[NETFILTER]: Convert x_tables matches/targets to centralized error checking
[linux-2.6.git] / net / netfilter / xt_dccp.c
1 /*
2  * iptables module for DCCP protocol header matching
3  *
4  * (C) 2005 by Harald Welte <laforge@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/spinlock.h>
14 #include <net/ip.h>
15 #include <linux/dccp.h>
16
17 #include <linux/netfilter/x_tables.h>
18 #include <linux/netfilter/xt_dccp.h>
19
20 #include <linux/netfilter_ipv4/ip_tables.h>
21 #include <linux/netfilter_ipv6/ip6_tables.h>
22
23 MODULE_LICENSE("GPL");
24 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
25 MODULE_DESCRIPTION("Match for DCCP protocol packets");
26 MODULE_ALIAS("ipt_dccp");
27
28 #define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
29                                   || (!!((invflag) & (option)) ^ (cond)))
30
31 static unsigned char *dccp_optbuf;
32 static DEFINE_SPINLOCK(dccp_buflock);
33
34 static inline int
35 dccp_find_option(u_int8_t option,
36                  const struct sk_buff *skb,
37                  unsigned int protoff,
38                  const struct dccp_hdr *dh,
39                  int *hotdrop)
40 {
41         /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
42         unsigned char *op;
43         unsigned int optoff = __dccp_hdr_len(dh);
44         unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh);
45         unsigned int i;
46
47         if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) {
48                 *hotdrop = 1;
49                 return 0;
50         }
51
52         if (!optlen)
53                 return 0;
54
55         spin_lock_bh(&dccp_buflock);
56         op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf);
57         if (op == NULL) {
58                 /* If we don't have the whole header, drop packet. */
59                 spin_unlock_bh(&dccp_buflock);
60                 *hotdrop = 1;
61                 return 0;
62         }
63
64         for (i = 0; i < optlen; ) {
65                 if (op[i] == option) {
66                         spin_unlock_bh(&dccp_buflock);
67                         return 1;
68                 }
69
70                 if (op[i] < 2) 
71                         i++;
72                 else 
73                         i += op[i+1]?:1;
74         }
75
76         spin_unlock_bh(&dccp_buflock);
77         return 0;
78 }
79
80
81 static inline int
82 match_types(const struct dccp_hdr *dh, u_int16_t typemask)
83 {
84         return (typemask & (1 << dh->dccph_type));
85 }
86
87 static inline int
88 match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff,
89              const struct dccp_hdr *dh, int *hotdrop)
90 {
91         return dccp_find_option(option, skb, protoff, dh, hotdrop);
92 }
93
94 static int
95 match(const struct sk_buff *skb,
96       const struct net_device *in,
97       const struct net_device *out,
98       const void *matchinfo,
99       int offset,
100       unsigned int protoff,
101       int *hotdrop)
102 {
103         const struct xt_dccp_info *info = 
104                                 (const struct xt_dccp_info *)matchinfo;
105         struct dccp_hdr _dh, *dh;
106
107         if (offset)
108                 return 0;
109         
110         dh = skb_header_pointer(skb, protoff, sizeof(_dh), &_dh);
111         if (dh == NULL) {
112                 *hotdrop = 1;
113                 return 0;
114         }
115
116         return  DCCHECK(((ntohs(dh->dccph_sport) >= info->spts[0]) 
117                         && (ntohs(dh->dccph_sport) <= info->spts[1])), 
118                         XT_DCCP_SRC_PORTS, info->flags, info->invflags)
119                 && DCCHECK(((ntohs(dh->dccph_dport) >= info->dpts[0]) 
120                         && (ntohs(dh->dccph_dport) <= info->dpts[1])), 
121                         XT_DCCP_DEST_PORTS, info->flags, info->invflags)
122                 && DCCHECK(match_types(dh, info->typemask),
123                            XT_DCCP_TYPE, info->flags, info->invflags)
124                 && DCCHECK(match_option(info->option, skb, protoff, dh,
125                                         hotdrop),
126                            XT_DCCP_OPTION, info->flags, info->invflags);
127 }
128
129 static int
130 checkentry(const char *tablename,
131            const void *inf,
132            void *matchinfo,
133            unsigned int matchsize,
134            unsigned int hook_mask)
135 {
136         const struct xt_dccp_info *info = matchinfo;
137
138         return !(info->flags & ~XT_DCCP_VALID_FLAGS)
139                 && !(info->invflags & ~XT_DCCP_VALID_FLAGS)
140                 && !(info->invflags & ~info->flags);
141 }
142
143 static struct xt_match dccp_match = 
144
145         .name           = "dccp",
146         .match          = match,
147         .matchsize      = sizeof(struct xt_dccp_info),
148         .proto          = IPPROTO_DCCP,
149         .checkentry     = checkentry,
150         .me             = THIS_MODULE,
151 };
152 static struct xt_match dccp6_match = 
153
154         .name           = "dccp",
155         .match          = match,
156         .matchsize      = sizeof(struct xt_dccp_info),
157         .proto          = IPPROTO_DCCP,
158         .checkentry     = checkentry,
159         .me             = THIS_MODULE,
160 };
161
162
163 static int __init init(void)
164 {
165         int ret;
166
167         /* doff is 8 bits, so the maximum option size is (4*256).  Don't put
168          * this in BSS since DaveM is worried about locked TLB's for kernel
169          * BSS. */
170         dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL);
171         if (!dccp_optbuf)
172                 return -ENOMEM;
173         ret = xt_register_match(AF_INET, &dccp_match);
174         if (ret)
175                 goto out_kfree;
176         ret = xt_register_match(AF_INET6, &dccp6_match);
177         if (ret)
178                 goto out_unreg;
179
180         return ret;
181
182 out_unreg:
183         xt_unregister_match(AF_INET, &dccp_match);
184 out_kfree:
185         kfree(dccp_optbuf);
186
187         return ret;
188 }
189
190 static void __exit fini(void)
191 {
192         xt_unregister_match(AF_INET6, &dccp6_match);
193         xt_unregister_match(AF_INET, &dccp_match);
194         kfree(dccp_optbuf);
195 }
196
197 module_init(init);
198 module_exit(fini);