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/*
* (C) 2007 by Sebastian Claßen <sebastian.classen@freenet.ag>
* (C) 2007-2010 by Jan Engelhardt <jengelh@medozas.de>
*
* Extracted from xt_TEE.c
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 or later, as
* published by the Free Software Foundation.
*/
#include <linux/ip.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/route.h>
#include <linux/skbuff.h>
#include <linux/netfilter.h>
#include <net/checksum.h>
#include <net/icmp.h>
#include <net/ip.h>
#include <net/route.h>
#include <net/netfilter/ipv4/nf_dup_ipv4.h>
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
#include <net/netfilter/nf_conntrack.h>
#endif
static bool nf_dup_ipv4_route(struct net *net, struct sk_buff *skb,
const struct in_addr *gw, int oif)
{
const struct iphdr *iph = ip_hdr(skb);
struct rtable *rt;
struct flowi4 fl4;
memset(&fl4, 0, sizeof(fl4));
if (oif != -1)
fl4.flowi4_oif = oif;
fl4.daddr = gw->s_addr;
fl4.flowi4_tos = RT_TOS(iph->tos);
fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
fl4.flowi4_flags = FLOWI_FLAG_KNOWN_NH;
rt = ip_route_output_key(net, &fl4);
if (IS_ERR(rt))
return false;
skb_dst_drop(skb);
skb_dst_set(skb, &rt->dst);
skb->dev = rt->dst.dev;
skb->protocol = htons(ETH_P_IP);
return true;
}
void nf_dup_ipv4(struct net *net, struct sk_buff *skb, unsigned int hooknum,
const struct in_addr *gw, int oif)
{
struct iphdr *iph;
if (this_cpu_read(nf_skb_duplicated))
return;
/*
* Copy the skb, and route the copy. Will later return %XT_CONTINUE for
* the original skb, which should continue on its way as if nothing has
* happened. The copy should be independently delivered to the gateway.
*/
skb = pskb_copy(skb, GFP_ATOMIC);
if (skb == NULL)
return;
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
/* Avoid counting cloned packets towards the original connection. */
nf_reset(skb);
nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
#endif
/*
* If we are in PREROUTING/INPUT, decrease the TTL to mitigate potential
* loops between two hosts.
*
* Set %IP_DF so that the original source is notified of a potentially
* decreased MTU on the clone route. IPv6 does this too.
*
* IP header checksum will be recalculated at ip_local_out.
*/
iph = ip_hdr(skb);
iph->frag_off |= htons(IP_DF);
if (hooknum == NF_INET_PRE_ROUTING ||
hooknum == NF_INET_LOCAL_IN)
--iph->ttl;
if (nf_dup_ipv4_route(net, skb, gw, oif)) {
__this_cpu_write(nf_skb_duplicated, true);
ip_local_out(net, skb->sk, skb);
__this_cpu_write(nf_skb_duplicated, false);
} else {
kfree_skb(skb);
}
}
EXPORT_SYMBOL_GPL(nf_dup_ipv4);
MODULE_AUTHOR("Sebastian Claßen <sebastian.classen@freenet.ag>");
MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
MODULE_DESCRIPTION("nf_dup_ipv4: Duplicate IPv4 packet");
MODULE_LICENSE("GPL");
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