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 21 MODULE_LICENSE("GPL"); 22 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>"); 23 MODULE_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 31 static 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 39 static unsigned int 40 ipt_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 && ret != NF_QUEUE) { 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. */ 78 static unsigned int 79 iptable_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 95 static struct nf_hook_ops *mangle_ops __read_mostly; 96 97 static 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 } 111 112 static void __net_exit iptable_mangle_net_exit(struct net *net) 113 { 114 ipt_unregister_table(net, net->ipv4.iptable_mangle); 115 } 116 117 static struct pernet_operations iptable_mangle_net_ops = { 118 .init = iptable_mangle_net_init, 119 .exit = iptable_mangle_net_exit, 120 }; 121 122 static 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 } 143 144 static void __exit iptable_mangle_fini(void) 145 { 146 xt_hook_unlink(&packet_mangler, mangle_ops); 147 unregister_pernet_subsys(&iptable_mangle_net_ops); 148 } 149 150 module_init(iptable_mangle_init); 151 module_exit(iptable_mangle_fini); 152