Checklist

• This is a bug report, not a question. Ask questions on discuss.ipfs.io.
• I have searched on the issue tracker for my bug.
• I am running the latest kubo version or have an issue updating.

Installation method

built from source

Version

Kubo version: 0.16.0
Repo version: 12
System version: amd64/linux
Golang version: go1.18.1

Config

Nothing of interest

Description

Run this command while the daemon is running

kubo/test/sharness/t0054-dag-car-import-export-data$ ipfs dag import lotus_testnet_export_128_v2.car
Error: operation not supported

This is the CAR imported in this test https://github.com/ipfs/kubo/blob/master/test/sharness/t0054-dag-car-import-export.sh#L257.

However, the test doesn't run with the daemon online (which is the most common way in which kubo is run).

IIUC the reason why this is happening is:

• The wrapper used to process files inbound over the HTTP API implements the ReaderSeeker interface, but errors if the underlying Reader does not support seeking (as is true for multipart). https://github.com/ipfs/go-ipfs-files/blob/30b08cadfb701548b99f14c5b92dda95e735de61/readerfile.go#L72-L78
• The CARv2 reader operates on ByteReaderSeeker so tries to convert/upgrade any Reader not implementing ByteReader or Seeker https://github.com/ipld/go-car/blob/50e029b9990efc2a9f70df098445fe5a5cf10df6/v2/block_reader.go#L79-L82
• This is done using interface casting https://github.com/ipld/go-car/blob/50e029b9990efc2a9f70df098445fe5a5cf10df6/v2/internal/io/converter.go#L54-L62
• The interface cast says the wrapper implements ReaderSeeker even though any calls to Seek will result in an ErrUnsupported
• This results in the first call to Seek failing and the import failing

There's are a number of ways to handle this since it's basically an API mismatch. I suspect @guseggert, @Jorropo and @rvagg might have some opinions on the right way to do this since it's a similar issue to ipfs/go-datastore#188, golang/go#41198 and involves the go-car v2 internals.

Note for the kubo maintainers: IMO sharness tests should either test when the daemon is running or both when running and not running since having a daemon running is the most commonly use for kubo and we have run into issues like this before where there's success when no HTTP API is used, but failures over the HTTP API.