SAFE public projects git trees. - safe/jmp/linux-2.6/blob - net/ipv4/netfilter/iptable_mangle.c

   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 <net/sock.h>
  16 #include <net/route.h>
  17 #include <linux/ip.h>
  18 #include <net/ip.h>
  19
  20 MODULE_LICENSE("GPL");
  21 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  22 MODULE_DESCRIPTION("iptables mangle table");
  23
  24 #define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
  25                             (1 << NF_INET_LOCAL_IN) | \
  26                             (1 << NF_INET_FORWARD) | \
  27                             (1 << NF_INET_LOCAL_OUT) | \
  28                             (1 << NF_INET_POST_ROUTING))
  29
  30 static const struct xt_table packet_mangler = {
  31         .name           = "mangle",
  32         .valid_hooks    = MANGLE_VALID_HOOKS,
  33         .me             = THIS_MODULE,
  34         .af             = NFPROTO_IPV4,
  35         .priority       = NF_IP_PRI_MANGLE,
  36 };
  37
  38 static unsigned int
  39 ipt_local_hook(unsigned int hook,
  40                    struct sk_buff *skb,
  41                    const struct net_device *in,
  42                    const struct net_device *out,
  43                    int (*okfn)(struct sk_buff *))
  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
  51         /* root is playing with raw sockets. */
  52         if (skb->len < sizeof(struct iphdr) ||
  53             ip_hdrlen(skb) < sizeof(struct iphdr))
  54                 return NF_ACCEPT;
  55
  56         /* Save things which could affect route */
  57         mark = skb->mark;
  58         iph = ip_hdr(skb);
  59         saddr = iph->saddr;
  60         daddr = iph->daddr;
  61         tos = iph->tos;
  62
  63         ret = ipt_do_table(skb, hook, in, out,
  64                            dev_net(out)->ipv4.iptable_mangle);
  65         /* Reroute for ANY change. */
  66         if (ret != NF_DROP && ret != NF_STOLEN && ret != NF_QUEUE) {
  67                 iph = ip_hdr(skb);
  68
  69                 if (iph->saddr != saddr ||
  70                     iph->daddr != daddr ||
  71                     skb->mark != mark ||
  72                     iph->tos != tos)
  73                         if (ip_route_me_harder(skb, RTN_UNSPEC))
  74                                 ret = NF_DROP;
  75         }
  76
  77         return ret;
  78 }
  79
  80 /* The work comes in here from netfilter.c. */
  81 static unsigned int
  82 iptable_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_local_hook(hook, skb, in, out, okfn);
  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
  98 static struct nf_hook_ops *mangle_ops __read_mostly;
  99
 100 static 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         if (IS_ERR(net->ipv4.iptable_mangle))
 111                 return PTR_ERR(net->ipv4.iptable_mangle);
 112         return 0;
 113 }
 114
 115 static void __net_exit iptable_mangle_net_exit(struct net *net)
 116 {
 117         ipt_unregister_table(net, net->ipv4.iptable_mangle);
 118 }
 119
 120 static struct pernet_operations iptable_mangle_net_ops = {
 121         .init = iptable_mangle_net_init,
 122         .exit = iptable_mangle_net_exit,
 123 };
 124
 125 static int __init iptable_mangle_init(void)
 126 {
 127         int ret;
 128
 129         ret = register_pernet_subsys(&iptable_mangle_net_ops);
 130         if (ret < 0)
 131                 return ret;
 132
 133         /* Register hooks */
 134         mangle_ops = xt_hook_link(&packet_mangler, iptable_mangle_hook);
 135         if (IS_ERR(mangle_ops)) {
 136                 ret = PTR_ERR(mangle_ops);
 137                 goto cleanup_table;
 138         }
 139
 140         return ret;
 141
 142  cleanup_table:
 143         unregister_pernet_subsys(&iptable_mangle_net_ops);
 144         return ret;
 145 }
 146
 147 static void __exit iptable_mangle_fini(void)
 148 {
 149         xt_hook_unlink(&packet_mangler, mangle_ops);
 150         unregister_pernet_subsys(&iptable_mangle_net_ops);
 151 }
 152
 153 module_init(iptable_mangle_init);
 154 module_exit(iptable_mangle_fini);