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   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
  14 MODULE_LICENSE("GPL");
  15 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  16 MODULE_DESCRIPTION("ip6tables mangle table");
  17
  18 #define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
  19                             (1 << NF_INET_LOCAL_IN) | \
  20                             (1 << NF_INET_FORWARD) | \
  21                             (1 << NF_INET_LOCAL_OUT) | \
  22                             (1 << NF_INET_POST_ROUTING))
  23
  24 static const struct xt_table packet_mangler = {
  25         .name           = "mangle",
  26         .valid_hooks    = MANGLE_VALID_HOOKS,
  27         .me             = THIS_MODULE,
  28         .af             = NFPROTO_IPV6,
  29         .priority       = NF_IP6_PRI_MANGLE,
  30 };
  31
  32 static unsigned int
  33 ip6t_local_out_hook(unsigned int hook,
  34                    struct sk_buff *skb,
  35                    const struct net_device *out,
  36                    int (*okfn)(struct sk_buff *))
  37 {
  38
  39         unsigned int ret;
  40         struct in6_addr saddr, daddr;
  41         u_int8_t hop_limit;
  42         u_int32_t flowlabel, mark;
  43
  44 #if 0
  45         /* root is playing with raw sockets. */
  46         if (skb->len < sizeof(struct iphdr) ||
  47             ip_hdrlen(skb) < sizeof(struct iphdr)) {
  48                 if (net_ratelimit())
  49                         printk("ip6t_hook: happy cracking.\n");
  50                 return NF_ACCEPT;
  51         }
  52 #endif
  53
  54         /* save source/dest address, mark, hoplimit, flowlabel, priority,  */
  55         memcpy(&saddr, &ipv6_hdr(skb)->saddr, sizeof(saddr));
  56         memcpy(&daddr, &ipv6_hdr(skb)->daddr, sizeof(daddr));
  57         mark = skb->mark;
  58         hop_limit = ipv6_hdr(skb)->hop_limit;
  59
  60         /* flowlabel and prio (includes version, which shouldn't change either */
  61         flowlabel = *((u_int32_t *)ipv6_hdr(skb));
  62
  63         ret = ip6t_do_table(skb, hook, NULL, out,
  64                             dev_net(out)->ipv6.ip6table_mangle);
  65
  66         if (ret != NF_DROP && ret != NF_STOLEN &&
  67             (memcmp(&ipv6_hdr(skb)->saddr, &saddr, sizeof(saddr)) ||
  68              memcmp(&ipv6_hdr(skb)->daddr, &daddr, sizeof(daddr)) ||
  69              skb->mark != mark ||
  70              ipv6_hdr(skb)->hop_limit != hop_limit))
  71                 return ip6_route_me_harder(skb) == 0 ? ret : NF_DROP;
  72
  73         return ret;
  74 }
  75
  76 /* The work comes in here from netfilter.c. */
  77 static unsigned int
  78 ip6table_mangle_hook(unsigned int hook, struct sk_buff *skb,
  79                      const struct net_device *in, const struct net_device *out,
  80                      int (*okfn)(struct sk_buff *))
  81 {
  82         if (hook == NF_INET_LOCAL_OUT)
  83                 return ip6t_local_out_hook(hook, skb, out, okfn);
  84
  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         if (IS_ERR(net->ipv6.ip6table_mangle))
 102                 return PTR_ERR(net->ipv6.ip6table_mangle);
 103         return 0;
 104 }
 105
 106 static void __net_exit ip6table_mangle_net_exit(struct net *net)
 107 {
 108         ip6t_unregister_table(net, net->ipv6.ip6table_mangle);
 109 }
 110
 111 static struct pernet_operations ip6table_mangle_net_ops = {
 112         .init = ip6table_mangle_net_init,
 113         .exit = ip6table_mangle_net_exit,
 114 };
 115
 116 static int __init ip6table_mangle_init(void)
 117 {
 118         int ret;
 119
 120         ret = register_pernet_subsys(&ip6table_mangle_net_ops);
 121         if (ret < 0)
 122                 return ret;
 123
 124         /* Register hooks */
 125         mangle_ops = xt_hook_link(&packet_mangler, ip6table_mangle_hook);
 126         if (IS_ERR(mangle_ops)) {
 127                 ret = PTR_ERR(mangle_ops);
 128                 goto cleanup_table;
 129         }
 130
 131         return ret;
 132
 133  cleanup_table:
 134         unregister_pernet_subsys(&ip6table_mangle_net_ops);
 135         return ret;
 136 }
 137
 138 static void __exit ip6table_mangle_fini(void)
 139 {
 140         xt_hook_unlink(&packet_mangler, mangle_ops);
 141         unregister_pernet_subsys(&ip6table_mangle_net_ops);
 142 }
 143
 144 module_init(ip6table_mangle_init);
 145 module_exit(ip6table_mangle_fini);