log/syslog: remove RFC5424 version number for greater compatibility

RFC5424 specifies a version number (currently 1) after the facility and
severity in a syslog message (e.g. <7>1 TIMESTAMP ...).  This causes
rsyslog to fail to parse syslog message because the rest of the message
is not fully compliant with RFC5424.

For the widest compatibility, drop the version (messages are in the
RFC3164 BSD syslog format (e.g. <7>TIMESTAMP ...). Have tested this with
syslog-ng, rsyslog and syslogd.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/7036050

src/pkg/log/syslog/syslog.go

@@ -202,14 +202,14 @@ func (w *Writer) writeString(p Priority, s string) (int, error) {
 }
 
 // writeString: generates and writes a syslog formatted string. The
-// format is as follows: <PRI>1 TIMESTAMP HOSTNAME TAG[PID]: MSG
+// format is as follows: <PRI>TIMESTAMP HOSTNAME TAG[PID]: MSG
 func (n netConn) writeString(p Priority, hostname, tag, msg string) (int, error) {
 	nl := ""
 	if len(msg) == 0 || msg[len(msg)-1] != '\n' {
 		nl = "\n"
 	}
 	timestamp := time.Now().Format(time.RFC3339)
-	if _, err := fmt.Fprintf(n.conn, "<%d>1 %s %s %s[%d]: %s%s", p, timestamp, hostname,
+	if _, err := fmt.Fprintf(n.conn, "<%d>%s %s %s[%d]: %s%s", p, timestamp, hostname,
 		tag, os.Getpid(), msg, nl); err != nil {
 		return 0, err
 	}

src/pkg/log/syslog/syslog_test.go

@@ -104,16 +104,15 @@ func TestUDPDial(t *testing.T) {
 	}
 	msg := "udp test"
 	l.Info(msg)
-	expected := fmt.Sprintf("<%d>1 ", LOG_USER+LOG_INFO) + "%s %s syslog_test[%d]: udp test\n"
+	expected := fmt.Sprintf("<%d>", LOG_USER+LOG_INFO) + "%s %s syslog_test[%d]: udp test\n"
 	rcvd := <-done
 	var parsedHostname, timestamp string
 	var pid int
 	if hostname, err := os.Hostname(); err != nil {
 		t.Fatalf("Error retrieving hostname")
 	} else {
-		if n, err := fmt.Sscanf(rcvd, expected, &timestamp, &parsedHostname, &pid); n != 3 ||
-			err != nil || hostname != parsedHostname {
-			t.Fatalf("s.Info() = '%q', didn't match '%q'", rcvd, expected)
+		if n, err := fmt.Sscanf(rcvd, expected, &timestamp, &parsedHostname, &pid); n != 3 || err != nil || hostname != parsedHostname {
+			t.Fatalf("'%q', didn't match '%q' (%d, %s)", rcvd, expected, n, err)
 		}
 	}
 }
@@ -146,12 +145,13 @@ func TestWrite(t *testing.T) {
 				t.Fatalf("WriteString() failed: %s", err)
 			}
 			rcvd := <-done
-			test.exp = fmt.Sprintf("<%d>1 ", test.pri) + test.exp
+			test.exp = fmt.Sprintf("<%d>", test.pri) + test.exp
 			var parsedHostname, timestamp string
 			var pid int
-			if n, err := fmt.Sscanf(rcvd, test.exp, &timestamp, &parsedHostname, &pid); n != 3 ||
-				err != nil || hostname != parsedHostname {
-				t.Fatalf("s.Info() = '%q', didn't match '%q'", rcvd, test.exp)
+			if n, err := fmt.Sscanf(rcvd, test.exp, &timestamp, &parsedHostname,
+				&pid); n != 3 || err != nil || hostname != parsedHostname {
+				t.Fatalf("'%q', didn't match '%q' (%d %s)", rcvd, test.exp,
+					n, err)
 			}
 		}
 	}