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 const struct xt_table packet_mangler = {
  32        .name           = "mangle",
  33        .valid_hooks    = MANGLE_VALID_HOOKS,
  34        .me             = THIS_MODULE,
  35        .af             = NFPROTO_IPV4,
  36        .priority       = NF_IP_PRI_MANGLE,
  37};
  38
  39static unsigned int
  40ipt_mangle_out(struct sk_buff *skb, const struct net_device *out)
  41{
  42        unsigned int ret;
  43        const struct iphdr *iph;
  44        u_int8_t tos;
  45        __be32 saddr, daddr;
  46        u_int32_t mark;
  47
  48        /* root is playing with raw sockets. */
  49        if (skb->len < sizeof(struct iphdr) ||
  50            ip_hdrlen(skb) < sizeof(struct iphdr))
  51                return NF_ACCEPT;
  52
  53        /* Save things which could affect route */
  54        mark = skb->mark;
  55        iph = ip_hdr(skb);
  56        saddr = iph->saddr;
  57        daddr = iph->daddr;
  58        tos = iph->tos;
  59
  60        ret = ipt_do_table(skb, NF_INET_LOCAL_OUT, NULL, out,
  61                           dev_net(out)->ipv4.iptable_mangle);
  62        /* Reroute for ANY change. */
  63        if (ret != NF_DROP && ret != NF_STOLEN) {
  64                iph = ip_hdr(skb);
  65
  66                if (iph->saddr != saddr ||
  67                    iph->daddr != daddr ||
  68                    skb->mark != mark ||
  69                    iph->tos != tos)
  70                        if (ip_route_me_harder(skb, RTN_UNSPEC))
  71                                ret = NF_DROP;
  72        }
  73
  74        return ret;
  75}
  76
  77/* The work comes in here from netfilter.c. */
  78static unsigned int
  79iptable_mangle_hook(unsigned int hook,
  80                     struct sk_buff *skb,
  81                     const struct net_device *in,
  82                     const struct net_device *out,
  83                     int (*okfn)(struct sk_buff *))
  84{
  85        if (hook == NF_INET_LOCAL_OUT)
  86                return ipt_mangle_out(skb, out);
  87        if (hook == NF_INET_POST_ROUTING)
  88                return ipt_do_table(skb, hook, in, out,
  89                                    dev_net(out)->ipv4.iptable_mangle);
  90        /* PREROUTING/INPUT/FORWARD: */
  91        return ipt_do_table(skb, hook, in, out,
  92                            dev_net(in)->ipv4.iptable_mangle);
  93}
  94
  95static struct nf_hook_ops *mangle_ops __read_mostly;
  96
  97static int __net_init iptable_mangle_net_init(struct net *net)
  98{
  99        struct ipt_replace *repl;
 100
 101        repl = ipt_alloc_initial_table(&packet_mangler);
 102        if (repl == NULL)
 103                return -ENOMEM;
 104        net->ipv4.iptable_mangle =
 105                ipt_register_table(net, &packet_mangler, repl);
 106        kfree(repl);
 107        if (IS_ERR(net->ipv4.iptable_mangle))
 108                return PTR_ERR(net->ipv4.iptable_mangle);
 109        return 0;
 110}
 111
 112static void __net_exit iptable_mangle_net_exit(struct net *net)
 113{
 114        ipt_unregister_table(net, net->ipv4.iptable_mangle);
 115}
 116
 117static struct pernet_operations iptable_mangle_net_ops = {
 118        .init = iptable_mangle_net_init,
 119        .exit = iptable_mangle_net_exit,
 120};
 121
 122static int __init iptable_mangle_init(void)
 123{
 124        int ret;
 125
 126        ret = register_pernet_subsys(&iptable_mangle_net_ops);
 127        if (ret < 0)
 128                return ret;
 129
 130        /* Register hooks */
 131        mangle_ops = xt_hook_link(&packet_mangler, iptable_mangle_hook);
 132        if (IS_ERR(mangle_ops)) {
 133                ret = PTR_ERR(mangle_ops);
 134                goto cleanup_table;
 135        }
 136
 137        return ret;
 138
 139 cleanup_table:
 140        unregister_pernet_subsys(&iptable_mangle_net_ops);
 141        return ret;
 142}
 143
 144static void __exit iptable_mangle_fini(void)
 145{
 146        xt_hook_unlink(&packet_mangler, mangle_ops);
 147        unregister_pernet_subsys(&iptable_mangle_net_ops);
 148}
 149
 150module_init(iptable_mangle_init);
 151module_exit(iptable_mangle_fini);
 152