1 files changed, 143 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/iptable_mangle.c b/net/ipv4/netfilter/iptable_mangle.c
new file mode 100644
index 000000000..3abb430af
--- /dev/null
+++ b/net/ipv4/netfilter/iptable_mangle.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
+ *
+ * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
+ * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
+ */
+#include <linux/module.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <net/sock.h>
+#include <net/route.h>
+#include <linux/ip.h>
+#include <net/ip.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
+MODULE_DESCRIPTION("iptables mangle table");
+
+#define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
+			    (1 << NF_INET_LOCAL_IN) | \
+			    (1 << NF_INET_FORWARD) | \
+			    (1 << NF_INET_LOCAL_OUT) | \
+			    (1 << NF_INET_POST_ROUTING))
+
+static const struct xt_table packet_mangler = {
+	.name		= "mangle",
+	.valid_hooks	= MANGLE_VALID_HOOKS,
+	.me		= THIS_MODULE,
+	.af		= NFPROTO_IPV4,
+	.priority	= NF_IP_PRI_MANGLE,
+};
+
+static unsigned int
+ipt_mangle_out(void *priv, struct sk_buff *skb, const struct nf_hook_state *state)
+{
+	unsigned int ret;
+	const struct iphdr *iph;
+	u_int8_t tos;
+	__be32 saddr, daddr;
+	u_int32_t mark;
+	int err;
+
+	/* Save things which could affect route */
+	mark = skb->mark;
+	iph = ip_hdr(skb);
+	saddr = iph->saddr;
+	daddr = iph->daddr;
+	tos = iph->tos;
+
+	ret = ipt_do_table(priv, skb, state);
+	/* Reroute for ANY change. */
+	if (ret != NF_DROP && ret != NF_STOLEN) {
+		iph = ip_hdr(skb);
+
+		if (iph->saddr != saddr ||
+		    iph->daddr != daddr ||
+		    skb->mark != mark ||
+		    iph->tos != tos) {
+			err = ip_route_me_harder(state->net, state->sk, skb, RTN_UNSPEC);
+			if (err < 0)
+				ret = NF_DROP_ERR(err);
+		}
+	}
+
+	return ret;
+}
+
+/* The work comes in here from netfilter.c. */
+static unsigned int
+iptable_mangle_hook(void *priv,
+		     struct sk_buff *skb,
+		     const struct nf_hook_state *state)
+{
+	if (state->hook == NF_INET_LOCAL_OUT)
+		return ipt_mangle_out(priv, skb, state);
+	return ipt_do_table(priv, skb, state);
+}
+
+static struct nf_hook_ops *mangle_ops __read_mostly;
+static int iptable_mangle_table_init(struct net *net)
+{
+	struct ipt_replace *repl;
+	int ret;
+
+	repl = ipt_alloc_initial_table(&packet_mangler);
+	if (repl == NULL)
+		return -ENOMEM;
+	ret = ipt_register_table(net, &packet_mangler, repl, mangle_ops);
+	kfree(repl);
+	return ret;
+}
+
+static void __net_exit iptable_mangle_net_pre_exit(struct net *net)
+{
+	ipt_unregister_table_pre_exit(net, "mangle");
+}
+
+static void __net_exit iptable_mangle_net_exit(struct net *net)
+{
+	ipt_unregister_table_exit(net, "mangle");
+}
+
+static struct pernet_operations iptable_mangle_net_ops = {
+	.pre_exit = iptable_mangle_net_pre_exit,
+	.exit = iptable_mangle_net_exit,
+};
+
+static int __init iptable_mangle_init(void)
+{
+	int ret = xt_register_template(&packet_mangler,
+				       iptable_mangle_table_init);
+	if (ret < 0)
+		return ret;
+
+	mangle_ops = xt_hook_ops_alloc(&packet_mangler, iptable_mangle_hook);
+	if (IS_ERR(mangle_ops)) {
+		xt_unregister_template(&packet_mangler);
+		ret = PTR_ERR(mangle_ops);
+		return ret;
+	}
+
+	ret = register_pernet_subsys(&iptable_mangle_net_ops);
+	if (ret < 0) {
+		xt_unregister_template(&packet_mangler);
+		kfree(mangle_ops);
+		return ret;
+	}
+
+	return ret;
+}
+
+static void __exit iptable_mangle_fini(void)
+{
+	unregister_pernet_subsys(&iptable_mangle_net_ops);
+	xt_unregister_template(&packet_mangler);
+	kfree(mangle_ops);
+}
+
+module_init(iptable_mangle_init);
+module_exit(iptable_mangle_fini);