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
|
/* Shared library add-on to iptables to add tcp MSS matching support. */
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>
#include <xtables.h>
#include <linux/netfilter/xt_tcpmss.h>
static void tcpmss_help(void)
{
printf(
"tcpmss match options:\n"
"[!] --mss value[:value] Match TCP MSS range.\n"
" (only valid for TCP SYN or SYN/ACK packets)\n");
}
static const struct option tcpmss_opts[] = {
{ "mss", 1, NULL, '1' },
{ .name = NULL }
};
static u_int16_t
parse_tcp_mssvalue(const char *mssvalue)
{
unsigned int mssvaluenum;
if (string_to_number(mssvalue, 0, UINT16_MAX, &mssvaluenum) != -1)
return mssvaluenum;
exit_error(PARAMETER_PROBLEM,
"Invalid mss `%s' specified", mssvalue);
}
static void
parse_tcp_mssvalues(const char *mssvaluestring,
u_int16_t *mss_min, u_int16_t *mss_max)
{
char *buffer;
char *cp;
buffer = strdup(mssvaluestring);
if ((cp = strchr(buffer, ':')) == NULL)
*mss_min = *mss_max = parse_tcp_mssvalue(buffer);
else {
*cp = '\0';
cp++;
*mss_min = buffer[0] ? parse_tcp_mssvalue(buffer) : 0;
*mss_max = cp[0] ? parse_tcp_mssvalue(cp) : 0xFFFF;
}
free(buffer);
}
static int
tcpmss_parse(int c, char **argv, int invert, unsigned int *flags,
const void *entry, struct xt_entry_match **match)
{
struct xt_tcpmss_match_info *mssinfo =
(struct xt_tcpmss_match_info *)(*match)->data;
switch (c) {
case '1':
if (*flags)
exit_error(PARAMETER_PROBLEM,
"Only one `--mss' allowed");
check_inverse(optarg, &invert, &optind, 0);
parse_tcp_mssvalues(argv[optind-1],
&mssinfo->mss_min, &mssinfo->mss_max);
if (invert)
mssinfo->invert = 1;
*flags = 1;
break;
default:
return 0;
}
return 1;
}
static void tcpmss_check(unsigned int flags)
{
if (!flags)
exit_error(PARAMETER_PROBLEM,
"tcpmss match: You must specify `--mss'");
}
static void
tcpmss_print(const void *ip, const struct xt_entry_match *match, int numeric)
{
const struct xt_tcpmss_match_info *info = (void *)match->data;
printf("tcpmss match %s", info->invert ? "!" : "");
if (info->mss_min == info->mss_max)
printf("%u ", info->mss_min);
else
printf("%u:%u ", info->mss_min, info->mss_max);
}
static void tcpmss_save(const void *ip, const struct xt_entry_match *match)
{
const struct xt_tcpmss_match_info *info = (void *)match->data;
printf("%s--mss ", info->invert ? "! " : "");
if (info->mss_min == info->mss_max)
printf("%u ", info->mss_min);
else
printf("%u:%u ", info->mss_min, info->mss_max);
}
static struct xtables_match tcpmss_match = {
.family = NFPROTO_IPV4,
.name = "tcpmss",
.version = XTABLES_VERSION,
.size = XT_ALIGN(sizeof(struct xt_tcpmss_match_info)),
.userspacesize = XT_ALIGN(sizeof(struct xt_tcpmss_match_info)),
.help = tcpmss_help,
.parse = tcpmss_parse,
.final_check = tcpmss_check,
.print = tcpmss_print,
.save = tcpmss_save,
.extra_opts = tcpmss_opts,
};
static struct xtables_match tcpmss_match6 = {
.family = NFPROTO_IPV6,
.name = "tcpmss",
.version = XTABLES_VERSION,
.size = XT_ALIGN(sizeof(struct xt_tcpmss_match_info)),
.userspacesize = XT_ALIGN(sizeof(struct xt_tcpmss_match_info)),
.help = tcpmss_help,
.parse = tcpmss_parse,
.final_check = tcpmss_check,
.print = tcpmss_print,
.save = tcpmss_save,
.extra_opts = tcpmss_opts,
};
void _init(void)
{
xtables_register_match(&tcpmss_match);
xtables_register_match(&tcpmss_match6);
}
|
