act_mirred: use the backlog for nested calls to mirred ingress

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@redhat.com>
CC: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index c8abb513649173af4c59ac94f8420b88c1590b91..8037ec9b1d311486d803159b3f2f77eedf6b31d3 100644 (file)
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -206,12 +206,19 @@ release_idr:
        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 = tcf_dev_queue_xmit(skb, dev_queue_xmit);
+       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 1e0a62f638fecc2c2a314b4f47672e6c18e6ca71..919c0dd9fe4bc7baf401ddb0c24e22c2db7c9918 100755 (executable)
--- a/tools/testing/selftests/net/forwarding/tc_actions.sh
+++ b/tools/testing/selftests/net/forwarding/tc_actions.sh
@@ -3,7 +3,8 @@
 
 ALL_TESTS="gact_drop_and_ok_test mirred_egress_redirect_test \
        mirred_egress_mirror_test matchall_mirred_egress_mirror_test \
-       gact_trap_test mirred_egress_to_ingress_test"
+       gact_trap_test mirred_egress_to_ingress_test \
+       mirred_egress_to_ingress_tcp_test"
 NUM_NETIFS=4
 source tc_common.sh
 source lib.sh
@@ -198,6 +199,52 @@ mirred_egress_to_ingress_test()
        log_test "mirred_egress_to_ingress ($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]}