net/ipv6/netfilter/ip6table_mangle.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * IPv6 packet mangling table, a port of the IPv4 mangle table to IPv6
   4  *
   5  * Copyright (C) 2000-2001 by Harald Welte <laforge@gnumonks.org>
   6  * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
   7  */
   8 #include <linux/module.h>
   9 #include <linux/netfilter_ipv6/ip6_tables.h>
  10 #include <linux/slab.h>
  11 #include <net/ipv6.h>
  12
  13 MODULE_LICENSE("GPL");
  14 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  15 MODULE_DESCRIPTION("ip6tables mangle table");
  16
  17 #define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
  18                             (1 << NF_INET_LOCAL_IN) | \
  19                             (1 << NF_INET_FORWARD) | \
  20                             (1 << NF_INET_LOCAL_OUT) | \
  21                             (1 << NF_INET_POST_ROUTING))
  22
  23 static const struct xt_table packet_mangler = {
  24         .name           = "mangle",
  25         .valid_hooks    = MANGLE_VALID_HOOKS,
  26         .me             = THIS_MODULE,
  27         .af             = NFPROTO_IPV6,
  28         .priority       = NF_IP6_PRI_MANGLE,
  29 };
  30
  31 static unsigned int
  32 ip6t_mangle_out(struct sk_buff *skb, const struct nf_hook_state *state, void *priv)
  33 {
  34         unsigned int ret;
  35         struct in6_addr saddr, daddr;
  36         u_int8_t hop_limit;
  37         u_int32_t flowlabel, mark;
  38         int err;
  39
  40         /* save source/dest address, mark, hoplimit, flowlabel, priority,  */
  41         memcpy(&saddr, &ipv6_hdr(skb)->saddr, sizeof(saddr));
  42         memcpy(&daddr, &ipv6_hdr(skb)->daddr, sizeof(daddr));
  43         mark = skb->mark;
  44         hop_limit = ipv6_hdr(skb)->hop_limit;
  45
  46         /* flowlabel and prio (includes version, which shouldn't change either */
  47         flowlabel = *((u_int32_t *)ipv6_hdr(skb));
  48
  49         ret = ip6t_do_table(skb, state, priv);
  50
  51         if (ret != NF_DROP && ret != NF_STOLEN &&
  52             (!ipv6_addr_equal(&ipv6_hdr(skb)->saddr, &saddr) ||
  53              !ipv6_addr_equal(&ipv6_hdr(skb)->daddr, &daddr) ||
  54              skb->mark != mark ||
  55              ipv6_hdr(skb)->hop_limit != hop_limit ||
  56              flowlabel != *((u_int32_t *)ipv6_hdr(skb)))) {
  57                 err = ip6_route_me_harder(state->net, state->sk, skb);
  58                 if (err < 0)
  59                         ret = NF_DROP_ERR(err);
  60         }
  61
  62         return ret;
  63 }
  64
  65 /* The work comes in here from netfilter.c. */
  66 static unsigned int
  67 ip6table_mangle_hook(void *priv, struct sk_buff *skb,
  68                      const struct nf_hook_state *state)
  69 {
  70         if (state->hook == NF_INET_LOCAL_OUT)
  71                 return ip6t_mangle_out(skb, state, priv);
  72         return ip6t_do_table(skb, state, priv);
  73 }
  74
  75 static struct nf_hook_ops *mangle_ops __read_mostly;
  76 static int ip6table_mangle_table_init(struct net *net)
  77 {
  78         struct ip6t_replace *repl;
  79         int ret;
  80
  81         repl = ip6t_alloc_initial_table(&packet_mangler);
  82         if (repl == NULL)
  83                 return -ENOMEM;
  84         ret = ip6t_register_table(net, &packet_mangler, repl, mangle_ops);
  85         kfree(repl);
  86         return ret;
  87 }
  88
  89 static void __net_exit ip6table_mangle_net_pre_exit(struct net *net)
  90 {
  91         ip6t_unregister_table_pre_exit(net, "mangle");
  92 }
  93
  94 static void __net_exit ip6table_mangle_net_exit(struct net *net)
  95 {
  96         ip6t_unregister_table_exit(net, "mangle");
  97 }
  98
  99 static struct pernet_operations ip6table_mangle_net_ops = {
 100         .pre_exit = ip6table_mangle_net_pre_exit,
 101         .exit = ip6table_mangle_net_exit,
 102 };
 103
 104 static int __init ip6table_mangle_init(void)
 105 {
 106         int ret = xt_register_template(&packet_mangler,
 107                                        ip6table_mangle_table_init);
 108
 109         if (ret < 0)
 110                 return ret;
 111
 112         mangle_ops = xt_hook_ops_alloc(&packet_mangler, ip6table_mangle_hook);
 113         if (IS_ERR(mangle_ops)) {
 114                 xt_unregister_template(&packet_mangler);
 115                 return PTR_ERR(mangle_ops);
 116         }
 117
 118         ret = register_pernet_subsys(&ip6table_mangle_net_ops);
 119         if (ret < 0) {
 120                 xt_unregister_template(&packet_mangler);
 121                 kfree(mangle_ops);
 122                 return ret;
 123         }
 124
 125         return ret;
 126 }
 127
 128 static void __exit ip6table_mangle_fini(void)
 129 {
 130         unregister_pernet_subsys(&ip6table_mangle_net_ops);
 131         xt_unregister_template(&packet_mangler);
 132         kfree(mangle_ops);
 133 }
 134
 135 module_init(ip6table_mangle_init);
 136 module_exit(ip6table_mangle_fini);