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- /* 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.
- */
- #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
- #include <linux/in.h>
- #include <linux/module.h>
- #include <linux/skbuff.h>
- #include <linux/ip.h>
- #include <net/ip.h>
- #include <linux/tcp.h>
- #include <net/checksum.h>
- #include <linux/netfilter/x_tables.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("Xtables: Explicit Congestion Notification (ECN) flag modification");
- /* set ECT codepoint from IP header.
- * return false if there was an error. */
- static inline bool
- set_ect_ip(struct sk_buff *skb, const struct ipt_ECN_info *einfo)
- {
- struct iphdr *iph = ip_hdr(skb);
- if ((iph->tos & IPT_ECN_IP_MASK) != (einfo->ip_ect & IPT_ECN_IP_MASK)) {
- __u8 oldtos;
- if (!skb_make_writable(skb, sizeof(struct iphdr)))
- return false;
- iph = ip_hdr(skb);
- oldtos = iph->tos;
- iph->tos &= ~IPT_ECN_IP_MASK;
- iph->tos |= (einfo->ip_ect & IPT_ECN_IP_MASK);
- csum_replace2(&iph->check, htons(oldtos), htons(iph->tos));
- }
- return true;
- }
- /* Return false if there was an error. */
- static inline bool
- set_ect_tcp(struct sk_buff *skb, const struct ipt_ECN_info *einfo)
- {
- struct tcphdr _tcph, *tcph;
- __be16 oldval;
- /* Not enough header? */
- tcph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_tcph), &_tcph);
- if (!tcph)
- return false;
- 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 true;
- if (!skb_make_writable(skb, ip_hdrlen(skb) + sizeof(*tcph)))
- return false;
- tcph = (void *)ip_hdr(skb) + ip_hdrlen(skb);
- oldval = ((__be16 *)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;
- inet_proto_csum_replace2(&tcph->check, skb,
- oldval, ((__be16 *)tcph)[6], false);
- return true;
- }
- static unsigned int
- ecn_tg(struct sk_buff *skb, const struct xt_action_param *par)
- {
- const struct ipt_ECN_info *einfo = par->targinfo;
- if (einfo->operation & IPT_ECN_OP_SET_IP)
- if (!set_ect_ip(skb, einfo))
- return NF_DROP;
- if (einfo->operation & (IPT_ECN_OP_SET_ECE | IPT_ECN_OP_SET_CWR) &&
- ip_hdr(skb)->protocol == IPPROTO_TCP)
- if (!set_ect_tcp(skb, einfo))
- return NF_DROP;
- return XT_CONTINUE;
- }
- static int ecn_tg_check(const struct xt_tgchk_param *par)
- {
- const struct ipt_ECN_info *einfo = par->targinfo;
- const struct ipt_entry *e = par->entryinfo;
- if (einfo->operation & IPT_ECN_OP_MASK) {
- pr_info("unsupported ECN operation %x\n", einfo->operation);
- return -EINVAL;
- }
- if (einfo->ip_ect & ~IPT_ECN_IP_MASK) {
- pr_info("new ECT codepoint %x out of mask\n", einfo->ip_ect);
- return -EINVAL;
- }
- if ((einfo->operation & (IPT_ECN_OP_SET_ECE|IPT_ECN_OP_SET_CWR)) &&
- (e->ip.proto != IPPROTO_TCP || (e->ip.invflags & XT_INV_PROTO))) {
- pr_info("cannot use TCP operations on a non-tcp rule\n");
- return -EINVAL;
- }
- return 0;
- }
- static struct xt_target ecn_tg_reg __read_mostly = {
- .name = "ECN",
- .family = NFPROTO_IPV4,
- .target = ecn_tg,
- .targetsize = sizeof(struct ipt_ECN_info),
- .table = "mangle",
- .checkentry = ecn_tg_check,
- .me = THIS_MODULE,
- };
- static int __init ecn_tg_init(void)
- {
- return xt_register_target(&ecn_tg_reg);
- }
- static void __exit ecn_tg_exit(void)
- {
- xt_unregister_target(&ecn_tg_reg);
- }
- module_init(ecn_tg_init);
- module_exit(ecn_tg_exit);
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