TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1846 at net/ipv4/af_inet.c:167 inet_sock_destruct+0x598/0x760 net/ipv4/af_inet.c:167()
TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 1846 Comm: kworker/0:2 Not tainted 4.4.139-g7ba5557 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: sock_diag_events sock_diag_broadcast_destroy_work
 0000000000000000 c449e731a85a1647 ffff8801d3b57a30 ffffffff81e0d58d
 ffffffff83a43da0 ffff8800b687e000 ffffffff83f10840 0000000000000009
 00000000000000a7 ffff8801d3b57af0 ffffffff8140a184 0000000041b58ab3
Call Trace:
 [<ffffffff81e0d58d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e0d58d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8140a184>] panic+0x19e/0x38d kernel/panic.c:112
 [<ffffffff8140a3a8>] warn_slowpath_common.cold.6+0x20/0x20 kernel/panic.c:455
 [<ffffffff81130159>] warn_slowpath_null+0x29/0x30 kernel/panic.c:492
 [<ffffffff832fb048>] inet_sock_destruct+0x598/0x760 net/ipv4/af_inet.c:167
 [<ffffffff8359edfe>] l2tp_tunnel_destruct+0x33e/0x590 net/l2tp/l2tp_core.c:1235
 [<ffffffff82f2e16c>] sk_destruct+0x4c/0x4c0 net/core/sock.c:1447
 [<ffffffff82fcb32a>] sock_diag_broadcast_destroy_work+0x21a/0x390 net/core/sock_diag.c:153
 [<ffffffff81181f4f>] process_one_work+0x7df/0x1600 kernel/workqueue.c:2064
 [<ffffffff81182e49>] worker_thread+0xd9/0xfc0 kernel/workqueue.c:2196
 [<ffffffff81190958>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff838c1c95>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..