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 /* root is playing with raw sockets. */ 53 if (skb->len < sizeof(struct iphdr) || 54 ip_hdrlen(skb) < sizeof(struct iphdr)) 55 return NF_ACCEPT; 56 57 /* Save things which could affect route */ 58 mark = skb->mark; 59 iph = ip_hdr(skb); 60 saddr = iph->saddr; 61 daddr = iph->daddr; 62 tos = iph->tos; 63 64 ret = ipt_do_table(skb, state, state->net->ipv4.iptable_mangle); 65 /* Reroute for ANY change. */ 66 if (ret != NF_DROP && ret != NF_STOLEN) { 67 iph = ip_hdr(skb); 68 69 if (iph->saddr != saddr || 70 iph->daddr != daddr || 71 skb->mark != mark || 72 iph->tos != tos) { 73 err = ip_route_me_harder(state->net, skb, RTN_UNSPEC); 74 if (err < 0) 75 ret = NF_DROP_ERR(err); 76 } 77 } 78 79 return ret; 80 } 81 82 /* The work comes in here from netfilter.c. */ 83 static unsigned int 84 iptable_mangle_hook(void *priv, 85 struct sk_buff *skb, 86 const struct nf_hook_state *state) 87 { 88 if (state->hook == NF_INET_LOCAL_OUT) 89 return ipt_mangle_out(skb, state); 90 return ipt_do_table(skb, state, state->net->ipv4.iptable_mangle); 91 } 92 93 static struct nf_hook_ops *mangle_ops __read_mostly; 94 static int __net_init iptable_mangle_table_init(struct net *net) 95 { 96 struct ipt_replace *repl; 97 int ret; 98 99 if (net->ipv4.iptable_mangle) 100 return 0; 101 102 repl = ipt_alloc_initial_table(&packet_mangler); 103 if (repl == NULL) 104 return -ENOMEM; 105 ret = ipt_register_table(net, &packet_mangler, repl, mangle_ops, 106 &net->ipv4.iptable_mangle); 107 kfree(repl); 108 return ret; 109 } 110 111 static void __net_exit iptable_mangle_net_exit(struct net *net) 112 { 113 if (!net->ipv4.iptable_mangle) 114 return; 115 ipt_unregister_table(net, net->ipv4.iptable_mangle, mangle_ops); 116 net->ipv4.iptable_mangle = NULL; 117 } 118 119 static struct pernet_operations iptable_mangle_net_ops = { 120 .exit = iptable_mangle_net_exit, 121 }; 122 123 static int __init iptable_mangle_init(void) 124 { 125 int ret; 126 127 mangle_ops = xt_hook_ops_alloc(&packet_mangler, iptable_mangle_hook); 128 if (IS_ERR(mangle_ops)) { 129 ret = PTR_ERR(mangle_ops); 130 return ret; 131 } 132 133 ret = register_pernet_subsys(&iptable_mangle_net_ops); 134 if (ret < 0) { 135 kfree(mangle_ops); 136 return ret; 137 } 138 139 ret = iptable_mangle_table_init(&init_net); 140 if (ret) { 141 unregister_pernet_subsys(&iptable_mangle_net_ops); 142 kfree(mangle_ops); 143 } 144 145 return ret; 146 } 147 148 static void __exit iptable_mangle_fini(void) 149 { 150 unregister_pernet_subsys(&iptable_mangle_net_ops); 151 kfree(mangle_ops); 152 } 153 154 module_init(iptable_mangle_init); 155 module_exit(iptable_mangle_fini); 156