iptables/iptables-1.4.7-xt_CHECKSUM.patch

diff --git a/extensions/libxt_CHECKSUM.c b/extensions/libxt_CHECKSUM.c
new file mode 100644
index 0000000..00fbd8f
--- /dev/null
+++ b/extensions/libxt_CHECKSUM.c
@@ -0,0 +1,99 @@
+/* Shared library add-on to xtables for CHECKSUM
+ *
+ * (C) 2002 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2010 by Red Hat, Inc
+ * Author: Michael S. Tsirkin <mst@redhat.com>
+ *
+ * This program is distributed under the terms of GNU GPL v2, 1991
+ *
+ * libxt_CHECKSUM.c borrowed some bits from libipt_ECN.c
+ *
+ * $Id$
+ */
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <getopt.h>
+
+#include <xtables.h>
+#include <linux/netfilter/xt_CHECKSUM.h>
+
+static void CHECKSUM_help(void)
+{
+	printf(
+"CHECKSUM target options\n"
+"  --checksum-fill			Fill in packet checksum.\n");
+}
+
+static const struct option CHECKSUM_opts[] = {
+	{ "checksum-fill", 0, NULL, 'F' },
+	{ .name = NULL }
+};
+
+static int CHECKSUM_parse(int c, char **argv, int invert, unsigned int *flags,
+                     const void *entry, struct xt_entry_target **target)
+{
+	struct xt_CHECKSUM_info *einfo
+		= (struct xt_CHECKSUM_info *)(*target)->data;
+
+	switch (c) {
+	case 'F':
+		if (*flags)
+			xtables_error(PARAMETER_PROBLEM,
+			        "CHECKSUM target: Only use --checksum-fill ONCE!");
+		einfo->operation = XT_CHECKSUM_OP_FILL;
+		*flags |= XT_CHECKSUM_OP_FILL;
+		break;
+	default:
+		return 0;
+	}
+
+	return 1;
+}
+
+static void CHECKSUM_check(unsigned int flags)
+{
+	if (!flags)
+		xtables_error(PARAMETER_PROBLEM,
+		           "CHECKSUM target: Parameter --checksum-fill is required");
+}
+
+static void CHECKSUM_print(const void *ip, const struct xt_entry_target *target,
+                      int numeric)
+{
+	const struct xt_CHECKSUM_info *einfo =
+		(const struct xt_CHECKSUM_info *)target->data;
+
+	printf("CHECKSUM ");
+
+	if (einfo->operation & XT_CHECKSUM_OP_FILL)
+		printf("fill ");
+}
+
+static void CHECKSUM_save(const void *ip, const struct xt_entry_target *target)
+{
+	const struct xt_CHECKSUM_info *einfo =
+		(const struct xt_CHECKSUM_info *)target->data;
+
+	if (einfo->operation & XT_CHECKSUM_OP_FILL)
+		printf("--checksum-fill ");
+}
+
+static struct xtables_target checksum_tg_reg = {
+	.name		= "CHECKSUM",
+	.version	= XTABLES_VERSION,
+	.family		= NFPROTO_UNSPEC,
+	.size		= XT_ALIGN(sizeof(struct xt_CHECKSUM_info)),
+	.userspacesize	= XT_ALIGN(sizeof(struct xt_CHECKSUM_info)),
+	.help		= CHECKSUM_help,
+	.parse		= CHECKSUM_parse,
+	.final_check	= CHECKSUM_check,
+	.print		= CHECKSUM_print,
+	.save		= CHECKSUM_save,
+	.extra_opts	= CHECKSUM_opts,
+};
+
+void _init(void)
+{
+	xtables_register_target(&checksum_tg_reg);
+}
diff --git a/extensions/libxt_CHECKSUM.man b/extensions/libxt_CHECKSUM.man
new file mode 100644
index 0000000..92ae700
--- /dev/null
+++ b/extensions/libxt_CHECKSUM.man
@@ -0,0 +1,8 @@
+This target allows to selectively work around broken/old applications.
+It can only be used in the mangle table.
+.TP
+\fB\-\-checksum\-fill\fP
+Compute and fill in the checksum in a packet that lacks a checksum.
+This is particularly useful, if you need to work around old applications
+such as dhcp clients, that do not work well with checksum offloads,
+but don't want to disable checksum offload in your device.