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 #if 0
  46         /* root is playing with raw sockets. */
  47         if (skb->len < sizeof(struct iphdr) ||
  48             ip_hdrlen(skb) < sizeof(struct iphdr)) {
  49                 net_warn_ratelimited("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, state, state->net->ipv6.ip6table_mangle);
  64
  65         if (ret != NF_DROP && ret != NF_STOLEN &&
  66             (!ipv6_addr_equal(&ipv6_hdr(skb)->saddr, &saddr) ||
  67              !ipv6_addr_equal(&ipv6_hdr(skb)->daddr, &daddr) ||
  68              skb->mark != mark ||
  69              ipv6_hdr(skb)->hop_limit != hop_limit ||
  70              flowlabel != *((u_int32_t *)ipv6_hdr(skb)))) {
  71                 err = ip6_route_me_harder(state->net, skb);
  72                 if (err < 0)
  73                         ret = NF_DROP_ERR(err);
  74         }
  75
  76         return ret;
  77 }
  78
  79 /* The work comes in here from netfilter.c. */
  80 static unsigned int
  81 ip6table_mangle_hook(void *priv, struct sk_buff *skb,
  82                      const struct nf_hook_state *state)
  83 {
  84         if (state->hook == NF_INET_LOCAL_OUT)
  85                 return ip6t_mangle_out(skb, state);
  86         if (state->hook == NF_INET_POST_ROUTING)
  87                 return ip6t_do_table(skb, state,
  88                                      state->net->ipv6.ip6table_mangle);
  89         /* INPUT/FORWARD */
  90         return ip6t_do_table(skb, state, state->net->ipv6.ip6table_mangle);
  91 }
  92
  93 static struct nf_hook_ops *mangle_ops __read_mostly;
  94 static int __net_init ip6table_mangle_table_init(struct net *net)
  95 {
  96         struct ip6t_replace *repl;
  97         int ret;
  98
  99         if (net->ipv6.ip6table_mangle)
 100                 return 0;
 101
 102         repl = ip6t_alloc_initial_table(&packet_mangler);
 103         if (repl == NULL)
 104                 return -ENOMEM;
 105         ret = ip6t_register_table(net, &packet_mangler, repl, mangle_ops,
 106                                   &net->ipv6.ip6table_mangle);
 107         kfree(repl);
 108         return ret;
 109 }
 110
 111 static void __net_exit ip6table_mangle_net_exit(struct net *net)
 112 {
 113         if (!net->ipv6.ip6table_mangle)
 114                 return;
 115
 116         ip6t_unregister_table(net, net->ipv6.ip6table_mangle, mangle_ops);
 117         net->ipv6.ip6table_mangle = NULL;
 118 }
 119
 120 static struct pernet_operations ip6table_mangle_net_ops = {
 121         .exit = ip6table_mangle_net_exit,
 122 };
 123
 124 static int __init ip6table_mangle_init(void)
 125 {
 126         int ret;
 127
 128         mangle_ops = xt_hook_ops_alloc(&packet_mangler, ip6table_mangle_hook);
 129         if (IS_ERR(mangle_ops))
 130                 return PTR_ERR(mangle_ops);
 131
 132         ret = register_pernet_subsys(&ip6table_mangle_net_ops);
 133         if (ret < 0) {
 134                 kfree(mangle_ops);
 135                 return ret;
 136         }
 137
 138         ret = ip6table_mangle_table_init(&init_net);
 139         if (ret) {
 140                 unregister_pernet_subsys(&ip6table_mangle_net_ops);
 141                 kfree(mangle_ops);
 142         }
 143         return ret;
 144 }
 145
 146 static void __exit ip6table_mangle_fini(void)
 147 {
 148         unregister_pernet_subsys(&ip6table_mangle_net_ops);
 149         kfree(mangle_ops);
 150 }
 151
 152 module_init(ip6table_mangle_init);
 153 module_exit(ip6table_mangle_fini);