From ca22da2fbd693b54dc8e3b7b54ccc9f7e9ba3640 Mon Sep 17 00:00:00 2001 From: Davide Caratti Date: Fri, 20 Jan 2023 18:01:40 +0100 Subject: 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 CC: Xin Long Signed-off-by: Davide Caratti Reviewed-by: Marcelo Ricardo Leitner Acked-by: Jamal Hadi Salim Signed-off-by: Paolo Abeni --- net/sched/act_mirred.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'net/sched/act_mirred.c') diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c index c8abb5136491..8037ec9b1d31 100644 --- 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); -- cgit v1.2.3