| /* iptables module for the IPv4 and TCP ECN bits, Version 1.5 |
| * |
| * (C) 2002 by Harald Welte <laforge@netfilter.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. |
| * |
| * ipt_ECN.c,v 1.5 2002/08/18 19:36:51 laforge Exp |
| */ |
| |
| #include <linux/module.h> |
| #include <linux/skbuff.h> |
| #include <linux/ip.h> |
| #include <linux/tcp.h> |
| #include <net/checksum.h> |
| |
| #include <linux/netfilter_ipv4/ip_tables.h> |
| #include <linux/netfilter_ipv4/ipt_ECN.h> |
| |
| MODULE_LICENSE("GPL"); |
| MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); |
| MODULE_DESCRIPTION("iptables ECN modification module"); |
| |
| /* set ECT codepoint from IP header. |
| * return 0 if there was an error. */ |
| static inline int |
| set_ect_ip(struct sk_buff **pskb, const struct ipt_ECN_info *einfo) |
| { |
| if (((*pskb)->nh.iph->tos & IPT_ECN_IP_MASK) |
| != (einfo->ip_ect & IPT_ECN_IP_MASK)) { |
| u_int16_t diffs[2]; |
| |
| if (!skb_ip_make_writable(pskb, sizeof(struct iphdr))) |
| return 0; |
| |
| diffs[0] = htons((*pskb)->nh.iph->tos) ^ 0xFFFF; |
| (*pskb)->nh.iph->tos &= ~IPT_ECN_IP_MASK; |
| (*pskb)->nh.iph->tos |= (einfo->ip_ect & IPT_ECN_IP_MASK); |
| diffs[1] = htons((*pskb)->nh.iph->tos); |
| (*pskb)->nh.iph->check |
| = csum_fold(csum_partial((char *)diffs, |
| sizeof(diffs), |
| (*pskb)->nh.iph->check |
| ^0xFFFF)); |
| (*pskb)->nfcache |= NFC_ALTERED; |
| } |
| return 1; |
| } |
| |
| /* Return 0 if there was an error. */ |
| static inline int |
| set_ect_tcp(struct sk_buff **pskb, const struct ipt_ECN_info *einfo, int inward) |
| { |
| struct tcphdr _tcph, *tcph; |
| u_int16_t diffs[2]; |
| |
| /* Not enought header? */ |
| tcph = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4, |
| sizeof(_tcph), &_tcph); |
| if (!tcph) |
| return 0; |
| |
| if (!(einfo->operation & IPT_ECN_OP_SET_ECE |
| || tcph->ece == einfo->proto.tcp.ece) |
| && (!(einfo->operation & IPT_ECN_OP_SET_CWR |
| || tcph->cwr == einfo->proto.tcp.cwr))) |
| return 1; |
| |
| if (!skb_ip_make_writable(pskb, (*pskb)->nh.iph->ihl*4+sizeof(*tcph))) |
| return 0; |
| tcph = (void *)(*pskb)->nh.iph + (*pskb)->nh.iph->ihl*4; |
| |
| diffs[0] = ((u_int16_t *)tcph)[6]; |
| if (einfo->operation & IPT_ECN_OP_SET_ECE) |
| tcph->ece = einfo->proto.tcp.ece; |
| if (einfo->operation & IPT_ECN_OP_SET_CWR) |
| tcph->cwr = einfo->proto.tcp.cwr; |
| diffs[1] = ((u_int16_t *)tcph)[6]; |
| diffs[0] = diffs[0] ^ 0xFFFF; |
| |
| if ((*pskb)->ip_summed != CHECKSUM_HW) |
| tcph->check = csum_fold(csum_partial((char *)diffs, |
| sizeof(diffs), |
| tcph->check^0xFFFF)); |
| else |
| if (skb_checksum_help(*pskb, inward)) |
| return 0; |
| (*pskb)->nfcache |= NFC_ALTERED; |
| return 1; |
| } |
| |
| static unsigned int |
| target(struct sk_buff **pskb, |
| const struct net_device *in, |
| const struct net_device *out, |
| unsigned int hooknum, |
| const void *targinfo, |
| void *userinfo) |
| { |
| const struct ipt_ECN_info *einfo = targinfo; |
| |
| if (einfo->operation & IPT_ECN_OP_SET_IP) |
| if (!set_ect_ip(pskb, einfo)) |
| return NF_DROP; |
| |
| if (einfo->operation & (IPT_ECN_OP_SET_ECE | IPT_ECN_OP_SET_CWR) |
| && (*pskb)->nh.iph->protocol == IPPROTO_TCP) |
| if (!set_ect_tcp(pskb, einfo, (out == NULL))) |
| return NF_DROP; |
| |
| return IPT_CONTINUE; |
| } |
| |
| static int |
| checkentry(const char *tablename, |
| const struct ipt_entry *e, |
| void *targinfo, |
| unsigned int targinfosize, |
| unsigned int hook_mask) |
| { |
| const struct ipt_ECN_info *einfo = (struct ipt_ECN_info *)targinfo; |
| |
| if (targinfosize != IPT_ALIGN(sizeof(struct ipt_ECN_info))) { |
| printk(KERN_WARNING "ECN: targinfosize %u != %Zu\n", |
| targinfosize, |
| IPT_ALIGN(sizeof(struct ipt_ECN_info))); |
| return 0; |
| } |
| |
| if (strcmp(tablename, "mangle") != 0) { |
| printk(KERN_WARNING "ECN: can only be called from \"mangle\" table, not \"%s\"\n", tablename); |
| return 0; |
| } |
| |
| if (einfo->operation & IPT_ECN_OP_MASK) { |
| printk(KERN_WARNING "ECN: unsupported ECN operation %x\n", |
| einfo->operation); |
| return 0; |
| } |
| if (einfo->ip_ect & ~IPT_ECN_IP_MASK) { |
| printk(KERN_WARNING "ECN: new ECT codepoint %x out of mask\n", |
| einfo->ip_ect); |
| return 0; |
| } |
| |
| if ((einfo->operation & (IPT_ECN_OP_SET_ECE|IPT_ECN_OP_SET_CWR)) |
| && (e->ip.proto != IPPROTO_TCP || (e->ip.invflags & IPT_INV_PROTO))) { |
| printk(KERN_WARNING "ECN: cannot use TCP operations on a " |
| "non-tcp rule\n"); |
| return 0; |
| } |
| |
| return 1; |
| } |
| |
| static struct ipt_target ipt_ecn_reg = { |
| .name = "ECN", |
| .target = target, |
| .checkentry = checkentry, |
| .me = THIS_MODULE, |
| }; |
| |
| static int __init init(void) |
| { |
| return ipt_register_target(&ipt_ecn_reg); |
| } |
| |
| static void __exit fini(void) |
| { |
| ipt_unregister_target(&ipt_ecn_reg); |
| } |
| |
| module_init(init); |
| module_exit(fini); |