Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame^] | 1 | /* IP tables module for matching the value of the IPv4 and TCP ECN bits |
| 2 | * |
| 3 | * ipt_ecn.c,v 1.3 2002/05/29 15:09:00 laforge Exp |
| 4 | * |
| 5 | * (C) 2002 by Harald Welte <laforge@gnumonks.org> |
| 6 | * |
| 7 | * This program is free software; you can redistribute it and/or modify |
| 8 | * it under the terms of the GNU General Public License version 2 as |
| 9 | * published by the Free Software Foundation. |
| 10 | */ |
| 11 | |
| 12 | #include <linux/module.h> |
| 13 | #include <linux/skbuff.h> |
| 14 | #include <linux/tcp.h> |
| 15 | |
| 16 | #include <linux/netfilter_ipv4/ip_tables.h> |
| 17 | #include <linux/netfilter_ipv4/ipt_ecn.h> |
| 18 | |
| 19 | MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); |
| 20 | MODULE_DESCRIPTION("iptables ECN matching module"); |
| 21 | MODULE_LICENSE("GPL"); |
| 22 | |
| 23 | static inline int match_ip(const struct sk_buff *skb, |
| 24 | const struct ipt_ecn_info *einfo) |
| 25 | { |
| 26 | return ((skb->nh.iph->tos&IPT_ECN_IP_MASK) == einfo->ip_ect); |
| 27 | } |
| 28 | |
| 29 | static inline int match_tcp(const struct sk_buff *skb, |
| 30 | const struct ipt_ecn_info *einfo, |
| 31 | int *hotdrop) |
| 32 | { |
| 33 | struct tcphdr _tcph, *th; |
| 34 | |
| 35 | /* In practice, TCP match does this, so can't fail. But let's |
| 36 | * be good citizens. |
| 37 | */ |
| 38 | th = skb_header_pointer(skb, skb->nh.iph->ihl * 4, |
| 39 | sizeof(_tcph), &_tcph); |
| 40 | if (th == NULL) { |
| 41 | *hotdrop = 0; |
| 42 | return 0; |
| 43 | } |
| 44 | |
| 45 | if (einfo->operation & IPT_ECN_OP_MATCH_ECE) { |
| 46 | if (einfo->invert & IPT_ECN_OP_MATCH_ECE) { |
| 47 | if (th->ece == 1) |
| 48 | return 0; |
| 49 | } else { |
| 50 | if (th->ece == 0) |
| 51 | return 0; |
| 52 | } |
| 53 | } |
| 54 | |
| 55 | if (einfo->operation & IPT_ECN_OP_MATCH_CWR) { |
| 56 | if (einfo->invert & IPT_ECN_OP_MATCH_CWR) { |
| 57 | if (th->cwr == 1) |
| 58 | return 0; |
| 59 | } else { |
| 60 | if (th->cwr == 0) |
| 61 | return 0; |
| 62 | } |
| 63 | } |
| 64 | |
| 65 | return 1; |
| 66 | } |
| 67 | |
| 68 | static int match(const struct sk_buff *skb, const struct net_device *in, |
| 69 | const struct net_device *out, const void *matchinfo, |
| 70 | int offset, int *hotdrop) |
| 71 | { |
| 72 | const struct ipt_ecn_info *info = matchinfo; |
| 73 | |
| 74 | if (info->operation & IPT_ECN_OP_MATCH_IP) |
| 75 | if (!match_ip(skb, info)) |
| 76 | return 0; |
| 77 | |
| 78 | if (info->operation & (IPT_ECN_OP_MATCH_ECE|IPT_ECN_OP_MATCH_CWR)) { |
| 79 | if (skb->nh.iph->protocol != IPPROTO_TCP) |
| 80 | return 0; |
| 81 | if (!match_tcp(skb, info, hotdrop)) |
| 82 | return 0; |
| 83 | } |
| 84 | |
| 85 | return 1; |
| 86 | } |
| 87 | |
| 88 | static int checkentry(const char *tablename, const struct ipt_ip *ip, |
| 89 | void *matchinfo, unsigned int matchsize, |
| 90 | unsigned int hook_mask) |
| 91 | { |
| 92 | const struct ipt_ecn_info *info = matchinfo; |
| 93 | |
| 94 | if (matchsize != IPT_ALIGN(sizeof(struct ipt_ecn_info))) |
| 95 | return 0; |
| 96 | |
| 97 | if (info->operation & IPT_ECN_OP_MATCH_MASK) |
| 98 | return 0; |
| 99 | |
| 100 | if (info->invert & IPT_ECN_OP_MATCH_MASK) |
| 101 | return 0; |
| 102 | |
| 103 | if (info->operation & (IPT_ECN_OP_MATCH_ECE|IPT_ECN_OP_MATCH_CWR) |
| 104 | && ip->proto != IPPROTO_TCP) { |
| 105 | printk(KERN_WARNING "ipt_ecn: can't match TCP bits in rule for" |
| 106 | " non-tcp packets\n"); |
| 107 | return 0; |
| 108 | } |
| 109 | |
| 110 | return 1; |
| 111 | } |
| 112 | |
| 113 | static struct ipt_match ecn_match = { |
| 114 | .name = "ecn", |
| 115 | .match = &match, |
| 116 | .checkentry = &checkentry, |
| 117 | .me = THIS_MODULE, |
| 118 | }; |
| 119 | |
| 120 | static int __init init(void) |
| 121 | { |
| 122 | return ipt_register_match(&ecn_match); |
| 123 | } |
| 124 | |
| 125 | static void __exit fini(void) |
| 126 | { |
| 127 | ipt_unregister_match(&ecn_match); |
| 128 | } |
| 129 | |
| 130 | module_init(init); |
| 131 | module_exit(fini); |