cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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ipt_ECN.c (3540B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/* iptables module for the IPv4 and TCP ECN bits, Version 1.5
      3 *
      4 * (C) 2002 by Harald Welte <laforge@netfilter.org>
      5*/
      6#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
      7#include <linux/in.h>
      8#include <linux/module.h>
      9#include <linux/skbuff.h>
     10#include <linux/ip.h>
     11#include <net/ip.h>
     12#include <linux/tcp.h>
     13#include <net/checksum.h>
     14
     15#include <linux/netfilter/x_tables.h>
     16#include <linux/netfilter_ipv4/ip_tables.h>
     17#include <linux/netfilter_ipv4/ipt_ECN.h>
     18
     19MODULE_LICENSE("GPL");
     20MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
     21MODULE_DESCRIPTION("Xtables: Explicit Congestion Notification (ECN) flag modification");
     22
     23/* set ECT codepoint from IP header.
     24 * 	return false if there was an error. */
     25static inline bool
     26set_ect_ip(struct sk_buff *skb, const struct ipt_ECN_info *einfo)
     27{
     28	struct iphdr *iph = ip_hdr(skb);
     29
     30	if ((iph->tos & IPT_ECN_IP_MASK) != (einfo->ip_ect & IPT_ECN_IP_MASK)) {
     31		__u8 oldtos;
     32		if (skb_ensure_writable(skb, sizeof(struct iphdr)))
     33			return false;
     34		iph = ip_hdr(skb);
     35		oldtos = iph->tos;
     36		iph->tos &= ~IPT_ECN_IP_MASK;
     37		iph->tos |= (einfo->ip_ect & IPT_ECN_IP_MASK);
     38		csum_replace2(&iph->check, htons(oldtos), htons(iph->tos));
     39	}
     40	return true;
     41}
     42
     43/* Return false if there was an error. */
     44static inline bool
     45set_ect_tcp(struct sk_buff *skb, const struct ipt_ECN_info *einfo)
     46{
     47	struct tcphdr _tcph, *tcph;
     48	__be16 oldval;
     49
     50	/* Not enough header? */
     51	tcph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_tcph), &_tcph);
     52	if (!tcph)
     53		return false;
     54
     55	if ((!(einfo->operation & IPT_ECN_OP_SET_ECE) ||
     56	     tcph->ece == einfo->proto.tcp.ece) &&
     57	    (!(einfo->operation & IPT_ECN_OP_SET_CWR) ||
     58	     tcph->cwr == einfo->proto.tcp.cwr))
     59		return true;
     60
     61	if (skb_ensure_writable(skb, ip_hdrlen(skb) + sizeof(*tcph)))
     62		return false;
     63	tcph = (void *)ip_hdr(skb) + ip_hdrlen(skb);
     64
     65	oldval = ((__be16 *)tcph)[6];
     66	if (einfo->operation & IPT_ECN_OP_SET_ECE)
     67		tcph->ece = einfo->proto.tcp.ece;
     68	if (einfo->operation & IPT_ECN_OP_SET_CWR)
     69		tcph->cwr = einfo->proto.tcp.cwr;
     70
     71	inet_proto_csum_replace2(&tcph->check, skb,
     72				 oldval, ((__be16 *)tcph)[6], false);
     73	return true;
     74}
     75
     76static unsigned int
     77ecn_tg(struct sk_buff *skb, const struct xt_action_param *par)
     78{
     79	const struct ipt_ECN_info *einfo = par->targinfo;
     80
     81	if (einfo->operation & IPT_ECN_OP_SET_IP)
     82		if (!set_ect_ip(skb, einfo))
     83			return NF_DROP;
     84
     85	if (einfo->operation & (IPT_ECN_OP_SET_ECE | IPT_ECN_OP_SET_CWR) &&
     86	    ip_hdr(skb)->protocol == IPPROTO_TCP)
     87		if (!set_ect_tcp(skb, einfo))
     88			return NF_DROP;
     89
     90	return XT_CONTINUE;
     91}
     92
     93static int ecn_tg_check(const struct xt_tgchk_param *par)
     94{
     95	const struct ipt_ECN_info *einfo = par->targinfo;
     96	const struct ipt_entry *e = par->entryinfo;
     97
     98	if (einfo->operation & IPT_ECN_OP_MASK)
     99		return -EINVAL;
    100
    101	if (einfo->ip_ect & ~IPT_ECN_IP_MASK)
    102		return -EINVAL;
    103
    104	if ((einfo->operation & (IPT_ECN_OP_SET_ECE|IPT_ECN_OP_SET_CWR)) &&
    105	    (e->ip.proto != IPPROTO_TCP || (e->ip.invflags & XT_INV_PROTO))) {
    106		pr_info_ratelimited("cannot use operation on non-tcp rule\n");
    107		return -EINVAL;
    108	}
    109	return 0;
    110}
    111
    112static struct xt_target ecn_tg_reg __read_mostly = {
    113	.name		= "ECN",
    114	.family		= NFPROTO_IPV4,
    115	.target		= ecn_tg,
    116	.targetsize	= sizeof(struct ipt_ECN_info),
    117	.table		= "mangle",
    118	.checkentry	= ecn_tg_check,
    119	.me		= THIS_MODULE,
    120};
    121
    122static int __init ecn_tg_init(void)
    123{
    124	return xt_register_target(&ecn_tg_reg);
    125}
    126
    127static void __exit ecn_tg_exit(void)
    128{
    129	xt_unregister_target(&ecn_tg_reg);
    130}
    131
    132module_init(ecn_tg_init);
    133module_exit(ecn_tg_exit);