net-test: Adds the --dry_run flag to packetdrill to verify but not start a run.

The --dry_run command line flag causes packetdrill to verify command
line args, load and parse the given script, but not execute it. If any
errors are found during these steps, packetdrill will print an error
as before.  Otherwise, it will exit(0) and produce no output.

Change-Id: Ibf4502c6ea326539346a58b58d7feb29d4b3da69

gtests/net/packetdrill/config.c

@@ -57,6 +57,7 @@ enum option_codes {
 	OPT_WIRE_SERVER_DEV,
 	OPT_TCP_TS_TICK_USECS,
 	OPT_NON_FATAL,
+	OPT_DRY_RUN,
 	OPT_VERBOSE = 'v',	/* our only single-letter option */
 };
 
@@ -84,6 +85,7 @@ struct option options[] = {
 	{ "wire_server_dev",	.has_arg = true,  NULL, OPT_WIRE_SERVER_DEV },
 	{ "tcp_ts_tick_usecs",	.has_arg = true,  NULL, OPT_TCP_TS_TICK_USECS },
 	{ "non_fatal",		.has_arg = true,  NULL, OPT_NON_FATAL },
+	{ "dry_run",		.has_arg = false, NULL, OPT_DRY_RUN },
 	{ "verbose",		.has_arg = false, NULL, OPT_VERBOSE },
 	{ NULL },
 };
@@ -113,6 +115,7 @@ void show_usage(void)
 		"\t[--wire_server_port=<server_port>]\n"
 		"\t[--wire_client_dev=<eth_dev_name>]\n"
 		"\t[--wire_server_dev=<eth_dev_name>]\n"
+		"\t[--dry_run]\n"
 		"\t[--verbose|-v]\n"
 		"\tscript_path ...\n");
 }
@@ -443,6 +446,9 @@ static void process_option(int opt, char *optarg, struct config *config,
 	case OPT_WIRE_SERVER_DEV:
 		config->wire_server_device = strdup(optarg);
 		break;
+	case OPT_DRY_RUN:
+		config->dry_run = true;
+		break;
 	case OPT_VERBOSE:
 		config->verbose = true;
 		break;

gtests/net/packetdrill/config.h

@@ -78,6 +78,8 @@ struct config {
 	bool non_fatal_packet;		/* treat packet asserts as non-fatal */
 	bool non_fatal_syscall;		/* treat syscall asserts as non-fatal */
 
+	bool dry_run;			/* parse script but don't execute? */
+
 	bool verbose;			/* print detailed debug info? */
 	char *script_path;		/* pathname of script file */
 
@@ -101,7 +103,6 @@ struct config {
 	struct ip_address wire_server_ip;  /* IP of on-the-wire server */
 	char *wire_server_ip_string;	   /* malloc-ed server IP string */
 	u16 wire_server_port;		   /* the port the server listens on */
-
 };
 
 /* Top-level info about the invocation of a test script */

gtests/net/packetdrill/packetdrill.c

@@ -101,6 +101,10 @@ int main(int argc, char *argv[])
 						script_path, NULL))
 			exit(EXIT_FAILURE);
 
+		/* If --dry_run, then don't actually execute the script. */
+		if (config.dry_run)
+			continue;
+
 		run_init_scripts(&config);
 		run_script(&config, &script);
 	}

gtests/net/packetdrill/parser.y

@@ -176,7 +176,7 @@ void read_script(const char *script_path, struct script *script)
 
 		/* Allocate a buffer big enough for the whole file. */
 		if (stat(script_path, &script_info) != 0)
-			die("stat() of script file '%s': %s\n",
+			die("parse error: stat() of script file '%s': %s\n",
 			    script_path, strerror(errno));
 
 		/* Pick a buffer size larger than the file, so we'll
@@ -190,12 +190,12 @@ void read_script(const char *script_path, struct script *script)
 		/* Read the file into our buffer. */
 		fd = open(script_path, O_RDONLY);
 		if (fd < 0)
-			die("error opening script file '%s': %s\n",
+			die("parse error opening script file '%s': %s\n",
 			    script_path, strerror(errno));
 
 		script->length = read(fd, script->buffer, size);
 		if (script->length < 0)
-			die("error reading script file '%s': %s\n",
+			die("parse error reading script file '%s': %s\n",
 			    script_path, strerror(errno));
 
 		/* If we filled the buffer, then probably another
@@ -239,7 +239,7 @@ int parse_script(const struct config *config,
 	/* Now parse the script from our buffer. */
 	yyin = fmemopen(script->buffer, script->length, "r");
 	if (yyin == NULL)
-		die_perror("fmemopen: error opening script buffer");
+		die_perror("fmemopen: parse error opening script buffer");
 
 	current_script_path = config->script_path;
 	in_config = config;
@@ -280,7 +280,7 @@ static void yyerror(const char *message)
 static void semantic_error(const char* message)
 {
 	assert(current_script_line >= 0);
-	die("%s:%d: error: %s\n",
+	die("%s:%d: semantic error: %s\n",
 	    current_script_path, current_script_line, message);
 }