xen: disable split pte locks for now
[linux-2.6] / net / ipv6 / netfilter / ip6t_HL.c
1 /*
2  * Hop Limit modification target for ip6tables
3  * Maciej Soltysiak <solt@dns.toxicfilms.tv>
4  * Based on HW's TTL module
5  *
6  * This software is distributed under the terms of GNU GPL
7  */
8
9 #include <linux/module.h>
10 #include <linux/skbuff.h>
11 #include <linux/ip.h>
12 #include <linux/ipv6.h>
13
14 #include <linux/netfilter/x_tables.h>
15 #include <linux/netfilter_ipv6/ip6t_HL.h>
16
17 MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>");
18 MODULE_DESCRIPTION("IP6 tables Hop Limit modification module");
19 MODULE_LICENSE("GPL");
20
21 static unsigned int ip6t_hl_target(struct sk_buff **pskb,
22                                    const struct net_device *in,
23                                    const struct net_device *out,
24                                    unsigned int hooknum,
25                                    const struct xt_target *target,
26                                    const void *targinfo)
27 {
28         struct ipv6hdr *ip6h;
29         const struct ip6t_HL_info *info = targinfo;
30         int new_hl;
31
32         if (!skb_make_writable(pskb, (*pskb)->len))
33                 return NF_DROP;
34
35         ip6h = ipv6_hdr(*pskb);
36
37         switch (info->mode) {
38                 case IP6T_HL_SET:
39                         new_hl = info->hop_limit;
40                         break;
41                 case IP6T_HL_INC:
42                         new_hl = ip6h->hop_limit + info->hop_limit;
43                         if (new_hl > 255)
44                                 new_hl = 255;
45                         break;
46                 case IP6T_HL_DEC:
47                         new_hl = ip6h->hop_limit - info->hop_limit;
48                         if (new_hl < 0)
49                                 new_hl = 0;
50                         break;
51                 default:
52                         new_hl = ip6h->hop_limit;
53                         break;
54         }
55
56         ip6h->hop_limit = new_hl;
57
58         return XT_CONTINUE;
59 }
60
61 static bool ip6t_hl_checkentry(const char *tablename,
62                 const void *entry,
63                 const struct xt_target *target,
64                 void *targinfo,
65                 unsigned int hook_mask)
66 {
67         const struct ip6t_HL_info *info = targinfo;
68
69         if (info->mode > IP6T_HL_MAXMODE) {
70                 printk(KERN_WARNING "ip6t_HL: invalid or unknown Mode %u\n",
71                         info->mode);
72                 return false;
73         }
74         if (info->mode != IP6T_HL_SET && info->hop_limit == 0) {
75                 printk(KERN_WARNING "ip6t_HL: increment/decrement doesn't "
76                         "make sense with value 0\n");
77                 return false;
78         }
79         return true;
80 }
81
82 static struct xt_target ip6t_HL __read_mostly = {
83         .name           = "HL",
84         .family         = AF_INET6,
85         .target         = ip6t_hl_target,
86         .targetsize     = sizeof(struct ip6t_HL_info),
87         .table          = "mangle",
88         .checkentry     = ip6t_hl_checkentry,
89         .me             = THIS_MODULE
90 };
91
92 static int __init ip6t_hl_init(void)
93 {
94         return xt_register_target(&ip6t_HL);
95 }
96
97 static void __exit ip6t_hl_fini(void)
98 {
99         xt_unregister_target(&ip6t_HL);
100 }
101
102 module_init(ip6t_hl_init);
103 module_exit(ip6t_hl_fini);