add -f background option to dbclient

--HG--
extra : convert_revision : 5ef61c30c0a634ac0da22a8c694ce235690e8170

cli-session.c

@@ -212,6 +212,23 @@ static void cli_sessionloop() {
 			*/
 
 		case USERAUTH_SUCCESS_RCVD:
+
+			if (cli_opts.backgrounded) {
+				int devnull;
+				// keeping stdin open steals input from the terminal and
+				// is confusing, though stdout/stderr could be useful.
+				devnull = open(_PATH_DEVNULL, O_RDONLY);
+				if (devnull < 0) {
+					dropbear_exit("opening /dev/null: %d %s",
+							errno, strerror(errno));
+				}
+				dup2(devnull, STDIN_FILENO);
+				if (daemon(0, 1) < 0) {
+					dropbear_exit("Backgrounding failed: %d %s", 
+							errno, strerror(errno));
+				}
+			}
+			
 #ifdef ENABLE_CLI_LOCALTCPFWD
 			setup_localtcp();
 #endif