[PATCH net v2 2/2] selftests: team: add non-Ethernet header_ops reproducer

[Jiayuan Chen <jiayuan.chen@linux.dev>]

From: Jiayuan Chen <jiayuan.chen@shopee.com>

Add a team selftest that sets up:
  g0 (gre) -> b0 (bond) -> t0 (team)

and triggers IPv6 traffic on t0. This reproduces the non-Ethernet
header_ops confusion scenario and protects against regressions in stacked
team/bond/gre configurations.

Using this script, the panic reported by syzkaller can be reproduced [1].

After the fix:

  # ./non_ether_header_ops.sh
  PASS: non-Ethernet header_ops stacking did not crash

[1] https://syzkaller.appspot.com/bug?extid=3d8bc31c45e11450f24c

Cc: Jiayuan Chen <jiayuan.chen@linux.dev>
Signed-off-by: Jiayuan Chen <jiayuan.chen@shopee.com>
---
 .../selftests/drivers/net/team/Makefile       |  1 +
 .../testing/selftests/drivers/net/team/config |  2 +
 .../drivers/net/team/non_ether_header_ops.sh  | 40 +++++++++++++++++++
 3 files changed, 43 insertions(+)
 create mode 100755 tools/testing/selftests/drivers/net/team/non_ether_header_ops.sh

diff --git a/tools/testing/selftests/drivers/net/team/Makefile b/tools/testing/selftests/drivers/net/team/Makefile
index 45a3e7ad3dcb..02d6f51d5a06 100644
--- a/tools/testing/selftests/drivers/net/team/Makefile
+++ b/tools/testing/selftests/drivers/net/team/Makefile
@@ -3,6 +3,7 @@
 
 TEST_PROGS := \
 	dev_addr_lists.sh \
+	non_ether_header_ops.sh \
 	options.sh \
 	propagation.sh \
 	refleak.sh \
diff --git a/tools/testing/selftests/drivers/net/team/config b/tools/testing/selftests/drivers/net/team/config
index 558e1d0cf565..40fdd5fbcbdb 100644
--- a/tools/testing/selftests/drivers/net/team/config
+++ b/tools/testing/selftests/drivers/net/team/config
@@ -1,5 +1,7 @@
+CONFIG_BONDING=y
 CONFIG_DUMMY=y
 CONFIG_IPV6=y
+CONFIG_NET_IPGRE=y
 CONFIG_MACVLAN=y
 CONFIG_NETDEVSIM=m
 CONFIG_NET_TEAM=y
diff --git a/tools/testing/selftests/drivers/net/team/non_ether_header_ops.sh b/tools/testing/selftests/drivers/net/team/non_ether_header_ops.sh
new file mode 100755
index 000000000000..19bd57f40688
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/team/non_ether_header_ops.sh
@@ -0,0 +1,40 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Reproduce the non-Ethernet header_ops confusion scenario with:
+#   g0 (gre) -> b0 (bond) -> t0 (team)
+#
+# Before the fix, direct header_ops inheritance in this stack could call
+# callbacks with the wrong net_device context and crash.
+
+lib_dir=$(dirname "$0")
+source "$lib_dir"/../../../net/lib.sh
+
+trap cleanup_all_ns EXIT
+
+setup_ns ns1
+
+ip -n "$ns1" link add d0 type dummy
+ip -n "$ns1" addr add 10.10.10.1/24 dev d0
+ip -n "$ns1" link set d0 up
+
+ip -n "$ns1" link add g0 type gre local 10.10.10.1
+ip -n "$ns1" link add b0 type bond mode active-backup
+ip -n "$ns1" link add t0 type team
+
+ip -n "$ns1" link set g0 master b0
+ip -n "$ns1" link set b0 master t0
+
+ip -n "$ns1" link set g0 up
+ip -n "$ns1" link set b0 up
+ip -n "$ns1" link set t0 up
+
+# GRE makes team inherit IFF_POINTOPOINT|IFF_NOARP, so IPv4 skips
+# dev_hard_header() entirely... use IPv6 NDP which still calls it.
+ip -n "$ns1" -6 addr add 2001:db8:1::1/64 dev t0 nodad
+for i in $(seq 1 20); do
+	ip netns exec "$ns1" ping -6 -I t0 ff02::1 -c1 -W1 &>/dev/null || true
+done
+
+echo "PASS: non-Ethernet header_ops stacking did not crash"
+exit "$EXIT_STATUS"
-- 
2.43.0