log/syslog: restore use of serverConn interface

Revision 15629 (8d71734a0cb0) removed the serverConn interface
that was introduce in revision 7718 (ee5e80c62862).  The
serverConn interface was there for use by gccgo on Solaris,
and it is still needed there.  Solaris does not support
connecting to the syslog daemon over TCP, and gccgo simply
calls the C library function.  This CL restores the
interface.

R=golang-dev, bradfitz, rsc
CC=golang-dev
https://golang.org/cl/11737043

src/pkg/log/syslog/syslog.go

@@ -88,6 +88,21 @@ type Writer struct {
 	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 can not
+// 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 {
 	conn net.Conn
 }
 
@@ -135,7 +150,7 @@ func Dial(network, raddr string, priority Priority, tag string) (*Writer, error)
 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.close()
 		w.conn = nil
 	}
 
@@ -148,7 +163,7 @@ func (w *Writer) connect() (err error) {
 		var c net.Conn
 		c, err = net.Dial(w.network, w.raddr)
 		if err == nil {
-			w.conn = c
+			w.conn = netConn{c}
 			if w.hostname == "" {
 				w.hostname = c.LocalAddr().String()
 			}
@@ -168,7 +183,7 @@ func (w *Writer) Close() error {
 	defer w.mu.Unlock()
 
 	if w.conn != nil {
-		err := w.conn.Close()
+		err := w.conn.close()
 		w.conn = nil
 		return err
 	}
@@ -257,10 +272,7 @@ func (w *Writer) write(p Priority, msg string) (int, error) {
 		nl = "\n"
 	}
 
-	timestamp := time.Now().Format(time.RFC3339)
-	_, err := fmt.Fprintf(w.conn, "<%d>%s %s %s[%d]: %s%s",
-		p, timestamp, w.hostname,
-		w.tag, os.Getpid(), msg, nl)
+	err := w.conn.writeString(p, w.hostname, w.tag, msg, nl)
 	if err != nil {
 		return 0, err
 	}
@@ -270,6 +282,18 @@ func (w *Writer) write(p Priority, msg string) (int, error) {
 	return len(msg), nil
 }
 
+func (n netConn) writeString(p Priority, hostname, tag, msg, nl string) error {
+	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. The logFlag
 // argument is the flag set passed through to log.New to create

src/pkg/log/syslog/syslog_unix.go

@@ -14,7 +14,7 @@ import (
 // unixSyslog opens a connection to the syslog daemon running on the
 // local machine using a Unix domain socket.
 
-func unixSyslog() (conn net.Conn, err error) {
+func unixSyslog() (conn serverConn, err error) {
 	logTypes := []string{"unixgram", "unix"}
 	logPaths := []string{"/dev/log", "/var/run/syslog"}
 	for _, network := range logTypes {
@@ -23,7 +23,7 @@ func unixSyslog() (conn net.Conn, err error) {
 			if err != nil {
 				continue
 			} else {
-				return conn, nil
+				return netConn{conn}, nil
 			}
 		}
 	}