// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* (C) 2007 by Sebastian Claßen <sebastian.classen@freenet.ag>
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* (C) 2007-2010 by Jan Engelhardt <jengelh@medozas.de>
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*
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* Extracted from xt_TEE.c
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*/
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#include <linux/ip.h>
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#include <linux/module.h>
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#include <linux/percpu.h>
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#include <linux/route.h>
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#include <linux/skbuff.h>
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#include <linux/netfilter.h>
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#include <net/checksum.h>
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#include <net/icmp.h>
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#include <net/ip.h>
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#include <net/route.h>
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#include <net/netfilter/ipv4/nf_dup_ipv4.h>
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#if IS_ENABLED(CONFIG_NF_CONNTRACK)
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#include <net/netfilter/nf_conntrack.h>
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#endif
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static bool nf_dup_ipv4_route(struct net *net, struct sk_buff *skb,
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const struct in_addr *gw, int oif)
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{
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const struct iphdr *iph = ip_hdr(skb);
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struct rtable *rt;
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struct flowi4 fl4;
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memset(&fl4, 0, sizeof(fl4));
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if (oif != -1)
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fl4.flowi4_oif = oif;
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fl4.daddr = gw->s_addr;
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fl4.flowi4_tos = RT_TOS(iph->tos);
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fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
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fl4.flowi4_flags = FLOWI_FLAG_KNOWN_NH;
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rt = ip_route_output_key(net, &fl4);
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if (IS_ERR(rt))
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return false;
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skb_dst_drop(skb);
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skb_dst_set(skb, &rt->dst);
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skb->dev = rt->dst.dev;
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skb->protocol = htons(ETH_P_IP);
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return true;
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}
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void nf_dup_ipv4(struct net *net, struct sk_buff *skb, unsigned int hooknum,
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const struct in_addr *gw, int oif)
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{
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struct iphdr *iph;
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if (this_cpu_read(nf_skb_duplicated))
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return;
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/*
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* Copy the skb, and route the copy. Will later return %XT_CONTINUE for
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* the original skb, which should continue on its way as if nothing has
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* happened. The copy should be independently delivered to the gateway.
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*/
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skb = pskb_copy(skb, GFP_ATOMIC);
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if (skb == NULL)
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return;
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#if IS_ENABLED(CONFIG_NF_CONNTRACK)
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/* Avoid counting cloned packets towards the original connection. */
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nf_reset_ct(skb);
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nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
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#endif
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/*
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* If we are in PREROUTING/INPUT, decrease the TTL to mitigate potential
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* loops between two hosts.
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*
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* Set %IP_DF so that the original source is notified of a potentially
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* decreased MTU on the clone route. IPv6 does this too.
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*
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* IP header checksum will be recalculated at ip_local_out.
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*/
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iph = ip_hdr(skb);
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iph->frag_off |= htons(IP_DF);
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if (hooknum == NF_INET_PRE_ROUTING ||
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hooknum == NF_INET_LOCAL_IN)
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--iph->ttl;
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if (nf_dup_ipv4_route(net, skb, gw, oif)) {
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__this_cpu_write(nf_skb_duplicated, true);
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ip_local_out(net, skb->sk, skb);
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__this_cpu_write(nf_skb_duplicated, false);
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} else {
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kfree_skb(skb);
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}
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}
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EXPORT_SYMBOL_GPL(nf_dup_ipv4);
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MODULE_AUTHOR("Sebastian Claßen <sebastian.classen@freenet.ag>");
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MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
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MODULE_DESCRIPTION("nf_dup_ipv4: Duplicate IPv4 packet");
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MODULE_LICENSE("GPL");
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