Message-Id: <20230516190040.636627-4-dragos.panait@windriver.com>
Date: Tue, 16 May 2023 22:00:40 +0300
From: Dragos-Marian Panait <dragos.panait@...driver.com>
To: stable@...r.kernel.org
Cc: wenxu <wenxu@...oud.cn>, Jakub Kicinski <kuba@...nel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Davide Caratti <dcaratti@...hat.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Paolo Abeni <pabeni@...hat.com>, William Zhao <wizhao@...hat.com>,
        Xin Long <lucien.xin@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>,
        Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH 5.10 3/3] act_mirred: use the backlog for nested calls to mirred ingress

From: Davide Caratti <dcaratti@...hat.com>

[ Upstream commit ca22da2fbd693b54dc8e3b7b54ccc9f7e9ba3640 ]

William reports kernel soft-lockups on some OVS topologies when TC mirred
egress->ingress action is hit by local TCP traffic [1].
The same can also be reproduced with SCTP (thanks Xin for verifying), when
client and server reach themselves through mirred egress to ingress, and
one of the two peers sends a "heartbeat" packet (from within a timer).

Enqueueing to backlog proved to fix this soft lockup; however, as Cong
noticed [2], we should preserve - when possible - the current mirred
behavior that counts as "overlimits" any eventual packet drop subsequent to
the mirred forwarding action [3]. A compromise solution might use the
backlog only when tcf_mirred_act() has a nest level greater than one:
change tcf_mirred_forward() accordingly.

Also, add a kselftest that can reproduce the lockup and verifies TC mirred
ability to account for further packet drops after TC mirred egress->ingress
(when the nest level is 1).

 [1] https://lore.kernel.org/netdev/33dc43f587ec1388ba456b4915c75f02a8aae226.1663945716.git.dcaratti@redhat.com/
 [2] https://lore.kernel.org/netdev/Y0w%2FWWY60gqrtGLp@pop-os.localdomain/
 [3] such behavior is not guaranteed: for example, if RPS or skb RX
     timestamping is enabled on the mirred target device, the kernel
     can defer receiving the skb and return NET_RX_SUCCESS inside
     tcf_mirred_forward().

Reported-by: William Zhao <wizhao@...hat.com>
CC: Xin Long <lucien.xin@...il.com>
Signed-off-by: Davide Caratti <dcaratti@...hat.com>
Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Acked-by: Jamal Hadi Salim <jhs@...atatu.com>
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
[DP: adjusted context for linux-5.10.y]
Signed-off-by: Dragos-Marian Panait <dragos.panait@...driver.com>
---
 net/sched/act_mirred.c                        |  7 +++
 .../selftests/net/forwarding/tc_actions.sh    | 48 ++++++++++++++++++-
 2 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index 01a44c3e8d6d..296af520817d 100644
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -206,12 +206,19 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla,
 	return err;
 }
 
+static bool is_mirred_nested(void)
+{
+	return unlikely(__this_cpu_read(mirred_nest_level) > 1);
+}
+
 static int tcf_mirred_forward(bool want_ingress, struct sk_buff *skb)
 {
 	int err;
 
 	if (!want_ingress)
 		err = dev_queue_xmit(skb);
+	else if (is_mirred_nested())
+		err = netif_rx(skb);
 	else
 		err = netif_receive_skb(skb);
 
diff --git a/tools/testing/selftests/net/forwarding/tc_actions.sh b/tools/testing/selftests/net/forwarding/tc_actions.sh
index d9eca227136b..1e27031288c8 100755
--- a/tools/testing/selftests/net/forwarding/tc_actions.sh
+++ b/tools/testing/selftests/net/forwarding/tc_actions.sh
@@ -3,7 +3,7 @@
 
 ALL_TESTS="gact_drop_and_ok_test mirred_egress_redirect_test \
 	mirred_egress_mirror_test matchall_mirred_egress_mirror_test \
-	gact_trap_test"
+	gact_trap_test mirred_egress_to_ingress_tcp_test"
 NUM_NETIFS=4
 source tc_common.sh
 source lib.sh
@@ -153,6 +153,52 @@ gact_trap_test()
 	log_test "trap ($tcflags)"
 }
 
+mirred_egress_to_ingress_tcp_test()
+{
+	local tmpfile=$(mktemp) tmpfile1=$(mktemp)
+
+	RET=0
+	dd conv=sparse status=none if=/dev/zero bs=1M count=2 of=$tmpfile
+	tc filter add dev $h1 protocol ip pref 100 handle 100 egress flower \
+		$tcflags ip_proto tcp src_ip 192.0.2.1 dst_ip 192.0.2.2 \
+			action ct commit nat src addr 192.0.2.2 pipe \
+			action ct clear pipe \
+			action ct commit nat dst addr 192.0.2.1 pipe \
+			action ct clear pipe \
+			action skbedit ptype host pipe \
+			action mirred ingress redirect dev $h1
+	tc filter add dev $h1 protocol ip pref 101 handle 101 egress flower \
+		$tcflags ip_proto icmp \
+			action mirred ingress redirect dev $h1
+	tc filter add dev $h1 protocol ip pref 102 handle 102 ingress flower \
+		ip_proto icmp \
+			action drop
+
+	ip vrf exec v$h1 nc --recv-only -w10 -l -p 12345 -o $tmpfile1  &
+	local rpid=$!
+	ip vrf exec v$h1 nc -w1 --send-only 192.0.2.2 12345 <$tmpfile
+	wait -n $rpid
+	cmp -s $tmpfile $tmpfile1
+	check_err $? "server output check failed"
+
+	$MZ $h1 -c 10 -p 64 -a $h1mac -b $h1mac -A 192.0.2.1 -B 192.0.2.1 \
+		-t icmp "ping,id=42,seq=5" -q
+	tc_check_packets "dev $h1 egress" 101 10
+	check_err $? "didn't mirred redirect ICMP"
+	tc_check_packets "dev $h1 ingress" 102 10
+	check_err $? "didn't drop mirred ICMP"
+	local overlimits=$(tc_rule_stats_get ${h1} 101 egress .overlimits)
+	test ${overlimits} = 10
+	check_err $? "wrong overlimits, expected 10 got ${overlimits}"
+
+	tc filter del dev $h1 egress protocol ip pref 100 handle 100 flower
+	tc filter del dev $h1 egress protocol ip pref 101 handle 101 flower
+	tc filter del dev $h1 ingress protocol ip pref 102 handle 102 flower
+
+	rm -f $tmpfile $tmpfile1
+	log_test "mirred_egress_to_ingress_tcp ($tcflags)"
+}
+
 setup_prepare()
 {
 	h1=${NETIFS[p1]}
-- 
2.40.1

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