2 * (C) 2007 by Sebastian Claßen <sebastian.classen@freenet.ag>
3 * (C) 2007-2010 by Jan Engelhardt <jengelh@medozas.de>
5 * Extracted from xt_TEE.c
7 * This program is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License version 2 or later, as
9 * published by the Free Software Foundation.
12 #include <linux/module.h>
13 #include <linux/percpu.h>
14 #include <linux/route.h>
15 #include <linux/skbuff.h>
16 #include <linux/netfilter.h>
17 #include <net/checksum.h>
20 #include <net/route.h>
21 #include <net/netfilter/ipv4/nf_dup_ipv4.h>
22 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
23 #include <net/netfilter/nf_conntrack.h>
26 static struct net *pick_net(struct sk_buff *skb)
29 const struct dst_entry *dst;
32 return dev_net(skb->dev);
34 if (dst != NULL && dst->dev != NULL)
35 return dev_net(dst->dev);
40 static bool nf_dup_ipv4_route(struct sk_buff *skb, const struct in_addr *gw,
43 const struct iphdr *iph = ip_hdr(skb);
44 struct net *net = pick_net(skb);
48 memset(&fl4, 0, sizeof(fl4));
52 fl4.daddr = gw->s_addr;
53 fl4.flowi4_tos = RT_TOS(iph->tos);
54 fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
55 fl4.flowi4_flags = FLOWI_FLAG_KNOWN_NH;
56 rt = ip_route_output_key(net, &fl4);
61 skb_dst_set(skb, &rt->dst);
62 skb->dev = rt->dst.dev;
63 skb->protocol = htons(ETH_P_IP);
68 void nf_dup_ipv4(struct sk_buff *skb, unsigned int hooknum,
69 const struct in_addr *gw, int oif)
73 if (this_cpu_read(nf_skb_duplicated))
76 * Copy the skb, and route the copy. Will later return %XT_CONTINUE for
77 * the original skb, which should continue on its way as if nothing has
78 * happened. The copy should be independently delivered to the gateway.
80 skb = pskb_copy(skb, GFP_ATOMIC);
84 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
85 /* Avoid counting cloned packets towards the original connection. */
86 nf_conntrack_put(skb->nfct);
87 skb->nfct = &nf_ct_untracked_get()->ct_general;
88 skb->nfctinfo = IP_CT_NEW;
89 nf_conntrack_get(skb->nfct);
92 * If we are in PREROUTING/INPUT, the checksum must be recalculated
93 * since the length could have changed as a result of defragmentation.
95 * We also decrease the TTL to mitigate potential loops between two
98 * Set %IP_DF so that the original source is notified of a potentially
99 * decreased MTU on the clone route. IPv6 does this too.
102 iph->frag_off |= htons(IP_DF);
103 if (hooknum == NF_INET_PRE_ROUTING ||
104 hooknum == NF_INET_LOCAL_IN)
108 if (nf_dup_ipv4_route(skb, gw, oif)) {
109 __this_cpu_write(nf_skb_duplicated, true);
111 __this_cpu_write(nf_skb_duplicated, false);
116 EXPORT_SYMBOL_GPL(nf_dup_ipv4);
118 MODULE_AUTHOR("Sebastian Claßen <sebastian.classen@freenet.ag>");
119 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
120 MODULE_DESCRIPTION("nf_dup_ipv4: Duplicate IPv4 packet");
121 MODULE_LICENSE("GPL");