r0 = socket$inet6_tcp(0xa, 0x1, 0x0)
ioctl$sock_inet6_SIOCDELRT(r0, 0x890b, &(0x7f0000000080)={@mcast1, @mcast1, @loopback, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1080100})