release/src/router/iptables/extensions/libipt_TCPMSS.c

   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
  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
  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
  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
  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
  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
 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
 131 void _init(void)
 132 {
 133         register_target(&mss);
 134 }