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 const struct xt_table packet_mangler = { |
29 | .name = "mangle" , |
30 | .valid_hooks = MANGLE_VALID_HOOKS, |
31 | .me = THIS_MODULE, |
32 | .af = NFPROTO_IPV4, |
33 | .priority = NF_IP_PRI_MANGLE, |
34 | }; |
35 | |
36 | static unsigned int |
37 | ipt_mangle_out(void *priv, struct sk_buff *skb, const struct nf_hook_state *state) |
38 | { |
39 | unsigned int ret, verdict; |
40 | const struct iphdr *iph; |
41 | __be32 saddr, daddr; |
42 | u32 mark; |
43 | int err; |
44 | u8 tos; |
45 | |
46 | /* Save things which could affect route */ |
47 | mark = skb->mark; |
48 | iph = ip_hdr(skb); |
49 | saddr = iph->saddr; |
50 | daddr = iph->daddr; |
51 | tos = iph->tos; |
52 | |
53 | ret = ipt_do_table(priv, skb, state); |
54 | verdict = ret & NF_VERDICT_MASK; |
55 | /* Reroute for ANY change. */ |
56 | if (verdict != NF_DROP && verdict != NF_STOLEN) { |
57 | iph = ip_hdr(skb); |
58 | |
59 | if (iph->saddr != saddr || |
60 | iph->daddr != daddr || |
61 | skb->mark != mark || |
62 | iph->tos != tos) { |
63 | err = ip_route_me_harder(net: state->net, sk: state->sk, skb, addr_type: RTN_UNSPEC); |
64 | if (err < 0) |
65 | ret = NF_DROP_ERR(err); |
66 | } |
67 | } |
68 | |
69 | return ret; |
70 | } |
71 | |
72 | /* The work comes in here from netfilter.c. */ |
73 | static unsigned int |
74 | iptable_mangle_hook(void *priv, |
75 | struct sk_buff *skb, |
76 | const struct nf_hook_state *state) |
77 | { |
78 | if (state->hook == NF_INET_LOCAL_OUT) |
79 | return ipt_mangle_out(priv, skb, state); |
80 | return ipt_do_table(priv, skb, state); |
81 | } |
82 | |
83 | static struct nf_hook_ops *mangle_ops __read_mostly; |
84 | static int iptable_mangle_table_init(struct net *net) |
85 | { |
86 | struct ipt_replace *repl; |
87 | int ret; |
88 | |
89 | repl = ipt_alloc_initial_table(&packet_mangler); |
90 | if (repl == NULL) |
91 | return -ENOMEM; |
92 | ret = ipt_register_table(net, table: &packet_mangler, repl, ops: mangle_ops); |
93 | kfree(objp: repl); |
94 | return ret; |
95 | } |
96 | |
97 | static void __net_exit iptable_mangle_net_pre_exit(struct net *net) |
98 | { |
99 | ipt_unregister_table_pre_exit(net, name: "mangle" ); |
100 | } |
101 | |
102 | static void __net_exit iptable_mangle_net_exit(struct net *net) |
103 | { |
104 | ipt_unregister_table_exit(net, name: "mangle" ); |
105 | } |
106 | |
107 | static struct pernet_operations iptable_mangle_net_ops = { |
108 | .pre_exit = iptable_mangle_net_pre_exit, |
109 | .exit = iptable_mangle_net_exit, |
110 | }; |
111 | |
112 | static int __init iptable_mangle_init(void) |
113 | { |
114 | int ret = xt_register_template(t: &packet_mangler, |
115 | table_init: iptable_mangle_table_init); |
116 | if (ret < 0) |
117 | return ret; |
118 | |
119 | mangle_ops = xt_hook_ops_alloc(&packet_mangler, iptable_mangle_hook); |
120 | if (IS_ERR(ptr: mangle_ops)) { |
121 | xt_unregister_template(t: &packet_mangler); |
122 | ret = PTR_ERR(ptr: mangle_ops); |
123 | return ret; |
124 | } |
125 | |
126 | ret = register_pernet_subsys(&iptable_mangle_net_ops); |
127 | if (ret < 0) { |
128 | xt_unregister_template(t: &packet_mangler); |
129 | kfree(objp: mangle_ops); |
130 | return ret; |
131 | } |
132 | |
133 | return ret; |
134 | } |
135 | |
136 | static void __exit iptable_mangle_fini(void) |
137 | { |
138 | unregister_pernet_subsys(&iptable_mangle_net_ops); |
139 | xt_unregister_template(t: &packet_mangler); |
140 | kfree(objp: mangle_ops); |
141 | } |
142 | |
143 | module_init(iptable_mangle_init); |
144 | module_exit(iptable_mangle_fini); |
145 | |