netdev - [PATCH netfilter] netfilter: conntrack: udp: generate event on switch to stream timeout

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Date:   Fri, 15 Oct 2021 02:09:34 -0700
From:   Maciej Żenczykowski <zenczykowski@...il.com>
To:     Maciej Żenczykowski <maze@...gle.com>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Florian Westphal <fw@...len.de>
Cc:     Linux Network Development Mailing List <netdev@...r.kernel.org>,
        Netfilter Development Mailing List 
        <netfilter-devel@...r.kernel.org>
Subject: [PATCH netfilter] netfilter: conntrack: udp: generate event on switch to stream timeout

From: Maciej Żenczykowski <maze@...gle.com>

Without this it's hard to offload udp due to lack of a conntrack event
at the appropriate time (ie. once udp stream is established and stream
timeout is in effect).

Without this udp conntrack events 'update/assured/timeout=30'
either need to be ignored, or polling loop needs to be <30 second
instead of <120 second.

With this change:
      [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]
   [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]
(the 3rd update/assured/120 event is new)

Cc: Florian Westphal <fw@...len.de>
Cc: Pablo Neira Ayuso <pablo@...filter.org>
Fixes: d535c8a69c19 'netfilter: conntrack: udp: only extend timeout to stream mode after 2s'
Signed-off-by: Maciej Żenczykowski <maze@...gle.com>
---
 include/net/netfilter/nf_conntrack.h             |  1 +
 .../uapi/linux/netfilter/nf_conntrack_common.h   |  1 +
 net/netfilter/nf_conntrack_proto_udp.c           | 16 ++++++++++++++--
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h
index cc663c68ddc4..12029d616cfa 100644
--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -26,6 +26,7 @@
 
 struct nf_ct_udp {
 	unsigned long	stream_ts;
+	bool		notified;
 };
 
 /* per conntrack: protocol private data */
diff --git a/include/uapi/linux/netfilter/nf_conntrack_common.h b/include/uapi/linux/netfilter/nf_conntrack_common.h
index 4b3395082d15..a8e91b5821fa 100644
--- a/include/uapi/linux/netfilter/nf_conntrack_common.h
+++ b/include/uapi/linux/netfilter/nf_conntrack_common.h
@@ -144,6 +144,7 @@ enum ip_conntrack_events {
 	IPCT_SECMARK,		/* new security mark has been set */
 	IPCT_LABEL,		/* new connlabel has been set */
 	IPCT_SYNPROXY,		/* synproxy has been set */
+	IPCT_UDPSTREAM,		/* udp stream has been set */
 #ifdef __KERNEL__
 	__IPCT_MAX
 #endif
diff --git a/net/netfilter/nf_conntrack_proto_udp.c b/net/netfilter/nf_conntrack_proto_udp.c
index 68911fcaa0f1..f0d9869aa30f 100644
--- a/net/netfilter/nf_conntrack_proto_udp.c
+++ b/net/netfilter/nf_conntrack_proto_udp.c
@@ -97,18 +97,23 @@ int nf_conntrack_udp_packet(struct nf_conn *ct,
 	if (!timeouts)
 		timeouts = udp_get_timeouts(nf_ct_net(ct));
 
-	if (!nf_ct_is_confirmed(ct))
+	if (!nf_ct_is_confirmed(ct)) {
 		ct->proto.udp.stream_ts = 2 * HZ + jiffies;
+		ct->proto.udp.notified = false;
+	}
 
 	/* If we've seen traffic both ways, this is some kind of UDP
 	 * stream. Set Assured.
 	 */
 	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);
 
@@ -116,9 +121,16 @@ int nf_conntrack_udp_packet(struct nf_conn *ct,
 		if (unlikely((ct->status & IPS_NAT_CLASH)))
 			return NF_ACCEPT;
 
+		if (stream) {
+			stream = !ct->proto.udp.notified;
+			ct->proto.udp.notified = true;
+		}
+
 		/* 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 if (stream)
+			nf_conntrack_event_cache(IPCT_UDPSTREAM, ct);
 	} else {
 		nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
 	}
-- 
2.33.0.1079.g6e70778dc9-goog