netdev - [PATCH net] selftests: forwarding: Fix race condition in mirror installation

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Date: Tue, 20 Jun 2023 14:45:15 +0200
From: Petr Machata <petrm@...dia.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, <netdev@...r.kernel.org>
CC: Petr Machata <petrm@...dia.com>, Danielle Ratson <danieller@...dia.com>,
	Shuah Khan <shuah@...nel.org>, <linux-kselftest@...r.kernel.org>,
	<mlxsw@...dia.com>
Subject: [PATCH net] selftests: forwarding: Fix race condition in mirror installation

From: Danielle Ratson <danieller@...dia.com>

When mirroring to a gretap in hardware the device expects to be
programmed with the egress port and all the encapsulating headers. This
requires the driver to resolve the path the packet will take in the
software data path and program the device accordingly.

If the path cannot be resolved (in this case because of an unresolved
neighbor), then mirror installation fails until the path is resolved.
This results in a race that causes the test to sometimes fail.

Fix this by setting the neighbor's state to permanent in a couple of
tests, so that it is always valid.

Fixes: 35c31d5c323f ("selftests: forwarding: Test mirror-to-gretap w/ UL 802.1d")
Fixes: 239e754af854 ("selftests: forwarding: Test mirror-to-gretap w/ UL 802.1q")
Signed-off-by: Danielle Ratson <danieller@...dia.com>
Reviewed-by: Petr Machata <petrm@...dia.com>
Signed-off-by: Petr Machata <petrm@...dia.com>
---
 .../testing/selftests/net/forwarding/mirror_gre_bridge_1d.sh  | 4 ++++
 .../testing/selftests/net/forwarding/mirror_gre_bridge_1q.sh  | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/tools/testing/selftests/net/forwarding/mirror_gre_bridge_1d.sh b/tools/testing/selftests/net/forwarding/mirror_gre_bridge_1d.sh
index c5095da7f6bf..aec752a22e9e 100755
--- a/tools/testing/selftests/net/forwarding/mirror_gre_bridge_1d.sh
+++ b/tools/testing/selftests/net/forwarding/mirror_gre_bridge_1d.sh
@@ -93,12 +93,16 @@ cleanup()
 
 test_gretap()
 {
+	ip neigh replace 192.0.2.130 lladdr $(mac_get $h3) \
+		 nud permanent dev br2
 	full_test_span_gre_dir gt4 ingress 8 0 "mirror to gretap"
 	full_test_span_gre_dir gt4 egress 0 8 "mirror to gretap"
 }
 
 test_ip6gretap()
 {
+	ip neigh replace 2001:db8:2::2 lladdr $(mac_get $h3) \
+		nud permanent dev br2
 	full_test_span_gre_dir gt6 ingress 8 0 "mirror to ip6gretap"
 	full_test_span_gre_dir gt6 egress 0 8 "mirror to ip6gretap"
 }
diff --git a/tools/testing/selftests/net/forwarding/mirror_gre_bridge_1q.sh b/tools/testing/selftests/net/forwarding/mirror_gre_bridge_1q.sh
index 9ff22f28032d..0cf4c47a46f9 100755
--- a/tools/testing/selftests/net/forwarding/mirror_gre_bridge_1q.sh
+++ b/tools/testing/selftests/net/forwarding/mirror_gre_bridge_1q.sh
@@ -90,12 +90,16 @@ cleanup()
 
 test_gretap()
 {
+	ip neigh replace 192.0.2.130 lladdr $(mac_get $h3) \
+		 nud permanent dev br1
 	full_test_span_gre_dir gt4 ingress 8 0 "mirror to gretap"
 	full_test_span_gre_dir gt4 egress 0 8 "mirror to gretap"
 }
 
 test_ip6gretap()
 {
+	ip neigh replace 2001:db8:2::2 lladdr $(mac_get $h3) \
+		nud permanent dev br1
 	full_test_span_gre_dir gt6 ingress 8 0 "mirror to ip6gretap"
 	full_test_span_gre_dir gt6 egress 0 8 "mirror to ip6gretap"
 }
-- 
2.40.1