nf_dup_ipv6.c

 1// SPDX-License-Identifier: GPL-2.0-or-later
 2/*
 3 * (C) 2007 by Sebastian Claßen <sebastian.classen@freenet.ag>
 4 * (C) 2007-2010 by Jan Engelhardt <jengelh@medozas.de>
 5 *
 6 * Extracted from xt_TEE.c
 7 */
 8#include <linux/module.h>
 9#include <linux/percpu.h>
10#include <linux/skbuff.h>
11#include <linux/netfilter.h>
12#include <net/ipv6.h>
13#include <net/ip6_route.h>
14#include <net/netfilter/ipv6/nf_dup_ipv6.h>
15#if IS_ENABLED(CONFIG_NF_CONNTRACK)
16#include <net/netfilter/nf_conntrack.h>
17#endif
18
19static bool nf_dup_ipv6_route(struct net *net, struct sk_buff *skb,
20			      const struct in6_addr *gw, int oif)
21{
22	const struct ipv6hdr *iph = ipv6_hdr(skb);
23	struct dst_entry *dst;
24	struct flowi6 fl6;
25
26	memset(&fl6, 0, sizeof(fl6));
27	if (oif != -1)
28		fl6.flowi6_oif = oif;
29
30	fl6.daddr = *gw;
31	fl6.flowlabel = (__force __be32)(((iph->flow_lbl[0] & 0xF) << 16) |
32			(iph->flow_lbl[1] << 8) | iph->flow_lbl[2]);
33	fl6.flowi6_flags = FLOWI_FLAG_KNOWN_NH;
34	dst = ip6_route_output(net, NULL, &fl6);
35	if (dst->error) {
36		dst_release(dst);
37		return false;
38	}
39	skb_dst_drop(skb);
40	skb_dst_set(skb, dst);
41	skb->dev      = dst_dev(dst);
42	skb->protocol = htons(ETH_P_IPV6);
43
44	return true;
45}
46
47void nf_dup_ipv6(struct net *net, struct sk_buff *skb, unsigned int hooknum,
48		 const struct in6_addr *gw, int oif)
49{
50	local_bh_disable();
51	if (current->in_nf_duplicate)
52		goto out;
53	skb = pskb_copy(skb, GFP_ATOMIC);
54	if (skb == NULL)
55		goto out;
56
57#if IS_ENABLED(CONFIG_NF_CONNTRACK)
58	nf_reset_ct(skb);
59	nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
60#endif
61	if (hooknum == NF_INET_PRE_ROUTING ||
62	    hooknum == NF_INET_LOCAL_IN) {
63		struct ipv6hdr *iph = ipv6_hdr(skb);
64		--iph->hop_limit;
65	}
66	if (nf_dup_ipv6_route(net, skb, gw, oif)) {
67		current->in_nf_duplicate = true;
68		ip6_local_out(net, skb->sk, skb);
69		current->in_nf_duplicate = false;
70	} else {
71		kfree_skb(skb);
72	}
73out:
74	local_bh_enable();
75}
76EXPORT_SYMBOL_GPL(nf_dup_ipv6);
77
78MODULE_AUTHOR("Sebastian Claßen <sebastian.classen@freenet.ag>");
79MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
80MODULE_DESCRIPTION("nf_dup_ipv6: IPv6 packet duplication");
81MODULE_LICENSE("GPL");