net/netfilter/nf_nat_redirect.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * (C) 1999-2001 Paul `Rusty' Russell
   4  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   5  * Copyright (c) 2011 Patrick McHardy <kaber@trash.net>
   6  *
   7  * Based on Rusty Russell's IPv4 REDIRECT target. Development of IPv6
   8  * NAT funded by Astaro.
   9  */
  10
  11 #include <linux/if.h>
  12 #include <linux/inetdevice.h>
  13 #include <linux/in.h>
  14 #include <linux/ip.h>
  15 #include <linux/kernel.h>
  16 #include <linux/netdevice.h>
  17 #include <linux/netfilter.h>
  18 #include <linux/types.h>
  19 #include <linux/netfilter_ipv4.h>
  20 #include <linux/netfilter_ipv6.h>
  21 #include <linux/netfilter/x_tables.h>
  22 #include <net/addrconf.h>
  23 #include <net/checksum.h>
  24 #include <net/protocol.h>
  25 #include <net/netfilter/nf_nat.h>
  26 #include <net/netfilter/nf_nat_redirect.h>
  27
  28 static unsigned int
  29 nf_nat_redirect(struct sk_buff *skb, const struct nf_nat_range2 *range,
  30                 const union nf_inet_addr *newdst)
  31 {
  32         struct nf_nat_range2 newrange;
  33         enum ip_conntrack_info ctinfo;
  34         struct nf_conn *ct;
  35
  36         ct = nf_ct_get(skb, &ctinfo);
  37
  38         memset(&newrange, 0, sizeof(newrange));
  39
  40         newrange.flags          = range->flags | NF_NAT_RANGE_MAP_IPS;
  41         newrange.min_addr       = *newdst;
  42         newrange.max_addr       = *newdst;
  43         newrange.min_proto      = range->min_proto;
  44         newrange.max_proto      = range->max_proto;
  45
  46         return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_DST);
  47 }
  48
  49 unsigned int
  50 nf_nat_redirect_ipv4(struct sk_buff *skb, const struct nf_nat_range2 *range,
  51                      unsigned int hooknum)
  52 {
  53         union nf_inet_addr newdst = {};
  54
  55         WARN_ON(hooknum != NF_INET_PRE_ROUTING &&
  56                 hooknum != NF_INET_LOCAL_OUT);
  57
  58         /* Local packets: make them go to loopback */
  59         if (hooknum == NF_INET_LOCAL_OUT) {
  60                 newdst.ip = htonl(INADDR_LOOPBACK);
  61         } else {
  62                 const struct in_device *indev;
  63
  64                 indev = __in_dev_get_rcu(skb->dev);
  65                 if (indev) {
  66                         const struct in_ifaddr *ifa;
  67
  68                         ifa = rcu_dereference(indev->ifa_list);
  69                         if (ifa)
  70                                 newdst.ip = ifa->ifa_local;
  71                 }
  72
  73                 if (!newdst.ip)
  74                         return NF_DROP;
  75         }
  76
  77         return nf_nat_redirect(skb, range, &newdst);
  78 }
  79 EXPORT_SYMBOL_GPL(nf_nat_redirect_ipv4);
  80
  81 static const struct in6_addr loopback_addr = IN6ADDR_LOOPBACK_INIT;
  82
  83 unsigned int
  84 nf_nat_redirect_ipv6(struct sk_buff *skb, const struct nf_nat_range2 *range,
  85                      unsigned int hooknum)
  86 {
  87         union nf_inet_addr newdst = {};
  88
  89         if (hooknum == NF_INET_LOCAL_OUT) {
  90                 newdst.in6 = loopback_addr;
  91         } else {
  92                 struct inet6_dev *idev;
  93                 struct inet6_ifaddr *ifa;
  94                 bool addr = false;
  95
  96                 idev = __in6_dev_get(skb->dev);
  97                 if (idev != NULL) {
  98                         read_lock_bh(&idev->lock);
  99                         list_for_each_entry(ifa, &idev->addr_list, if_list) {
 100                                 newdst.in6 = ifa->addr;
 101                                 addr = true;
 102                                 break;
 103                         }
 104                         read_unlock_bh(&idev->lock);
 105                 }
 106
 107                 if (!addr)
 108                         return NF_DROP;
 109         }
 110
 111         return nf_nat_redirect(skb, range, &newdst);
 112 }
 113 EXPORT_SYMBOL_GPL(nf_nat_redirect_ipv6);