TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
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WARNING: CPU: 0 PID: 1833 at net/ipv4/af_inet.c:167 inet_sock_destruct+0x598/0x760 net/ipv4/af_inet.c:167
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 1833 Comm: kworker/0:2 Not tainted 4.9.119-g9dc978d #75
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: sock_diag_events sock_diag_broadcast_destroy_work
 ffff8801ce25fa00 ffffffff81eb4be9 ffffffff83c48980 00000000ffffffff
 0000000000000000 0000000000000000 00000000000000a7 ffff8801ce25fac0
 ffffffff81421c95 0000000041b58ab3 ffffffff843bc020 ffffffff81421ad6
Call Trace:
 [<ffffffff81eb4be9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb4be9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81421c95>] panic+0x1bf/0x3bc kernel/panic.c:179
 [<ffffffff81421f81>] __warn.cold.9+0xc1/0x17f kernel/panic.c:542
 [<ffffffff8113683c>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
 [<ffffffff83427758>] inet_sock_destruct+0x598/0x760 net/ipv4/af_inet.c:167
 [<ffffffff836c0ac9>] l2tp_tunnel_destruct+0x339/0x590 net/l2tp/l2tp_core.c:1329
 [<ffffffff830230f5>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff8302ab83>] sk_destruct+0x63/0x80 net/core/sock.c:1463
 [<ffffffff830da7da>] sock_diag_broadcast_destroy_work+0x21a/0x390 net/core/sock_diag.c:154
 [<ffffffff8118d181>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df76>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d0ed>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fce9c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..