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(void *priv, struct sk_buff *skb, const struct nf_hook_state *state)
  33 {
  34         struct in6_addr saddr, daddr;
  35         unsigned int ret, verdict;
  36         u32 flowlabel, mark;
  37         u8 hop_limit;
  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(priv, skb, state);
  50         verdict = ret & NF_VERDICT_MASK;
  51
  52         if (verdict != NF_DROP && verdict != NF_STOLEN &&
  53             (!ipv6_addr_equal(&ipv6_hdr(skb)->saddr, &saddr) ||
  54              !ipv6_addr_equal(&ipv6_hdr(skb)->daddr, &daddr) ||
  55              skb->mark != mark ||
  56              ipv6_hdr(skb)->hop_limit != hop_limit ||
  57              flowlabel != *((u_int32_t *)ipv6_hdr(skb)))) {
  58                 err = ip6_route_me_harder(state->net, state->sk, skb);
  59                 if (err < 0)
  60                         ret = NF_DROP_ERR(err);
  61         }
  62
  63         return ret;
  64 }
  65
  66 /* The work comes in here from netfilter.c. */
  67 static unsigned int
  68 ip6table_mangle_hook(void *priv, struct sk_buff *skb,
  69                      const struct nf_hook_state *state)
  70 {
  71         if (state->hook == NF_INET_LOCAL_OUT)
  72                 return ip6t_mangle_out(priv, skb, state);
  73         return ip6t_do_table(priv, skb, state);
  74 }
  75
  76 static struct nf_hook_ops *mangle_ops __read_mostly;
  77 static int ip6table_mangle_table_init(struct net *net)
  78 {
  79         struct ip6t_replace *repl;
  80         int ret;
  81
  82         repl = ip6t_alloc_initial_table(&packet_mangler);
  83         if (repl == NULL)
  84                 return -ENOMEM;
  85         ret = ip6t_register_table(net, &packet_mangler, repl, mangle_ops);
  86         kfree(repl);
  87         return ret;
  88 }
  89
  90 static void __net_exit ip6table_mangle_net_pre_exit(struct net *net)
  91 {
  92         ip6t_unregister_table_pre_exit(net, "mangle");
  93 }
  94
  95 static void __net_exit ip6table_mangle_net_exit(struct net *net)
  96 {
  97         ip6t_unregister_table_exit(net, "mangle");
  98 }
  99
 100 static struct pernet_operations ip6table_mangle_net_ops = {
 101         .pre_exit = ip6table_mangle_net_pre_exit,
 102         .exit = ip6table_mangle_net_exit,
 103 };
 104
 105 static int __init ip6table_mangle_init(void)
 106 {
 107         int ret = xt_register_template(&packet_mangler,
 108                                        ip6table_mangle_table_init);
 109
 110         if (ret < 0)
 111                 return ret;
 112
 113         mangle_ops = xt_hook_ops_alloc(&packet_mangler, ip6table_mangle_hook);
 114         if (IS_ERR(mangle_ops)) {
 115                 xt_unregister_template(&packet_mangler);
 116                 return PTR_ERR(mangle_ops);
 117         }
 118
 119         ret = register_pernet_subsys(&ip6table_mangle_net_ops);
 120         if (ret < 0) {
 121                 xt_unregister_template(&packet_mangler);
 122                 kfree(mangle_ops);
 123                 return ret;
 124         }
 125
 126         return ret;
 127 }
 128
 129 static void __exit ip6table_mangle_fini(void)
 130 {
 131         unregister_pernet_subsys(&ip6table_mangle_net_ops);
 132         xt_unregister_template(&packet_mangler);
 133         kfree(mangle_ops);
 134 }
 135
 136 module_init(ip6table_mangle_init);
 137 module_exit(ip6table_mangle_fini);