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![Jan Engelhardt](/assets/img/avatar_default.png)
One simplification of an if clause. Signed-off-by: Jan Engelhardt <jengelh@medozas.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
179 lines
4.4 KiB
C
179 lines
4.4 KiB
C
/*
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* Xtables module for matching the value of the IPv4/IPv6 and TCP ECN bits
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*
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* (C) 2002 by Harald Welte <laforge@gnumonks.org>
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* (C) 2011 Patrick McHardy <kaber@trash.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/in.h>
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#include <linux/ip.h>
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#include <net/ip.h>
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/tcp.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter/xt_ecn.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#include <linux/netfilter_ipv6/ip6_tables.h>
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MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
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MODULE_DESCRIPTION("Xtables: Explicit Congestion Notification (ECN) flag match");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("ipt_ecn");
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MODULE_ALIAS("ip6t_ecn");
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static bool match_tcp(const struct sk_buff *skb, struct xt_action_param *par)
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{
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const struct xt_ecn_info *einfo = par->matchinfo;
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struct tcphdr _tcph;
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const struct tcphdr *th;
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/* In practice, TCP match does this, so can't fail. But let's
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* be good citizens.
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*/
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th = skb_header_pointer(skb, par->thoff, sizeof(_tcph), &_tcph);
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if (th == NULL)
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return false;
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if (einfo->operation & XT_ECN_OP_MATCH_ECE) {
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if (einfo->invert & XT_ECN_OP_MATCH_ECE) {
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if (th->ece == 1)
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return false;
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} else {
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if (th->ece == 0)
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return false;
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}
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}
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if (einfo->operation & XT_ECN_OP_MATCH_CWR) {
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if (einfo->invert & XT_ECN_OP_MATCH_CWR) {
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if (th->cwr == 1)
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return false;
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} else {
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if (th->cwr == 0)
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return false;
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}
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}
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return true;
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}
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static inline bool match_ip(const struct sk_buff *skb,
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const struct xt_ecn_info *einfo)
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{
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return ((ip_hdr(skb)->tos & XT_ECN_IP_MASK) == einfo->ip_ect) ^
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!!(einfo->invert & XT_ECN_OP_MATCH_IP);
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}
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static bool ecn_mt4(const struct sk_buff *skb, struct xt_action_param *par)
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{
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const struct xt_ecn_info *info = par->matchinfo;
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if (info->operation & XT_ECN_OP_MATCH_IP && !match_ip(skb, info))
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return false;
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if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) &&
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!match_tcp(skb, par))
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return false;
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return true;
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}
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static int ecn_mt_check4(const struct xt_mtchk_param *par)
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{
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const struct xt_ecn_info *info = par->matchinfo;
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const struct ipt_ip *ip = par->entryinfo;
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if (info->operation & XT_ECN_OP_MATCH_MASK)
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return -EINVAL;
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if (info->invert & XT_ECN_OP_MATCH_MASK)
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return -EINVAL;
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if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) &&
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(ip->proto != IPPROTO_TCP || ip->invflags & IPT_INV_PROTO)) {
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pr_info("cannot match TCP bits in rule for non-tcp packets\n");
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return -EINVAL;
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}
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return 0;
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}
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static inline bool match_ipv6(const struct sk_buff *skb,
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const struct xt_ecn_info *einfo)
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{
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return (((ipv6_hdr(skb)->flow_lbl[0] >> 4) & XT_ECN_IP_MASK) ==
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einfo->ip_ect) ^
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!!(einfo->invert & XT_ECN_OP_MATCH_IP);
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}
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static bool ecn_mt6(const struct sk_buff *skb, struct xt_action_param *par)
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{
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const struct xt_ecn_info *info = par->matchinfo;
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if (info->operation & XT_ECN_OP_MATCH_IP && !match_ipv6(skb, info))
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return false;
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if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) &&
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!match_tcp(skb, par))
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return false;
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return true;
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}
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static int ecn_mt_check6(const struct xt_mtchk_param *par)
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{
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const struct xt_ecn_info *info = par->matchinfo;
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const struct ip6t_ip6 *ip = par->entryinfo;
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if (info->operation & XT_ECN_OP_MATCH_MASK)
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return -EINVAL;
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if (info->invert & XT_ECN_OP_MATCH_MASK)
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return -EINVAL;
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if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) &&
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(ip->proto != IPPROTO_TCP || ip->invflags & IP6T_INV_PROTO)) {
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pr_info("cannot match TCP bits in rule for non-tcp packets\n");
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return -EINVAL;
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}
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return 0;
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}
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static struct xt_match ecn_mt_reg[] __read_mostly = {
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{
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.name = "ecn",
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.family = NFPROTO_IPV4,
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.match = ecn_mt4,
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.matchsize = sizeof(struct xt_ecn_info),
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.checkentry = ecn_mt_check4,
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.me = THIS_MODULE,
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},
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{
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.name = "ecn",
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.family = NFPROTO_IPV6,
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.match = ecn_mt6,
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.matchsize = sizeof(struct xt_ecn_info),
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.checkentry = ecn_mt_check6,
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.me = THIS_MODULE,
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},
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};
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static int __init ecn_mt_init(void)
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{
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return xt_register_matches(ecn_mt_reg, ARRAY_SIZE(ecn_mt_reg));
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}
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static void __exit ecn_mt_exit(void)
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{
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xt_unregister_matches(ecn_mt_reg, ARRAY_SIZE(ecn_mt_reg));
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}
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module_init(ecn_mt_init);
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module_exit(ecn_mt_exit);
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