github.com/coreos/go-tcmu/scsi

Go SCSI emulation via the Linux TCM in Userspace module


License
Apache-2.0
Install
go get github.com/coreos/go-tcmu/scsi

Documentation

go-tcmu

GoDoc

Go bindings to attach Go Readers and Writers to the Linux kernel via SCSI.

It connects to the TCM Userspace kernel API, and provides a loopback device that responds to SCSI commands. This project is based on open-iscsi/tcmu-runner, but in pure Go.

Overview

This package creates two types of Handlers (much like net/http) for SCSI block device commands. It wraps the implementation details of the kernel API, and sets up (a) a TCMU SCSI device and connect that to (b) a loopback SCSI target.

From here, the Linux IO Target kernel stack can expose the SCSI target however it likes. This includes iSCSI, vHost, etc. For further details, see the LIO wiki.

Usage

First, to use this package at all, you'll need the appropriate kernel module:

sudo modprobe target_core_user

Now that that's settled, there's tcmufile.go for a quick example binary that serves an image file under /dev/tcmufile/myfile.

For creating your custom SCSI targets based on a ReadWriterAt:

handler := &tcmu.SCSIHandler{
        HBA: 30, // Choose a virtual HBA number. 30 is fine.
        LUN: 0,  // The LUN attached to this HBA. Multiple LUNs can work on the same HBA, this differentiates them.
        WWN: tcmu.NaaWWN{
                OUI:      "000000",                    // Or provide your OUI
                VendorID: GenerateSerial("foobar"), // Or provide a vendor id/serial number
                // Optional: Provide further information for your WWN
                // VendorIDExt: "0123456789abcdef", 
        },
        VolumeName: "myVolName", // The name of your volume.
        DataSizes: tcmu.DataSizes{
                VolumeSize: 5 * 1024 * 1024, // Size in bytes, eg, 5GiB
                BlockSize:  1024,            // Size of logical blocks, eg, 1K
        },
        DevReady: tcmu.SingleThreadedDevReady(
                ReadWriterAtCmdHandler{      // Or replace with your own handler
                        RW: rw,
                }),
}
d, _ := tcmu.OpenTCMUDevice("/dev/myDevDirectory", handler)
defer d.Close()

This will create a device named /dev/myDevDirectory/myVolName with the mentioned details. It is now ready for formatting and treating like a block device.

If you wish to handle more SCSI commands, you can implement a replacement for the ReadWriterAtCmdHandler following the interface:

type SCSICmdHandler interface {
    HandleCommand(cmd *SCSICmd) (SCSIResponse, error)
}

If the default functionality was acceptable, the library contains a number of helpful Emulate functions that you can call to achieve the basic functionality.