[WATCHDOG] Merge code clean-up's from Alan Cox.
[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("Xtables: IPv6 Hop Limit field modification target");
19 MODULE_LICENSE("GPL");
20
21 static unsigned int
22 hl_tg6(struct sk_buff *skb, const struct net_device *in,
23        const struct net_device *out, unsigned int hooknum,
24        const struct xt_target *target, const void *targinfo)
25 {
26         struct ipv6hdr *ip6h;
27         const struct ip6t_HL_info *info = targinfo;
28         int new_hl;
29
30         if (!skb_make_writable(skb, skb->len))
31                 return NF_DROP;
32
33         ip6h = ipv6_hdr(skb);
34
35         switch (info->mode) {
36                 case IP6T_HL_SET:
37                         new_hl = info->hop_limit;
38                         break;
39                 case IP6T_HL_INC:
40                         new_hl = ip6h->hop_limit + info->hop_limit;
41                         if (new_hl > 255)
42                                 new_hl = 255;
43                         break;
44                 case IP6T_HL_DEC:
45                         new_hl = ip6h->hop_limit - info->hop_limit;
46                         if (new_hl < 0)
47                                 new_hl = 0;
48                         break;
49                 default:
50                         new_hl = ip6h->hop_limit;
51                         break;
52         }
53
54         ip6h->hop_limit = new_hl;
55
56         return XT_CONTINUE;
57 }
58
59 static bool
60 hl_tg6_check(const char *tablename, const void *entry,
61              const struct xt_target *target, void *targinfo,
62              unsigned int hook_mask)
63 {
64         const struct ip6t_HL_info *info = targinfo;
65
66         if (info->mode > IP6T_HL_MAXMODE) {
67                 printk(KERN_WARNING "ip6t_HL: invalid or unknown Mode %u\n",
68                         info->mode);
69                 return false;
70         }
71         if (info->mode != IP6T_HL_SET && info->hop_limit == 0) {
72                 printk(KERN_WARNING "ip6t_HL: increment/decrement doesn't "
73                         "make sense with value 0\n");
74                 return false;
75         }
76         return true;
77 }
78
79 static struct xt_target hl_tg6_reg __read_mostly = {
80         .name           = "HL",
81         .family         = AF_INET6,
82         .target         = hl_tg6,
83         .targetsize     = sizeof(struct ip6t_HL_info),
84         .table          = "mangle",
85         .checkentry     = hl_tg6_check,
86         .me             = THIS_MODULE
87 };
88
89 static int __init hl_tg6_init(void)
90 {
91         return xt_register_target(&hl_tg6_reg);
92 }
93
94 static void __exit hl_tg6_exit(void)
95 {
96         xt_unregister_target(&hl_tg6_reg);
97 }
98
99 module_init(hl_tg6_init);
100 module_exit(hl_tg6_exit);