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