dhclient: fix updating the DUID in multiline lease files

The nm_dhcp_dhclient_save_duid() function will save a newly generated
DUID to a previously existing lease file. The function will only save
the DUID if not present in the lease file: in this case, should preserve
the other contents of the lease file.
A dhclient lease file for IPv6 generated by NetworkManager will always
add the DUID as a first item: so in practice finding a lease file
without DUID will never happen.
This has hidden a bug in the function: the loop that is meant to append
the non-duid lines in the lease file would strip all the newlines,
mangling the lease file.
Fix the function allowing to keep the original lines and add a test to
check this functionality is kept well functioning.

FIXME: the new test and the other duid ones already there  store the file
in the current working-directory. Tests should not do that.

2 files changed, 40 insertions, 7 deletions

diff --git a/src/dhcp/nm-dhcp-dhclient-utils.c b/src/dhcp/nm-dhcp-dhclient-utils.c
index 16a76d23eb..a38411ba95 100644
--- a/src/dhcp/nm-dhcp-dhclient-utils.c
+++ b/src/dhcp/nm-dhcp-dhclient-utils.c
@@ -630,8 +630,13 @@ nm_dhcp_dhclient_save_duid (const char *leasefile,
 
 	/* Preserve existing leasefile contents */
 	if (lines) {
-		for (iter = lines; iter && *iter; iter++)
-			g_string_append (s, *iter[0] ? *iter : "\n");
+		for (iter = lines; iter && *iter; iter++) {
+			if (*iter[0])
+				g_string_append (s, *iter);
+			/* avoid to add an extra '\n' at the end of file */
+			if ((iter[1]) != NULL)
+				g_string_append_c (s, '\n');
+		}
 		g_strfreev (lines);
 	}
 
diff --git a/src/dhcp/tests/test-dhcp-dhclient.c b/src/dhcp/tests/test-dhcp-dhclient.c
index a8284b23de..348c625afb 100644
--- a/src/dhcp/tests/test-dhcp-dhclient.c
+++ b/src/dhcp/tests/test-dhcp-dhclient.c
@@ -811,14 +811,14 @@ test_write_existing_duid (void)
 	g_free (contents);
 }
 
+#define DUID "\\000\\001\\000\\001\\023o\\023n\\000\\\"\\372\\214\\326\\302"
 static void
 test_write_existing_commented_duid (void)
 {
-	#define DUID "\\000\\001\\000\\001\\023o\\023n\\000\\\"\\372\\214\\326\\302"
-	#define ORIG_CONTENTS "#default-duid \"\\000\\001\\000\\001\\027X\\350X\\000#\\025\\010~\\254\";\n"
-	const char *expected_contents = \
-		"default-duid \"" DUID "\";\n"
-		ORIG_CONTENTS;
+#define ORIG_CONTENTS "#default-duid \"\\000\\001\\000\\001\\027X\\350X\\000#\\025\\010~\\254\";\n"
+	const char *expected_contents =
+	    "default-duid \"" DUID "\";\n"
+	    ORIG_CONTENTS;
 	GError *error = NULL;
 	char *contents = NULL;
 	gboolean success;
@@ -842,6 +842,33 @@ test_write_existing_commented_duid (void)
 	g_assert_cmpstr (expected_contents, ==, contents);
 
 	g_free (contents);
+#undef ORIG_CONTENTS
+}
+
+static void
+test_write_existing_multiline_duid (void)
+{
+#define ORIG_CONTENTS "### Commented old DUID ###\n" \
+                      "#default-duid \"\\000\\001\\000\\001\\027X\\350X\\000#\\025\\010~\\254\";\n"
+	const char *expected_contents = \
+	    "default-duid \"" DUID "\";\n"
+	    ORIG_CONTENTS;
+	GError *error = NULL;
+	gs_free char *contents = NULL;
+	gboolean success;
+	nmtst_auto_unlinkfile char *path = g_strdup ("test-dhclient-write-existing-multiline-duid.leases");
+
+	success = g_file_set_contents (path, ORIG_CONTENTS, -1, &error);
+	nmtst_assert_success (success, error);
+
+	success = nm_dhcp_dhclient_save_duid (path, DUID, &error);
+	nmtst_assert_success (success, error);
+
+	success = g_file_get_contents (path, &contents, NULL, &error);
+	nmtst_assert_success (success, error);
+
+	g_assert_cmpstr (expected_contents, ==, contents);
+#undef ORIG_CONTENTS
 }
 
 /*****************************************************************************/
@@ -1025,6 +1052,7 @@ main (int argc, char **argv)
 	g_test_add_func ("/dhcp/dhclient/write_duid", test_write_duid);
 	g_test_add_func ("/dhcp/dhclient/write_existing_duid", test_write_existing_duid);
 	g_test_add_func ("/dhcp/dhclient/write_existing_commented_duid", test_write_existing_commented_duid);
+	g_test_add_func ("/dhcp/dhclient/write_existing_multiline_duid", test_write_existing_multiline_duid);
 
 	return g_test_run ();
 }