the same on Linux, BSD, and OS X.
LOG_EMERG Priority = iota
LOG_ALERT
LOG_CRIT
LOG_ERR
LOG_WARNING
LOG_NOTICE
LOG_INFO
LOG_DEBUG
)
const (
// Facility.
// From /usr/include/sys/syslog.h.
// These are the same up to LOG_FTP on Linux, BSD, and OS X.
LOG_KERN Priority = iota << 3
LOG_USER
LOG_MAIL
LOG_DAEMON
LOG_AUTH
LOG_SYSLOG
LOG_LPR
LOG_NEWS
LOG_UUCP
LOG_CRON
LOG_AUTHPRIV
LOG_FTP
_ // unused
_ // unused
_ // unused
_ // unused
LOG_LOCAL0
LOG_LOCAL1
LOG_LOCAL2
LOG_LOCAL3
LOG_LOCAL4
LOG_LOCAL5
LOG_LOCAL6
LOG_LOCAL7
)
// A Writer is a connection to a syslog server.
type Writer struct {
priority Priority
tag string
hostname string
network string
raddr string
mu sync.Mutex // guards conn
conn serverConn
}
// This interface and the separate syslog_unix.go file exist for
// Solaris support as implemented by gccgo. On Solaris you cannot
// simply open a TCP connection to the syslog daemon. The gccgo
// sources have a syslog_solaris.go file that implements unixSyslog to
// return a type that satisfies this interface and simply calls the C
// library syslog function.
type serverConn interface {
writeString(p Priority, hostname, tag, s, nl string) error
close() error
}
type netConn struct {
local bool
conn net.Conn
}
// New establishes a new connection to the system log daemon. Each
// write to the returned writer sends a log message with the given
// priority (a combination of the syslog facility and severity) and
// prefix tag. If tag is empty, the os.Args[0] is used.
func New(priority Priority, tag string) (*Writer, error) {
return Dial("", "", priority, tag)
}
// Dial establishes a connection to a log daemon by connecting to
// address raddr on the specified network. Each write to the returned
// writer sends a log message with the facility and severity
// (from priority) and tag. If tag is empty, the os.Args[0] is used.
// If network is empty, Dial will connect to the local syslog server.
// Otherwise, see the documentation for net.Dial for valid values
// of network and raddr.
func Dial(network, raddr string, priority Priority, tag string) (*Writer, error) {
if priority < 0 || priority > LOG_LOCAL7|LOG_DEBUG {
return nil, errors.New("log/syslog: invalid priority")
}
if tag == "" {
tag = os.Args[0]
}
hostname, _ := os.Hostname()
w := &Writer{
priority: priority,
tag: tag,
hostname: hostname,
network: network,
raddr: raddr,
}
w.mu.Lock()
defer w.mu.Unlock()
err := w.connect()
if err != nil {
return nil, err
}
return w, err
}
// connect makes a connection to the syslog server.
// It must be called with w.mu held.
func (w *Writer) connect() (err error) {
if w.conn != nil {
// ignore err from close, it makes sense to continue anyway
w.conn.close()
w.conn = nil
}
if w.network == "" {
w.conn, err = unixSyslog()
if w.hostname == "" {
w.hostname = "localhost"
}
} else {
var c net.Conn
c, err = net.Dial(w.network, w.raddr)
if err == nil {
w.conn = &netConn{
conn: c,
local: w.network == "unixgram" || w.network == "unix",
}
if w.hostname == "" {
w.hostname = c.LocalAddr().String()
}
}
}
return
}
// Write sends a log message to the syslog daemon.
func (w *Writer) Write(b []byte) (int, error) {
return w.writeAndRetry(w.priority, string(b))
}
// Close closes a connection to the syslog daemon.
func (w *Writer) Close() error {
w.mu.Lock()
defer w.mu.Unlock()
if w.conn != nil {
err := w.conn.close()
w.conn = nil
return err
}
return nil
}
// Emerg logs a message with severity LOG_EMERG, ignoring the severity
// passed to New.
func (w *Writer) Emerg(m string) error {
_, err := w.writeAndRetry(LOG_EMERG, m)
return err
}
// Alert logs a message with severity LOG_ALERT, ignoring the severity
// passed to New.
func (w *Writer) Alert(m string) error {
_, err := w.writeAndRetry(LOG_ALERT, m)
return err
}
// Crit logs a message with severity LOG_CRIT, ignoring the severity
// passed to New.
func (w *Writer) Crit(m string) error {
_, err := w.writeAndRetry(LOG_CRIT, m)
return err
}
// Err logs a message with severity LOG_ERR, ignoring the severity
// passed to New.
func (w *Writer) Err(m string) error {
_, err := w.writeAndRetry(LOG_ERR, m)
return err
}
// Warning logs a message with severity LOG_WARNING, ignoring the
// severity passed to New.
func (w *Writer) Warning(m string) error {
_, err := w.writeAndRetry(LOG_WARNING, m)
return err
}
// Notice logs a message with severity LOG_NOTICE, ignoring the
// severity passed to New.
func (w *Writer) Notice(m string) error {
_, err := w.writeAndRetry(LOG_NOTICE, m)
return err
}
// Info logs a message with severity LOG_INFO, ignoring the severity
// passed to New.
func (w *Writer) Info(m string) error {
_, err := w.writeAndRetry(LOG_INFO, m)
return err
}
// Debug logs a message with severity LOG_DEBUG, ignoring the severity
// passed to New.
func (w *Writer) Debug(m string) error {
_, err := w.writeAndRetry(LOG_DEBUG, m)
return err
}
func (w *Writer) writeAndRetry(p Priority, s string) (int, error) {
pr := (w.priority & facilityMask) | (p & severityMask)
w.mu.Lock()
defer w.mu.Unlock()
if w.conn != nil {
if n, err := w.write(pr, s); err == nil {
return n, err
}
}
if err := w.connect(); err != nil {
return 0, err
}
return w.write(pr, s)
}
// write generates and writes a syslog formatted string. The
// format is as follows: <PRI>TIMESTAMP HOSTNAME TAG[PID]: MSG
func (w *Writer) write(p Priority, msg string) (int, error) {
// ensure it ends in a \n
nl := ""
if !strings.HasSuffix(msg, "\n") {
nl = "\n"
}
err := w.conn.writeString(p, w.hostname, w.tag, msg, nl)
if err != nil {
return 0, err
}
// Note: return the length of the input, not the number of
// bytes printed by Fprintf, because this must behave like
// an io.Writer.
return len(msg), nil
}
func (n *netConn) writeString(p Priority, hostname, tag, msg, nl string) error {
if n.local {
// Compared to the network form below, the changes are:
// 1. Use time.Stamp instead of time.RFC3339.
// 2. Drop the hostname field from the Fprintf.
timestamp := time.Now().Format(time.Stamp)
_, err := fmt.Fprintf(n.conn, "<%d>%s %s[%d]: %s%s",
p, timestamp,
tag, os.Getpid(), msg, nl)
return err
}
timestamp := time.Now().Format(time.RFC3339)
_, err := fmt.Fprintf(n.conn, "<%d>%s %s %s[%d]: %s%s",
p, timestamp, hostname,
tag, os.Getpid(), msg, nl)
return err
}
func (n *netConn) close() error {
return n.conn.Close()
}
// NewLogger creates a log.Logger whose output is written to the
// system log service with the specified priority, a combination of
// the syslog facility and severity. The logFlag argument is the flag
// set passed through to log.New to create the Logger.
func NewLogger(p Priority, logFlag int) (*log.Logger, error) {
s, err := New(p, "")
if err != nil {
return nil, err
}
return log.New(s, "", logFlag), nil
}