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
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
|
/*
Shared library add-on to iptables to add match support for every Nth packet
This file is distributed under the terms of the GNU General Public
License (GPL). Copies of the GPL can be obtained from:
ftp://prep.ai.mit.edu/pub/gnu/GPL
2001-07-17 Fabrice MARIE <fabrice@celestix.com> : initial development.
2001-09-20 Richard Wagner (rwagner@cloudnet.com)
* added support for multiple counters
* added support for matching on individual packets
in the counter cycle
*/
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <syslog.h>
#include <getopt.h>
#include <iptables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_nth.h>
/* Function which prints out usage message. */
static void
help(void)
{
printf(
"nth v%s options:\n"
" --every Nth Match every Nth packet\n"
" [--counter] num Use counter 0-%u (default:0)\n"
" [--start] num Initialize the counter at the number 'num'\n"
" instead of 0. Must be between 0 and Nth-1\n"
" [--packet] num Match on 'num' packet. Must be between 0\n"
" and Nth-1.\n\n"
" If --packet is used for a counter than\n"
" there must be Nth number of --packet\n"
" rules, covering all values between 0 and\n"
" Nth-1 inclusively.\n",
NETFILTER_VERSION, IPT_NTH_NUM_COUNTERS-1);
}
static struct option opts[] = {
{ "every", 1, 0, '1' },
{ "start", 1, 0, '2' },
{ "counter", 1, 0, '3' },
{ "packet", 1, 0, '4' },
{ 0 }
};
/* Initialize the target. */
static void
init(struct ipt_entry_match *m, unsigned int *nfcache)
{
*nfcache |= NFC_UNKNOWN;
}
#define IPT_NTH_OPT_EVERY 0x01
#define IPT_NTH_OPT_NOT_EVERY 0x02
#define IPT_NTH_OPT_START 0x04
#define IPT_NTH_OPT_COUNTER 0x08
#define IPT_NTH_OPT_PACKET 0x10
/* Function which parses command options; returns true if it
ate an option */
static int
parse(int c, char **argv, int invert, unsigned int *flags,
const struct ipt_entry *entry,
unsigned int *nfcache,
struct ipt_entry_match **match)
{
struct ipt_nth_info *nthinfo = (struct ipt_nth_info *)(*match)->data;
unsigned int num;
switch (c) {
case '1':
/* check for common mistakes... */
if ((!invert) && (*flags & IPT_NTH_OPT_EVERY))
exit_error(PARAMETER_PROBLEM,
"Can't specify --every twice");
if (invert && (*flags & IPT_NTH_OPT_NOT_EVERY))
exit_error(PARAMETER_PROBLEM,
"Can't specify ! --every twice");
if ((!invert) && (*flags & IPT_NTH_OPT_NOT_EVERY))
exit_error(PARAMETER_PROBLEM,
"Can't specify --every with ! --every");
if (invert && (*flags & IPT_NTH_OPT_EVERY))
exit_error(PARAMETER_PROBLEM,
"Can't specify ! --every with --every");
/* Remember, this function will interpret a leading 0 to be
Octal, a leading 0x to be hexdecimal... */
if (string_to_number(optarg, 2, 100, &num) == -1 || num < 2)
exit_error(PARAMETER_PROBLEM,
"bad --every `%s', must be between 2 and 100", optarg);
/* assign the values */
nthinfo->every = num-1;
nthinfo->startat = 0;
nthinfo->packet = 0xFF;
if(!(*flags & IPT_NTH_OPT_EVERY))
{
nthinfo->counter = 0;
}
if (invert)
{
*flags |= IPT_NTH_OPT_NOT_EVERY;
nthinfo->not = 1;
}
else
{
*flags |= IPT_NTH_OPT_EVERY;
nthinfo->not = 0;
}
break;
case '2':
/* check for common mistakes... */
if (!((*flags & IPT_NTH_OPT_EVERY) ||
(*flags & IPT_NTH_OPT_NOT_EVERY)))
exit_error(PARAMETER_PROBLEM,
"Can't specify --start before --every");
if (invert)
exit_error(PARAMETER_PROBLEM,
"Can't specify with ! --start");
if (*flags & IPT_NTH_OPT_START)
exit_error(PARAMETER_PROBLEM,
"Can't specify --start twice");
if (string_to_number(optarg, 0, nthinfo->every, &num) == -1)
exit_error(PARAMETER_PROBLEM,
"bad --start `%s', must between 0 and %u", optarg, nthinfo->every);
*flags |= IPT_NTH_OPT_START;
nthinfo->startat = num;
break;
case '3':
/* check for common mistakes... */
if (invert)
exit_error(PARAMETER_PROBLEM,
"Can't specify with ! --counter");
if (*flags & IPT_NTH_OPT_COUNTER)
exit_error(PARAMETER_PROBLEM,
"Can't specify --counter twice");
if (string_to_number(optarg, 0, IPT_NTH_NUM_COUNTERS-1, &num) == -1)
exit_error(PARAMETER_PROBLEM,
"bad --counter `%s', must between 0 and %u", optarg, IPT_NTH_NUM_COUNTERS-1);
/* assign the values */
*flags |= IPT_NTH_OPT_COUNTER;
nthinfo->counter = num;
break;
case '4':
/* check for common mistakes... */
if (!((*flags & IPT_NTH_OPT_EVERY) ||
(*flags & IPT_NTH_OPT_NOT_EVERY)))
exit_error(PARAMETER_PROBLEM,
"Can't specify --packet before --every");
if ((*flags & IPT_NTH_OPT_NOT_EVERY))
exit_error(PARAMETER_PROBLEM,
"Can't specify --packet with ! --every");
if (invert)
exit_error(PARAMETER_PROBLEM,
"Can't specify with ! --packet");
if (*flags & IPT_NTH_OPT_PACKET)
exit_error(PARAMETER_PROBLEM,
"Can't specify --packet twice");
if (string_to_number(optarg, 0, nthinfo->every, &num) == -1)
exit_error(PARAMETER_PROBLEM,
"bad --packet `%s', must between 0 and %u", optarg, nthinfo->every);
*flags |= IPT_NTH_OPT_PACKET;
nthinfo->packet = num;
break;
default:
return 0;
}
return 1;
}
/* Final check; nothing. */
static void final_check(unsigned int flags)
{
}
/* Prints out the targinfo. */
static void
print(const struct ipt_ip *ip,
const struct ipt_entry_match *match,
int numeric)
{
const struct ipt_nth_info *nthinfo
= (const struct ipt_nth_info *)match->data;
if (nthinfo->not == 1)
printf(" !");
printf("every %uth ", (nthinfo->every +1));
if (nthinfo->counter != 0)
printf("counter #%u ", (nthinfo->counter));
if (nthinfo->packet != 0xFF)
printf("packet #%u ", nthinfo->packet);
if (nthinfo->startat != 0)
printf("start at %u ", nthinfo->startat);
}
/* Saves the union ipt_targinfo in parsable form to stdout. */
static void
save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
{
const struct ipt_nth_info *nthinfo
= (const struct ipt_nth_info *)match->data;
if (nthinfo->not == 1)
printf("! ");
printf("--every %u ", (nthinfo->every +1));
printf("--counter %u ", (nthinfo->counter));
if (nthinfo->startat != 0)
printf("--start %u ", nthinfo->startat );
if (nthinfo->packet != 0xFF)
printf("--packet %u ", nthinfo->packet );
}
struct iptables_match nth
= { NULL,
"nth",
NETFILTER_VERSION,
IPT_ALIGN(sizeof(struct ipt_nth_info)),
IPT_ALIGN(sizeof(struct ipt_nth_info)),
&help,
&init,
&parse,
&final_check,
&print,
&save,
opts
};
void _init(void)
{
register_match(&nth);
}
|