1 files changed, 133 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/ipt_ECN.c b/net/ipv4/netfilter/ipt_ECN.c
new file mode 100644
index 000000000..5930d3b02
--- /dev/null
+++ b/net/ipv4/netfilter/ipt_ECN.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* iptables module for the IPv4 and TCP ECN bits, Version 1.5
+ *
+ * (C) 2002 by Harald Welte <laforge@netfilter.org>
+*/
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/in.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/ip.h>
+#include <net/ip.h>
+#include <linux/tcp.h>
+#include <net/checksum.h>
+
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv4/ipt_ECN.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
+MODULE_DESCRIPTION("Xtables: Explicit Congestion Notification (ECN) flag modification");
+
+/* set ECT codepoint from IP header.
+ * 	return false if there was an error. */
+static inline bool
+set_ect_ip(struct sk_buff *skb, const struct ipt_ECN_info *einfo)
+{
+	struct iphdr *iph = ip_hdr(skb);
+
+	if ((iph->tos & IPT_ECN_IP_MASK) != (einfo->ip_ect & IPT_ECN_IP_MASK)) {
+		__u8 oldtos;
+		if (skb_ensure_writable(skb, sizeof(struct iphdr)))
+			return false;
+		iph = ip_hdr(skb);
+		oldtos = iph->tos;
+		iph->tos &= ~IPT_ECN_IP_MASK;
+		iph->tos |= (einfo->ip_ect & IPT_ECN_IP_MASK);
+		csum_replace2(&iph->check, htons(oldtos), htons(iph->tos));
+	}
+	return true;
+}
+
+/* Return false if there was an error. */
+static inline bool
+set_ect_tcp(struct sk_buff *skb, const struct ipt_ECN_info *einfo)
+{
+	struct tcphdr _tcph, *tcph;
+	__be16 oldval;
+
+	/* Not enough header? */
+	tcph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_tcph), &_tcph);
+	if (!tcph)
+		return false;
+
+	if ((!(einfo->operation & IPT_ECN_OP_SET_ECE) ||
+	     tcph->ece == einfo->proto.tcp.ece) &&
+	    (!(einfo->operation & IPT_ECN_OP_SET_CWR) ||
+	     tcph->cwr == einfo->proto.tcp.cwr))
+		return true;
+
+	if (skb_ensure_writable(skb, ip_hdrlen(skb) + sizeof(*tcph)))
+		return false;
+	tcph = (void *)ip_hdr(skb) + ip_hdrlen(skb);
+
+	oldval = ((__be16 *)tcph)[6];
+	if (einfo->operation & IPT_ECN_OP_SET_ECE)
+		tcph->ece = einfo->proto.tcp.ece;
+	if (einfo->operation & IPT_ECN_OP_SET_CWR)
+		tcph->cwr = einfo->proto.tcp.cwr;
+
+	inet_proto_csum_replace2(&tcph->check, skb,
+				 oldval, ((__be16 *)tcph)[6], false);
+	return true;
+}
+
+static unsigned int
+ecn_tg(struct sk_buff *skb, const struct xt_action_param *par)
+{
+	const struct ipt_ECN_info *einfo = par->targinfo;
+
+	if (einfo->operation & IPT_ECN_OP_SET_IP)
+		if (!set_ect_ip(skb, einfo))
+			return NF_DROP;
+
+	if (einfo->operation & (IPT_ECN_OP_SET_ECE | IPT_ECN_OP_SET_CWR) &&
+	    ip_hdr(skb)->protocol == IPPROTO_TCP)
+		if (!set_ect_tcp(skb, einfo))
+			return NF_DROP;
+
+	return XT_CONTINUE;
+}
+
+static int ecn_tg_check(const struct xt_tgchk_param *par)
+{
+	const struct ipt_ECN_info *einfo = par->targinfo;
+	const struct ipt_entry *e = par->entryinfo;
+
+	if (einfo->operation & IPT_ECN_OP_MASK)
+		return -EINVAL;
+
+	if (einfo->ip_ect & ~IPT_ECN_IP_MASK)
+		return -EINVAL;
+
+	if ((einfo->operation & (IPT_ECN_OP_SET_ECE|IPT_ECN_OP_SET_CWR)) &&
+	    (e->ip.proto != IPPROTO_TCP || (e->ip.invflags & XT_INV_PROTO))) {
+		pr_info_ratelimited("cannot use operation on non-tcp rule\n");
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static struct xt_target ecn_tg_reg __read_mostly = {
+	.name		= "ECN",
+	.family		= NFPROTO_IPV4,
+	.target		= ecn_tg,
+	.targetsize	= sizeof(struct ipt_ECN_info),
+	.table		= "mangle",
+	.checkentry	= ecn_tg_check,
+	.me		= THIS_MODULE,
+};
+
+static int __init ecn_tg_init(void)
+{
+	return xt_register_target(&ecn_tg_reg);
+}
+
+static void __exit ecn_tg_exit(void)
+{
+	xt_unregister_target(&ecn_tg_reg);
+}
+
+module_init(ecn_tg_init);
+module_exit(ecn_tg_exit);