diff options
Diffstat (limited to 'net/ipv4/netfilter/ipt_ECN.c')
| -rw-r--r-- | net/ipv4/netfilter/ipt_ECN.c | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/ipt_ECN.c b/net/ipv4/netfilter/ipt_ECN.c new file mode 100644 index 00000000000..ada9911118e --- /dev/null +++ b/net/ipv4/netfilter/ipt_ECN.c @@ -0,0 +1,175 @@ +/* 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); |