Revision a82c25c366b0963d33ddf699196e6cf57f6d89b1 authored by Florian Westphal on 08 March 2022, 12:52:11 UTC, committed by Florian Westphal on 08 March 2022, 12:52:11 UTC
This reverts commit 878aed8db324bec64f3c3f956e64d5ae7375a5de. This change breaks existing setups where conntrack is used with asymmetric paths. In these cases, the NAT transformation occurs on the syn-ack instead of the syn: 1. SYN x:12345 -> y -> 443 // sent by initiator, receiverd by responder 2. SYNACK y:443 -> x:12345 // First packet seen by conntrack, as sent by responder 3. tuple_force_port_remap() gets called, sees: 'tcp from 443 to port 12345 NAT' -> pick a new source port, inititor receives 4. SYNACK y:$RANDOM -> x:12345 // connection is never established While its possible to avoid the breakage with NOTRACK rules, a kernel update should not break working setups. An alternative to the revert is to augment conntrack to tag mid-stream connections plus more code in the nat core to skip NAT for such connections, however, this leads to more interaction/integration between conntrack and NAT. Therefore, revert, users will need to add explicit nat rules to avoid port shadowing. Link: https://lore.kernel.org/netfilter-devel/20220302105908.GA5852@breakpoint.cc/#R Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2051413 Signed-off-by: Florian Westphal <fw@strlen.de>
1 parent f8e9bd3
xt_osf.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (c) 2003+ Evgeniy Polyakov <zbr@ioremap.net>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/capability.h>
#include <linux/if.h>
#include <linux/inetdevice.h>
#include <linux/ip.h>
#include <linux/list.h>
#include <linux/rculist.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/tcp.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/x_tables.h>
#include <net/netfilter/nf_log.h>
#include <linux/netfilter/xt_osf.h>
static bool
xt_osf_match_packet(const struct sk_buff *skb, struct xt_action_param *p)
{
return nf_osf_match(skb, xt_family(p), xt_hooknum(p), xt_in(p),
xt_out(p), p->matchinfo, xt_net(p), nf_osf_fingers);
}
static struct xt_match xt_osf_match = {
.name = "osf",
.revision = 0,
.family = NFPROTO_IPV4,
.proto = IPPROTO_TCP,
.hooks = (1 << NF_INET_LOCAL_IN) |
(1 << NF_INET_PRE_ROUTING) |
(1 << NF_INET_FORWARD),
.match = xt_osf_match_packet,
.matchsize = sizeof(struct xt_osf_info),
.me = THIS_MODULE,
};
static int __init xt_osf_init(void)
{
int err;
err = xt_register_match(&xt_osf_match);
if (err) {
pr_err("Failed to register OS fingerprint "
"matching module (%d)\n", err);
return err;
}
return 0;
}
static void __exit xt_osf_fini(void)
{
xt_unregister_match(&xt_osf_match);
}
module_init(xt_osf_init);
module_exit(xt_osf_fini);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
MODULE_DESCRIPTION("Passive OS fingerprint matching.");
MODULE_ALIAS("ipt_osf");
MODULE_ALIAS("ip6t_osf");
MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_OSF);
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