LXR linux/net/ipv4/netfilter/iptable

   1/*
   2 * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
   3 *
   4 * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
   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_ipv4/ip_tables.h>
  13#include <linux/netdevice.h>
  14#include <linux/skbuff.h>
  15#include <linux/slab.h>
  16#include <net/sock.h>
  17#include <net/route.h>
  18#include <linux/ip.h>
  19#include <net/ip.h>
  20
  21MODULE_LICENSE("GPL");
  22MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  23MODULE_DESCRIPTION("iptables mangle table");
  24
  25#define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
  26                            (1 << NF_INET_LOCAL_IN) | \
  27                            (1 << NF_INET_FORWARD) | \
  28                            (1 << NF_INET_LOCAL_OUT) | \
  29                            (1 << NF_INET_POST_ROUTING))
  30
  31static int __net_init iptable_mangle_table_init(struct net *net);
  32
  33static const struct xt_table packet_mangler = {
  34        .name           = "mangle",
  35        .valid_hooks    = MANGLE_VALID_HOOKS,
  36        .me             = THIS_MODULE,
  37        .af             = NFPROTO_IPV4,
  38        .priority       = NF_IP_PRI_MANGLE,
  39        .table_init     = iptable_mangle_table_init,
  40};
  41
  42static unsigned int
  43ipt_mangle_out(struct sk_buff *skb, const struct nf_hook_state *state)
  44{
  45        unsigned int ret;
  46        const struct iphdr *iph;
  47        u_int8_t tos;
  48        __be32 saddr, daddr;
  49        u_int32_t mark;
  50        int err;
  51
  52        /* root is playing with raw sockets. */
  53        if (skb->len < sizeof(struct iphdr) ||
  54            ip_hdrlen(skb) < sizeof(struct iphdr))
  55                return NF_ACCEPT;
  56
  57        /* Save things which could affect route */
  58        mark = skb->mark;
  59        iph = ip_hdr(skb);
  60        saddr = iph->saddr;
  61        daddr = iph->daddr;
  62        tos = iph->tos;
  63
  64        ret = ipt_do_table(skb, state, state->net->ipv4.iptable_mangle);
  65        /* Reroute for ANY change. */
  66        if (ret != NF_DROP && ret != NF_STOLEN) {
  67                iph = ip_hdr(skb);
  68
  69                if (iph->saddr != saddr ||
  70                    iph->daddr != daddr ||
  71                    skb->mark != mark ||
  72                    iph->tos != tos) {
  73                        err = ip_route_me_harder(state->net, skb, RTN_UNSPEC);
  74                        if (err < 0)
  75                                ret = NF_DROP_ERR(err);
  76                }
  77        }
  78
  79        return ret;
  80}
  81
  82/* The work comes in here from netfilter.c. */
  83static unsigned int
  84iptable_mangle_hook(void *priv,
  85                     struct sk_buff *skb,
  86                     const struct nf_hook_state *state)
  87{
  88        if (state->hook == NF_INET_LOCAL_OUT)
  89                return ipt_mangle_out(skb, state);
  90        return ipt_do_table(skb, state, state->net->ipv4.iptable_mangle);
  91}
  92
  93static struct nf_hook_ops *mangle_ops __read_mostly;
  94static int __net_init iptable_mangle_table_init(struct net *net)
  95{
  96        struct ipt_replace *repl;
  97        int ret;
  98
  99        if (net->ipv4.iptable_mangle)
 100                return 0;
 101
 102        repl = ipt_alloc_initial_table(&packet_mangler);
 103        if (repl == NULL)
 104                return -ENOMEM;
 105        ret = ipt_register_table(net, &packet_mangler, repl, mangle_ops,
 106                                 &net->ipv4.iptable_mangle);
 107        kfree(repl);
 108        return ret;
 109}
 110
 111static void __net_exit iptable_mangle_net_exit(struct net *net)
 112{
 113        if (!net->ipv4.iptable_mangle)
 114                return;
 115        ipt_unregister_table(net, net->ipv4.iptable_mangle, mangle_ops);
 116        net->ipv4.iptable_mangle = NULL;
 117}
 118
 119static struct pernet_operations iptable_mangle_net_ops = {
 120        .exit = iptable_mangle_net_exit,
 121};
 122
 123static int __init iptable_mangle_init(void)
 124{
 125        int ret;
 126
 127        mangle_ops = xt_hook_ops_alloc(&packet_mangler, iptable_mangle_hook);
 128        if (IS_ERR(mangle_ops)) {
 129                ret = PTR_ERR(mangle_ops);
 130                return ret;
 131        }
 132
 133        ret = register_pernet_subsys(&iptable_mangle_net_ops);
 134        if (ret < 0) {
 135                kfree(mangle_ops);
 136                return ret;
 137        }
 138
 139        ret = iptable_mangle_table_init(&init_net);
 140        if (ret) {
 141                unregister_pernet_subsys(&iptable_mangle_net_ops);
 142                kfree(mangle_ops);
 143        }
 144
 145        return ret;
 146}
 147
 148static void __exit iptable_mangle_fini(void)
 149{
 150        unregister_pernet_subsys(&iptable_mangle_net_ops);
 151        kfree(mangle_ops);
 152}
 153
 154module_init(iptable_mangle_init);
 155module_exit(iptable_mangle_fini);
 156