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