tools: bpftool: add support for quotations in batch files

Improve argument parsing from batch input files in order to support
arguments enclosed between single (') or double quotes ("). For example,
this command can now be parsed in batch mode:

    bpftool prog dump xlated id 1337 file "/tmp/my file with spaces"

The function responsible for parsing command arguments is copied from
its counterpart in lib/utils.c in iproute2 package.
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/bpf/bpftool/main.c

@@ -160,6 +160,54 @@ void fprint_hex(FILE *f, void *arg, unsigned int n, const char *sep)
 	}
 }
 
+/* Split command line into argument vector. */
+static int make_args(char *line, char *n_argv[], int maxargs, int cmd_nb)
+{
+	static const char ws[] = " \t\r\n";
+	char *cp = line;
+	int n_argc = 0;
+
+	while (*cp) {
+		/* Skip leading whitespace. */
+		cp += strspn(cp, ws);
+
+		if (*cp == '\0')
+			break;
+
+		if (n_argc >= (maxargs - 1)) {
+			p_err("too many arguments to command %d", cmd_nb);
+			return -1;
+		}
+
+		/* Word begins with quote. */
+		if (*cp == '\'' || *cp == '"') {
+			char quote = *cp++;
+
+			n_argv[n_argc++] = cp;
+			/* Find ending quote. */
+			cp = strchr(cp, quote);
+			if (!cp) {
+				p_err("unterminated quoted string in command %d",
+				      cmd_nb);
+				return -1;
+			}
+		} else {
+			n_argv[n_argc++] = cp;
+
+			/* Find end of word. */
+			cp += strcspn(cp, ws);
+			if (*cp == '\0')
+				break;
+		}
+
+		/* Separate words. */
+		*cp++ = 0;
+	}
+	n_argv[n_argc] = NULL;
+
+	return n_argc;
+}
+
 static int do_batch(int argc, char **argv);
 
 static const struct cmd cmds[] = {
@@ -241,22 +289,11 @@ static int do_batch(int argc, char **argv)
 			strcat(buf, contline);
 		}
 
-		n_argc = 0;
-		n_argv[n_argc] = strtok(buf, " \t\n");
-
-		while (n_argv[n_argc]) {
-			n_argc++;
-			if (n_argc == ARRAY_SIZE(n_argv)) {
-				p_err("command %d has too many arguments, skip",
-				      lines);
-				n_argc = 0;
-				break;
-			}
-			n_argv[n_argc] = strtok(NULL, " \t\n");
-		}
-
+		n_argc = make_args(buf, n_argv, BATCH_ARG_NB_MAX, lines);
 		if (!n_argc)
 			continue;
+		if (n_argc < 0)
+			goto err_close;
 
 		if (json_output) {
 			jsonw_start_object(json_wtr);