Netdev Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Pablo Neira Ayuso <pablo@netfilter.org>
To: netfilter-devel@vger.kernel.org
Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org
Subject: [PATCH 8/8] netfilter: conntrack: do not auto-delete clash entries on reply
Date: Mon, 31 Aug 2020 11:36:48 +0200	[thread overview]
Message-ID: <20200831093648.20765-9-pablo@netfilter.org> (raw)
In-Reply-To: <20200831093648.20765-1-pablo@netfilter.org>

From: Florian Westphal <fw@strlen.de>

Its possible that we have more than one packet with the same ct tuple
simultaneously, e.g. when an application emits n packets on same UDP
socket from multiple threads.

NAT rules might be applied to those packets. With the right set of rules,
n packets will be mapped to m destinations, where at least two packets end
up with the same destination.

When this happens, the existing clash resolution may merge the skb that
is processed after the first has been received with the identical tuple
already in hash table.

However, its possible that this identical tuple is a NAT_CLASH tuple.
In that case the second skb will be sent, but no reply can be received
since the reply that is processed first removes the NAT_CLASH tuple.

Do not auto-delete, this gives a 1 second window for replies to be passed
back to originator.

Packets that are coming later (udp stream case) will not be affected:
they match the original ct entry, not a NAT_CLASH one.

Also prevent NAT_CLASH entries from getting offloaded.

Fixes: 6a757c07e51f ("netfilter: conntrack: allow insertion of clashing entries")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_conntrack_proto_udp.c | 26 ++++++++++----------------
 net/netfilter/nft_flow_offload.c       |  2 +-
 2 files changed, 11 insertions(+), 17 deletions(-)

diff --git a/net/netfilter/nf_conntrack_proto_udp.c b/net/netfilter/nf_conntrack_proto_udp.c
index 760ca2422816..af402f458ee0 100644
--- a/net/netfilter/nf_conntrack_proto_udp.c
+++ b/net/netfilter/nf_conntrack_proto_udp.c
@@ -81,18 +81,6 @@ static bool udp_error(struct sk_buff *skb,
 	return false;
 }
 
-static void nf_conntrack_udp_refresh_unreplied(struct nf_conn *ct,
-					       struct sk_buff *skb,
-					       enum ip_conntrack_info ctinfo,
-					       u32 extra_jiffies)
-{
-	if (unlikely(ctinfo == IP_CT_ESTABLISHED_REPLY &&
-		     ct->status & IPS_NAT_CLASH))
-		nf_ct_kill(ct);
-	else
-		nf_ct_refresh_acct(ct, ctinfo, skb, extra_jiffies);
-}
-
 /* Returns verdict for packet, and may modify conntracktype */
 int nf_conntrack_udp_packet(struct nf_conn *ct,
 			    struct sk_buff *skb,
@@ -124,12 +112,15 @@ int nf_conntrack_udp_packet(struct nf_conn *ct,
 
 		nf_ct_refresh_acct(ct, ctinfo, skb, extra);
 
+		/* never set ASSURED for IPS_NAT_CLASH, they time out soon */
+		if (unlikely((ct->status & IPS_NAT_CLASH)))
+			return NF_ACCEPT;
+
 		/* Also, more likely to be important, and not a probe */
 		if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
 			nf_conntrack_event_cache(IPCT_ASSURED, ct);
 	} else {
-		nf_conntrack_udp_refresh_unreplied(ct, skb, ctinfo,
-						   timeouts[UDP_CT_UNREPLIED]);
+		nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
 	}
 	return NF_ACCEPT;
 }
@@ -206,12 +197,15 @@ int nf_conntrack_udplite_packet(struct nf_conn *ct,
 	if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
 		nf_ct_refresh_acct(ct, ctinfo, skb,
 				   timeouts[UDP_CT_REPLIED]);
+
+		if (unlikely((ct->status & IPS_NAT_CLASH)))
+			return NF_ACCEPT;
+
 		/* Also, more likely to be important, and not a probe */
 		if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
 			nf_conntrack_event_cache(IPCT_ASSURED, ct);
 	} else {
-		nf_conntrack_udp_refresh_unreplied(ct, skb, ctinfo,
-						   timeouts[UDP_CT_UNREPLIED]);
+		nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
 	}
 	return NF_ACCEPT;
 }
diff --git a/net/netfilter/nft_flow_offload.c b/net/netfilter/nft_flow_offload.c
index 3b9b97aa4b32..3a6c84fb2c90 100644
--- a/net/netfilter/nft_flow_offload.c
+++ b/net/netfilter/nft_flow_offload.c
@@ -102,7 +102,7 @@ static void nft_flow_offload_eval(const struct nft_expr *expr,
 	}
 
 	if (nf_ct_ext_exist(ct, NF_CT_EXT_HELPER) ||
-	    ct->status & IPS_SEQ_ADJUST)
+	    ct->status & (IPS_SEQ_ADJUST | IPS_NAT_CLASH))
 		goto out;
 
 	if (!nf_ct_is_confirmed(ct))
-- 
2.20.1


  parent reply	other threads:[~2020-08-31  9:37 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-31  9:36 [PATCH 0/8] Netfilter fixes for net Pablo Neira Ayuso
2020-08-31  9:36 ` [PATCH 1/8] netfilter: delete repeated words Pablo Neira Ayuso
2020-08-31  9:36 ` [PATCH 2/8] netfilter: nfnetlink: nfnetlink_unicast() reports EAGAIN instead of ENOBUFS Pablo Neira Ayuso
2020-08-31  9:36 ` [PATCH 3/8] selftests: netfilter: fix header example Pablo Neira Ayuso
2020-08-31  9:36 ` [PATCH 4/8] selftests: netfilter: exit on invalid parameters Pablo Neira Ayuso
2020-08-31  9:36 ` [PATCH 5/8] selftests: netfilter: remove unused variable in make_file() Pablo Neira Ayuso
2020-08-31  9:36 ` [PATCH 6/8] selftests: netfilter: simplify command testing Pablo Neira Ayuso
2020-08-31  9:36 ` [PATCH 7/8] selftests: netfilter: add command usage Pablo Neira Ayuso
2020-08-31  9:36 ` Pablo Neira Ayuso [this message]
2020-08-31 18:22 ` [PATCH 0/8] Netfilter fixes for net David Miller

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200831093648.20765-9-pablo@netfilter.org \
    --to=pablo@netfilter.org \
    --cc=davem@davemloft.net \
    --cc=kuba@kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=netfilter-devel@vger.kernel.org \
    --subject='Re: [PATCH 8/8] netfilter: conntrack: do not auto-delete clash entries on reply' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).