Add a prolog/epilog to the logging that always gets logged.

The prolog prints the version as soon as logging is enabled, but before
the pluggable transport configuration is done.  The epilog is printed as
the code returns from main, as long as either client or server pt
configuration succeded.

obfs4proxy/log.go

@@ -41,6 +41,13 @@ const (
 
 var logLevel = levelInfo
 
+func noticef(format string, a ...interface{}) {
+	if enableLogging {
+		msg := fmt.Sprintf(format, a...)
+		log.Print("[NOTICE]: " + msg)
+	}
+}
+
 func errorf(format string, a ...interface{}) {
 	if enableLogging && logLevel >= levelError {
 		msg := fmt.Sprintf(format, a...)

obfs4proxy/obfs4proxy.go

@@ -383,9 +383,8 @@ func ptInitializeLogging(enable bool) error {
 	return nil
 }
 
-func version() {
-	fmt.Printf("obfs4proxy-%s\n", obfs4proxyVersion)
-	os.Exit(0)
+func getVersion() string {
+	return fmt.Sprintf("obfs4proxy-%s", obfs4proxyVersion)
 }
 
 func main() {
@@ -398,7 +397,8 @@ func main() {
 	flag.Parse()
 
 	if *showVer {
-		version()
+		fmt.Printf("%s\n", getVersion())
+		os.Exit(0)
 	}
 	if err := setLogLevel(*logLevelStr); err != nil {
 		log.Fatalf("[ERROR]: failed to set log level: %s", err)
@@ -418,6 +418,8 @@ func main() {
 	}
 	if err = ptInitializeLogging(enableLogging); err != nil {
 		log.Fatalf("[ERROR]: %s - failed to initialize logging", execName)
+	} else {
+		noticef("%s - launched", getVersion())
 	}
 	if isClient {
 		infof("%s - initializing client transport listeners", execName)
@@ -432,9 +434,9 @@ func main() {
 		os.Exit(-1)
 	}
 
-	infof("%s - launched and accepting connections", execName)
+	infof("%s - accepting connections", execName)
 	defer func() {
-		infof("%s - terminated", execName)
+		noticef("%s - terminated", execName)
 	}()
 
 	// At this point, the pt config protocol is finished, and incoming