server: add option to stay in foreground

Fixes mobile-shell#1091

man/mosh-server.1

@@ -20,6 +20,7 @@ mosh-server \- server-side helper for mosh
 .SH SYNOPSIS
 .B mosh-server
 new
+[\-D]
 [\-s]
 [\-v]
 [\-i \fIIP\fP]
@@ -54,6 +55,10 @@ and the client's current IP address.
 The argument "new" must be first on the command line to use
 command-line options.
 
+.TP
+.B \-D
+stay in the foreground instead of forking into the background
+
 .TP
 .B \-s
 bind to the local interface used for an incoming SSH connection, given

src/frontend/mosh-server.cc

@@ -105,7 +105,8 @@ static void serve( int host_fd,
 
 static int run_server( const char *desired_ip, const char *desired_port,
 		       const string &command_path, char *command_argv[],
-		       const int colors, unsigned int verbose, bool with_motd );
+		       const int colors, unsigned int verbose, bool with_motd,
+               bool foreground );
 
 
 static void print_version( FILE *file )
@@ -119,7 +120,7 @@ static void print_version( FILE *file )
 
 static void print_usage( FILE *stream, const char *argv0 )
 {
-  fprintf( stream, "Usage: %s new [-s] [-v] [-i LOCALADDR] [-p PORT[:PORT2]] [-c COLORS] [-l NAME=VALUE] [-- COMMAND...]\n", argv0 );
+  fprintf( stream, "Usage: %s new [-D] [-s] [-v] [-i LOCALADDR] [-p PORT[:PORT2]] [-c COLORS] [-l NAME=VALUE] [-- COMMAND...]\n", argv0 );
 }
 
 static bool print_motd( const char *filename );
@@ -183,6 +184,7 @@ int main( int argc, char *argv[] )
   char **command_argv = NULL;
   int colors = 0;
   unsigned int verbose = 0; /* don't close stdin/stdout/stderr */
+  bool foreground = false; /* stay in the foreground, don't fork into background */
   /* Will cause mosh-server not to correctly detach on old versions of sshd. */
   list<string> locale_vars;
 
@@ -210,7 +212,7 @@ int main( int argc, char *argv[] )
        && (strcmp( argv[ 1 ], "new" ) == 0) ) {
     /* new option syntax */
     int opt;
-    while ( (opt = getopt( argc - 1, argv + 1, "@:i:p:c:svl:" )) != -1 ) {
+    while ( (opt = getopt( argc - 1, argv + 1, "@:i:p:c:svl:D" )) != -1 ) {
       switch ( opt ) {
 	/*
 	 * This undocumented option does nothing but eat its argument.
@@ -251,6 +253,9 @@ int main( int argc, char *argv[] )
       case 'l':
 	locale_vars.push_back( string( optarg ) );
 	break;
+      case 'D':
+	foreground = true;
+	break;
       default:
 	/* don't die on unknown options */
 	print_usage( stderr, argv[ 0 ] );
@@ -364,7 +369,7 @@ int main( int argc, char *argv[] )
   }
 
   try {
-    return run_server( desired_ip, desired_port, command_path, command_argv, colors, verbose, with_motd );
+    return run_server( desired_ip, desired_port, command_path, command_argv, colors, verbose, with_motd, foreground );
   } catch ( const Network::NetworkException &e ) {
     fprintf( stderr, "Network exception: %s\n",
 	     e.what() );
@@ -378,7 +383,8 @@ int main( int argc, char *argv[] )
 
 static int run_server( const char *desired_ip, const char *desired_port,
 		       const string &command_path, char *command_argv[],
-		       const int colors, unsigned int verbose, bool with_motd ) {
+		       const int colors, unsigned int verbose, bool with_motd,
+               bool foreground ) {
   /* get network idle timeout */
   long network_timeout = 0;
   char *timeout_envar = getenv( "MOSH_SERVER_NETWORK_TMOUT" );
@@ -448,34 +454,41 @@ static int run_server( const char *desired_ip, const char *desired_port,
   fatal_assert( 0 == sigaction( SIGHUP, &sa, NULL ) );
   fatal_assert( 0 == sigaction( SIGPIPE, &sa, NULL ) );
 
+  pid_t the_pid = -1;
+  if (!foreground) {
+    /* detach from terminal */
+    fflush( NULL );
+    the_pid = fork();
+  }
 
-  /* detach from terminal */
-  fflush( NULL );
-  pid_t the_pid = fork();
-  if ( the_pid < 0 ) {
+  if ( the_pid < 0  && !foreground) {
     perror( "fork" );
-  } else if ( the_pid > 0 ) {
+  } else if ( the_pid > 0 || foreground ) {
     fputs( "\nmosh-server (" PACKAGE_STRING ") [build " BUILD_VERSION "]\n"
-	   "Copyright 2012 Keith Winstein <[email protected]>\n"
-	   "License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.\n"
-	   "This is free software: you are free to change and redistribute it.\n"
-	   "There is NO WARRANTY, to the extent permitted by law.\n\n", stderr );
+      "Copyright 2012 Keith Winstein <[email protected]>\n"
+      "License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.\n"
+      "This is free software: you are free to change and redistribute it.\n"
+      "There is NO WARRANTY, to the extent permitted by law.\n\n", stderr );
 
-    fprintf( stderr, "[mosh-server detached, pid = %d]\n", static_cast<int>(the_pid) );
+    if (!foreground) {
+        fprintf( stderr, "[mosh-server detached, pid = %d]\n", static_cast<int>(the_pid) );
+    }
 #ifndef HAVE_IUTF8
     fputs( "\nWarning: termios IUTF8 flag not defined.\n"
-	   "Character-erase of multibyte character sequence\n"
-	   "probably does not work properly on this platform.\n", stderr );
+      "Character-erase of multibyte character sequence\n"
+      "probably does not work properly on this platform.\n", stderr );
 #endif /* HAVE_IUTF8 */
 
-    fflush( NULL );
-    if ( isatty( STDOUT_FILENO ) ) {
-      tcdrain( STDOUT_FILENO );
-    }
-    if ( isatty( STDERR_FILENO ) ) {
-      tcdrain( STDERR_FILENO );
+    if (!foreground) {
+      fflush( NULL );
+      if ( isatty( STDOUT_FILENO ) ) {
+        tcdrain( STDOUT_FILENO );
+      }
+      if ( isatty( STDERR_FILENO ) ) {
+        tcdrain( STDERR_FILENO );
+      }
+      exit( 0 );
     }
-    exit( 0 );
   }
 
   int master;