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
|
/* Shared library add-on to iptables to add packet length matching support. */
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>
#include <iptables.h>
#include <linux/netfilter_ipv4/ipt_length.h>
/* Function which prints out usage message. */
static void
help(void)
{
printf(
"length v%s options:\n"
"[!] --length length[:length] Match packet length against value or range\n"
" of values (inclusive)\n",
IPTABLES_VERSION);
}
static struct option opts[] = {
{ "length", 1, 0, '1' },
{0}
};
static u_int16_t
parse_length(const char *s)
{
unsigned int len;
if (string_to_number(s, 0, 0xFFFF, &len) == -1)
exit_error(PARAMETER_PROBLEM, "length invalid: `%s'\n", s);
else
return (u_int16_t )len;
}
/* If a single value is provided, min and max are both set to the value */
static void
parse_lengths(const char *s, struct ipt_length_info *info)
{
char *buffer;
char *cp;
buffer = strdup(s);
if ((cp = strchr(buffer, ':')) == NULL)
info->min = info->max = parse_length(buffer);
else {
*cp = '\0';
cp++;
info->min = buffer[0] ? parse_length(buffer) : 0;
info->max = cp[0] ? parse_length(cp) : 0xFFFF;
}
free(buffer);
if (info->min > info->max)
exit_error(PARAMETER_PROBLEM,
"length min. range value `%u' greater than max. "
"range value `%u'", info->min, info->max);
}
/* 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 xt_entry_match **match)
{
struct ipt_length_info *info = (struct ipt_length_info *)(*match)->data;
switch (c) {
case '1':
if (*flags)
exit_error(PARAMETER_PROBLEM,
"length: `--length' may only be "
"specified once");
check_inverse(optarg, &invert, &optind, 0);
parse_lengths(argv[optind-1], info);
if (invert)
info->invert = 1;
*flags = 1;
break;
default:
return 0;
}
return 1;
}
/* Final check; must have specified --length. */
static void
final_check(unsigned int flags)
{
if (!flags)
exit_error(PARAMETER_PROBLEM,
"length: You must specify `--length'");
}
/* Common match printing code. */
static void
print_length(struct ipt_length_info *info)
{
if (info->invert)
printf("! ");
if (info->max == info->min)
printf("%u ", info->min);
else
printf("%u:%u ", info->min, info->max);
}
/* Prints out the matchinfo. */
static void
print(const struct ipt_ip *ip,
const struct xt_entry_match *match,
int numeric)
{
printf("length ");
print_length((struct ipt_length_info *)match->data);
}
/* Saves the union ipt_matchinfo in parsable form to stdout. */
static void
save(const struct ipt_ip *ip, const struct xt_entry_match *match)
{
printf("--length ");
print_length((struct ipt_length_info *)match->data);
}
static struct iptables_match length = {
.next = NULL,
.name = "length",
.version = IPTABLES_VERSION,
.size = IPT_ALIGN(sizeof(struct ipt_length_info)),
.userspacesize = IPT_ALIGN(sizeof(struct ipt_length_info)),
.help = &help,
.parse = &parse,
.final_check = &final_check,
.print = &print,
.save = &save,
.extra_opts = opts
};
void _init(void)
{
register_match(&length);
}
|
