[PATCH] knfsd: Allow max size of NFSd payload to be configured
[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
13 #include <linux/netfilter_ipv6/ip6_tables.h>
14 #include <linux/netfilter_ipv6/ip6t_HL.h>
15
16 MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>");
17 MODULE_DESCRIPTION("IP tables Hop Limit modification module");
18 MODULE_LICENSE("GPL");
19
20 static unsigned int ip6t_hl_target(struct sk_buff **pskb, 
21                                    const struct net_device *in,
22                                    const struct net_device *out,
23                                    unsigned int hooknum,
24                                    const struct xt_target *target,
25                                    const void *targinfo)
26 {
27         struct ipv6hdr *ip6h;
28         const struct ip6t_HL_info *info = targinfo;
29         int new_hl;
30
31         if (!skb_make_writable(pskb, (*pskb)->len))
32                 return NF_DROP;
33
34         ip6h = (*pskb)->nh.ipv6h;
35
36         switch (info->mode) {
37                 case IP6T_HL_SET:
38                         new_hl = info->hop_limit;
39                         break;
40                 case IP6T_HL_INC:
41                         new_hl = ip6h->hop_limit + info->hop_limit;
42                         if (new_hl > 255)
43                                 new_hl = 255;
44                         break;
45                 case IP6T_HL_DEC:
46                         new_hl = ip6h->hop_limit - info->hop_limit;
47                         if (new_hl < 0)
48                                 new_hl = 0;
49                         break;
50                 default:
51                         new_hl = ip6h->hop_limit;
52                         break;
53         }
54
55         if (new_hl != ip6h->hop_limit)
56                 ip6h->hop_limit = new_hl;
57
58         return IP6T_CONTINUE;
59 }
60
61 static int 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         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 0;
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 0;
78         }
79         return 1;
80 }
81
82 static struct ip6t_target ip6t_HL = { 
83         .name           = "HL", 
84         .target         = ip6t_hl_target, 
85         .targetsize     = sizeof(struct ip6t_HL_info),
86         .table          = "mangle",
87         .checkentry     = ip6t_hl_checkentry, 
88         .me             = THIS_MODULE
89 };
90
91 static int __init ip6t_hl_init(void)
92 {
93         return ip6t_register_target(&ip6t_HL);
94 }
95
96 static void __exit ip6t_hl_fini(void)
97 {
98         ip6t_unregister_target(&ip6t_HL);
99 }
100
101 module_init(ip6t_hl_init);
102 module_exit(ip6t_hl_fini);