tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
23MODULE_LICENSE("GPL");
24MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
25MODULE_DESCRIPTION("Xtables: DCCP protocol packet match");
26MODULE_ALIAS("ipt_dccp");
27MODULE_ALIAS("ip6t_dccp");
28
29#define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
30 || (!!((invflag) & (option)) ^ (cond)))
31
32static unsigned char *dccp_optbuf;
33static DEFINE_SPINLOCK(dccp_buflock);
34
35static inline bool
36dccp_find_option(u_int8_t option,
37 const struct sk_buff *skb,
38 unsigned int protoff,
39 const struct dccp_hdr *dh,
40 bool *hotdrop)
41{
42 /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
43 const unsigned char *op;
44 unsigned int optoff = __dccp_hdr_len(dh);
45 unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh);
46 unsigned int i;
47
48 if (dh->dccph_doff * 4 < __dccp_hdr_len(dh))
49 goto invalid;
50
51 if (!optlen)
52 return false;
53
54 spin_lock_bh(&dccp_buflock);
55 op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf);
56 if (op == NULL) {
57 /* If we don't have the whole header, drop packet. */
58 goto partial;
59 }
60
61 for (i = 0; i < optlen; ) {
62 if (op[i] == option) {
63 spin_unlock_bh(&dccp_buflock);
64 return true;
65 }
66
67 if (op[i] < 2)
68 i++;
69 else
70 i += op[i+1]?:1;
71 }
72
73 spin_unlock_bh(&dccp_buflock);
74 return false;
75
76partial:
77 spin_unlock_bh(&dccp_buflock);
78invalid:
79 *hotdrop = true;
80 return false;
81}
82
83
84static inline bool
85match_types(const struct dccp_hdr *dh, u_int16_t typemask)
86{
87 return typemask & (1 << dh->dccph_type);
88}
89
90static inline bool
91match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff,
92 const struct dccp_hdr *dh, bool *hotdrop)
93{
94 return dccp_find_option(option, skb, protoff, dh, hotdrop);
95}
96
97static bool
98dccp_mt(const struct sk_buff *skb, const struct xt_match_param *par)
99{
100 const struct xt_dccp_info *info = par->matchinfo;
101 const struct dccp_hdr *dh;
102 struct dccp_hdr _dh;
103
104 if (par->fragoff != 0)
105 return false;
106
107 dh = skb_header_pointer(skb, par->thoff, sizeof(_dh), &_dh);
108 if (dh == NULL) {
109 *par->hotdrop = true;
110 return false;
111 }
112
113 return DCCHECK(ntohs(dh->dccph_sport) >= info->spts[0]
114 && ntohs(dh->dccph_sport) <= info->spts[1],
115 XT_DCCP_SRC_PORTS, info->flags, info->invflags)
116 && DCCHECK(ntohs(dh->dccph_dport) >= info->dpts[0]
117 && ntohs(dh->dccph_dport) <= info->dpts[1],
118 XT_DCCP_DEST_PORTS, info->flags, info->invflags)
119 && DCCHECK(match_types(dh, info->typemask),
120 XT_DCCP_TYPE, info->flags, info->invflags)
121 && DCCHECK(match_option(info->option, skb, par->thoff, dh,
122 par->hotdrop),
123 XT_DCCP_OPTION, info->flags, info->invflags);
124}
125
126static bool dccp_mt_check(const struct xt_mtchk_param *par)
127{
128 const struct xt_dccp_info *info = par->matchinfo;
129
130 return !(info->flags & ~XT_DCCP_VALID_FLAGS)
131 && !(info->invflags & ~XT_DCCP_VALID_FLAGS)
132 && !(info->invflags & ~info->flags);
133}
134
135static struct xt_match dccp_mt_reg[] __read_mostly = {
136 {
137 .name = "dccp",
138 .family = NFPROTO_IPV4,
139 .checkentry = dccp_mt_check,
140 .match = dccp_mt,
141 .matchsize = sizeof(struct xt_dccp_info),
142 .proto = IPPROTO_DCCP,
143 .me = THIS_MODULE,
144 },
145 {
146 .name = "dccp",
147 .family = NFPROTO_IPV6,
148 .checkentry = dccp_mt_check,
149 .match = dccp_mt,
150 .matchsize = sizeof(struct xt_dccp_info),
151 .proto = IPPROTO_DCCP,
152 .me = THIS_MODULE,
153 },
154};
155
156static int __init dccp_mt_init(void)
157{
158 int ret;
159
160 /* doff is 8 bits, so the maximum option size is (4*256). Don't put
161 * this in BSS since DaveM is worried about locked TLB's for kernel
162 * BSS. */
163 dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL);
164 if (!dccp_optbuf)
165 return -ENOMEM;
166 ret = xt_register_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg));
167 if (ret)
168 goto out_kfree;
169 return ret;
170
171out_kfree:
172 kfree(dccp_optbuf);
173 return ret;
174}
175
176static void __exit dccp_mt_exit(void)
177{
178 xt_unregister_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg));
179 kfree(dccp_optbuf);
180}
181
182module_init(dccp_mt_init);
183module_exit(dccp_mt_exit);