1 /* This is a module which is used for setting the TOS field of a packet. */
2
3 /* (C) 1999-2001 Paul `Rusty' Russell
4 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 */
10
11 #include <linux/module.h>
12 #include <linux/skbuff.h>
13 #include <linux/ip.h>
14 #include <net/checksum.h>
15
16 #include <linux/netfilter_ipv4/ip_tables.h>
17 #include <linux/netfilter_ipv4/ipt_TOS.h>
18
19 MODULE_LICENSE("GPL");
20 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
21 MODULE_DESCRIPTION("iptables TOS mangling module");
22
23 static unsigned int
24 target(struct sk_buff **pskb,
25 const struct net_device *in,
26 const struct net_device *out,
27 unsigned int hooknum,
28 const void *targinfo,
29 void *userinfo)
30 {
31 const struct ipt_tos_target_info *tosinfo = targinfo;
32
33 if (((*pskb)->nh.iph->tos & IPTOS_TOS_MASK) != tosinfo->tos) {
34 u_int16_t diffs[2];
35
36 if (!skb_ip_make_writable(pskb, sizeof(struct iphdr)))
37 return NF_DROP;
38
39 diffs[0] = htons((*pskb)->nh.iph->tos) ^ 0xFFFF;
40 (*pskb)->nh.iph->tos
41 = ((*pskb)->nh.iph->tos & IPTOS_PREC_MASK)
42 | tosinfo->tos;
43 diffs[1] = htons((*pskb)->nh.iph->tos);
44 (*pskb)->nh.iph->check
45 = csum_fold(csum_partial((char *)diffs,
46 sizeof(diffs),
47 (*pskb)->nh.iph->check
48 ^0xFFFF));
49 (*pskb)->nfcache |= NFC_ALTERED;
50 }
51 return IPT_CONTINUE;
52 }
53
54 static int
55 checkentry(const char *tablename,
56 const struct ipt_entry *e,
57 void *targinfo,
58 unsigned int targinfosize,
59 unsigned int hook_mask)
60 {
61 const u_int8_t tos = ((struct ipt_tos_target_info *)targinfo)->tos;
62
63 if (targinfosize != IPT_ALIGN(sizeof(struct ipt_tos_target_info))) {
64 printk(KERN_WARNING "TOS: targinfosize %u != %Zu\n",
65 targinfosize,
66 IPT_ALIGN(sizeof(struct ipt_tos_target_info)));
67 return 0;
68 }
69
70 if (strcmp(tablename, "mangle") != 0) {
71 printk(KERN_WARNING "TOS: can only be called from \"mangle\" table, not \"%s\"\n", tablename);
72 return 0;
73 }
74
75 if (tos != IPTOS_LOWDELAY
76 && tos != IPTOS_THROUGHPUT
77 && tos != IPTOS_RELIABILITY
78 && tos != IPTOS_MINCOST
79 && tos != IPTOS_NORMALSVC) {
80 printk(KERN_WARNING "TOS: bad tos value %#x\n", tos);
81 return 0;
82 }
83
84 return 1;
85 }
86
87 static struct ipt_target ipt_tos_reg = {
88 .name = "TOS",
89 .target = target,
90 .checkentry = checkentry,
91 .me = THIS_MODULE,
92 };
93
94 static int __init init(void)
95 {
96 return ipt_register_target(&ipt_tos_reg);
97 }
98
99 static void __exit fini(void)
100 {
101 ipt_unregister_target(&ipt_tos_reg);
102 }
103
104 module_init(init);
105 module_exit(fini);
106
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