diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 71709c104081..f61c306de1d0 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -771,13 +771,13 @@ config NETFILTER_XT_TARGET_CHECKSUM
 	depends on NETFILTER_ADVANCED
 	---help---
 	  This option adds a `CHECKSUM' target, which can be used in the iptables mangle
-	  table.
+	  table to work around buggy DHCP clients in virtualized environments.
 
-	  You can use this target to 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.
+	  Some old DHCP clients drop packets because they are not aware
+	  that the checksum would normally be offloaded to hardware and
+	  thus should be considered valid.
+	  This target can be used to fill in the checksum using iptables
+	  when such packets are sent via a virtual network device.
 
 	  To compile it as a module, choose M here.  If unsure, say N.
 
diff --git a/net/netfilter/xt_CHECKSUM.c b/net/netfilter/xt_CHECKSUM.c
index 9f4151ec3e06..6c7aa6a0a0d2 100644
--- a/net/netfilter/xt_CHECKSUM.c
+++ b/net/netfilter/xt_CHECKSUM.c
@@ -16,6 +16,9 @@
 #include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/xt_CHECKSUM.h>
 
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv6/ip6_tables.h>
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Michael S. Tsirkin <mst@redhat.com>");
 MODULE_DESCRIPTION("Xtables: checksum modification");
@@ -25,7 +28,7 @@ MODULE_ALIAS("ip6t_CHECKSUM");
 static unsigned int
 checksum_tg(struct sk_buff *skb, const struct xt_action_param *par)
 {
-	if (skb->ip_summed == CHECKSUM_PARTIAL)
+	if (skb->ip_summed == CHECKSUM_PARTIAL && !skb_is_gso(skb))
 		skb_checksum_help(skb);
 
 	return XT_CONTINUE;
@@ -34,6 +37,8 @@ checksum_tg(struct sk_buff *skb, const struct xt_action_param *par)
 static int checksum_tg_check(const struct xt_tgchk_param *par)
 {
 	const struct xt_CHECKSUM_info *einfo = par->targinfo;
+	const struct ip6t_ip6 *i6 = par->entryinfo;
+	const struct ipt_ip *i4 = par->entryinfo;
 
 	if (einfo->operation & ~XT_CHECKSUM_OP_FILL) {
 		pr_info_ratelimited("unsupported CHECKSUM operation %x\n",
@@ -43,6 +48,21 @@ static int checksum_tg_check(const struct xt_tgchk_param *par)
 	if (!einfo->operation)
 		return -EINVAL;
 
+	switch (par->family) {
+	case NFPROTO_IPV4:
+		if (i4->proto == IPPROTO_UDP &&
+		    (i4->invflags & XT_INV_PROTO) == 0)
+			return 0;
+		break;
+	case NFPROTO_IPV6:
+		if ((i6->flags & IP6T_F_PROTO) &&
+		    i6->proto == IPPROTO_UDP &&
+		    (i6->invflags & XT_INV_PROTO) == 0)
+			return 0;
+		break;
+	}
+
+	pr_warn_once("CHECKSUM should be avoided.  If really needed, restrict with \"-p udp\" and only use in OUTPUT\n");
 	return 0;
 }