Pablo Neira Ayuso | bbde9fc | 2015-05-31 17:54:44 +0200 | [diff] [blame] | 1 | /* |
| 2 | * (C) 2007 by Sebastian Claßen <sebastian.classen@freenet.ag> |
| 3 | * (C) 2007-2010 by Jan Engelhardt <jengelh@medozas.de> |
| 4 | * |
| 5 | * Extracted from xt_TEE.c |
| 6 | * |
| 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. |
| 10 | */ |
| 11 | #include <linux/ip.h> |
| 12 | #include <linux/module.h> |
| 13 | #include <linux/percpu.h> |
| 14 | #include <linux/route.h> |
| 15 | #include <linux/skbuff.h> |
Daniel Borkmann | a82b0e6 | 2015-09-02 20:54:02 +0200 | [diff] [blame] | 16 | #include <linux/netfilter.h> |
Pablo Neira Ayuso | bbde9fc | 2015-05-31 17:54:44 +0200 | [diff] [blame] | 17 | #include <net/checksum.h> |
| 18 | #include <net/icmp.h> |
| 19 | #include <net/ip.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> |
| 24 | #endif |
| 25 | |
| 26 | static struct net *pick_net(struct sk_buff *skb) |
| 27 | { |
| 28 | #ifdef CONFIG_NET_NS |
| 29 | const struct dst_entry *dst; |
| 30 | |
| 31 | if (skb->dev != NULL) |
| 32 | return dev_net(skb->dev); |
| 33 | dst = skb_dst(skb); |
| 34 | if (dst != NULL && dst->dev != NULL) |
| 35 | return dev_net(dst->dev); |
| 36 | #endif |
| 37 | return &init_net; |
| 38 | } |
| 39 | |
| 40 | static bool nf_dup_ipv4_route(struct sk_buff *skb, const struct in_addr *gw, |
| 41 | int oif) |
| 42 | { |
| 43 | const struct iphdr *iph = ip_hdr(skb); |
| 44 | struct net *net = pick_net(skb); |
| 45 | struct rtable *rt; |
| 46 | struct flowi4 fl4; |
| 47 | |
| 48 | memset(&fl4, 0, sizeof(fl4)); |
| 49 | if (oif != -1) |
| 50 | fl4.flowi4_oif = oif; |
| 51 | |
| 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); |
| 57 | if (IS_ERR(rt)) |
| 58 | return false; |
| 59 | |
| 60 | skb_dst_drop(skb); |
| 61 | skb_dst_set(skb, &rt->dst); |
| 62 | skb->dev = rt->dst.dev; |
| 63 | skb->protocol = htons(ETH_P_IP); |
| 64 | |
| 65 | return true; |
| 66 | } |
| 67 | |
| 68 | void nf_dup_ipv4(struct sk_buff *skb, unsigned int hooknum, |
| 69 | const struct in_addr *gw, int oif) |
| 70 | { |
| 71 | struct iphdr *iph; |
| 72 | |
Pablo Neira Ayuso | d877f07 | 2015-05-31 18:04:11 +0200 | [diff] [blame] | 73 | if (this_cpu_read(nf_skb_duplicated)) |
Pablo Neira Ayuso | bbde9fc | 2015-05-31 17:54:44 +0200 | [diff] [blame] | 74 | return; |
| 75 | /* |
| 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. |
| 79 | */ |
| 80 | skb = pskb_copy(skb, GFP_ATOMIC); |
| 81 | if (skb == NULL) |
| 82 | return; |
| 83 | |
| 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); |
| 90 | #endif |
| 91 | /* |
| 92 | * If we are in PREROUTING/INPUT, the checksum must be recalculated |
| 93 | * since the length could have changed as a result of defragmentation. |
| 94 | * |
| 95 | * We also decrease the TTL to mitigate potential loops between two |
| 96 | * hosts. |
| 97 | * |
| 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. |
| 100 | */ |
| 101 | iph = ip_hdr(skb); |
| 102 | iph->frag_off |= htons(IP_DF); |
| 103 | if (hooknum == NF_INET_PRE_ROUTING || |
| 104 | hooknum == NF_INET_LOCAL_IN) |
| 105 | --iph->ttl; |
| 106 | ip_send_check(iph); |
| 107 | |
| 108 | if (nf_dup_ipv4_route(skb, gw, oif)) { |
| 109 | __this_cpu_write(nf_skb_duplicated, true); |
| 110 | ip_local_out(skb); |
| 111 | __this_cpu_write(nf_skb_duplicated, false); |
| 112 | } else { |
| 113 | kfree_skb(skb); |
| 114 | } |
| 115 | } |
| 116 | EXPORT_SYMBOL_GPL(nf_dup_ipv4); |
| 117 | |
| 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"); |