linux-kernel - [PATCH 5.10 260/575] netfilter: conntrack: set on IPS_ASSURED if flows enters internal stream state

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Date:   Mon, 15 Nov 2021 17:59:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Maciej Żenczykowski <zenczykowski@...il.com>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 260/575] netfilter: conntrack: set on IPS_ASSURED if flows enters internal stream state

From: Pablo Neira Ayuso <pablo@...filter.org>

[ Upstream commit b7b1d02fc43925a4d569ec221715db2dfa1ce4f5 ]

The internal stream state sets the timeout to 120 seconds 2 seconds
after the creation of the flow, attach this internal stream state to the
IPS_ASSURED flag for consistent event reporting.

Before this patch:

      [NEW] udp      17 30 src=10.246.11.13 dst=216.239.35.0 sport=37282 dport=123 [UNREPLIED] src=216.239.35.0 dst=10.246.11.13 sport=123 dport=37282
   [UPDATE] udp      17 30 src=10.246.11.13 dst=216.239.35.0 sport=37282 dport=123 src=216.239.35.0 dst=10.246.11.13 sport=123 dport=37282
   [UPDATE] udp      17 30 src=10.246.11.13 dst=216.239.35.0 sport=37282 dport=123 src=216.239.35.0 dst=10.246.11.13 sport=123 dport=37282 [ASSURED]
  [DESTROY] udp      17 src=10.246.11.13 dst=216.239.35.0 sport=37282 dport=123 src=216.239.35.0 dst=10.246.11.13 sport=123 dport=37282 [ASSURED]

Note IPS_ASSURED for the flow not yet in the internal stream state.

after this update:

      [NEW] udp      17 30 src=10.246.11.13 dst=216.239.35.0 sport=37282 dport=123 [UNREPLIED] src=216.239.35.0 dst=10.246.11.13 sport=123 dport=37282
   [UPDATE] udp      17 30 src=10.246.11.13 dst=216.239.35.0 sport=37282 dport=123 src=216.239.35.0 dst=10.246.11.13 sport=123 dport=37282
   [UPDATE] udp      17 120 src=10.246.11.13 dst=216.239.35.0 sport=37282 dport=123 src=216.239.35.0 dst=10.246.11.13 sport=123 dport=37282 [ASSURED]
  [DESTROY] udp      17 src=10.246.11.13 dst=216.239.35.0 sport=37282 dport=123 src=216.239.35.0 dst=10.246.11.13 sport=123 dport=37282 [ASSURED]

Before this patch, short-lived UDP flows never entered IPS_ASSURED, so
they were already candidate flow to be deleted by early_drop under
stress.

Before this patch, IPS_ASSURED is set on regardless the internal stream
state, attach this internal stream state to IPS_ASSURED.

packet #1 (original direction) enters NEW state
packet #2 (reply direction) enters ESTABLISHED state, sets on IPS_SEEN_REPLY
paclet #3 (any direction) sets on IPS_ASSURED (if 2 seconds since the
          creation has passed by).

Reported-by: Maciej Żenczykowski <zenczykowski@...il.com>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/netfilter/nf_conntrack_proto_udp.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_conntrack_proto_udp.c b/net/netfilter/nf_conntrack_proto_udp.c
index af402f458ee02..0528e9c26cebd 100644
--- a/net/netfilter/nf_conntrack_proto_udp.c
+++ b/net/netfilter/nf_conntrack_proto_udp.c
@@ -105,10 +105,13 @@ int nf_conntrack_udp_packet(struct nf_conn *ct,
 	 */
 	if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
 		unsigned long extra = timeouts[UDP_CT_UNREPLIED];
+		bool stream = false;
 
 		/* Still active after two seconds? Extend timeout. */
-		if (time_after(jiffies, ct->proto.udp.stream_ts))
+		if (time_after(jiffies, ct->proto.udp.stream_ts)) {
 			extra = timeouts[UDP_CT_REPLIED];
+			stream = true;
+		}
 
 		nf_ct_refresh_acct(ct, ctinfo, skb, extra);
 
@@ -117,7 +120,7 @@ int nf_conntrack_udp_packet(struct nf_conn *ct,
 			return NF_ACCEPT;
 
 		/* Also, more likely to be important, and not a probe */
-		if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
+		if (stream && !test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
 			nf_conntrack_event_cache(IPCT_ASSURED, ct);
 	} else {
 		nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
-- 
2.33.0