1 /* Shared library add-on to iptables to add TCPMSS target support.
2 *
3 * Copyright (c) 2000 Marc Boucher
4 */
5 #include <stdio.h>
6 #include <string.h>
7 #include <stdlib.h>
8 #include <getopt.h>
9
10 #include <iptables.h>
11 #include <linux/netfilter_ipv4/ip_tables.h>
12 #include <linux/netfilter_ipv4/ipt_TCPMSS.h>
13
14 struct mssinfo {
15 struct ipt_entry_target t;
16 struct ipt_tcpmss_info mss;
17 };
18
19 /* Function which prints out usage message. */
20 static void
help(void)21 help(void)
22 {
23 printf(
24 "TCPMSS target v%s mutually-exclusive options:\n"
25 " --set-mss value explicitly set MSS option to specified value\n"
26 " --clamp-mss-to-pmtu automatically clamp MSS value to (path_MTU - 40)\n",
27 IPTABLES_VERSION);
28 }
29
30 static struct option opts[] = {
31 { "set-mss", 1, 0, '1' },
32 { "clamp-mss-to-pmtu", 0, 0, '2' },
33 { 0 }
34 };
35
36 /* Initialize the target. */
37 static void
init(struct ipt_entry_target * t,unsigned int * nfcache)38 init(struct ipt_entry_target *t, unsigned int *nfcache)
39 {
40 }
41
42 /* Function which parses command options; returns true if it
43 ate an option */
44 static int
parse(int c,char ** argv,int invert,unsigned int * flags,const struct ipt_entry * entry,struct ipt_entry_target ** target)45 parse(int c, char **argv, int invert, unsigned int *flags,
46 const struct ipt_entry *entry,
47 struct ipt_entry_target **target)
48 {
49 struct ipt_tcpmss_info *mssinfo
50 = (struct ipt_tcpmss_info *)(*target)->data;
51
52 switch (c) {
53 unsigned int mssval;
54
55 case '1':
56 if (*flags)
57 exit_error(PARAMETER_PROBLEM,
58 "TCPMSS target: Only one option may be specified");
59 if (string_to_number(optarg, 0, 65535 - 40, &mssval) == -1)
60 exit_error(PARAMETER_PROBLEM, "Bad TCPMSS value `%s'", optarg);
61
62 mssinfo->mss = mssval;
63 *flags = 1;
64 break;
65
66 case '2':
67 if (*flags)
68 exit_error(PARAMETER_PROBLEM,
69 "TCPMSS target: Only one option may be specified");
70 mssinfo->mss = IPT_TCPMSS_CLAMP_PMTU;
71 *flags = 1;
72 break;
73
74 default:
75 return 0;
76 }
77
78 return 1;
79 }
80
81 static void
final_check(unsigned int flags)82 final_check(unsigned int flags)
83 {
84 if (!flags)
85 exit_error(PARAMETER_PROBLEM,
86 "TCPMSS target: At least one parameter is required");
87 }
88
89 /* Prints out the targinfo. */
90 static void
print(const struct ipt_ip * ip,const struct ipt_entry_target * target,int numeric)91 print(const struct ipt_ip *ip,
92 const struct ipt_entry_target *target,
93 int numeric)
94 {
95 const struct ipt_tcpmss_info *mssinfo =
96 (const struct ipt_tcpmss_info *)target->data;
97 if(mssinfo->mss == IPT_TCPMSS_CLAMP_PMTU)
98 printf("TCPMSS clamp to PMTU ");
99 else
100 printf("TCPMSS set %u ", mssinfo->mss);
101 }
102
103 /* Saves the union ipt_targinfo in parsable form to stdout. */
104 static void
save(const struct ipt_ip * ip,const struct ipt_entry_target * target)105 save(const struct ipt_ip *ip, const struct ipt_entry_target *target)
106 {
107 const struct ipt_tcpmss_info *mssinfo =
108 (const struct ipt_tcpmss_info *)target->data;
109
110 if(mssinfo->mss == IPT_TCPMSS_CLAMP_PMTU)
111 printf("--clamp-mss-to-pmtu ");
112 else
113 printf("--set-mss %u ", mssinfo->mss);
114 }
115
116 static struct iptables_target mss = {
117 .next = NULL,
118 .name = "TCPMSS",
119 .version = IPTABLES_VERSION,
120 .size = IPT_ALIGN(sizeof(struct ipt_tcpmss_info)),
121 .userspacesize = IPT_ALIGN(sizeof(struct ipt_tcpmss_info)),
122 .help = &help,
123 .init = &init,
124 .parse = &parse,
125 .final_check = &final_check,
126 .print = &print,
127 .save = &save,
128 .extra_opts = opts
129 };
130
ipt_TCPMSS_init(void)131 void ipt_TCPMSS_init(void)
132 {
133 register_target(&mss);
134 }
135