[SRU][F:linux-bluefield][PATCH 01/10] net: Fix return value of qdisc ingress handling on success

[Bodong Wang]

From: Paul Blakey <paulb at nvidia.com>

BugLink: https://bugs.launchpad.net/bugs/1995004

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

 #ingress forwarding veth1 <-> veth2
 $ 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

 #steal packet from peer1 egress to veth2 ingress, bypassing the veth pipe
 $ tc qdisc add dev peer1 clsact
 $ tc filter add dev peer1 egress prio 20 proto ip flower \
   action mirred ingress redirect dev veth1

 #run iperf and see connection not running
 $ iperf3 -s&
 $ ip netns exec ns0 iperf3 -c 5.5.5.6 -i 1

 #delete egress rule, and run again, now should work
 $ 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")
Change-Id: Id58956f315aef88399aa8ecd7ab29f545cb9465e
Signed-off-by: Paul Blakey <paulb at nvidia.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(Backported from upstream 672e97ef689a38cb20c2cc6a1814298fea34461e)
Signed-off-by: Bodong Wang <bodong at nvidia.com>
---
 net/core/dev.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index d88558b..3cb38d0 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4617,11 +4617,13 @@ static __latent_entropy void net_tx_action(struct softirq_action *h)
 	case TC_ACT_SHOT:
 		mini_qdisc_qstats_cpu_drop(miniq);
 		kfree_skb(skb);
+		*ret = NET_RX_DROP;
 		return NULL;
 	case TC_ACT_STOLEN:
 	case TC_ACT_QUEUED:
 	case TC_ACT_TRAP:
 		consume_skb(skb);
+		*ret = NET_RX_SUCCESS;
 		return NULL;
 	case TC_ACT_REDIRECT:
 		/* skb_mac_header check was done by cls/act_bpf, so
@@ -4630,8 +4632,10 @@ static __latent_entropy void net_tx_action(struct softirq_action *h)
 		 */
 		__skb_push(skb, skb->mac_len);
 		skb_do_redirect(skb);
+		*ret = NET_RX_SUCCESS;
 		return NULL;
 	case TC_ACT_CONSUMED:
+		*ret = NET_RX_SUCCESS;
 		return NULL;
 	default:
 		break;
-- 
1.8.3.1