Re: [Libguestfs] [PATCH 1/2] spec: Recommend cap on NBD_REPLY_TYPE_BLOCK_STATUS length

This is a malicious server. A good client will drop the connection when receiving the first 1 byte chunk. The real issue here is not enforcing or suggesting a limit on the number of extent the server returns, but enforcing a limit on the minimum size of a chunk. Since this is the network *block device* protocol it should not allow chunks smaller than the device block size, so anything smaller than 512 bytes should be invalid response from the server. Even the last chunk should not be smaller than 512 bytes. The fact that you can serve a file with size that is not aligned to 512 bytes does not mean that the export size can be unaligned to the logical block size. There are no real block devices that have such alignment so the protocol should not allow this. A good server will round the file size down the logical block size to avoid this issue. How about letting the client set a minimum size of a chunk? This way we avoid the issue of limiting the number of chunks. Merging small chunks is best done on the server side instead of wasting bandwidth and doing this on the client side.