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 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. */ 81 static unsigned int 82 iptable_mangle_hook(const struct nf_hook_ops *ops, 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 (ops->hooknum == NF_INET_LOCAL_OUT) 89 return ipt_mangle_out(skb, out); 90 if (ops->hooknum == NF_INET_POST_ROUTING) 91 return ipt_do_table(skb, ops->hooknum, in, out, 92 dev_net(out)->ipv4.iptable_mangle); 93 /* PREROUTING/INPUT/FORWARD: */ 94 return ipt_do_table(skb, ops->hooknum, 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 return PTR_ERR_OR_ZERO(net->ipv4.iptable_mangle); 111 } 112 113 static void __net_exit iptable_mangle_net_exit(struct net *net) 114 { 115 ipt_unregister_table(net, net->ipv4.iptable_mangle); 116 } 117 118 static struct pernet_operations iptable_mangle_net_ops = { 119 .init = iptable_mangle_net_init, 120 .exit = iptable_mangle_net_exit, 121 }; 122 123 static 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 } 140 141 static void __exit iptable_mangle_fini(void) 142 { 143 xt_hook_unlink(&packet_mangler, mangle_ops); 144 unregister_pernet_subsys(&iptable_mangle_net_ops); 145 } 146 147 module_init(iptable_mangle_init); 148 module_exit(iptable_mangle_fini); 149