ccon: Use original stderr for logging after set_terminal

By dup()ing the original stderr to some other file descriptor and
closing that descriptor just before executing another program.  This
avoids polluting the terminal output with ccon logging even if ccon is
called with --verbose.

I've also set an explicit initial value for 'verbose'.  The lack of
one didn't seem to be causing problems, but it doesn't hurt to be
explicit ;).

Author: wking

ccon.c

@@ -77,9 +77,10 @@ static pid_t child_pid;
 static pid_t hook_pid;
 
 /* logging */
-static int verbose;
-#define LOG(...) do {if (verbose) {fprintf(stderr, __VA_ARGS__);}} while(0)
-#define PERROR(...) do {if (verbose) {perror(__VA_ARGS__);}} while(0)
+static int verbose = 0;
+static int log_fd = STDERR_FILENO;
+#define LOG(...) do {if (verbose && log_fd >= 0) {dprintf(log_fd, __VA_ARGS__);}} while(0)
+#define PERROR(s) do {LOG("%s: %s\n", s, strerror(errno));} while(0)
 
 static int parse_args(int argc, char **argv, const char **config_path,
 		      const char **config_string);
@@ -888,6 +889,16 @@ static int set_terminal(json_t * process, int console, int dup_stdin,
 				goto cleanup;
 			}
 
+			if (log_fd == STDERR_FILENO) {
+				log_fd = dup(STDERR_FILENO);
+				if (log_fd == -1) {
+					log_fd = STDERR_FILENO;
+					PERROR("dup");
+					err = 1;
+					goto cleanup;
+				}
+			}
+
 			if (dup2(slave, STDERR_FILENO) == -1) {
 				PERROR("dup2");
 				err = 1;
@@ -909,6 +920,11 @@ static int set_terminal(json_t * process, int console, int dup_stdin,
 			err = 1;
 		}
 	}
+	if (err != 0 && log_fd >= 0 && log_fd != STDERR_FILENO) {
+		if (close(log_fd)) {
+			PERROR("close log file descriptor");
+		}
+	}
 	return err;
 }
 
@@ -1140,6 +1156,13 @@ static void exec_process(json_t * process, int console, int dup_stdin,
 			LOG(" %s", argv[i]);
 		}
 		LOG("\n");
+		if (log_fd != STDERR_FILENO) {
+			if (close(log_fd) == -1) {
+				PERROR("close log file descriptor");
+				goto cleanup;
+			}
+			log_fd = -1;
+		}
 		execveat(*exec_fd, "", argv, env, AT_EMPTY_PATH);
 		PERROR("execveat");
 		goto cleanup;
@@ -1154,22 +1177,24 @@ static void exec_process(json_t * process, int console, int dup_stdin,
 		}
 
 		LOG("execute [%s]:", path);
-		for (i = 0; argv[i]; i++) {
-			LOG(" %s", argv[i]);
-		}
-		LOG("\n");
-		execvpe(path, argv, env);
-		PERROR("execvpe");
 	} else {
-
+		path = argv[0];
 		LOG("execute:");
-		for (i = 0; argv[i]; i++) {
-			LOG(" %s", argv[i]);
+	}
+	for (i = 0; argv[i]; i++) {
+		LOG(" %s", argv[i]);
+	}
+	LOG("\n");
+
+	if (log_fd != STDERR_FILENO) {
+		if (close(log_fd) == -1) {
+			PERROR("close log file descriptor");
+			goto cleanup;
 		}
-		LOG("\n");
-		execvpe(argv[0], argv, env);
-		PERROR("execvpe");
+		log_fd = -1;
 	}
+	execvpe(path, argv, env);
+	PERROR("execvpe");
 
  cleanup:
 	if (argv) {

test/t1008-console.t

@@ -57,7 +57,7 @@ test_expect_success PRINTF,SHELL 'Test console' "
 	test_cmp expected actual
 "
 
-test_expect_success GREP,PRINTF,SHELL 'Test console and terminal' "
+test_expect_success PRINTF,SHELL 'Test console and terminal' "
 	ccon --verbose --config-string '{
 		  \"version\": \"0.4.0\",
 		  \"namespaces\": {
@@ -69,7 +69,7 @@ test_expect_success GREP,PRINTF,SHELL 'Test console and terminal' "
 		    \"terminal\": true,
 		    \"args\": [\"sh\", \"-c\", \"echo hello >>/dev/console && echo goodbye\"]
 		  }
-		}' | grep -v /dev/console >actual &&
+		}' >actual &&
 	printf 'hello\r\ngoodbye\r\n' >expected &&
 	test_cmp expected actual
 "