| /* |
| * (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_conntrack_put(skb->nfct); |
| skb->nfct = &nf_ct_untracked_get()->ct_general; |
| skb->nfctinfo = IP_CT_NEW; |
| nf_conntrack_get(skb->nfct); |
| #endif |
| /* |
| * If we are in PREROUTING/INPUT, the checksum must be recalculated |
| * since the length could have changed as a result of defragmentation. |
| * |
| * We also 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. |
| */ |
| iph = ip_hdr(skb); |
| iph->frag_off |= htons(IP_DF); |
| if (hooknum == NF_INET_PRE_ROUTING || |
| hooknum == NF_INET_LOCAL_IN) |
| --iph->ttl; |
| ip_send_check(iph); |
| |
| 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"); |