Commit | Line | Data |
---|---|---|
1d3de414 HW |
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_ipv4/ip_tables.h> | |
18 | #include <linux/netfilter_ipv4/ipt_dccp.h> | |
19 | ||
20 | #define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \ | |
21 | || (!!((invflag) & (option)) ^ (cond))) | |
22 | ||
23 | static unsigned char *dccp_optbuf; | |
24 | static DEFINE_SPINLOCK(dccp_buflock); | |
25 | ||
26 | static inline int | |
27 | dccp_find_option(u_int8_t option, | |
28 | const struct sk_buff *skb, | |
29 | const struct dccp_hdr *dh, | |
30 | int *hotdrop) | |
31 | { | |
32 | /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ | |
33 | unsigned char *op; | |
34 | unsigned int optoff = __dccp_hdr_len(dh); | |
35 | unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh); | |
36 | unsigned int i; | |
37 | ||
38 | if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) { | |
39 | *hotdrop = 1; | |
40 | return 0; | |
41 | } | |
42 | ||
43 | if (!optlen) | |
44 | return 0; | |
45 | ||
46 | spin_lock_bh(&dccp_buflock); | |
47 | op = skb_header_pointer(skb, | |
48 | skb->nh.iph->ihl*4 + optoff, | |
49 | optlen, dccp_optbuf); | |
50 | if (op == NULL) { | |
51 | /* If we don't have the whole header, drop packet. */ | |
52 | spin_unlock_bh(&dccp_buflock); | |
53 | *hotdrop = 1; | |
54 | return 0; | |
55 | } | |
56 | ||
57 | for (i = 0; i < optlen; ) { | |
58 | if (op[i] == option) { | |
59 | spin_unlock_bh(&dccp_buflock); | |
60 | return 1; | |
61 | } | |
62 | ||
63 | if (op[i] < 2) | |
64 | i++; | |
65 | else | |
66 | i += op[i+1]?:1; | |
67 | } | |
68 | ||
69 | spin_unlock_bh(&dccp_buflock); | |
70 | return 0; | |
71 | } | |
72 | ||
73 | ||
74 | static inline int | |
75 | match_types(const struct dccp_hdr *dh, u_int16_t typemask) | |
76 | { | |
77 | return (typemask & (1 << dh->dccph_type)); | |
78 | } | |
79 | ||
80 | static inline int | |
81 | match_option(u_int8_t option, const struct sk_buff *skb, | |
82 | const struct dccp_hdr *dh, int *hotdrop) | |
83 | { | |
84 | return dccp_find_option(option, skb, dh, hotdrop); | |
85 | } | |
86 | ||
87 | static int | |
88 | match(const struct sk_buff *skb, | |
89 | const struct net_device *in, | |
90 | const struct net_device *out, | |
91 | const void *matchinfo, | |
92 | int offset, | |
93 | int *hotdrop) | |
94 | { | |
95 | const struct ipt_dccp_info *info = | |
96 | (const struct ipt_dccp_info *)matchinfo; | |
97 | struct dccp_hdr _dh, *dh; | |
98 | ||
99 | if (offset) | |
100 | return 0; | |
101 | ||
102 | dh = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_dh), &_dh); | |
103 | if (dh == NULL) { | |
104 | *hotdrop = 1; | |
105 | return 0; | |
106 | } | |
107 | ||
108 | return DCCHECK(((ntohs(dh->dccph_sport) >= info->spts[0]) | |
109 | && (ntohs(dh->dccph_sport) <= info->spts[1])), | |
110 | IPT_DCCP_SRC_PORTS, info->flags, info->invflags) | |
111 | && DCCHECK(((ntohs(dh->dccph_dport) >= info->dpts[0]) | |
112 | && (ntohs(dh->dccph_dport) <= info->dpts[1])), | |
113 | IPT_DCCP_DEST_PORTS, info->flags, info->invflags) | |
114 | && DCCHECK(match_types(dh, info->typemask), | |
115 | IPT_DCCP_TYPE, info->flags, info->invflags) | |
116 | && DCCHECK(match_option(info->option, skb, dh, hotdrop), | |
117 | IPT_DCCP_OPTION, info->flags, info->invflags); | |
118 | } | |
119 | ||
120 | static int | |
121 | checkentry(const char *tablename, | |
122 | const struct ipt_ip *ip, | |
123 | void *matchinfo, | |
124 | unsigned int matchsize, | |
125 | unsigned int hook_mask) | |
126 | { | |
127 | const struct ipt_dccp_info *info; | |
128 | ||
129 | info = (const struct ipt_dccp_info *)matchinfo; | |
130 | ||
131 | return ip->proto == IPPROTO_DCCP | |
132 | && !(ip->invflags & IPT_INV_PROTO) | |
133 | && matchsize == IPT_ALIGN(sizeof(struct ipt_dccp_info)) | |
134 | && !(info->flags & ~IPT_DCCP_VALID_FLAGS) | |
135 | && !(info->invflags & ~IPT_DCCP_VALID_FLAGS) | |
136 | && !(info->invflags & ~info->flags); | |
137 | } | |
138 | ||
139 | static struct ipt_match dccp_match = | |
140 | { | |
141 | .name = "dccp", | |
142 | .match = &match, | |
143 | .checkentry = &checkentry, | |
144 | .me = THIS_MODULE, | |
145 | }; | |
146 | ||
147 | static int __init init(void) | |
148 | { | |
149 | int ret; | |
150 | ||
151 | /* doff is 8 bits, so the maximum option size is (4*256). Don't put | |
152 | * this in BSS since DaveM is worried about locked TLB's for kernel | |
153 | * BSS. */ | |
154 | dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL); | |
155 | if (!dccp_optbuf) | |
156 | return -ENOMEM; | |
157 | ret = ipt_register_match(&dccp_match); | |
158 | if (ret) | |
159 | kfree(dccp_optbuf); | |
160 | ||
161 | return ret; | |
162 | } | |
163 | ||
164 | static void __exit fini(void) | |
165 | { | |
166 | ipt_unregister_match(&dccp_match); | |
167 | kfree(dccp_optbuf); | |
168 | } | |
169 | ||
170 | module_init(init); | |
171 | module_exit(fini); | |
172 | ||
173 | MODULE_LICENSE("GPL"); | |
174 | MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); | |
175 | MODULE_DESCRIPTION("Match for DCCP protocol packets"); | |
176 |