panic: UserChainTarget should never be called.

goroutine 1143 gp=0x6a43494dba40 m=18 mp=0x6a4348b5c008 [running]:
panic({0xd05280?, 0x10526f0?})
	GOROOT/src/runtime/panic.go:879 +0x15c fp=0x6a43493eff00 sp=0x6a43493efe50 pc=0x960ac
gvisor.dev/gvisor/pkg/tcpip/stack.(*UserChainTarget).Action(...)
	pkg/tcpip/stack/iptables_targets.go:174
gvisor.dev/gvisor/pkg/sentry/socket/netfilter.(*userChainTarget).Action(0x0?, 0x0?, 0x0?, 0x10?, {0x0?, 0x0?})
	<autogenerated>:1 +0x30 fp=0x6a43493eff20 sp=0x6a43493eff00 pc=0x6ffbf0
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).checkRule(0x2?, 0x1, 0x6a4348a40420, {{0x6a434963a808, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, ...}, ...}, ...)
	pkg/tcpip/stack/iptables.go:774 +0x1b0 fp=0x6a43493f0130 sp=0x6a43493eff20 pc=0x5d4ea0
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).checkChain(0x6a4348dc6c08, 0x1, 0x6a4348a40420, {{0x6a434963a808, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, ...}, ...}, ...)
	pkg/tcpip/stack/iptables.go:705 +0xb0 fp=0x6a43493f0220 sp=0x6a43493f0130 pc=0x5d4b20
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).check(0xffffffffffffffff?, {{0x6a434963a808, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, 0xffffffffffffffff}, {0xffffffffffffffff, ...}}, ...)
	pkg/tcpip/stack/iptables.go:650 +0xa0 fp=0x6a43493f03f0 sp=0x6a43493f0220 pc=0x5d46e0
gvisor.dev/gvisor/pkg/tcpip/stack.check(0x6a4348a40420?, {{0x6a434963a808, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, 0xffffffffffffffff}, {0xffffffffffffffff, ...}}, ...)
	pkg/tcpip/stack/iptables.go:640 +0x58 fp=0x6a43493f04c0 sp=0x6a43493f03f0 pc=0x5d45f8
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).CheckInput(0x6a4348dc6c08, 0x6a4348a40420, {0x6a43485d0be8, 0x7})
	pkg/tcpip/stack/iptables.go:459 +0x188 fp=0x6a43493f07f0 sp=0x6a43493f04c0 pc=0x5d3c48
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).deliverPacketLocally(0x6a4348c35508, {0x6a43489cc10e, 0x30, 0x72}, 0x6a4348a40420, {0x6a43485d0be8?, 0x5?})
	pkg/tcpip/network/ipv6/ipv6.go:1436 +0x88 fp=0x6a43493f0a50 sp=0x6a43493f07f0 pc=0x77c5d8
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).handleValidatedPacket(0x6a4348c35508, {0x6a43489cc10e, 0x30, 0x72}, 0x6a4348a40420, {0x6a43485d0be8, 0x7})
	pkg/tcpip/network/ipv6/ipv6.go:1425 +0x4b8 fp=0x6a43493f0d40 sp=0x6a43493f0a50 pc=0x77c4f8
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).HandlePacket(0x6a4348c35508, 0x6a4348a40420)
	pkg/tcpip/network/ipv6/ipv6.go:1195 +0x740 fp=0x6a43493f12a0 sp=0x6a43493f0d40 pc=0x77a880
gvisor.dev/gvisor/pkg/tcpip/stack.(*nic).DeliverNetworkPacket(0x6a43487d1b08, 0x86dd, 0x6a4348a40420)
	pkg/tcpip/stack/nic.go:781 +0x1a0 fp=0x6a43493f12e0 sp=0x6a43493f12a0 pc=0x5e0b80
gvisor.dev/gvisor/pkg/tcpip/link/nested.(*Endpoint).DeliverNetworkPacket(0x6a43493f1348?, 0x86dd, 0x6a4348a40420)
	pkg/tcpip/link/nested/nested.go:61 +0xa8 fp=0x6a43493f1320 sp=0x6a43493f12e0 pc=0x799048
gvisor.dev/gvisor/pkg/tcpip/link/packetsocket.(*Endpoint).DeliverNetworkPacket(0x6a4348ed64b0, 0x86dd, 0x6a4348a40420)
	pkg/tcpip/link/packetsocket/packetsocket.go:50 +0x3c fp=0x6a43493f1350 sp=0x6a43493f1320 pc=0x79a7dc
gvisor.dev/gvisor/pkg/tcpip/link/channel.(*Endpoint).InjectInbound(0x6a4348ba2a80, 0x86dd, 0x6a4348a40420)
	pkg/tcpip/link/channel/channel.go:208 +0x6c fp=0x6a43493f1390 sp=0x6a43493f1350 pc=0x79d9dc
gvisor.dev/gvisor/pkg/tcpip/link/tun.(*Device).Write(0x6a43492230b0, 0x6a4349487410)
	pkg/tcpip/link/tun/device.go:279 +0x4a4 fp=0x6a43493f1540 sp=0x6a43493f1390 pc=0x7a0194
gvisor.dev/gvisor/pkg/sentry/devices/tundev.(*tunFD).Write(0x6a43489c3808?, {0x107ed00, 0x6a434914b208}, {{0x10749b8, 0x6a434908e008}, {0x0, 0x1, 0x200001c0, 0x4a}, {0x0}}, ...)
	pkg/sentry/devices/tundev/tundev.go:176 +0x20c fp=0x6a43493f1600 sp=0x6a43493f1540 pc=0xa74c2c
gvisor.dev/gvisor/pkg/sentry/vfs.(*FileDescription).Write(0x6a4349223040, {0x107ed00, 0x6a434914b208}, {{0x10749b8, 0x6a434908e008}, {0x0, 0x1, 0x200001c0, 0x4a}, {0x0}}, ...)
	pkg/sentry/vfs/file_description.go:728 +0x58 fp=0x6a43493f1680 sp=0x6a43493f1600 pc=0x416a68
gvisor.dev/gvisor/pkg/sentry/syscalls/linux.write(0x6a434914b208, 0x6a4349223040, {{0x10749b8, 0x6a434908e008}, {0x0, 0x1, 0x200001c0, 0x4a}, {0x0}}, {0x0?})
	pkg/sentry/syscalls/linux/sys_read_write.go:333 +0x70 fp=0x6a43493f1800 sp=0x6a43493f1680 pc=0x817490
gvisor.dev/gvisor/pkg/sentry/syscalls/linux.Write(0x6a434914b208, 0x0?, {{0xc8}, {0x200001c0}, {0x4a}, {0x0}, {0x0}, {0x0}})
	pkg/sentry/syscalls/linux/sys_read_write.go:304 +0x100 fp=0x6a43493f1940 sp=0x6a43493f1800 pc=0x816980
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0x6a434914b208, 0x40, {{0xc8}, {0x200001c0}, {0x4a}, {0x0}, {0x0}, {0x0}})
	pkg/sentry/kernel/task_syscall.go:143 +0x4e4 fp=0x6a43493f1c80 sp=0x6a43493f1940 pc=0x6a25b4
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0x6a434914b208, 0x40, {{0xc8}, {0x200001c0}, {0x4a}, {0x0}, {0x0}, {0x0}})
	pkg/sentry/kernel/task_syscall.go:323 +0x3c fp=0x6a43493f1ce0 sp=0x6a43493f1c80 pc=0x6a33dc
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0x6a434914b208, 0x40, {{0xc8}, {0x200001c0}, {0x4a}, {0x0}, {0x0}, {0x0}})
	pkg/sentry/kernel/task_syscall.go:283 +0x58 fp=0x6a43493f1d30 sp=0x6a43493f1ce0 pc=0x6a3108
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0x6a4348a32f20?)
	pkg/sentry/kernel/task_syscall.go:258 +0x238 fp=0x6a43493f1e10 sp=0x6a43493f1d30 pc=0x6a2ec8
gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0x6a4349028900?, 0x6a434914b208)
	pkg/sentry/kernel/task_run.go:258 +0xd04 fp=0x6a43493f1f10 sp=0x6a43493f1e10 pc=0x6993a4
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0x6a434914b208, 0x5b)
	pkg/sentry/kernel/task_run.go:89 +0x1a8 fp=0x6a43493f1fb0 sp=0x6a43493f1f10 pc=0x6981f8
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start.gowrap1()
	pkg/sentry/kernel/task_start.go:531 +0x20 fp=0x6a43493f1fd0 sp=0x6a43493f1fb0 pc=0x6a1330
runtime.goexit({})
	src/runtime/asm_arm64.s:1447 +0x4 fp=0x6a43493f1fd0 sp=0x6a43493f1fd0 pc=0x9e984
created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start in goroutine 917
	pkg/sentry/kernel/task_start.go:531 +0xc0