net/ipv6/netfilter/ip6table_mangle.c

   1 /*
   2  * IPv6 packet mangling table, a port of the IPv4 mangle table to IPv6
   3  *
   4  * Copyright (C) 2000-2001 by Harald Welte <laforge@gnumonks.org>
   5  * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11 #include <linux/module.h>
  12 #include <linux/netfilter_ipv6/ip6_tables.h>
  13 #include <linux/slab.h>
  14 #include <net/ipv6.h>
  15
  16 MODULE_LICENSE("GPL");
  17 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  18 MODULE_DESCRIPTION("ip6tables mangle table");
  19
  20 #define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
  21                             (1 << NF_INET_LOCAL_IN) | \
  22                             (1 << NF_INET_FORWARD) | \
  23                             (1 << NF_INET_LOCAL_OUT) | \
  24                             (1 << NF_INET_POST_ROUTING))
  25
  26 static const struct xt_table packet_mangler = {
  27         .name           = "mangle",
  28         .valid_hooks    = MANGLE_VALID_HOOKS,
  29         .me             = THIS_MODULE,
  30         .af             = NFPROTO_IPV6,
  31         .priority       = NF_IP6_PRI_MANGLE,
  32 };
  33
  34 static unsigned int
  35 ip6t_mangle_out(struct sk_buff *skb, const struct net_device *out)
  36 {
  37         unsigned int ret;
  38         struct in6_addr saddr, daddr;
  39         u_int8_t hop_limit;
  40         u_int32_t flowlabel, mark;
  41
  42 #if 0
  43         /* root is playing with raw sockets. */
  44         if (skb->len < sizeof(struct iphdr) ||
  45             ip_hdrlen(skb) < sizeof(struct iphdr)) {
  46                 net_warn_ratelimited("ip6t_hook: happy cracking\n");
  47                 return NF_ACCEPT;
  48         }
  49 #endif
  50
  51         /* save source/dest address, mark, hoplimit, flowlabel, priority,  */
  52         memcpy(&saddr, &ipv6_hdr(skb)->saddr, sizeof(saddr));
  53         memcpy(&daddr, &ipv6_hdr(skb)->daddr, sizeof(daddr));
  54         mark = skb->mark;
  55         hop_limit = ipv6_hdr(skb)->hop_limit;
  56
  57         /* flowlabel and prio (includes version, which shouldn't change either */
  58         flowlabel = *((u_int32_t *)ipv6_hdr(skb));
  59
  60         ret = ip6t_do_table(skb, NF_INET_LOCAL_OUT, NULL, out,
  61                             dev_net(out)->ipv6.ip6table_mangle);
  62
  63         if (ret != NF_DROP && ret != NF_STOLEN &&
  64             (!ipv6_addr_equal(&ipv6_hdr(skb)->saddr, &saddr) ||
  65              !ipv6_addr_equal(&ipv6_hdr(skb)->daddr, &daddr) ||
  66              skb->mark != mark ||
  67              ipv6_hdr(skb)->hop_limit != hop_limit ||
  68              flowlabel != *((u_int32_t *)ipv6_hdr(skb))))
  69                 return ip6_route_me_harder(skb) == 0 ? ret : NF_DROP;
  70
  71         return ret;
  72 }
  73
  74 /* The work comes in here from netfilter.c. */
  75 static unsigned int
  76 ip6table_mangle_hook(unsigned int hook, struct sk_buff *skb,
  77                      const struct net_device *in, const struct net_device *out,
  78                      int (*okfn)(struct sk_buff *))
  79 {
  80         if (hook == NF_INET_LOCAL_OUT)
  81                 return ip6t_mangle_out(skb, out);
  82         if (hook == NF_INET_POST_ROUTING)
  83                 return ip6t_do_table(skb, hook, in, out,
  84                                      dev_net(out)->ipv6.ip6table_mangle);
  85         /* INPUT/FORWARD */
  86         return ip6t_do_table(skb, hook, in, out,
  87                              dev_net(in)->ipv6.ip6table_mangle);
  88 }
  89
  90 static struct nf_hook_ops *mangle_ops __read_mostly;
  91 static int __net_init ip6table_mangle_net_init(struct net *net)
  92 {
  93         struct ip6t_replace *repl;
  94
  95         repl = ip6t_alloc_initial_table(&packet_mangler);
  96         if (repl == NULL)
  97                 return -ENOMEM;
  98         net->ipv6.ip6table_mangle =
  99                 ip6t_register_table(net, &packet_mangler, repl);
 100         kfree(repl);
 101         return PTR_RET(net->ipv6.ip6table_mangle);
 102 }
 103
 104 static void __net_exit ip6table_mangle_net_exit(struct net *net)
 105 {
 106         ip6t_unregister_table(net, net->ipv6.ip6table_mangle);
 107 }
 108
 109 static struct pernet_operations ip6table_mangle_net_ops = {
 110         .init = ip6table_mangle_net_init,
 111         .exit = ip6table_mangle_net_exit,
 112 };
 113
 114 static int __init ip6table_mangle_init(void)
 115 {
 116         int ret;
 117
 118         ret = register_pernet_subsys(&ip6table_mangle_net_ops);
 119         if (ret < 0)
 120                 return ret;
 121
 122         /* Register hooks */
 123         mangle_ops = xt_hook_link(&packet_mangler, ip6table_mangle_hook);
 124         if (IS_ERR(mangle_ops)) {
 125                 ret = PTR_ERR(mangle_ops);
 126                 goto cleanup_table;
 127         }
 128
 129         return ret;
 130
 131  cleanup_table:
 132         unregister_pernet_subsys(&ip6table_mangle_net_ops);
 133         return ret;
 134 }
 135
 136 static void __exit ip6table_mangle_fini(void)
 137 {
 138         xt_hook_unlink(&packet_mangler, mangle_ops);
 139         unregister_pernet_subsys(&ip6table_mangle_net_ops);
 140 }
 141
 142 module_init(ip6table_mangle_init);
 143 module_exit(ip6table_mangle_fini);