| /* 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) |
| return -EINVAL; |
| |
| if (einfo->ip_ect & ~IPT_ECN_IP_MASK) |
| 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_ratelimited("cannot use operation on 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); |