1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
|
/*
* iptables module for DCCP protocol header matching
*
* (C) 2005 by Harald Welte <laforge@netfilter.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>
#include <net/ip.h>
#include <linux/dccp.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_dccp.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("Xtables: DCCP protocol packet match");
MODULE_ALIAS("ipt_dccp");
MODULE_ALIAS("ip6t_dccp");
#define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
|| (!!((invflag) & (option)) ^ (cond)))
static unsigned char *dccp_optbuf;
static DEFINE_SPINLOCK(dccp_buflock);
static inline bool
dccp_find_option(u_int8_t option,
const struct sk_buff *skb,
unsigned int protoff,
const struct dccp_hdr *dh,
bool *hotdrop)
{
/* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
const unsigned char *op;
unsigned int optoff = __dccp_hdr_len(dh);
unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh);
unsigned int i;
if (dh->dccph_doff * 4 < __dccp_hdr_len(dh))
goto invalid;
if (!optlen)
return false;
spin_lock_bh(&dccp_buflock);
op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf);
if (op == NULL) {
/* If we don't have the whole header, drop packet. */
goto partial;
}
for (i = 0; i < optlen; ) {
if (op[i] == option) {
spin_unlock_bh(&dccp_buflock);
return true;
}
if (op[i] < 2)
i++;
else
i += op[i+1]?:1;
}
spin_unlock_bh(&dccp_buflock);
return false;
partial:
spin_unlock_bh(&dccp_buflock);
invalid:
*hotdrop = true;
return false;
}
static inline bool
match_types(const struct dccp_hdr *dh, u_int16_t typemask)
{
return typemask & (1 << dh->dccph_type);
}
static inline bool
match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff,
const struct dccp_hdr *dh, bool *hotdrop)
{
return dccp_find_option(option, skb, protoff, dh, hotdrop);
}
static bool
dccp_mt(const struct sk_buff *skb, const struct xt_match_param *par)
{
const struct xt_dccp_info *info = par->matchinfo;
const struct dccp_hdr *dh;
struct dccp_hdr _dh;
if (par->fragoff != 0)
return false;
dh = skb_header_pointer(skb, par->thoff, sizeof(_dh), &_dh);
if (dh == NULL) {
*par->hotdrop = true;
return false;
}
return DCCHECK(ntohs(dh->dccph_sport) >= info->spts[0]
&& ntohs(dh->dccph_sport) <= info->spts[1],
XT_DCCP_SRC_PORTS, info->flags, info->invflags)
&& DCCHECK(ntohs(dh->dccph_dport) >= info->dpts[0]
&& ntohs(dh->dccph_dport) <= info->dpts[1],
XT_DCCP_DEST_PORTS, info->flags, info->invflags)
&& DCCHECK(match_types(dh, info->typemask),
XT_DCCP_TYPE, info->flags, info->invflags)
&& DCCHECK(match_option(info->option, skb, par->thoff, dh,
par->hotdrop),
XT_DCCP_OPTION, info->flags, info->invflags);
}
static bool dccp_mt_check(const struct xt_mtchk_param *par)
{
const struct xt_dccp_info *info = par->matchinfo;
return !(info->flags & ~XT_DCCP_VALID_FLAGS)
&& !(info->invflags & ~XT_DCCP_VALID_FLAGS)
&& !(info->invflags & ~info->flags);
}
static struct xt_match dccp_mt_reg[] __read_mostly = {
{
.name = "dccp",
.family = NFPROTO_IPV4,
.checkentry = dccp_mt_check,
.match = dccp_mt,
.matchsize = sizeof(struct xt_dccp_info),
.proto = IPPROTO_DCCP,
.me = THIS_MODULE,
},
{
.name = "dccp",
.family = NFPROTO_IPV6,
.checkentry = dccp_mt_check,
.match = dccp_mt,
.matchsize = sizeof(struct xt_dccp_info),
.proto = IPPROTO_DCCP,
.me = THIS_MODULE,
},
};
static int __init dccp_mt_init(void)
{
int ret;
/* doff is 8 bits, so the maximum option size is (4*256). Don't put
* this in BSS since DaveM is worried about locked TLB's for kernel
* BSS. */
dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL);
if (!dccp_optbuf)
return -ENOMEM;
ret = xt_register_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg));
if (ret)
goto out_kfree;
return ret;
out_kfree:
kfree(dccp_optbuf);
return ret;
}
static void __exit dccp_mt_exit(void)
{
xt_unregister_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg));
kfree(dccp_optbuf);
}
module_init(dccp_mt_init);
module_exit(dccp_mt_exit);
|
