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- // SPDX-License-Identifier: GPL-2.0-or-later
- /*
- * (C) 2007 by Sebastian Claßen <sebastian.classen@freenet.ag>
- * (C) 2007-2010 by Jan Engelhardt <jengelh@medozas.de>
- *
- * Extracted from xt_TEE.c
- */
- #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_ct(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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