/* Shared library add-on to iptables to add TCPMSS target support.
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*
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* Copyright (c) 2000 Marc Boucher
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*/
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#include "config.h"
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#include <stdio.h>
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#include <xtables.h>
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#include <netinet/ip.h>
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#include <linux/netfilter/xt_TCPMSS.h>
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enum {
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O_SET_MSS = 0,
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O_CLAMP_MSS,
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};
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struct mssinfo {
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struct xt_entry_target t;
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struct xt_tcpmss_info mss;
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};
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static void __TCPMSS_help(int hdrsize)
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{
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printf(
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"TCPMSS target mutually-exclusive options:\n"
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" --set-mss value explicitly set MSS option to specified value\n"
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" --clamp-mss-to-pmtu automatically clamp MSS value to (path_MTU - %d)\n",
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hdrsize);
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}
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static void TCPMSS_help(void)
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{
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__TCPMSS_help(sizeof(struct iphdr));
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}
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static void TCPMSS_help6(void)
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{
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__TCPMSS_help(SIZEOF_STRUCT_IP6_HDR);
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}
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static const struct xt_option_entry TCPMSS4_opts[] = {
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{.name = "set-mss", .id = O_SET_MSS, .type = XTTYPE_UINT16,
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.min = 0, .max = UINT16_MAX - sizeof(struct iphdr),
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.flags = XTOPT_PUT, XTOPT_POINTER(struct xt_tcpmss_info, mss)},
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{.name = "clamp-mss-to-pmtu", .id = O_CLAMP_MSS, .type = XTTYPE_NONE},
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XTOPT_TABLEEND,
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};
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static const struct xt_option_entry TCPMSS6_opts[] = {
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{.name = "set-mss", .id = O_SET_MSS, .type = XTTYPE_UINT16,
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.min = 0, .max = UINT16_MAX - SIZEOF_STRUCT_IP6_HDR,
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.flags = XTOPT_PUT, XTOPT_POINTER(struct xt_tcpmss_info, mss)},
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{.name = "clamp-mss-to-pmtu", .id = O_CLAMP_MSS, .type = XTTYPE_NONE},
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XTOPT_TABLEEND,
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};
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static void TCPMSS_parse(struct xt_option_call *cb)
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{
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struct xt_tcpmss_info *mssinfo = cb->data;
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xtables_option_parse(cb);
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if (cb->entry->id == O_CLAMP_MSS)
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mssinfo->mss = XT_TCPMSS_CLAMP_PMTU;
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}
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static void TCPMSS_check(struct xt_fcheck_call *cb)
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{
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if (cb->xflags == 0)
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xtables_error(PARAMETER_PROBLEM,
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"TCPMSS target: At least one parameter is required");
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}
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static void TCPMSS_print(const void *ip, const struct xt_entry_target *target,
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int numeric)
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{
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const struct xt_tcpmss_info *mssinfo =
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(const struct xt_tcpmss_info *)target->data;
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if(mssinfo->mss == XT_TCPMSS_CLAMP_PMTU)
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printf(" TCPMSS clamp to PMTU");
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else
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printf(" TCPMSS set %u", mssinfo->mss);
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}
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static void TCPMSS_save(const void *ip, const struct xt_entry_target *target)
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{
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const struct xt_tcpmss_info *mssinfo =
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(const struct xt_tcpmss_info *)target->data;
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if(mssinfo->mss == XT_TCPMSS_CLAMP_PMTU)
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printf(" --clamp-mss-to-pmtu");
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else
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printf(" --set-mss %u", mssinfo->mss);
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}
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static struct xtables_target tcpmss_tg_reg[] = {
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{
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.family = NFPROTO_IPV4,
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.name = "TCPMSS",
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.version = XTABLES_VERSION,
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.size = XT_ALIGN(sizeof(struct xt_tcpmss_info)),
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.userspacesize = XT_ALIGN(sizeof(struct xt_tcpmss_info)),
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.help = TCPMSS_help,
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.print = TCPMSS_print,
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.save = TCPMSS_save,
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.x6_parse = TCPMSS_parse,
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.x6_fcheck = TCPMSS_check,
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.x6_options = TCPMSS4_opts,
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},
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{
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.family = NFPROTO_IPV6,
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.name = "TCPMSS",
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.version = XTABLES_VERSION,
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.size = XT_ALIGN(sizeof(struct xt_tcpmss_info)),
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.userspacesize = XT_ALIGN(sizeof(struct xt_tcpmss_info)),
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.help = TCPMSS_help6,
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.print = TCPMSS_print,
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.save = TCPMSS_save,
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.x6_parse = TCPMSS_parse,
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.x6_fcheck = TCPMSS_check,
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.x6_options = TCPMSS6_opts,
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},
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};
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void _init(void)
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{
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xtables_register_targets(tcpmss_tg_reg, ARRAY_SIZE(tcpmss_tg_reg));
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}
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