r0 = socket$inet6_udp(0xa, 0x2, 0x0)
ioctl$sock_ipv6_tunnel_SIOCCHGTUNNEL(r0, 0x89f3, &(0x7f00000000c0)={'sit0\x00', &(0x7f0000000000)={'sit0\x00', 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, @loopback={0x4500000000000000}, @ipv4={'\x00', '\xff\xff', @loopback}}})