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net: Fix return value of qdisc ingress handling on success

Paolo Abeni requested to merge pabeni/centos-stream-9:bz2162711_tc_ret into main

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2162711 Tested: vs bz reproducer

Upstream commit: commit 672e97ef689a38cb20c2cc6a1814298fea34461e Author: Paul Blakey paulb@nvidia.com Date: Tue Oct 18 10:34:38 2022 +0300

net: Fix return value of qdisc ingress handling on success

Currently qdisc ingress handling (sch_handle_ingress()) doesn't
set a return value and it is left to the old return value of
the caller (__netif_receive_skb_core()) which is RX drop, so if
the packet is consumed, caller will stop and return this value
as if the packet was dropped.

This causes a problem in the kernel tcp stack when having a
egress tc rule forwarding to a ingress tc rule.
The tcp stack sending packets on the device having the egress rule
will see the packets as not successfully transmitted (although they
actually were), will not advance it's internal state of sent data,
and packets returning on such tcp stream will be dropped by the tcp
stack with reason ack-of-unsent-data. See reproduction in [0] below.

Fix that by setting the return value to RX success if
the packet was handled successfully.

[0] Reproduction steps:
 $ ip link add veth1 type veth peer name peer1
 $ ip link add veth2 type veth peer name peer2
 $ ifconfig peer1 5.5.5.6/24 up
 $ ip netns add ns0
 $ ip link set dev peer2 netns ns0
 $ ip netns exec ns0 ifconfig peer2 5.5.5.5/24 up
 $ ifconfig veth2 0 up
 $ ifconfig veth1 0 up
 $ tc qdisc add dev veth2 ingress
 $ tc qdisc add dev veth1 ingress
 $ tc filter add dev veth2 ingress prio 1 proto all flower \
   action mirred egress redirect dev veth1
 $ tc filter add dev veth1 ingress prio 1 proto all flower \
   action mirred egress redirect dev veth2
 $ tc qdisc add dev peer1 clsact
 $ tc filter add dev peer1 egress prio 20 proto ip flower \
   action mirred ingress redirect dev veth1
 $ iperf3 -s&
 $ ip netns exec ns0 iperf3 -c 5.5.5.6 -i 1
 $ tc filter del dev peer1 egress
 $ ip netns exec ns0 iperf3 -c 5.5.5.6 -i 1

Fixes: f697c3e8b35c ("[NET]: Avoid unnecessary cloning for ingress filtering")
Signed-off-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Paolo Abeni pabeni@redhat.com

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