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
  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_mangle_out(struct sk_buff *skb, const struct net_device *out)
  34 {
  35         unsigned int ret;
  36         struct in6_addr saddr, daddr;
  37         u_int8_t hop_limit;
  38         u_int32_t flowlabel, mark;
  39
  40 #if 0
  41         /* root is playing with raw sockets. */
  42         if (skb->len < sizeof(struct iphdr) ||
  43             ip_hdrlen(skb) < sizeof(struct iphdr)) {
  44                 if (net_ratelimit())
  45                         printk("ip6t_hook: happy cracking.\n");
  46                 return NF_ACCEPT;
  47         }
  48 #endif
  49
  50         /* save source/dest address, mark, hoplimit, flowlabel, priority,  */
  51         memcpy(&saddr, &ipv6_hdr(skb)->saddr, sizeof(saddr));
  52         memcpy(&daddr, &ipv6_hdr(skb)->daddr, sizeof(daddr));
  53         mark = skb->mark;
  54         hop_limit = ipv6_hdr(skb)->hop_limit;
  55
  56         /* flowlabel and prio (includes version, which shouldn't change either */
  57         flowlabel = *((u_int32_t *)ipv6_hdr(skb));
  58
  59         ret = ip6t_do_table(skb, NF_INET_LOCAL_OUT, NULL, out,
  60                             dev_net(out)->ipv6.ip6table_mangle);
  61
  62         if (ret != NF_DROP && ret != NF_STOLEN &&
  63             (memcmp(&ipv6_hdr(skb)->saddr, &saddr, sizeof(saddr)) ||
  64              memcmp(&ipv6_hdr(skb)->daddr, &daddr, sizeof(daddr)) ||
  65              skb->mark != mark ||
  66              ipv6_hdr(skb)->hop_limit != hop_limit))
  67                 return ip6_route_me_harder(skb) == 0 ? ret : NF_DROP;
  68
  69         return ret;
  70 }
  71
  72 /* The work comes in here from netfilter.c. */
  73 static unsigned int
  74 ip6table_mangle_hook(unsigned int hook, struct sk_buff *skb,
  75                      const struct net_device *in, const struct net_device *out,
  76                      int (*okfn)(struct sk_buff *))
  77 {
  78         if (hook == NF_INET_LOCAL_OUT)
  79                 return ip6t_mangle_out(skb, out);
  80         if (hook == NF_INET_POST_ROUTING)
  81                 return ip6t_do_table(skb, hook, in, out,
  82                                      dev_net(out)->ipv6.ip6table_mangle);
  83         /* INPUT/FORWARD */
  84         return ip6t_do_table(skb, hook, in, out,
  85                              dev_net(in)->ipv6.ip6table_mangle);
  86 }
  87
  88 static struct nf_hook_ops *mangle_ops __read_mostly;
  89 static int __net_init ip6table_mangle_net_init(struct net *net)
  90 {
  91         struct ip6t_replace *repl;
  92
  93         repl = ip6t_alloc_initial_table(&packet_mangler);
  94         if (repl == NULL)
  95                 return -ENOMEM;
  96         net->ipv6.ip6table_mangle =
  97                 ip6t_register_table(net, &packet_mangler, repl);
  98         kfree(repl);
  99         if (IS_ERR(net->ipv6.ip6table_mangle))
 100                 return PTR_ERR(net->ipv6.ip6table_mangle);
 101         return 0;
 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);