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