Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* iptables module for the IPv4 and TCP ECN bits, Version 1.5 |
| 2 | * |
| 3 | * (C) 2002 by Harald Welte <laforge@netfilter.org> |
| 4 | * |
| 5 | * This program is free software; you can redistribute it and/or modify |
| 6 | * it under the terms of the GNU General Public License version 2 as |
| 7 | * published by the Free Software Foundation. |
| 8 | * |
| 9 | * ipt_ECN.c,v 1.5 2002/08/18 19:36:51 laforge Exp |
| 10 | */ |
| 11 | |
| 12 | #include <linux/module.h> |
| 13 | #include <linux/skbuff.h> |
| 14 | #include <linux/ip.h> |
| 15 | #include <linux/tcp.h> |
| 16 | #include <net/checksum.h> |
| 17 | |
| 18 | #include <linux/netfilter_ipv4/ip_tables.h> |
| 19 | #include <linux/netfilter_ipv4/ipt_ECN.h> |
| 20 | |
| 21 | MODULE_LICENSE("GPL"); |
| 22 | MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); |
| 23 | MODULE_DESCRIPTION("iptables ECN modification module"); |
| 24 | |
| 25 | /* set ECT codepoint from IP header. |
| 26 | * return 0 if there was an error. */ |
| 27 | static inline int |
| 28 | set_ect_ip(struct sk_buff **pskb, const struct ipt_ECN_info *einfo) |
| 29 | { |
| 30 | if (((*pskb)->nh.iph->tos & IPT_ECN_IP_MASK) |
| 31 | != (einfo->ip_ect & IPT_ECN_IP_MASK)) { |
| 32 | u_int16_t diffs[2]; |
| 33 | |
| 34 | if (!skb_ip_make_writable(pskb, sizeof(struct iphdr))) |
| 35 | return 0; |
| 36 | |
| 37 | diffs[0] = htons((*pskb)->nh.iph->tos) ^ 0xFFFF; |
| 38 | (*pskb)->nh.iph->tos &= ~IPT_ECN_IP_MASK; |
| 39 | (*pskb)->nh.iph->tos |= (einfo->ip_ect & IPT_ECN_IP_MASK); |
| 40 | diffs[1] = htons((*pskb)->nh.iph->tos); |
| 41 | (*pskb)->nh.iph->check |
| 42 | = csum_fold(csum_partial((char *)diffs, |
| 43 | sizeof(diffs), |
| 44 | (*pskb)->nh.iph->check |
| 45 | ^0xFFFF)); |
| 46 | (*pskb)->nfcache |= NFC_ALTERED; |
| 47 | } |
| 48 | return 1; |
| 49 | } |
| 50 | |
| 51 | /* Return 0 if there was an error. */ |
| 52 | static inline int |
| 53 | set_ect_tcp(struct sk_buff **pskb, const struct ipt_ECN_info *einfo, int inward) |
| 54 | { |
| 55 | struct tcphdr _tcph, *tcph; |
| 56 | u_int16_t diffs[2]; |
| 57 | |
| 58 | /* Not enought header? */ |
| 59 | tcph = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4, |
| 60 | sizeof(_tcph), &_tcph); |
| 61 | if (!tcph) |
| 62 | return 0; |
| 63 | |
| 64 | if (!(einfo->operation & IPT_ECN_OP_SET_ECE |
| 65 | || tcph->ece == einfo->proto.tcp.ece) |
| 66 | && (!(einfo->operation & IPT_ECN_OP_SET_CWR |
| 67 | || tcph->cwr == einfo->proto.tcp.cwr))) |
| 68 | return 1; |
| 69 | |
| 70 | if (!skb_ip_make_writable(pskb, (*pskb)->nh.iph->ihl*4+sizeof(*tcph))) |
| 71 | return 0; |
| 72 | tcph = (void *)(*pskb)->nh.iph + (*pskb)->nh.iph->ihl*4; |
| 73 | |
| 74 | diffs[0] = ((u_int16_t *)tcph)[6]; |
| 75 | if (einfo->operation & IPT_ECN_OP_SET_ECE) |
| 76 | tcph->ece = einfo->proto.tcp.ece; |
| 77 | if (einfo->operation & IPT_ECN_OP_SET_CWR) |
| 78 | tcph->cwr = einfo->proto.tcp.cwr; |
| 79 | diffs[1] = ((u_int16_t *)tcph)[6]; |
| 80 | diffs[0] = diffs[0] ^ 0xFFFF; |
| 81 | |
| 82 | if ((*pskb)->ip_summed != CHECKSUM_HW) |
| 83 | tcph->check = csum_fold(csum_partial((char *)diffs, |
| 84 | sizeof(diffs), |
| 85 | tcph->check^0xFFFF)); |
| 86 | else |
| 87 | if (skb_checksum_help(*pskb, inward)) |
| 88 | return 0; |
| 89 | (*pskb)->nfcache |= NFC_ALTERED; |
| 90 | return 1; |
| 91 | } |
| 92 | |
| 93 | static unsigned int |
| 94 | target(struct sk_buff **pskb, |
| 95 | const struct net_device *in, |
| 96 | const struct net_device *out, |
| 97 | unsigned int hooknum, |
| 98 | const void *targinfo, |
| 99 | void *userinfo) |
| 100 | { |
| 101 | const struct ipt_ECN_info *einfo = targinfo; |
| 102 | |
| 103 | if (einfo->operation & IPT_ECN_OP_SET_IP) |
| 104 | if (!set_ect_ip(pskb, einfo)) |
| 105 | return NF_DROP; |
| 106 | |
| 107 | if (einfo->operation & (IPT_ECN_OP_SET_ECE | IPT_ECN_OP_SET_CWR) |
| 108 | && (*pskb)->nh.iph->protocol == IPPROTO_TCP) |
| 109 | if (!set_ect_tcp(pskb, einfo, (out == NULL))) |
| 110 | return NF_DROP; |
| 111 | |
| 112 | return IPT_CONTINUE; |
| 113 | } |
| 114 | |
| 115 | static int |
| 116 | checkentry(const char *tablename, |
| 117 | const struct ipt_entry *e, |
| 118 | void *targinfo, |
| 119 | unsigned int targinfosize, |
| 120 | unsigned int hook_mask) |
| 121 | { |
| 122 | const struct ipt_ECN_info *einfo = (struct ipt_ECN_info *)targinfo; |
| 123 | |
| 124 | if (targinfosize != IPT_ALIGN(sizeof(struct ipt_ECN_info))) { |
| 125 | printk(KERN_WARNING "ECN: targinfosize %u != %Zu\n", |
| 126 | targinfosize, |
| 127 | IPT_ALIGN(sizeof(struct ipt_ECN_info))); |
| 128 | return 0; |
| 129 | } |
| 130 | |
| 131 | if (strcmp(tablename, "mangle") != 0) { |
| 132 | printk(KERN_WARNING "ECN: can only be called from \"mangle\" table, not \"%s\"\n", tablename); |
| 133 | return 0; |
| 134 | } |
| 135 | |
| 136 | if (einfo->operation & IPT_ECN_OP_MASK) { |
| 137 | printk(KERN_WARNING "ECN: unsupported ECN operation %x\n", |
| 138 | einfo->operation); |
| 139 | return 0; |
| 140 | } |
| 141 | if (einfo->ip_ect & ~IPT_ECN_IP_MASK) { |
| 142 | printk(KERN_WARNING "ECN: new ECT codepoint %x out of mask\n", |
| 143 | einfo->ip_ect); |
| 144 | return 0; |
| 145 | } |
| 146 | |
| 147 | if ((einfo->operation & (IPT_ECN_OP_SET_ECE|IPT_ECN_OP_SET_CWR)) |
| 148 | && (e->ip.proto != IPPROTO_TCP || (e->ip.invflags & IPT_INV_PROTO))) { |
| 149 | printk(KERN_WARNING "ECN: cannot use TCP operations on a " |
| 150 | "non-tcp rule\n"); |
| 151 | return 0; |
| 152 | } |
| 153 | |
| 154 | return 1; |
| 155 | } |
| 156 | |
| 157 | static struct ipt_target ipt_ecn_reg = { |
| 158 | .name = "ECN", |
| 159 | .target = target, |
| 160 | .checkentry = checkentry, |
| 161 | .me = THIS_MODULE, |
| 162 | }; |
| 163 | |
| 164 | static int __init init(void) |
| 165 | { |
| 166 | return ipt_register_target(&ipt_ecn_reg); |
| 167 | } |
| 168 | |
| 169 | static void __exit fini(void) |
| 170 | { |
| 171 | ipt_unregister_target(&ipt_ecn_reg); |
| 172 | } |
| 173 | |
| 174 | module_init(init); |
| 175 | module_exit(fini); |