Currently, ctr image import as well as the transfer service import with NewImageImportStream does not support archives that are compressed (gzip, zstd).

I've tried passing a decompressed stream like so:

	decompressor, err := compression.DecompressStream(f)
	if err != nil {
		return nil, fmt.Errorf("failed to create stream decompressor: %w", err)
	}
	defer decompressor.Close()

	src := tarchive.NewImageImportStream(decompressor, "")

However, I believe there is a bug in the proxy transfer service because it fails during untarBlob with failed to read expected number of bytes: unexpected EOF. Patching containerd, I found it errors in this line with the following parameters: copied 34860544, size 34877440, ws.Offset 0, size-ws.Offset 34877440:

https://github.com/containerd/containerd/blob/v1.7.13/content/helpers.go#L184

When doing the decompression either with a local store local.NewStore or on the server-side (this patch), then it works perfectly fine.