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 21MODULE_LICENSE("GPL"); 22MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>"); 23MODULE_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 31static 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 39static unsigned int 40ipt_mangle_out(struct sk_buff *skb, const struct nf_hook_state *state) 41{ 42 struct net_device *out = state->out; 43 unsigned int ret; 44 const struct iphdr *iph; 45 u_int8_t tos; 46 __be32 saddr, daddr; 47 u_int32_t mark; 48 int err; 49 50 /* root is playing with raw sockets. */ 51 if (skb->len < sizeof(struct iphdr) || 52 ip_hdrlen(skb) < sizeof(struct iphdr)) 53 return NF_ACCEPT; 54 55 /* Save things which could affect route */ 56 mark = skb->mark; 57 iph = ip_hdr(skb); 58 saddr = iph->saddr; 59 daddr = iph->daddr; 60 tos = iph->tos; 61 62 ret = ipt_do_table(skb, NF_INET_LOCAL_OUT, state, 63 dev_net(out)->ipv4.iptable_mangle); 64 /* Reroute for ANY change. */ 65 if (ret != NF_DROP && ret != NF_STOLEN) { 66 iph = ip_hdr(skb); 67 68 if (iph->saddr != saddr || 69 iph->daddr != daddr || 70 skb->mark != mark || 71 iph->tos != tos) { 72 err = ip_route_me_harder(skb, RTN_UNSPEC); 73 if (err < 0) 74 ret = NF_DROP_ERR(err); 75 } 76 } 77 78 return ret; 79} 80 81/* The work comes in here from netfilter.c. */ 82static unsigned int 83iptable_mangle_hook(const struct nf_hook_ops *ops, 84 struct sk_buff *skb, 85 const struct nf_hook_state *state) 86{ 87 if (ops->hooknum == NF_INET_LOCAL_OUT) 88 return ipt_mangle_out(skb, state); 89 if (ops->hooknum == NF_INET_POST_ROUTING) 90 return ipt_do_table(skb, ops->hooknum, state, 91 dev_net(state->out)->ipv4.iptable_mangle); 92 /* PREROUTING/INPUT/FORWARD: */ 93 return ipt_do_table(skb, ops->hooknum, state, 94 dev_net(state->in)->ipv4.iptable_mangle); 95} 96 97static struct nf_hook_ops *mangle_ops __read_mostly; 98 99static int __net_init iptable_mangle_net_init(struct net *net) 100{ 101 struct ipt_replace *repl; 102 103 repl = ipt_alloc_initial_table(&packet_mangler); 104 if (repl == NULL) 105 return -ENOMEM; 106 net->ipv4.iptable_mangle = 107 ipt_register_table(net, &packet_mangler, repl); 108 kfree(repl); 109 return PTR_ERR_OR_ZERO(net->ipv4.iptable_mangle); 110} 111 112static void __net_exit iptable_mangle_net_exit(struct net *net) 113{ 114 ipt_unregister_table(net, net->ipv4.iptable_mangle); 115} 116 117static struct pernet_operations iptable_mangle_net_ops = { 118 .init = iptable_mangle_net_init, 119 .exit = iptable_mangle_net_exit, 120}; 121 122static 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 unregister_pernet_subsys(&iptable_mangle_net_ops); 135 } 136 137 return ret; 138} 139 140static void __exit iptable_mangle_fini(void) 141{ 142 xt_hook_unlink(&packet_mangler, mangle_ops); 143 unregister_pernet_subsys(&iptable_mangle_net_ops); 144} 145 146module_init(iptable_mangle_init); 147module_exit(iptable_mangle_fini); 148