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
  15 MODULE_LICENSE("GPL");
  16 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  17 MODULE_DESCRIPTION("ip6tables mangle table");
  18
  19 #define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
  20                             (1 << NF_INET_LOCAL_IN) | \
  21                             (1 << NF_INET_FORWARD) | \
  22                             (1 << NF_INET_LOCAL_OUT) | \
  23                             (1 << NF_INET_POST_ROUTING))
  24
  25 static const struct xt_table packet_mangler = {
  26         .name           = "mangle",
  27         .valid_hooks    = MANGLE_VALID_HOOKS,
  28         .me             = THIS_MODULE,
  29         .af             = NFPROTO_IPV6,
  30         .priority       = NF_IP6_PRI_MANGLE,
  31 };
  32
  33 static unsigned int
  34 ip6t_mangle_out(struct sk_buff *skb, const struct net_device *out)
  35 {
  36         unsigned int ret;
  37         struct in6_addr saddr, daddr;
  38         u_int8_t hop_limit;
  39         u_int32_t flowlabel, mark;
  40
  41 #if 0
  42         /* root is playing with raw sockets. */
  43         if (skb->len < sizeof(struct iphdr) ||
  44             ip_hdrlen(skb) < sizeof(struct iphdr)) {
  45                 net_warn_ratelimited("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              flowlabel != *((u_int32_t *)ipv6_hdr(skb))))
  68                 return ip6_route_me_harder(skb) == 0 ? ret : NF_DROP;
  69
  70         return ret;
  71 }
  72
  73 /* The work comes in here from netfilter.c. */
  74 static unsigned int
  75 ip6table_mangle_hook(unsigned int hook, struct sk_buff *skb,
  76                      const struct net_device *in, const struct net_device *out,
  77                      int (*okfn)(struct sk_buff *))
  78 {
  79         if (hook == NF_INET_LOCAL_OUT)
  80                 return ip6t_mangle_out(skb, out);
  81         if (hook == NF_INET_POST_ROUTING)
  82                 return ip6t_do_table(skb, hook, in, out,
  83                                      dev_net(out)->ipv6.ip6table_mangle);
  84         /* INPUT/FORWARD */
  85         return ip6t_do_table(skb, hook, in, out,
  86                              dev_net(in)->ipv6.ip6table_mangle);
  87 }
  88
  89 static struct nf_hook_ops *mangle_ops __read_mostly;
  90 static int __net_init ip6table_mangle_net_init(struct net *net)
  91 {
  92         struct ip6t_replace *repl;
  93
  94         repl = ip6t_alloc_initial_table(&packet_mangler);
  95         if (repl == NULL)
  96                 return -ENOMEM;
  97         net->ipv6.ip6table_mangle =
  98                 ip6t_register_table(net, &packet_mangler, repl);
  99         kfree(repl);
 100         return PTR_RET(net->ipv6.ip6table_mangle);
 101 }
 102
 103 static void __net_exit ip6table_mangle_net_exit(struct net *net)
 104 {
 105         ip6t_unregister_table(net, net->ipv6.ip6table_mangle);
 106 }
 107
 108 static struct pernet_operations ip6table_mangle_net_ops = {
 109         .init = ip6table_mangle_net_init,
 110         .exit = ip6table_mangle_net_exit,
 111 };
 112
 113 static int __init ip6table_mangle_init(void)
 114 {
 115         int ret;
 116
 117         ret = register_pernet_subsys(&ip6table_mangle_net_ops);
 118         if (ret < 0)
 119                 return ret;
 120
 121         /* Register hooks */
 122         mangle_ops = xt_hook_link(&packet_mangler, ip6table_mangle_hook);
 123         if (IS_ERR(mangle_ops)) {
 124                 ret = PTR_ERR(mangle_ops);
 125                 goto cleanup_table;
 126         }
 127
 128         return ret;
 129
 130  cleanup_table:
 131         unregister_pernet_subsys(&ip6table_mangle_net_ops);
 132         return ret;
 133 }
 134
 135 static void __exit ip6table_mangle_fini(void)
 136 {
 137         xt_hook_unlink(&packet_mangler, mangle_ops);
 138         unregister_pernet_subsys(&ip6table_mangle_net_ops);
 139 }
 140
 141 module_init(ip6table_mangle_init);
 142 module_exit(ip6table_mangle_fini);