| /* IP tables module for matching the value of the IPv4 and TCP ECN bits |
| * |
| * (C) 2002 by Harald Welte <laforge@gnumonks.org> |
| * |
| * 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_ipv4/ip_tables.h> |
| #include <linux/netfilter_ipv4/ipt_ecn.h> |
| |
| MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); |
| MODULE_DESCRIPTION("Xtables: Explicit Congestion Notification (ECN) flag match for IPv4"); |
| MODULE_LICENSE("GPL"); |
| |
| static inline bool match_ip(const struct sk_buff *skb, |
| const struct ipt_ecn_info *einfo) |
| { |
| return ((ip_hdr(skb)->tos & IPT_ECN_IP_MASK) == einfo->ip_ect) ^ |
| !!(einfo->invert & IPT_ECN_OP_MATCH_IP); |
| } |
| |
| static inline bool match_tcp(const struct sk_buff *skb, |
| const struct ipt_ecn_info *einfo, |
| bool *hotdrop) |
| { |
| 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, ip_hdrlen(skb), sizeof(_tcph), &_tcph); |
| if (th == NULL) { |
| *hotdrop = false; |
| return false; |
| } |
| |
| if (einfo->operation & IPT_ECN_OP_MATCH_ECE) { |
| if (einfo->invert & IPT_ECN_OP_MATCH_ECE) { |
| if (th->ece == 1) |
| return false; |
| } else { |
| if (th->ece == 0) |
| return false; |
| } |
| } |
| |
| if (einfo->operation & IPT_ECN_OP_MATCH_CWR) { |
| if (einfo->invert & IPT_ECN_OP_MATCH_CWR) { |
| if (th->cwr == 1) |
| return false; |
| } else { |
| if (th->cwr == 0) |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| |
| static bool ecn_mt(const struct sk_buff *skb, struct xt_action_param *par) |
| { |
| const struct ipt_ecn_info *info = par->matchinfo; |
| |
| if (info->operation & IPT_ECN_OP_MATCH_IP) |
| if (!match_ip(skb, info)) |
| return false; |
| |
| if (info->operation & (IPT_ECN_OP_MATCH_ECE|IPT_ECN_OP_MATCH_CWR)) { |
| if (!match_tcp(skb, info, &par->hotdrop)) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| static int ecn_mt_check(const struct xt_mtchk_param *par) |
| { |
| const struct ipt_ecn_info *info = par->matchinfo; |
| const struct ipt_ip *ip = par->entryinfo; |
| |
| if (info->operation & IPT_ECN_OP_MATCH_MASK) |
| return -EINVAL; |
| |
| if (info->invert & IPT_ECN_OP_MATCH_MASK) |
| return -EINVAL; |
| |
| if (info->operation & (IPT_ECN_OP_MATCH_ECE|IPT_ECN_OP_MATCH_CWR) && |
| (ip->proto != IPPROTO_TCP || ip->invflags & IPT_INV_PROTO)) { |
| pr_info("cannot match TCP bits in rule 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_mt, |
| .matchsize = sizeof(struct ipt_ecn_info), |
| .checkentry = ecn_mt_check, |
| .me = THIS_MODULE, |
| }; |
| |
| static int __init ecn_mt_init(void) |
| { |
| return xt_register_match(&ecn_mt_reg); |
| } |
| |
| static void __exit ecn_mt_exit(void) |
| { |
| xt_unregister_match(&ecn_mt_reg); |
| } |
| |
| module_init(ecn_mt_init); |
| module_exit(ecn_mt_exit); |