1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x. 4 * 5 * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling 6 * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org> 7 */ 8 #include <linux/module.h> 9 #include <linux/netfilter_ipv4/ip_tables.h> 10 #include <linux/netdevice.h> 11 #include <linux/skbuff.h> 12 #include <linux/slab.h> 13 #include <net/sock.h> 14 #include <net/route.h> 15 #include <linux/ip.h> 16 #include <net/ip.h> 17 18 MODULE_LICENSE("GPL"); 19 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>"); 20 MODULE_DESCRIPTION("iptables mangle table"); 21 22 #define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \ 23 (1 << NF_INET_LOCAL_IN) | \ 24 (1 << NF_INET_FORWARD) | \ 25 (1 << NF_INET_LOCAL_OUT) | \ 26 (1 << NF_INET_POST_ROUTING)) 27 28 static int __net_init iptable_mangle_table_init(struct net *net); 29 30 static const struct xt_table packet_mangler = { 31 .name = "mangle", 32 .valid_hooks = MANGLE_VALID_HOOKS, 33 .me = THIS_MODULE, 34 .af = NFPROTO_IPV4, 35 .priority = NF_IP_PRI_MANGLE, 36 .table_init = iptable_mangle_table_init, 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 /* Save things which could affect route */ 50 mark = skb->mark; 51 iph = ip_hdr(skb); 52 saddr = iph->saddr; 53 daddr = iph->daddr; 54 tos = iph->tos; 55 56 ret = ipt_do_table(skb, state, state->net->ipv4.iptable_mangle); 57 /* Reroute for ANY change. */ 58 if (ret != NF_DROP && ret != NF_STOLEN) { 59 iph = ip_hdr(skb); 60 61 if (iph->saddr != saddr || 62 iph->daddr != daddr || 63 skb->mark != mark || 64 iph->tos != tos) { 65 err = ip_route_me_harder(state->net, state->sk, skb, RTN_UNSPEC); 66 if (err < 0) 67 ret = NF_DROP_ERR(err); 68 } 69 } 70 71 return ret; 72 } 73 74 /* The work comes in here from netfilter.c. */ 75 static unsigned int 76 iptable_mangle_hook(void *priv, 77 struct sk_buff *skb, 78 const struct nf_hook_state *state) 79 { 80 if (state->hook == NF_INET_LOCAL_OUT) 81 return ipt_mangle_out(skb, state); 82 return ipt_do_table(skb, state, state->net->ipv4.iptable_mangle); 83 } 84 85 static struct nf_hook_ops *mangle_ops __read_mostly; 86 static int __net_init iptable_mangle_table_init(struct net *net) 87 { 88 struct ipt_replace *repl; 89 int ret; 90 91 if (net->ipv4.iptable_mangle) 92 return 0; 93 94 repl = ipt_alloc_initial_table(&packet_mangler); 95 if (repl == NULL) 96 return -ENOMEM; 97 ret = ipt_register_table(net, &packet_mangler, repl, mangle_ops, 98 &net->ipv4.iptable_mangle); 99 kfree(repl); 100 return ret; 101 } 102 103 static void __net_exit iptable_mangle_net_pre_exit(struct net *net) 104 { 105 if (net->ipv4.iptable_mangle) 106 ipt_unregister_table_pre_exit(net, net->ipv4.iptable_mangle, 107 mangle_ops); 108 } 109 110 static void __net_exit iptable_mangle_net_exit(struct net *net) 111 { 112 if (!net->ipv4.iptable_mangle) 113 return; 114 ipt_unregister_table_exit(net, net->ipv4.iptable_mangle); 115 net->ipv4.iptable_mangle = NULL; 116 } 117 118 static struct pernet_operations iptable_mangle_net_ops = { 119 .pre_exit = iptable_mangle_net_pre_exit, 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