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 nf_hook_state *state) 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, state, state->net->ipv4.iptable_mangle); 62 /* Reroute for ANY change. */ 63 if (ret != NF_DROP && ret != NF_STOLEN) { 64 iph = ip_hdr(skb); 65 66 if (iph->saddr != saddr || 67 iph->daddr != daddr || 68 skb->mark != mark || 69 iph->tos != tos) { 70 err = ip_route_me_harder(state->net, skb, RTN_UNSPEC); 71 if (err < 0) 72 ret = NF_DROP_ERR(err); 73 } 74 } 75 76 return ret; 77 } 78 79 /* The work comes in here from netfilter.c. */ 80 static unsigned int 81 iptable_mangle_hook(void *priv, 82 struct sk_buff *skb, 83 const struct nf_hook_state *state) 84 { 85 if (state->hook == NF_INET_LOCAL_OUT) 86 return ipt_mangle_out(skb, state); 87 if (state->hook == NF_INET_POST_ROUTING) 88 return ipt_do_table(skb, state, 89 state->net->ipv4.iptable_mangle); 90 /* PREROUTING/INPUT/FORWARD: */ 91 return ipt_do_table(skb, state, state->net->ipv4.iptable_mangle); 92 } 93 94 static struct nf_hook_ops *mangle_ops __read_mostly; 95 96 static int __net_init iptable_mangle_net_init(struct net *net) 97 { 98 struct ipt_replace *repl; 99 100 repl = ipt_alloc_initial_table(&packet_mangler); 101 if (repl == NULL) 102 return -ENOMEM; 103 net->ipv4.iptable_mangle = 104 ipt_register_table(net, &packet_mangler, repl); 105 kfree(repl); 106 return PTR_ERR_OR_ZERO(net->ipv4.iptable_mangle); 107 } 108 109 static void __net_exit iptable_mangle_net_exit(struct net *net) 110 { 111 ipt_unregister_table(net, net->ipv4.iptable_mangle); 112 } 113 114 static struct pernet_operations iptable_mangle_net_ops = { 115 .init = iptable_mangle_net_init, 116 .exit = iptable_mangle_net_exit, 117 }; 118 119 static int __init iptable_mangle_init(void) 120 { 121 int ret; 122 123 ret = register_pernet_subsys(&iptable_mangle_net_ops); 124 if (ret < 0) 125 return ret; 126 127 /* Register hooks */ 128 mangle_ops = xt_hook_link(&packet_mangler, iptable_mangle_hook); 129 if (IS_ERR(mangle_ops)) { 130 ret = PTR_ERR(mangle_ops); 131 unregister_pernet_subsys(&iptable_mangle_net_ops); 132 } 133 134 return ret; 135 } 136 137 static void __exit iptable_mangle_fini(void) 138 { 139 xt_hook_unlink(&packet_mangler, mangle_ops); 140 unregister_pernet_subsys(&iptable_mangle_net_ops); 141 } 142 143 module_init(iptable_mangle_init); 144 module_exit(iptable_mangle_fini); 145