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 int __net_init ip6table_mangle_table_init(struct net *net);
  27
  28 static const struct xt_table packet_mangler = {
  29         .name           = "mangle",
  30         .valid_hooks    = MANGLE_VALID_HOOKS,
  31         .me             = THIS_MODULE,
  32         .af             = NFPROTO_IPV6,
  33         .priority       = NF_IP6_PRI_MANGLE,
  34         .table_init     = ip6table_mangle_table_init,
  35 };
  36
  37 static unsigned int
  38 ip6t_mangle_out(struct sk_buff *skb, const struct nf_hook_state *state)
  39 {
  40         unsigned int ret;
  41         struct in6_addr saddr, daddr;
  42         u_int8_t hop_limit;
  43         u_int32_t flowlabel, mark;
  44         int err;
  45
  46         /* save source/dest address, mark, hoplimit, flowlabel, priority,  */
  47         memcpy(&saddr, &ipv6_hdr(skb)->saddr, sizeof(saddr));
  48         memcpy(&daddr, &ipv6_hdr(skb)->daddr, sizeof(daddr));
  49         mark = skb->mark;
  50         hop_limit = ipv6_hdr(skb)->hop_limit;
  51
  52         /* flowlabel and prio (includes version, which shouldn't change either */
  53         flowlabel = *((u_int32_t *)ipv6_hdr(skb));
  54
  55         ret = ip6t_do_table(skb, state, state->net->ipv6.ip6table_mangle);
  56
  57         if (ret != NF_DROP && ret != NF_STOLEN &&
  58             (!ipv6_addr_equal(&ipv6_hdr(skb)->saddr, &saddr) ||
  59              !ipv6_addr_equal(&ipv6_hdr(skb)->daddr, &daddr) ||
  60              skb->mark != mark ||
  61              ipv6_hdr(skb)->hop_limit != hop_limit ||
  62              flowlabel != *((u_int32_t *)ipv6_hdr(skb)))) {
  63                 err = ip6_route_me_harder(state->net, skb);
  64                 if (err < 0)
  65                         ret = NF_DROP_ERR(err);
  66         }
  67
  68         return ret;
  69 }
  70
  71 /* The work comes in here from netfilter.c. */
  72 static unsigned int
  73 ip6table_mangle_hook(void *priv, struct sk_buff *skb,
  74                      const struct nf_hook_state *state)
  75 {
  76         if (state->hook == NF_INET_LOCAL_OUT)
  77                 return ip6t_mangle_out(skb, state);
  78         return ip6t_do_table(skb, state, state->net->ipv6.ip6table_mangle);
  79 }
  80
  81 static struct nf_hook_ops *mangle_ops __read_mostly;
  82 static int __net_init ip6table_mangle_table_init(struct net *net)
  83 {
  84         struct ip6t_replace *repl;
  85         int ret;
  86
  87         if (net->ipv6.ip6table_mangle)
  88                 return 0;
  89
  90         repl = ip6t_alloc_initial_table(&packet_mangler);
  91         if (repl == NULL)
  92                 return -ENOMEM;
  93         ret = ip6t_register_table(net, &packet_mangler, repl, mangle_ops,
  94                                   &net->ipv6.ip6table_mangle);
  95         kfree(repl);
  96         return ret;
  97 }
  98
  99 static void __net_exit ip6table_mangle_net_exit(struct net *net)
 100 {
 101         if (!net->ipv6.ip6table_mangle)
 102                 return;
 103
 104         ip6t_unregister_table(net, net->ipv6.ip6table_mangle, mangle_ops);
 105         net->ipv6.ip6table_mangle = NULL;
 106 }
 107
 108 static struct pernet_operations ip6table_mangle_net_ops = {
 109         .exit = ip6table_mangle_net_exit,
 110 };
 111
 112 static int __init ip6table_mangle_init(void)
 113 {
 114         int ret;
 115
 116         mangle_ops = xt_hook_ops_alloc(&packet_mangler, ip6table_mangle_hook);
 117         if (IS_ERR(mangle_ops))
 118                 return PTR_ERR(mangle_ops);
 119
 120         ret = register_pernet_subsys(&ip6table_mangle_net_ops);
 121         if (ret < 0) {
 122                 kfree(mangle_ops);
 123                 return ret;
 124         }
 125
 126         ret = ip6table_mangle_table_init(&init_net);
 127         if (ret) {
 128                 unregister_pernet_subsys(&ip6table_mangle_net_ops);
 129                 kfree(mangle_ops);
 130         }
 131         return ret;
 132 }
 133
 134 static void __exit ip6table_mangle_fini(void)
 135 {
 136         unregister_pernet_subsys(&ip6table_mangle_net_ops);
 137         kfree(mangle_ops);
 138 }
 139
 140 module_init(ip6table_mangle_init);
 141 module_exit(ip6table_mangle_fini);