summaryrefslogtreecommitdiffstats
path: root/extensions/libxt_TCPMSS.c
blob: 304cf718d7b497e6fbfdf7c7211fccd49a5abda1 (plain)
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
/* Shared library add-on to iptables to add TCPMSS target support.
 *
 * Copyright (c) 2000 Marc Boucher
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>

#include <xtables.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_TCPMSS.h>

struct mssinfo {
	struct xt_entry_target t;
	struct xt_tcpmss_info mss;
};

/* Function which prints out usage message. */
static void __help(int hdrsize)
{
	printf(
"TCPMSS target v%s mutually-exclusive options:\n"
"  --set-mss value               explicitly set MSS option to specified value\n"
"  --clamp-mss-to-pmtu           automatically clamp MSS value to (path_MTU - %d)\n",
IPTABLES_VERSION, hdrsize);
}

static void help(void)
{
	__help(40);
}

static void help6(void)
{
	__help(60);
}

static const struct option opts[] = {
	{ "set-mss", 1, NULL, '1' },
	{ "clamp-mss-to-pmtu", 0, NULL, '2' },
	{ }
};

/* Initialize the target. */
static void
init(struct xt_entry_target *t)
{
}

/* 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 void *entry,
      struct xt_entry_target **target,
      int hdrsize)
{
	struct xt_tcpmss_info *mssinfo
		= (struct xt_tcpmss_info *)(*target)->data;

	switch (c) {
		unsigned int mssval;

	case '1':
		if (*flags)
			exit_error(PARAMETER_PROBLEM,
			           "TCPMSS target: Only one option may be specified");
		if (string_to_number(optarg, 0, 65535 - hdrsize, &mssval) == -1)
			exit_error(PARAMETER_PROBLEM, "Bad TCPMSS value `%s'", optarg);
		
		mssinfo->mss = mssval;
		*flags = 1;
		break;

	case '2':
		if (*flags)
			exit_error(PARAMETER_PROBLEM,
			           "TCPMSS target: Only one option may be specified");
		mssinfo->mss = XT_TCPMSS_CLAMP_PMTU;
		*flags = 1;
		break;

	default:
		return 0;
	}

	return 1;
}

static int
parse(int c, char **argv, int invert, unsigned int *flags,
      const void *entry,
      struct xt_entry_target **target)
{
	return __parse(c, argv, invert, flags, entry, target, 40);
}

static int
parse6(int c, char **argv, int invert, unsigned int *flags,
      const void *entry,
      struct xt_entry_target **target)
{
	return __parse(c, argv, invert, flags, entry, target, 60);
}

static void
final_check(unsigned int flags)
{
	if (!flags)
		exit_error(PARAMETER_PROBLEM,
		           "TCPMSS target: At least one parameter is required");
}

/* Prints out the targinfo. */
static void
print(const void *ip,
      const struct xt_entry_target *target,
      int numeric)
{
	const struct xt_tcpmss_info *mssinfo =
		(const struct xt_tcpmss_info *)target->data;
	if(mssinfo->mss == XT_TCPMSS_CLAMP_PMTU)
		printf("TCPMSS clamp to PMTU ");
	else
		printf("TCPMSS set %u ", mssinfo->mss);
}

/* Saves the union ipt_targinfo in parsable form to stdout. */
static void
save(const void *ip, const struct xt_entry_target *target)
{
	const struct xt_tcpmss_info *mssinfo =
		(const struct xt_tcpmss_info *)target->data;

	if(mssinfo->mss == XT_TCPMSS_CLAMP_PMTU)
		printf("--clamp-mss-to-pmtu ");
	else
		printf("--set-mss %u ", mssinfo->mss);
}

static struct xtables_target mss = {
	.family		= AF_INET,
	.name		= "TCPMSS",
	.version	= IPTABLES_VERSION,
	.size		= XT_ALIGN(sizeof(struct xt_tcpmss_info)),
	.userspacesize	= XT_ALIGN(sizeof(struct xt_tcpmss_info)),
	.help		= &help,
	.init		= &init,
	.parse		= &parse,
	.final_check	= &final_check,
	.print		= &print,
	.save		= &save,
	.extra_opts	= opts
};

static struct xtables_target mss6 = {
	.family		= AF_INET6,
	.name		= "TCPMSS",
	.version	= IPTABLES_VERSION,
	.size		= XT_ALIGN(sizeof(struct xt_tcpmss_info)),
	.userspacesize	= XT_ALIGN(sizeof(struct xt_tcpmss_info)),
	.help		= &help6,
	.init		= &init,
	.parse		= &parse6,
	.final_check	= &final_check,
	.print		= &print,
	.save		= &save,
	.extra_opts	= opts
};

void _init(void)
{
	xtables_register_target(&mss);
	xtables_register_target(&mss6);
}